Nuclear Medicine Imaging in Tumors

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Questions and Answers

What is the main radionuclide used for imaging the parathyroid?

111In

123I

67Ga

99mTc-sestamibi (correct)

How long does the first phase of the parathyroid imaging begin after injection?

1 hour

15 to 20 minutes (correct)

30 to 35 minutes

5 to 10 minutes

Which type of tumor is NOT mentioned as a focus of nuclear medicine imaging in the content?

Lung Cancer

Prostate Cancer

Renal Cell Carcinoma (correct)

Breast Cancer

What is the purpose of radionuclide therapies in oncology?

To provide pain relief for metastatic bone pain Signup and view all the answers

Which imaging modality has evolved from 67Ga to 99mTc for infection imaging?

Nuclear medicine techniques Signup and view all the answers

What is the main purpose of Indium-111–capromab pendetide (ProstaScint) in prostate cancer treatment?

To target prostate-specific membrane antigen (PSMA) Signup and view all the answers

At what time frame post-injection is imaging for Indium-111–capromab pendetide recommended for optimal results?

96 to 120 hours Signup and view all the answers

Which imaging procedure is used for the diagnostic evaluation of recurrent or metastatic colorectal cancer?

Technetium-99m-arcitumomab (CEA-Scan) Signup and view all the answers

What is the dosage of Indium-111-pentetreotide (OctreoScan) for adults in neuroendocrine tumor visualization?

6 mCi (222 MBq) Signup and view all the answers

Pheochromocytomas are tumors that secrete what type of hormones?

Catecholamines Signup and view all the answers

In the context of radionuclide therapy, what is a primary application for metastatic bone pain patients?

Radionuclide therapies specifically targeting tumors Signup and view all the answers

What is the primary advantage of using 99mTc-sestamibi in parathyroid imaging?

Ability to distinguish between normal and abnormal parathyroid tissue Signup and view all the answers

Which of the following is a characteristic of the imaging procedure used for neuroendocrine tumors?

Involves administration of Indium-111-pentetreotide Signup and view all the answers

What role does radioimmunotherapy primarily serve in the context of lymphomas?

Targeting specific malignant cells with antibodies Signup and view all the answers

Which imaging phase occurs approximately 2 hours after the injection of 99mTc-sestamibi for parathyroid assessment?

Parathyroid phase for detailed evaluation Signup and view all the answers

When comparing the evolution of infection imaging, which radionuclide was not involved in the transition from older methods?

123I Signup and view all the answers

In terms of tumor types, which one is specifically noted in the context of radionuclide therapies besides lymphomas?

Metastatic Bone Pain Signup and view all the answers

Which property distinguishes murine monoclonal antibodies used in imaging from traditional antibodies?

Specificity to bind certain antigens relevant to oncological imaging Signup and view all the answers

What is a characteristic feature of pheochromocytoma and neuroblastoma that necessitates special imaging consideration?

They can secrete catecholamines, impacting imaging results Signup and view all the answers

What is the primary antigen targeted by Indium-111–capromab pendetide (ProstaScint) in prostate cancer detection?

Prostate-specific membrane antigen (PSMA) Signup and view all the answers

What is the imaging time frame for optimal results after the injection of Indium-111–capromab pendetide?

96 to 120 hours Signup and view all the answers

What is the primary use of Technetium-99m-arcitumomab (CEA-Scan) in colorectal cancer?

Evaluating recurrent or metastatic disease Signup and view all the answers

How long after injection should images be acquired for Technetium-99m-arcitumomab in colorectal cancer detection?

2 to 5 hours Signup and view all the answers

What is the dosage range for Indium-111-pentetreotide (OctreoScan) used in adults?

6 mCi Signup and view all the answers

How often are images taken after administering Indium-111-pentetreotide (OctreoScan)?

At 4, 24, and 48 hours Signup and view all the answers

Pheochromocytomas are characterized by the secretion of which substance?

Catecholamines Signup and view all the answers

Which group of tumors is primarily associated with neuroendocrine functions?

Pheochromocytomas and neuroblastomas Signup and view all the answers

What specific imaging technique is utilized to visualize neuroendocrine tumors?

Indium-111-pentetreotide (OctreoScan) Signup and view all the answers

What is the primary feature of neuroblastomas?

Malignant tumors of the sympathetic nervous system Signup and view all the answers

Which imaging technique is more likely to suggest benign breast disease based on radiotracer uptake characteristics?

Diffuse or patchy uptake of mild to moderate intensity Signup and view all the answers

What recommendation should be made concerning SPECT imaging according to clinical guidelines?

Its utility should be correlated with clinical findings. Signup and view all the answers

What positioning is required for accurate marker placement during imaging to minimize lesion location changes?

Prone position after patient positioning Signup and view all the answers

Which specific feature in imaging is strongly suggestive of axillary lymph node metastatic involvement?

Focal increased uptake in the ipsilateral axilla Signup and view all the answers

What is an important consideration regarding the use of radioactive markers in relation to imaging accuracy?

Placement after patient positioning can alter lesion localization. Signup and view all the answers

What is the main factor affecting the diagnostic accuracy in breast cancer evaluations when mammography is inconclusive?

Density of breast tissue Signup and view all the answers

What is a potential limitation stated regarding the use of clinical guidelines in nuclear medicine?

They may not address individual patient circumstances. Signup and view all the answers

Which method is most critical to ensure prior to conducting breast cancer evaluations?

Availability of prior imaging studies Signup and view all the answers

How should practitioners respond when clinical guidelines conflict with a patient's unique clinical situation?

Make a clinical decision based on the situation's context. Signup and view all the answers

What is one key consideration for imaging procedures in patients with breast cancer?

Circumstances may warrant deviations from guidelines. Signup and view all the answers

Which statement best reflects the concepts of sensitivity and specificity in breast cancer imaging guidelines?

Sensitivity is crucial for detecting all potential abnormalities. Signup and view all the answers

Which of the following factors does NOT impact the interpretation of breast imaging based on the guidelines?

Level of physician's training Signup and view all the answers

What is the primary benefit of using 99mTc-sestamibi in breast scintigraphy?

Improved sensitivity for detecting metastases Signup and view all the answers

What patient preparation is required before performing breast scintigraphy?

Removal of clothing and jewelry above the waist Signup and view all the answers

Which imaging technique is typically employed during breast scintigraphy?

Single-photon emission computed tomography (SPECT) Signup and view all the answers

In breast scintigraphy, what could potentially affect the diagnostic accuracy?

All of the above Signup and view all the answers

What is the role of the technologist or physician during the breast scintigraphy procedure?

Provide a thorough explanation of the test Signup and view all the answers

Which principle best describes the evaluation of neoadjuvant chemotherapy effectiveness in breast cancer using scintigraphy?

It measures metabolic activity in the breast tissue. Signup and view all the answers

What is a key characteristic of scintimammography in terms of sensitivity?

Enhanced sensitivity at the expense of specificity Signup and view all the answers

What is a critical aspect of clinical guidelines for breast scintigraphy?

Standardized protocols for imaging and interpretation Signup and view all the answers

How does breast scintigraphy differ in terms of sensitivity when compared to traditional imaging methods?

It has higher sensitivity for localized breast tumors. Signup and view all the answers

Which statement correctly describes the precautions necessary before performing breast scintigraphy on a pregnant or lactating patient?

Determine if the patient should proceed, and provide appropriate radiation safety recommendations. Signup and view all the answers

What is a critical factor to consider regarding the timing of breast scintigraphy after a core or excisional biopsy?

