Tumor Imaging Techniques Quiz

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Questions and Answers

What is the average adult dose for a parathyroid imaging study using 99mTc-sestamibi?

20 mCi (740 MBq) (correct)

30 mCi (1110 MBq)

40 mCi (1480 MBq)

10 mCi (370 MBq)

Which imaging phase occurs 15 to 20 minutes post injection during a parathyroid study?

Circulation phase

Parathyroid phase

Thyroid phase (correct)

Engorgement phase

Which tumors are associated with radionuclide therapies mentioned?

Hodgkin lymphoma and neuroblastoma only

Breast and lung tumors only

Lymphomas and metastatic bone pain (correct)

Metastatic bone pain and non-Hodgkin lymphoma only

What is the method of imaging for parathyroid tumors using 99mTc-sestamibi?

Flow study with immediate acquisition Signup and view all the answers

Which radionuclide represents the evolution in infection imaging from earlier methods?

99mTc Signup and view all the answers

What type of lymphoma is specifically mentioned in connection with radioimmunotherapy?

Non-Hodgkin lymphoma Signup and view all the answers

What is the primary radionuclide used for parathyroid imaging?

Technetium-99m Signup and view all the answers

Which of the following cancers is NOT mentioned in the context of tumor imaging?

Pancreatic cancer Signup and view all the answers

What is one of the techniques for treating metastatic bone pain mentioned?

Radionuclide therapies Signup and view all the answers

Which imaging procedure is used to assess breast tumors?

99mTc imaging Signup and view all the answers

What is the primary target of the Indium-111–capromab pendetide (ProstaScint) used in prostate cancer imaging?

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

When is the optimal time for imaging following the injection of Indium-111–capromab pendetide?

96 to 120 hours post injection Signup and view all the answers

What imaging technique is primarily used for Technetium-99m-arcitumomab (CEA-Scan) in colorectal cancer evaluation?

Plantar images or whole-body scans Signup and view all the answers

At what doses is Indium-111-pentetreotide (OctreoScan) administered to adults for neuroendocrine tumors?

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

What imaging timeline is followed after administering Indium-111-pentetreotide (OctreoScan) for neuroendocrine tumors?

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

Which condition is primarily associated with catecholamine secretion?

Pheochromocytoma Signup and view all the answers

In which age group is neuroblastoma most frequently found?

Newborns and infants Signup and view all the answers

What is the administered dose range for Technetium-99m-arcitumomab (CEA-Scan) in colorectal cancer diagnostics?

20 to 30 mCi (740 to 1110 MBq) Signup and view all the answers

What imaging method is described for blood pool activity assessment in prostate cancer imaging?

Planar imaging Signup and view all the answers

Which of the following depicts a characteristic of neuroendocrine tumors?

Can secrete hormones Signup and view all the answers

What is the purpose of the guidelines written by the Society of Nuclear Medicine (SNM)?

To promote the cost-effective use of nuclear medicine procedures. Signup and view all the answers

What condition may affect the interpretation of mammography?

Scar tissue in the breast. Signup and view all the answers

Which of the following statements is true regarding the application of SNM guidelines?

Differences from the guidelines may be justified. Signup and view all the answers

Which information is deemed necessary before performing a procedure related to breast cancer evaluation?

Availability of prior imaging studies. Signup and view all the answers

How should practitioners use the guidelines as mentioned in the content?

As an educational tool that guides decision-making. Signup and view all the answers

What is the preferred method for administering 99mTc-sestamibi?

Intravenous injection in an arm vein contralateral to the abnormality Signup and view all the answers

Which of the following is included in the normal distribution of 99mTc-sestamibi?

Salivary glands and liver Signup and view all the answers

What is the recommended action after administering the radiopharmaceutical?

Flush the vein with 10 cc of saline Signup and view all the answers

When should imaging typically begin after the administration of the radiopharmaceutical?

5–10 minutes post-administration Signup and view all the answers

Which of the following best describes the technique for acquiring planar images of the breast?

Acquiring images for 10 minutes each using a 128 × 128 or larger matrix Signup and view all the answers

What should be avoided when the camera system does not allow a zoom in anterior position?

Focal increased uptake with well-delineated contours Signup and view all the answers

What is a strong indicator of axillary lymph node metastatic involvement?

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

Which feature suggests a benign disease of the breast?

Diffuse or patchy radiotracer uptake Signup and view all the answers

What effect does the position of the markers have on breast lesion location?

May change significantly if markers are placed in different positions Signup and view all the answers

What current consensus exists regarding SPECT imaging?

The utility of SPECT imaging remains uncertain Signup and view all the answers

In what scenario is the use of radioactive markers optional?

Over palpable abnormalities Signup and view all the answers

What is indicated by mild-to-intense radiotracer uptake with ill-defined edges?

High suspicion of malignancy Signup and view all the answers

What is a likely outcome if a patient is poorly positioned during imaging?