The procedure can yield false-positive results if performed within 4–6 weeks after the biopsy. Signup and view all the answers

Which component is essential for optimizing the quality of imaging during a breast physical examination?

Positioning the patient to minimize patient motion and increase image clarity. Signup and view all the answers

What specific attention should a nuclear medicine physician give during a breast scintigraphy examination?

Be aware of physical signs and symptoms, including the patient's prior surgical history. Signup and view all the answers

Which factor is NOT significant when determining the appropriateness of a breast physical examination for scintigraphy?

The patient's dietary habits prior to the examination. Signup and view all the answers

What is the primary advantage of using 99mTc-sestamibi in breast scintigraphy?

It facilitates the evaluation of neoadjuvant chemotherapy effectiveness. Signup and view all the answers

Which positioning is recommended for patients during the breast scintigraphy procedure to ensure accurate imaging?

Prone position with arms extended. Signup and view all the answers

What is a key consideration regarding the diagnostic accuracy in breast cancer evaluations when mammography is inconclusive?

The necessity for scintigraphy to confirm findings. Signup and view all the answers

In the context of breast scintigraphy, which of the following factors could potentially compromise the imaging process?

Use of radiopharmaceuticals external to the study. Signup and view all the answers

What is a critical aspect of clinical guidelines for breast scintigraphy regarding patient information?

Patients must provide a detailed medical history prior to the procedure. Signup and view all the answers

What is a critical contraindication for the use of blue dye in medical procedures?

Pregnant women Signup and view all the answers

Which factor is essential for the increased sensitivity of detection probes during radioguided surgery?

Sensitivity to detect weakly active sentinel lymph nodes (SLNs) Signup and view all the answers

In lymphoscintigraphy, what advantage does combining blue dye with LS/probe information provide?

It decreases false-negative findings and increases sensitivity Signup and view all the answers

What must be documented in the report to the referring physician regarding the use of blue dye?

The dose and volume of activity injected Signup and view all the answers

What specific feature of a detection probe is vital for accurately discriminating activity within a sentinel lymph node?

A detachable collimator for small angle view Signup and view all the answers

Which of the following is a common misconception about blue dye utilization in surgical procedures?

It is completely safe for all patients without any side effects Signup and view all the answers

What aspect of patient management is crucial while preparing for the use of blue dye?

Verifying prior allergic reactions to similar agents Signup and view all the answers

How should critical information regarding the use of blue dye be communicated if electronic form is unavailable?

Directly relayed to the surgical team Signup and view all the answers

What is a primary consideration for the use of blue dye in breast cancer procedures?

It can affect the interpretation of lymph node status Signup and view all the answers

Which technique in lymphoscintigraphy is critical for the accurate localization of sentinel lymph nodes?

Combining radiopharmaceutical injection with colored dye Signup and view all the answers

What is a key factor that can influence the choice of radiopharmaceuticals in nuclear medicine procedures?

The availability of the radiopharmaceutical and local regulations Signup and view all the answers

Which contraindication should be considered before administering blue dye in surgical procedures?

If there is a risk of an allergic reaction in the patient Signup and view all the answers

What procedural step is essential for ensuring effective radioguided surgery before lymph node dissection?

Having all imaging results accessible to the surgeon at the time of surgery Signup and view all the answers

What is the recommended action for nursing mothers after receiving radiopharmaceuticals?

Suspend breastfeeding for 24 hours Signup and view all the answers

Which of the following is NOT considered a benefit of preoperative imaging?

Eliminating the need for radiopharmaceuticals Signup and view all the answers

What is the primary limitation faced by some surgeons regarding lymphoscintigraphy?

Scheduling delays due to procedural requirements Signup and view all the answers

What is essential for surgeons intending to perform sentinel lymph node studies?

A minimum of 30 procedures under guidance Signup and view all the answers

What must be considered concerning the psychological aspects of admitting a pregnant woman to a nuclear medicine department?

Potential anxiety related to radiation exposure Signup and view all the answers

What role does recent imaging play prior to a patient's arrival at the nuclear medicine department?

It aids in informed decision-making based on prior findings Signup and view all the answers

Which of the following is commonly a concern when using blue dye during radioguided surgery procedures?

Possible allergic reactions in patients Signup and view all the answers

What is an important consideration for performing lymphoscintigraphy in breast cancer patients?

Selection of appropriate radiopharmaceuticals Signup and view all the answers

Which factor has NOT been suggested as a requirement for personnel involved in sentinel lymph node studies?

Completion of specific training courses in oncology Signup and view all the answers

Which statement correctly reflects the ongoing debates regarding lymphoscintigraphy?

Its effectiveness varies based on surgeon experience Signup and view all the answers

What is a primary benefit of using blue dye in sentinel lymph node procedures?

Enhances visualization of lymphatic drainage Signup and view all the answers

When utilizing lymphoscintigraphy, which radiopharmaceutical is most commonly employed for visualizing lymphatic flow?

Technetium-99m Signup and view all the answers

Which of the following is a known contraindication for using blue dye in surgical procedures?

Patient history of allergic reactions to radiopharmaceuticals Signup and view all the answers

In the context of radioguided surgery, what role does the gamma probe serve?

To detect radioactivity in tissues for locating sentinel nodes Signup and view all the answers

What is a significant risk associated with lymphoscintigraphy procedures that practitioners must be aware of?

Local infection at the injection site Signup and view all the answers

Which factor is critical for determining the dose of blue dye used in sentinel lymph node mapping?

Patient's body weight and specific clinical considerations Signup and view all the answers

Which imaging technique can be combined with blue dye injection to enhance detection of sentinel nodes?

Nuclear imaging with gamma cameras Signup and view all the answers

When is lymphoscintigraphy generally recommended to be performed in relation to surgery?

On the day of surgery, before the beginning of the procedure Signup and view all the answers

Which of the following considerations is essential for ensuring accurate lymphoscintigraphy results?

Timing of radiopharmaceutical injection Signup and view all the answers

What safety measure should be implemented when using blue dye in surgical settings?

Monitor for signs of anaphylactic shock during surgery Signup and view all the answers

What is an important consideration regarding the use of colloids for sentinel lymph node identification?

The particle size does not affect the accumulation in sentinel lymph nodes. Signup and view all the answers

Which aspect impacts the determination of injected activity for lymphoscintigraphy?

The time between lymphoscintigraphy and subsequent surgery. Signup and view all the answers

What is the significance of tilting the syringe before the injection of Technetium-99m-tilmanocept?

It aids in distributing the tracer evenly throughout the suspension. Signup and view all the answers

What is a major factor that can affect the interpretation of results during completion lymph node dissection?

Timing and physical decay of the injected activity. Signup and view all the answers

How does the Blue Dye Technique assist in sentinel lymph node identification?

It enhances the contrast between targeted lymph nodes and surrounding tissues. Signup and view all the answers

What is a benefit of warming the injection site with a hot-water bag during a sentinel lymph node biopsy?

It enhances the drainage of the radiotracer. Signup and view all the answers

Which factor is crucial to rule out before performing a sentinel lymph node biopsy in older patients?

Constriction of lymphatic vessels Signup and view all the answers

In what scenario might repeated imaging be deemed necessary during a sentinel lymph node biopsy process?

If there is suspicion of false injection of the radiotracer. Signup and view all the answers

How is the identification of the afferent lymph vessel optimized in sentinel lymph node biopsies?

Through dynamic lymphoscintigrams along with skin marking. Signup and view all the answers

What percentage of sentinel lymph nodes are known to be identified as only radioactive during a biopsy?

13% Signup and view all the answers

What technique involves injecting blue dye at the beginning of an operation for sentinel lymph node mapping?

Blue dye procedure Signup and view all the answers

What is essential for marking the sentinel lymph nodes on the skin during the procedure?

Indelible ink or a tattoo for accurate marking. Signup and view all the answers

What role does massage of the injection site serve during sentinel lymph node procedures?

It accelerates lymphatic drainage to enhance imaging. Signup and view all the answers

What imaging method is recommended during the first 10 minutes post-injection for detecting sentinel lymph nodes (SLNs)?

Dynamic imaging capturing one frame per minute Signup and view all the answers

Which type of gamma camera is preferred for optimal coverage of drainage regions during SLN imaging?

Dual-head gamma camera with large field of view Signup and view all the answers

What is the primary purpose of acquiring early static images after dynamic imaging during SLN detection?

To identify true SLNs from false positives Signup and view all the answers

Which factor is critical for distinguishing individual SLNs when using gamma cameras?

Low-energy high-resolution collimators Signup and view all the answers

What is the recommended energy window setting when using 99mTc for SLN detection?

15% centered on the 140-keV photopeak Signup and view all the answers

In which anatomical regions is dynamic imaging particularly important for detecting SLNs in melanoma of the hand or leg?

Axilla and groin Signup and view all the answers

What role does body contouring play in the imaging process of SLNs?

Facilitates localization of hot spots Signup and view all the answers

What is a possible limitation of using a single-head gamma camera compared to a dual-head camera in SLN imaging?

It may increase imaging time Signup and view all the answers

What is the purpose of using a 99mTc or 57Co flood source in imaging?

To aid in transmission imaging for localization Signup and view all the answers

What is the primary role of histopathological assessment in sentinel lymph node biopsies?

To confirm the presence of lymph node metastases Signup and view all the answers

What is a disadvantage of frozen section analysis in sentinel lymph node examination?

It has a low sensitivity of 47% Signup and view all the answers

In what situation is the use of blue dye contraindicated during surgical procedures?

When the patient is pregnant due to anaphylactic risks Signup and view all the answers

What is the main advantage of using a gamma probe during surgery?

It allows for real-time detection of radiopharmaceuticals Signup and view all the answers

What percentage of patients with a positive sentinel lymph node are found to have involvement of additional lymph nodes?

12 – 25% Signup and view all the answers

Which of the following statements about the blue dye technique is accurate?

It provides certainty in identifying direct lymphatic drainage pathways Signup and view all the answers

What is a typical histological method employed for assessing sentinel lymph nodes?

Haematoxylin and eosin staining Signup and view all the answers

What challenge is commonly associated with probe-guided operations in lymph node tracking?

Identifying the correct node when multiple nodes are involved Signup and view all the answers

Which immunohistochemical stain is commonly used in the assessment of sentinel lymph nodes?

MART-1/Melan-A Signup and view all the answers

What does completion lymph node dissection typically aim to improve in patients with positive SLNs?

Disease-free survival and melanoma-specific survival Signup and view all the answers

Which advantage is associated with pet imaging compared to conventional imaging in breast cancer cases?

It leads to fewer false positives and a shorter time to therapy. Signup and view all the answers

What is a notable characteristic of lobular breast cancer with respect to imaging techniques?

It can be difficult to detect on regular imaging but may show up on estrogen pet imaging. Signup and view all the answers

What is the significance of the estrogen pet imaging technology that was approved in 2020?

It enables visualization of estrogen-receptor positive breast cancers that are hard to detect otherwise. Signup and view all the answers

In terms of financial implications, how does pet imaging compare to conventional imaging for breast cancer patients?

Pet imaging may be more expensive initially but can save money over time due to better accuracy. Signup and view all the answers

What aspect distinguishes the newly developed estrogen pet imaging from traditional imaging methods?

It allows for the visualization of estrogen distribution in the body, revealing cancer that is otherwise hard to see. Signup and view all the answers

What is a primary focus of nuclear medicine in breast cancer evaluation?

Evaluating the functional characteristics of cells Signup and view all the answers

Which imaging technique mentioned allows for less compression compared to standard mammograms?

Molecular breast imaging Signup and view all the answers

What aspect of breast density significantly affects tumor visibility in mammograms?

The amount of glandular versus fatty tissue Signup and view all the answers

Which type of medical professional is specifically trained as both a radiologist and a nuclear medicine physician?

Nuclear radiologist Signup and view all the answers

Which imaging technique is primarily used for identifying tumor spread in the body beyond the breast?

Positron emission tomography (PET) Signup and view all the answers

What is the typical structure of a mammogram compared to positron emission mammography (PEM)?

Mammograms generally compress the breast more than PEM Signup and view all the answers

What is a primary advantage of molecular breast imaging over traditional mammography?

It can identify tumors hidden in dense breast tissue Signup and view all the answers

What determines the amount of breast tissue density?

Genetic factors Signup and view all the answers

What is the primary reason for conducting lymphocentigraphy before surgery?

To identify the location of the sentinel lymph node Signup and view all the answers

What imaging technique combines information about tissue structure and metabolic activity?

PET/CT hybrid imaging Signup and view all the answers

Why is a radioactive tracer used in molecular imaging for tumors?

To visualize the distribution of glucose in the body Signup and view all the answers

What outcome can be monitored by comparing pre- and post-treatment PET scans?

Response of the tumor to chemotherapy Signup and view all the answers

What is the primary purpose of using a gamma camera in lymphocentigraphy?

To capture images of radioactive tracers in the body Signup and view all the answers

What unusual finding might indicate the need for additional imaging in a patient with previously removed lymph nodes?

Sentinel lymph node activity on the opposite side Signup and view all the answers

What anatomical feature is primarily visible in the CT component of a PET/CT scan?

Soft tissue density and organs Signup and view all the answers

What type of imaging would likely be used first to evaluate a patient with suspected bone metastases?

Positron Emission Tomography (PET) scan Signup and view all the answers

What does the term 'hot spot' refer to in the context of molecular imaging?

An area of high tracer concentration indicating potential tumor presence Signup and view all the answers

What does the PET scan reveal regarding the tumor's characteristics?

The tumor had numerous active estrogen receptors. Signup and view all the answers

What is the significance of the sentinel lymph node in breast cancer surgery?

It is the first lymph node to filter lymphatic fluid from the breast. Signup and view all the answers

What role do lymph nodes play in the immune response to tumors?

They help catch and filter out harmful substances, including tumor cells. Signup and view all the answers

Why is it important to check the status of the sentinel lymph node?

Its status determines if further lymph nodes need to be examined. Signup and view all the answers

What method is employed to locate the sentinel lymph node during surgery?

Injecting a radioactive substance into the breast. Signup and view all the answers

How is the PET scan used to evaluate the effectiveness of cancer therapy?

It reveals metabolic activity related to estrogen receptors. Signup and view all the answers

Which factor complicates the identification of the sentinel lymph node?

The random configuration of lymph nodes can vary per person. Signup and view all the answers

What is a potential outcome if cancer is found in the sentinel lymph node?

More lymph nodes need to be removed and examined. Signup and view all the answers

What does a negative finding in the sentinel lymph node typically indicate?

There is a greater than 95% chance that other lymph nodes are cancer-free. Signup and view all the answers

What is the primary advantage of using a theranostic approach in tumor imaging?

It combines therapeutic and diagnostic capabilities into a single agent. Signup and view all the answers

Which radiopharmaceutical is specifically mentioned as being used diagnostically in differentiated thyroid cancer?

Sodium iodide labeled with iodine-123 Signup and view all the answers

Which type of radionuclide is primarily used for therapeutic purposes in thyroid cancer treatments?