Misinterpretation of images Signup and view all the answers

What should be recommended in the report to the referring physician?

Correlation with clinical findings and other studies Signup and view all the answers

What can be inferred about axillary uptake on lateral views?

It corresponds to uptake in skin folds Signup and view all the answers

What must a medical professional consider when deviating from established guidelines?

Unique circumstances of each case Signup and view all the answers

What is a key purpose of the proposed guidelines mentioned?

To provide general information about the SLN procedure Signup and view all the answers

How do the guidelines view approaches that differ from what is recommended?

They may be valid if properly justified Signup and view all the answers

What should these guidelines not be interpreted as?

A comprehensive list of all procedures Signup and view all the answers

What aspect of medical practice do the guidelines emphasize along with scientific knowledge?

The art of medical decision-making Signup and view all the answers

What is one of the main difficulties in diagnosing melanoma and predicting treatment responses?

The vast international differences in healthcare resources Signup and view all the answers

Which statement describes the expected outcome of adhering to the established guidelines for melanoma treatment?

They assist practitioners in developing a reasonable course of action Signup and view all the answers

Which risk factor is identified as contributing to the development of melanoma?

Intermittent high UV exposure Signup and view all the answers

What is the prognostic trend for patients with melanoma based on the stage of disease?

Prognosis generally worsens with regional or distant metastases Signup and view all the answers

What is emphasized regarding the resources available for melanoma treatment across different regions?

They vary significantly from one medical institution to another Signup and view all the answers

What role does a dual-head gamma camera play in imaging?

It acquires simultaneous emission and transmission images, aiding in node differentiation. Signup and view all the answers

When is quality control of the imaging system and gamma probe particularly important?

At routine intervals regardless of usage. Signup and view all the answers

What is the purpose of lead shielding during imaging procedures?

To reduce scattering artefacts from the injection site. Signup and view all the answers

In what scenario is body scanning from neck to groin required?

When faint uptake in sentinel lymph nodes may be missed. Signup and view all the answers

How are delayed static images utilized in the imaging process?

To identify all relevant sentinel lymph nodes after a specified time period. Signup and view all the answers

What is the expected outcome of using a 153Gd source integrated into a gamma camera?

It aids in attenuation correction for SPECT images. Signup and view all the answers

What imaging technique is recommended for addressing faint uptake in SLNs?

Acquiring bilateral static images and body scans. Signup and view all the answers

Which practices are suggested to enhance the quality of static images?

Regular calibration of gamma cameras and probes. Signup and view all the answers

Why is appropriate contour tracing necessary in imaging procedures?

To assist in identifying the exact location of tumors. Signup and view all the answers

What is the recommended approach for administering tracers in pregnant patients undergoing SLN biopsy?

Prefer dual injections to maximize visualization. Signup and view all the answers

Which of the following is NOT a reason to prefer SLN biopsy over axillary lymphadenectomy?

Significantly improved local control of disease. Signup and view all the answers

What best describes the evidence surrounding controversial indications for SLN biopsy?

Evidence is limited or absent for certain indications. Signup and view all the answers

What is a stated precaution for performing SLN biopsy in pregnant patients?

Superficial injections are preferred over deeper injections. Signup and view all the answers

What reason justifies the use of SLN mapping during pregnancy or lactation?

The risks associated with axillary dissection are higher. Signup and view all the answers

What positioning maximizes imaging of the axilla in breast cancer patients?

Arms positioned above the head toward the midline Signup and view all the answers

Which imaging technique is beneficial when conventional imaging does not visualize sentinel lymph nodes?

SPECT/CT imaging Signup and view all the answers

What is a primary advantage of SPECT/CT imaging compared to planar images?

Enhanced three-dimensional visualization Signup and view all the answers

What should be done if a 45° anterior rotation for imaging is not feasible?

Position the camera to acquire images despite the rotation Signup and view all the answers

Which factor is NOT indicated as a reason for using SPECT/CT imaging according to the observations presented?

Desire to visualize all lymph nodes Signup and view all the answers

What is the recommended pixel size for a system with conventional CT for anatomical localization?

2 mm Signup and view all the answers

Which imaging method should be performed immediately after completion of all injections for SLN localization?

Dynamic (flow) imaging Signup and view all the answers

When should planar imaging ideally be conducted after the injection?

15–30 minutes Signup and view all the answers

What matrix size is recommended for SPECT reconstruction when a system with large FOV detectors is used?

256×256 Signup and view all the answers

For dynamic imaging in SLN procedures, what is the standard projection time?

20–25 seconds Signup and view all the answers

What is the primary purpose of using low-dose CT in conjunction with imaging procedures?

Providing anatomical detail Signup and view all the answers

What is an essential characteristic of SPECT acquisition for SLN detection?