Iodine-131 Signup and view all the answers

What characteristic distinguishes tumor-imaging radiopharmaceuticals targeting specific antigens from nonspecific ones?

Targeting specific tumor antigens or metabolic processes. Signup and view all the answers

What is a notable trend in the development of tumor imaging agents over the past decade?

Increased availability of sensitive and specific agents. Signup and view all the answers

Which of the following substances is used as a radionuclide for therapy in neuroendocrine malignancies?

Somatostatin receptor radiopharmaceuticals Signup and view all the answers

Which radiopharmaceutical is specifically noted for its affinity to gliomas?

Thallium-201 Chloride Signup and view all the answers

What type of tumors primarily use somatostatin receptor imaging for visualization?

Neuroendocrine tumors Signup and view all the answers

Which of the following radiopharmaceuticals is recommended for imaging thyroid carcinomas?

Iodine-123 or -131 Sodium Iodide Signup and view all the answers

What is the primary imaging method used after the initial administration of 111In-pentetreotide for detecting neuroendocrine tumors?

SPECT Imaging Signup and view all the answers

Which feature of octreotide enhances its role in imaging neuroendocrine tumors?

Predominantly renal clearance Signup and view all the answers

Which of the following tumors is NOT typically imaged using Gallium-67 Citrate?

Thyroid carcinoma Signup and view all the answers

What is a significant advantage of using Ga-labeled somatostatin for PET/CT over pentetreotide?

Greater in vivo stability Signup and view all the answers

Which tumor type demonstrates variable receptor expression and can hinder detectability during imaging?

Medullary thyroid carcinoma Signup and view all the answers

What is the primary reason Indium-111-pentetreotide is ineffective in imaging pancreatic carcinomas of exocrine origin?

Lack of somatostatin receptor expression Signup and view all the answers

In what manner does Gallium-67 citrate imaging compare to 18F-FDG PET/CT in detecting neoplastic disease?

Less sensitive and specific Signup and view all the answers

Which type of tumor is best evaluated with 111In-pentetreotide due to its high sensitivity?

Carcinoid tumor Signup and view all the answers

What characteristic of gallium is highlighted regarding its role in neoplastic imaging?

Affinity for transferrin receptors Signup and view all the answers

What potential false-positive source might complicate somatostatin receptor imaging?

Inflammatory processes such as sarcoidosis Signup and view all the answers

Which imaging technique is the primary choice for screening somatostatin receptor-expressing tumors?

Whole-body gamma camera imaging Signup and view all the answers

Which type of tumor exhibits subtype 2 somatostatin receptor absence that can lead to reduced imaging sensitivity?

Medullary thyroid carcinoma Signup and view all the answers

How does thallium-201 chloride's imaging characteristics present challenges compared to other methodologies?

Low energic efficiency and high radiation dosage Signup and view all the answers

What is the main advantage of using 99mTc-sestamibi in conjunction with mammography in breast cancer detection?

It significantly increases the detection rate of node-negative breast cancers. Signup and view all the answers

Which statement accurately reflects the role of sensitivity in mammography and MBI for breast cancer detection?

Combined use of MBI and mammography can reach a sensitivity of 100% in many studies. Signup and view all the answers

In which scenario might a false-negative result occur when using MBI?

When dealing with small lesions located at significant depths. Signup and view all the answers

What is the implication of a negative MBI scan in the presence of a palpable breast lesion?

It suggests that cancer is possible but unlikely. Signup and view all the answers

What is the primary utility of lymphoscintigraphy in oncology?

To identify the first lymph node that drains from a tumor. Signup and view all the answers

Which of the following conditions can potentially lead to false-positive results in breast imaging with 99mTc-sestamibi?

The presence of atypical ductal hyperplasia. Signup and view all the answers

What is considered when using sentinel lymph node biopsies in oncology?

They help direct further therapeutic decisions based on tumor involvement. Signup and view all the answers

Which imaging characteristic is suggested to be indicative of lymph node metastatic involvement?

A discrete focus of increased activity in the ipsilateral axilla. Signup and view all the answers

What is the significance of thallium uptake in high-grade gliomas compared to low-grade gliomas?

High-grade gliomas demonstrate markedly increased thallium activity. Signup and view all the answers

Which statement best describes the relationship between gallium and thallium uptake in lymphomas?

Thallium avidity decreases in less aggressive lymphoma lesions. Signup and view all the answers

What imaging characteristic strongly suggests recurrence of a tumor post-treatment?

Focal uptake of thallium on delayed images. Signup and view all the answers

What limitation exists with gallium imaging in the abdomen?

Physiologic excretion leads to overlaps in imaging results. Signup and view all the answers

Which non-neoplastic process can lead to false-positive findings in imaging?

Graves disease. Signup and view all the answers

How does Technetium-99m-sestamibi primarily localize in tumor cells?

Passive transport across membranes and active uptake by mitochondria. Signup and view all the answers

What condition is suggested if gallium uptake in a thoracic lesion occurs without corresponding thallium uptake?

Mycobacterial infection. Signup and view all the answers

Which statement about benign parathyroid adenomas concerning imaging is accurate?

99mTc-sestamibi is preferred due to better sensitivity. Signup and view all the answers

What does peak thallium uptake time in active neoplasms generally occur?

10 to 20 minutes post-injection. Signup and view all the answers

Which factor influences the diagnostic sensitivity of 111In-pentetreotide used in imaging?

Size and subtype of tumor. Signup and view all the answers

Study Notes

Tumor Imaging

Nuclear medicine plays a role in diagnosing and treating infections and tumors

Parathyroid

99mTc-sestamibi is used to image parathyroid tumors
The average dose for an adult is 20 mCi (740 MBq)
Imaging is done in 3 phases:
- Flow Study: Acquired immediately after injection
- First (thyroid) phase: Acquired 15 to 20 minutes after injection
- Second (parathyroid) phase: Acquired 2 hours after injection

Prostate Cancer

Indium-111–capromab pendetide (ProstaScint) is used for imaging
It is a murine monoclonal antibody that targets prostate-specific membrane antigen (PSMA)
The procedure takes 96 to 120 hours
Dose: 5 mCi (185 MBq) of 111In–capromab pendetide is infused over 3 to 5 minutes
Imaging is done between 30 minutes to 4 hours or 96 to 120 hours after injection to capture optimal targeting and minimal blood pool activity

Colorectal Cancer

Technetium-99m-arcitumomab (CEA-Scan) is used to evaluate recurrent or metastatic colorectal cancer
Dose: 20 to 30 mCi (740 to 1110 MBq)
Imaging is done 2 to 5 hours after injection
Anterior/posterior 800,000 to 1 million planar or whole-body images of the chest, abdomen, and pelvis are acquired

Neuroendocrine Tumors

Indium-111-pentetreotide (OctreoScan) is used to visualize primary neuroendocrine tumors and metastasis
Dose: 6 mCi (222 MBq) for adults and 0.14 mCi/kg (5 MBq/kg) for children
Imaging is done at 4, 24, and 48 hours following injection

Pheochromocytoma and Neuroblastoma

Pheochromocytomas are catecholamine-secreting tumors found in the adrenal medulla
Neuroblastomas are malignant tumors of the sympathetic nervous system; they are most commonly found in infants and children

Tumor Imaging

Nuclear medicine plays an important role in treating and diagnosing infections and tumors.
The evolution of infection imaging:
- Gallium- 67
- Indium-111
- Technetium-99m
Imaging for parathyroid, prostate, colorectal, neuroendocrine, adrenal, breast, and lung tumors is commonly used.
Radioimmunotherapy is used to treat lymphomas, and radionuclide therapy is used to treat metastatic bone pain and other maladies.

Parathyroid

Technetium-99m-sestamibi is the radionuclide used for imaging.
The average adult dose is 20mCi (740 MBq).
Imaging is done in 3 phases
- Flow study, begins immediately after injection
- First (thyroid) phase, 15-20 minutes after injection
- Second (parathyroid) phase, 2 hours after injection

Prostate Cancer

Indium-111-capromab pendetide (ProstaScint) is used for imaging.
It is an IgG1 murine monoclonal antibody (mab) that targets prostate-specific membrane antigen (PSMA), a glycoprotein expressed by prostate epithelium.
The procedure is performed over 96 to 120 hours.
Day 1: 5 mCi (185 MBq) of 111In–capromab pendetide is injected over 3 to 5 minutes.
Blood pool activity images can be acquired 30 minutes to 4 hours after injection.
Optimal targeting and minimal blood pool activity is observed when images are acquired at 96 to 120 hours post injection.

Colorectal Cancer

Technetium-99m-arcitumomab (CEA-Scan) is used to diagnose recurrent or metastatic colorectal cancer.
The dose is 20 to 30 mCi (740 to 1110 MBq).
Anterior/posterior 800,000 to 1 million planar or whole-body images of the chest, abdomen, and pelvis are acquired 2 to 5 hours post-injection.

Neuroendocrine Tumors

Indium-111-pentetreotide (OctreoScan) is used to visualize primary neuroendocrine tumors and neuroendocrine metastasis.
The dose is 6 mCi (222 MBq) for adults and 0.14 mCi/kg (5 MBq/kg) for children.
Images are acquired at 4, 24, and 48 hours.

Pheochromocytoma and Neuroblastoma

Pheochromocytomas are catecholamine-secreting tumors found in the adrenal medulla.
Neuroblastomas are malignant tumors located in the sympathetic nervous system, more common in infants and children.

Breast Scintigraphy

Breast scintigraphy is a nuclear medicine procedure that uses 99mTc-sestamibi to detect breast cancer.
The Society of Nuclear Medicine (SNM) has developed guidelines for breast scintigraphy that are intended to assist nuclear medicine practitioners.
The SNM guidelines are not intended to establish a legal standard of care.
Breast scintigraphy is performed after intravenous administration of 99mTc-sestamibi and includes planar and/or single-photon emission computed tomography (SPECT).
The procedure is typically performed after the patient removes all clothing and jewelry above the waist.
The patient should wear a hospital gown open in front.

Procedure

Prior mammograms, ultrasounds, and MRIs should be available for review.
The technologist should provide a thorough explanation of the test to the patient.

Clinical Applications

May be used to evaluate breast cancer in patients with non-diagnostic mammograms, equivocal mammograms, or mammograms difficult to interpret.
May be helpful in identifying multicentric and multifocal carcinomas in patients with tissue diagnosis of breast cancer.
May be useful for evaluating the effectiveness of neoadjuvant chemotherapy for breast carcinoma.

Image Features

Focal increased uptake, relatively well-delineated contours with mild-to-intense radiotracer uptake are suggestive of malignancy.
Focal increased uptake in the ipsilateral axilla, in the presence of a primary lesion in the breast, is strongly suggestive of axillary lymph node metastatic involvement.
Diffuse or patchy radiotracer uptake of mild to moderate intensity, often bilateral, with edges that are not visually well-defined are more suggestive of benign disease.

Reporting

Reports to the referring physician should recommend correlation with clinical findings, as well as the results of other imaging studies.

Quality Control

Routine scintillation camera quality control should be performed as described in the Society of Nuclear Medicine Procedure Guideline for General Imaging.

Breast Scintigraphy

The Society of Nuclear Medicine Procedure Guideline for Breast Scintigraphy (mammoscintigraphy, scintimammography) provides guidelines for the recommendation, performance, interpretation, and reporting of 99mTc-sestamibi breast scintigraphy.
The procedure involves intravenous administration of 99mTc-sestamibi followed by planar and/or single-photon emission computed tomography (SPECT).
The procedure may assist in the evaluation of breast lesions in patients with tissue diagnosis of breast cancer, and the effectiveness of neoadjuvant chemotherapy for breast carcinoma.

Patient Preparation

No special preparation for the test is needed, but a thorough explanation of the test should be provided by the technologist or physician.
Patients should remove all clothing and jewelry above the waist, and wear a gown.
Before radiopharmaceutical injection, the technologist may have the patient attempt the prone position with arms extended to assess the feasibility of the study.

Procedure

A breast physical examination should be performed by either the nuclear medicine physician or the referring physician.
The time of last menses and pregnancy and lactating status of the patient should be determined. If the patient is pregnant or lactating, determination should be made as to whether to proceed with the examination.
Breast scintigraphy should be delayed at least 2 weeks after a cyst aspiration or fine needle aspiration, and 4-6 weeks after a core or excisional biopsy.
The nuclear medicine physician should be aware of physical signs and symptoms, prior surgical procedures, or therapy.

Injection

740-1,110 MBq (20-30 mCi) 99mTc-sestamibi should be administered intravenously in an arm vein contralateral to the breast with the suspected abnormality.
If the disease is bilateral, the injection is ideally administered in a foot vein.
The radiopharmaceutical should be administered using an indwelling catheter or butterfly needle and followed by 10 cc of saline to flush the vein.
Normal distribution of the radiopharmaceutical includes salivary and thyroid glands, myocardium, liver, gallbladder, small and large intestine, kidneys, bladder, and skeletal muscles.

Image Acquisition

Imaging begins 5-10 minutes after the administration of the radiopharmaceutical.
Images are acquired using a standard scintillation camera equipped with a low-energy, high-resolution collimator.
A symmetric 10% energy window should be centered over the 140-keV photopeak of 99mTc.

Imaging Positions

The patient lies prone with the breast to be imaged dependent from the imaging table.
The contralateral breast should be compressed against the table to prevent cross-talk of activity.
A breast-positioning device should be used to minimize patient motion.
The arms should be raised to expose the axillae.
The head should be turned away from the detector to minimize shine-through of normal head and neck activity.
The detector should touch the patient’s side for improved resolution.
The anterior image may be acquired with the patient supine or upright.

Image Types

Planar images are acquired for 10 minutes each, using a 128 x 128 or larger matrix to allow for pixel overload from the liver, heart, etc.
These images should be acquired:
- Prone lateral image of the breast with the suspected abnormality.
- Prone posterior oblique image of the ipsilateral breast (if needed).
- Prone lateral and posterior oblique images of the contralateral breast (if needed).
- Anterior supine or upright chest image.

Image Processing

Abdominal organs should be masked from the final images to improve visualization of breast tissue.

Interpretation Criteria

Focal increased uptake of the radiopharmaceutical in the breast or axilla (in the absence of radiopharmaceutical infiltration) is suspicious for malignancy.
Mild homogeneous uptake of the radiopharmaceutical in the breast or axilla is consistent with a normal study.
Patchy or diffuse increased radiopharmaceutical uptake in the breasts is probably not consistent with malignancy.
There is a great variability of intensity of focal uptake.

Quality Control

Quality control measures and radiation safety precautions should be followed as described in the Society of Nuclear Medicine Procedure Guideline for Use of Radiopharmaceuticals.

Sources of Error

Infiltration of the radiopharmaceutical administered in an arm vein may cause false-positive uptake in the axillary lymph nodes.
Patient positioning that does not allow the breast to be fully dependent will decrease the accuracy of the test.
Patient motion will decrease the accuracy of the test.
If both breasts are dependent, cross-talk of activity may result in a false-positive result in the contralateral breast.

Sensitivity and Accuracy

The sensitivity, specificity, and accuracy of this test depend upon several factors, including the size of the breast tumor being imaged.
The sensitivity of this test for tumors smaller than 1 cm in diameter is very low with nuclear medicine cameras in current use.

Sentinel Lymph Node (SLN) Procedure Guidelines

SLN procedure guidelines are published for professionals in nuclear medicine and cover a wide range of topics, including:
- Qualifications and responsibilities of personnel
- Procedures in nuclear medicine
- Procedures in the surgical suite
- Radiation Dosimetry
- Issues requiring further clarification
Goal of guidelines is to assist in optimizing the information obtained from SLN procedures.
Benefits of SLN guidance include better accuracy and reduced morbidity compared to using hand-held gamma probes alone.
Preoperative imaging serves as quality control for the procedure, ensuring appropriate usage of the radiotracer.
Preoperative imaging can help identify possible issues such as:
- Failure of injection
- Failure of the radiopharmaceutical
- Incorrect breast and/or axilla injection
- Incorrect side (L/R) injection.
SLN Studies are performed by surgeons and nuclear medicine specialists trained to perform such procedures.
Nuclear medicine specialists and surgeons need specific training.
Training requirement: At least 30 procedures under guidance is recommended for each surgeon performing SLN biopsies although a definition of required training has not been validated.
Pregnancy in relation to SLN procedures requires careful considerations:
- Pregnancy admission to the Nuclear Medicine department requires careful assessment of risks and potential psychological concerns.
- Nursing Mothers should suspend breastfeeding for 24 hours after radiopharmaceutical administration.
SLN Procedure may involve a combination of procedures including:
- Radiopharmaceutical
- Coloured or fluorescent dye
- Preoperative scintigraphic Imaging
- Intraoperative detection of SLNs
Controversies remain in SLN procedures, including:
- Particle size of the radiotracer
- Optimal injection route
- Timing of scintigraphy and intraoperative detection
- Whether extra-axillary lymph nodes should be considered
- Specific radiotracer and technique used are guided by local availabilities, regulations, and practices.
False-negative rates and axillary recurrence rates are similar regardless of injection site.
Blue dye can induce anaphylactic reactions which require resuscitation in 0.5 to 1.0% of patients.
Contraindications for using Blue dye:
- Hypersensitivity to the product.
- Pregnancy.
- Prior history of allergic reaction.
- Severe renal impairment.
Preoperative preparation for patients undergoing SLN procedures:
- No special preparation is required.
- Recent mammograms, breast ultrasound images, and MRI should be available for review by the physician.
- Pregnancy status and lactating status should be determined.
- Physical Examination: Should be performed before radiopharmaceutical injection.
- Communication with the surgeon: Physician should communicate prior to and after imaging procedures, especially if the final report is not available before surgery.
- All images should be available to the surgeon at the time of surgery.

Radioguided Surgery:

Detection probes must be sensitive enough to detect weakly active SLNs from the skin surface and within surgical cavities.
- Sensitivity is required to identify a weakly active SLN up to 5 cm below the skin surface.
- Probe Collimation is necessary to discriminate activity within a SLN, which requires a small angle view.
Collimator should be detachable to make the probe more compact when not needed.

Lymphatic Drainage Enhancement

If no lymphatic drainage is observed in the early images, a massage of the injection site or along the lymph vessels can be helpful
The patient or technologist should wear gloves during a massage to prevent contamination
The injection site can be warmed with a hot water bag to improve drainage
Constricted lymphatic vessels should also be ruled out as a cause for delayed drainage
Older patients (above 50 years old) typically exhibit slow lymphatic flow
In cases of extremity melanoma, passive exercise of the limb can be helpful

Skin Marking

Marking the location of the SLN directly on the skin is useful for identifying the region of interest in the operating room
Marks should be made with indelible ink or tattoo, facilitating follow-up in the event the SLN is not removed
The surgeon should palpate the region of interest to identify enlarged, hard, and non-radioactive or non-blue nodes, which are likely metastatic and should be removed

Surgical Techniques

The surgeon's repertoire should include both blue dye and radiotracer techniques
Blue dye is reliable for identifying nodes on a direct lymphatic drainage pathway, but requires a delicate surgical technique
Probe-guided surgery is more straightforward, but may be difficult if there are multiple nodes with radiopharmaceutical accumulation
In cases of blue dye use, 0.5-1 ml of patent blue V or isosulfan blue is injected intradermally around the melanoma or biopsy site
Blue dye injection site massage accelerates lymphatic drainage
Dynamic lymphoscintigrams guide the site of incision in conjunction with the skin marking
The blue vessel is dissected and followed to the SLN under the subcutaneous fascia
The blue dye technique is contraindicated in pregnancy due to the risk of anaphylaxis

Gamma Probe Use

The gamma probe should be designed for intraoperative usage and placed within a sterile sheet
The probe should provide both instantaneous and cumulative readings

Histopathological Assessment

Histopathological assessment of the SLNs is the gold standard for confirming lymph node metastases
Frozen sections are not typically used anymore due to low sensitivity
Serial sections are obtained and stained with hematoxylin and eosin and immunohistochemical stains

Completion Lymph Node Dissection

Patients with a positive SLN are offered completion lymph node dissection
Approximately 12-25% of these patients have involvement of additional lymph nodes
Based on the MSLT-1 study, completion lymph node dissection prolongs disease-free survival in patients with tumors thicker than 1.2 mm and improves melanoma-specific survival in patients with nodal metastases from tumors of intermediate Breslow thickness

Image Acquisition

All possible drainage regions should be covered during image acquisition
A dual-head gamma camera with large field of view detectors is preferred for covering larger areas
A single-head camera can also be used
Low-energy, high-resolution, or ultra-high-resolution collimation is recommended to distinguish individual SLNs.

Early Static Images

Static planar 5-minute images (anteroposterior and lateral) should be acquired with a 256×256 matrix over the basin of the expected SLN
Early images aid in discriminating true SLNs from non-SLNs

Dynamic Imaging

Lymphatic channels and direct drainage pathways are visualized in dynamic imaging series
Dynamic imaging should be performed whenever possible for facilitating image interpretation
Dynamic imaging (10-20 minutes, one frame per minute in a 128 × 128 matrix in word mode) during the first 10 minutes following injection is recommended for detecting SLNs in head and neck melanoma
Dynamic imaging is usually required for melanoma of the hand/forearm or foot/leg, starting over the injection site and following the lymphatic drainage to the knee or elbow and axilla or groin
In-transit nodes are also reliably detected by dynamic imaging

Radiopharmaceutical Administration

99mTc-sulphur colloid, with a particle size of 350-5,000 nm, should be filtered through a 100- to 200-nm membrane filter after preparation to select smaller particles
99mTc-tilmanocept (Lymphoseek®) is an alternative tracer that binds to mannose receptors expressed by reticuloendothelial tissue in lymph nodes
Tilmanocept targets the CD206 receptor and has a molecular size of 7 nm
A maximum injected activity of 20 MBq in 0.2 ml at the time of injection is recommended, adjusting for time between lymphoscintigraphy and surgery
The syringe should be tilted but not shaken before injection to homogenously distribute the tracer
The selected injected activity is dependent on the time between lymphoscintigraphy and surgery and can vary between published studies
The amount of injected activity should be reduced with a longer time between lymphoscintigraphy and surgery
The injected activity should be adjusted for the physical decay process and the intended residual activity in the operating room

Nuclear Radiologist Definition

A nuclear radiologist is a physician with board certification in both radiology and nuclear medicine
This requires 4 years of medical school, 5 years of radiology residency, and 1 year of nuclear medicine fellowship training

Radiology vs. Nuclear Medicine

Radiology focuses on the structural details of the body, including anatomy, location, and size of organs
Radiology includes imaging modalities like mammograms, ultrasounds, and MRIs, which are all used to visualize the breast
Nuclear medicine focuses on the functional aspects of the body, examining cell types, receptor presence (e.g., estrogen receptors), and cellular processes
Nuclear medicine imaging techniques include molecular breast imaging, lymphocentigraphy, and PET scans

Molecular Imaging in Breast Cancer

Tumor Detection in the Breast:
- Positron emission mammography (PEM) is a comfortable imaging technique that helps visualize tumors in dense breast tissue
- Molecular breast imaging (MBI) uses a similar setup to PEM and also provides enhanced tumor visualization
- Dedicated breast PET is another molecular imaging technique that resembles a breast MRI and can be used for better comparison with MRI findings
- These technologies can provide complementary information to mammograms and breast MRIs

Surgical Planning in Breast Cancer

Sentinel Lymph Node Identification:
- Surgeons remove the sentinel lymph node during surgery to determine if cancer has spread beyond the breast.
- The sentinel lymph node is the first lymph node that drains the breast, acting as a "sentinel" for tumor spread.
- Lymphocentigraphy is used to visualize the sentinel lymph node by injecting a tracer into the breast.
Lymphocentigraphy:
- Lymphocentigraphy utilizes a SPECT scanner with a gamma camera
- The technique creates planar images (2D) or cross-sectional views (3D) of the body
- It helps identify the sentinel lymph node by visualizing the radioactive tracer's path in the lymphatic system

Metastatic Disease Detection (Whole Body)

PET Scanning:
- PET scans use a radioactive tracer, often a sugar analogue, to visualize areas of high metabolic activity, which is characteristic of tumors.
- PET-CT scans combine information from PET and CT scans to provide a comprehensive view of both structural and functional information.
- PET scans are useful for diagnosing and monitoring the response to treatment of metastatic disease.
Estrogen PET:
- Estrogen PET uses a tracer that targets estrogen receptors, which are often overexpressed in certain breast cancers.
- This type of PET can detect metastatic disease in estrogen-receptor positive breast cancers, which may be difficult to visualize in regular imaging or sugar-based PET scans.

Non-PET Tumor Imaging

Tumor targeting radiopharmaceuticals can be broadly classified into two categories: Specific targeting agents and Nonspecific agents.
Specific targeting agents target specific tumor antigens, receptors, or metabolic processes, including monoclonal antibodies, peptides, and metaiodobenzylguanidine (MIBG).
Nonspecific agents lack specificity and can be used to image a range of tumors in various organs. These include gallium-67 citrate, thallium-201 chloride, technetium-99m (99mTc) sestamibi, and 18F-FDG.

Neuropeptide Receptor Imaging

Somatostatin (Octreotide) Receptor Imaging is a specific targeting method utilizing radiolabeled somatostatin analogs to image various tumors.
Somatostatin is a naturally occurring neuro-polypeptide synthesized and released by endocrine or nerve cells. It exhibits a wide range of pharmacologic effects, including inhibition of growth hormone secretion.
Overexpression of somatostatin receptors occurs in numerous neuroendocrine and some non-neuroendocrine tumors.
111In-labeled pentetreotide (OctreoScan), a cyclic structural modification of octreotide, is commonly employed for imaging. It exhibits high specificity for somatostatin receptors, especially subtypes 2 and 5.
Indium-111 Pentetreotide, often administered intravenously at 6.0 mCi (222 MBq), is particularly useful for imaging neuroendocrine tumors, especially carcinoid and gastrinoma. It can also be used to assess a wider spectrum of tumors, including nonendocrine solid tumors.
Whole-body gamma camera imaging, particularly with SPECT and SPECT/CT, can provide effective screening for somatostatin receptor-expressing tumors.
Radiolabeled somatostatin analogs, such as 177Lu-DOTATATE, offer therapeutic potential in patients with octreotide-avid tumors.

Adrenal Tumor Imaging

Iodine-123 or -131 MIBG imaging is effective for detecting and evaluating primary sympathoadrenal system tumors like pheochromocytomas, neuroblastomas, and paragangliomas, as well as their metastases.

Nonspecific Tumor Imaging

Gallium-67 Imaging was previously a valuable tool for neoplastic disease diagnosis but has been largely replaced by 18F-FDG PET/CT. Its mechanism of action relies on its affinity for transferrin receptors on tumor cells.
Thallium-201 Chloride Imaging, a potassium analog, concentrates in certain tumors. It is also useful in distinguishing postradiation necrosis from recurrent tumor in treated patients with equivocal MRI findings.
Technetium-99m Sestamibi Tumor Imaging concentrates in a variety of tumors, including breast and thyroid cancers, but is primarily used for imaging parathyroid adenomas.

Table 10.1: Affinity and Sensitivity of Indium-111 Pentetreotide for Neuroendocrine Tumors

The table summarizes various neuroendocrine tumors and their sensitivity to 111In Pentetreotide.
It also notes the presence of other tumors with variable or low affinity for the radiopharmaceutical.
The table mentions non-neoplastic processes that can lead to false-positive results.

Note on Theranostics

The text briefly introduces the emerging field of theranostics, combining diagnostic imaging and targeted therapy with the same molecule.
The simplest example is sodium iodide used for diagnostic imaging of differentiated thyroid cancer (labeled with iodine-123) and therapeutic treatment (labeled with iodine-131).
More sophisticated compounds and their analogs are under development for targeting other tumors, such as somatostatin receptor radiopharmaceuticals for neuroendocrine malignancies.

Breast-Specific Gamma Imaging (BSGI)

BSGI uses 99mTc-sestamibi to detect breast cancer.
It's optimally performed using dedicated high-resolution gamma cameras with solid-state detectors.
This procedure is also called low-dose molecular breast imaging (MBI).
99mTc-sestamibi concentrates in malignant breast tumors, with a mean contrast ratio approaching 6:1 compared to normal breast tissue or surrounding fat.
MBI has a reported sensitivity and specificity of 85% to 95% for carcinomas less than or equal to 10 mm.
MBI sensitivity for detecting ductal carcinoma in situ (DCIS) is as high as 88% to 94%.
Combining MBI with mammography has achieved 100% sensitivity in some studies.
A negative scan with a palpable lesion makes breast cancer possible but unlikely.
MBI is a noninvasive adjunct to mammography and/or breast ultrasound when used for judicious patient selection.
Adding MBI to mammography significantly increased the detection of node-negative breast cancer in dense breasts by 7 to 8 per 1000 women screened.
In one study, the sensitivity of mammography alone was 27%, while combined mammography and dedicated sestamibi imaging (BSGI) was 91% in at-risk women.
Imaging protocol: Low-dose MBI is performed 15 to 20 minutes after injecting 6.5 to 8.0 mCi (240 to 296 MBq) of 99mTc-sestamibi in an arm vein contralateral to the suspected breast lesion.
Higher doses: Considerably higher administered doses (20 to 25 mCi [740 to 925 MBq]) are required with BSGI using standard gamma camera technology.
Image acquisition: Images are performed in standard mammographic projections, with special projections used as needed.
Washout: Little sestamibi washout occurs from malignant lesions, allowing for delayed imaging up to 2 hours.
Normal appearance: 99mTc-sestamibi distributes homogeneously in the normal breast, regardless of breast density on mammograms, and is typically of low intensity.
Increased breast activity: Some patients exhibit diffusely increased activity in one or both breasts, potentially related to hormone levels at the time of imaging, and tends to be lowest around mid-cycle in premenopausal patients, especially those younger than 30 years.
Positive study: A positive study presents as a discrete focus of increased activity in the breast or axilla, exceeding adjacent breast activity.
Localization of nonpalpable foci: Specialized localization systems are available for biopsy.
Axillary lymph node involvement: Focally increased activity in the ipsilateral axilla with a primary lesion strongly suggests axillary lymph node metastasis.
Sensitivity for axillary metastasis: Sensitivity for axillary metastasis is variable and not sufficient to warrant using the procedure for this purpose.
False-positive results: May be related to benign conditions like fibroadenomas, active fibrocystic change, adenosis, inflammation (including inflammatory fat necrosis and foreign-body giant cell reaction), and benign conditions that confer a higher risk for developing carcinoma, like atypical ductal hyperplasia and complex lobular neoplasia.
False-positive results: Imaging after recent needle or stereotactic biopsy can also cause increased activity.
False-negative results: May occur in small (< 1 cm), deep lesions or in tumors with less avidity for sestamibi.
Current role: MBI is viewed as an adjunct procedure.
Screening: Use of the technique as a screening procedure is not recommended.
Breast tomosynthesis: With the advent of breast tomosynthesis, or three-dimensional mammography, to greatly improve the detection of cancers in dense breasts, a consistent role for BSGI remains undefined.

Lymphoscintigraphy

Lymphoscintigraphy: Procedure where a small amount of radioactive colloidal tracer is injected into the skin or tissue of an organ, transported by draining lymphatics to localize in regional lymph node basins.
Oncologic application: Injection is made near a primary neoplasm to determine lymph node(s) receiving drainage, potentially containing metastasizing tumor cells.
Sentinel lymph node (SLN): The first lymph node(s) on a direct lymphatic drainage pathway from a primary tumor site.
SLN biopsy: Used to assess the regional metastatic potential of the tumor.
SLN significance: SLNs free of tumor obviate the need for extensive lymph node dissection, reducing morbidity.
Positive sentinel nodes: Direct therapeutic management decisions, including radiation therapy fields and additional surgical approaches.
Standard of care: In breast and malignant melanoma, lymphoscintigraphy has replaced axillary lymph node dissection, significantly reducing postsurgical lymphedema.
Preferred tracer: 99mTc-sulfur colloid with a range of particle sizes (average size of 300 to 350 nm).
Alternative tracer: 99mTc-tilmanocept (Lymphoseek), a noncolloidal radiopharmaceutical, binds to dextran-mannose receptors on surface macrophages and dendritic cells in lymph nodes.
Injection volume: Small volumes (0.05 to 0.5 mL) for superficial skin injections (periareolar, subdermal, intradermal, or subareolar), with larger volumes (0.5 to 1.0 mL) for peritumoral injections.
Injection considerations: Direct injection into the tumor or accidentally into a post-biopsy seroma should be avoided.
Activity: The activity used depends on whether the procedure is performed on the day of the SLN surgical excision (typically ≤ 1.0 mCi [37 MBq]) or the afternoon before (3 to 4 mCi [111 to 148 MBq]).
Imaging: Serial 3- to 5-minute planar images up to 1 hour document tracer migration.
Delayed imaging: Delayed images (2 to 4 hours) are useful for truncal or head and neck melanomas to detect less obvious drainage pathways.
Early or dynamic images: Help pinpoint the first-draining node when multiple nodes are identified on delayed images.
Transmission images: Delineate the body contour and SLNs for accurate localization.
SLN marking: Some surgeons mark the SLN site on the patient's skin for localization during surgery.
Unexpected drainage patterns: Drainage may occur in the breast to the ipsilateral axillary lymph nodes, internal mammary, supraclavicular, intercostal, and other chest wall lymph nodes.
Melanoma drainage: Drainage in truncal melanoma is typically to the axillary basins (~90%). However, some lesions on the back drain to multiple basins, and half of melanomas on the upper back may drain to a contralateral basin.
SLN localization: A sterilized handheld gamma probe is used in the surgical suite to localize the radioactive SLN before removal.
Variable SLN removal: There's significant variability in the radioactive threshold used for SLN removal and the number of lymph nodes removed as SLNs at different institutions.
SLN threshold: Some recommend removing the node with the greatest activity and any other nodes with 10% or more of that activity in counts per minute.
Number of SLNs removed: Studies show that removing more than three to four SLNs does not improve sensitivity.
Missed SLN metastasis: Approximately 1% to 2% of patients with SLN metastases are missed when using a threshold of four SLNs for biopsy in breast cancer.
Combined localization: Many surgeons integrate lymphoscintigraphy probe information with blue dye injected during surgery to decrease false-negative findings and boost sensitivity.

Lymphedema

Lymphoscintigraphy: Used to diagnose edematous extremities.
Procedure: Interdigital injection of radiocolloid in the involved extremity or a single injection on the dorsum of the hand or foot for visualization of lymphatic channels and lymph nodes.
Primary (congenital) lymphedema: Presents with a few lymphatic channels, often unobstructed, with activity in the node basins.
Secondary (obstructive) lymphedema: Shows evidence of obstructed lymphatics, including lack of radiocolloid migration from the injection site, diffuse dermal activity, or multiple tortuous collateral channels.
High-grade lymphatic obstruction: May require very delayed images (3 to 5 hours).

Radionuclide Tumor Antibody Imaging and Therapy

Numerous monoclonal antibodies target pancarcinoma antigens shared by various neoplastic lesions (e.g., carcinoembryonic antigen (CEA)) or antigens specific to certain tumor types.
Antibody accuracy: Accuracy depends largely on the uniqueness of the targeted antigen and the monoclonal antibody's specificity in recognizing the antigen.
Cross-reaction: Cross-reaction with normal or other malignant tissues reduces specificity.
Current generation: Latest antibodies include 111In- and 99mTc-labeled antibody fragments targeting specific tumor antigens.
Imaging with antibody fragments: Depends on delivering sufficient labeled antibodies intravenously to tumor sites to overcome background activity in normal tissues and organs (liver, kidneys, lungs), circulating plasma antigens, and nonspecific leakage into the extravascular space.
Recent monoclonal imaging radiopharmaceuticals: Focus on ovarian, prostate, and colon carcinomas.
FDA approval: An increasing number of monoclonal antibodies with higher specificity have received FDA approval.
Limitations: Despite FDA approval, these antibodies are not widely used due to relatively low sensitivity and specificity (50% to 70%).

Radioimmunotherapy for Lymphoma

- Monoclonal antibody labeling: Labeling a monoclonal antibody against lymphoma antigens with therapeutic radionuclides to treat lymphomas.
- Ibritumomab tiuxetan: Widely used monoclonal therapeutic radiopharmaceutical that targets the CD20 antigen present on over 90% of B-cell lymphomas (non-Hodgkin lymphomas).
- 90Y-ibritumomab tiuxetan (Zevalin): Approved as a first-line treatment for diffuse non-Hodgkin lymphoma and for refractory or relapsed disease following conventional therapies.
- Mouse-derived antibodies: Some patients may experience mild side effects from mouse-derived antibodies.

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Explore the crucial role of nuclear medicine in diagnosing and treating various tumors, including parathyroid and prostate cancer. This quiz covers imaging techniques, dosages, and specific radiopharmaceuticals used in clinical practices. Test your knowledge on the phases of imaging and their significance in tumor detection.