It should have a matrix size of 256×256 Signup and view all the answers

What should be the first step if conventional images for a procedure are difficult to interpret?

Conduct SPECT/CT Signup and view all the answers

What is recommended regarding the image acquisition time frame after injection for planar imaging?

Three times within 18–24 hours Signup and view all the answers

What should be ensured about pixel size when acquiring images?

The smallest pixel size available should be used Signup and view all the answers

What is the primary focus of a nuclear radiologist’s work compared to a regular radiologist?

Evaluating the functional aspects of cells and their characteristics. Signup and view all the answers

In which scenario is mammography likely to be least effective in detecting tumors?

In patients with dense breast tissue. Signup and view all the answers

Which imaging technology is highlighted as being more comfortable than traditional mammography?

Positron emission mammogram (PEM). Signup and view all the answers

What is one advantage of molecular imaging techniques in breast cancer diagnosis?

They can detect tumors that are not visible on standard mammograms. Signup and view all the answers

What does lymphocintigraphy help identify in the context of breast cancer surgery?

The lymph node involvement to assist in surgical planning. Signup and view all the answers

What is the primary purpose of lymphocentigraphy in patients who have undergone lymph node removal?

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

What type of imaging technique combines both structural and functional data for a comprehensive view?

PET-CT imaging Signup and view all the answers

Which radioactive tracer is most commonly used in PET scans to target tumor cells?

Fluorodeoxyglucose (FDG) Signup and view all the answers

What potential problem can arise when a patient has had multiple lymph nodes removed?

Undetectable tracer in the expected sentinel node location Signup and view all the answers

How does a SPECT scanner differ from a standard planar imaging technique?

It generates three-dimensional images through rotation Signup and view all the answers

What is the role of the gamma camera in molecular imaging?

To detect the radiation emitted from radiotracers Signup and view all the answers

What indicates a successful response to chemotherapy in a patient based on imaging results?

Decreased radiotracer uptake on PET scans Signup and view all the answers

What is the primary purpose of using PET scans in breast cancer treatment?

To identify active estrogen receptors in tumors Signup and view all the answers

What defines the sentinel lymph node's role in breast cancer surgery?

It is the first lymph node to filter lymph from the tumor site. Signup and view all the answers

What happens if cancer is found in the sentinel lymph node during surgery?

More lymph nodes must be checked for cancer spread. Signup and view all the answers

What technique is used to locate the sentinel lymph node during surgery?

Injection of a radioactive substance Signup and view all the answers

How does the status of the sentinel lymph node influence breast cancer prognosis?

It correlates with a high likelihood of no cancer in other lymph nodes. Signup and view all the answers

What is a major limitation of the traditional visualization methods for identifying sentinel lymph nodes?

They cannot adapt to individual variations in lymphatic anatomy. Signup and view all the answers

What was an unexpected result observed in a patient's follow-up after treatment for breast cancer?

The tumor remained unchanged in size on the MRI. Signup and view all the answers

What are the complementary technologies mentioned for breast imaging?

Positron emission mammography and dedicated breast PET Signup and view all the answers

What is a primary clinical indication for performing a CEA scan?

To detect recurrent or metastatic colorectal carcinoma in patients with a confirmed diagnosis Signup and view all the answers

Which critical organ is primarily associated with the effective dose equivalent of 13.1 μSv/MBq for 99mTc-arcitumomab?

Kidney Signup and view all the answers

What preparation is required for patients undergoing imaging with 111In-pentetreotide?

Adequate hydration and a mild laxative the evening before and after the injection Signup and view all the answers

How is the dose of 111In-pentetreotide adjusted for pediatric patients?

0.14 mCi/kg based on the child's weight Signup and view all the answers

Which tumor types are indicated to express somatostatin receptors and can be visualized using 111In-pentetreotide?

Adrenal medullary tumors and medullary thyroid carcinomas Signup and view all the answers

What role did 67Ga primarily serve in the context of tumor imaging?

Diagnosing the presence and extent of tumors Signup and view all the answers

Which of the following factors is essential for the successful targeting of radiolabeled antibodies?

The affinity to the antigens expressed by the cells Signup and view all the answers

What is the most common diagnostic method mentioned for identifying parathyroid adenomas?

Radionuclide imaging with 99mTc-sestamibi Signup and view all the answers

Which demographic is at the highest risk for developing primary hyperparathyroidism?

Women over the age of 60 Signup and view all the answers

What is the standard imaging protocol for parathyroid imaging developed by Taillefer et al. in 1992?

Dual-phase study using 99mTc-sestamibi Signup and view all the answers

What condition is typically indicated by elevated serum calcium and parathyroid hormone levels?

Primary hyperparathyroidism Signup and view all the answers

Which of the following statements accurately describes the capabilities of commercially available radiolabeled antibodies?

They can localize disease with sensitivities equal to or exceeding standard imaging Signup and view all the answers

What is characterized by a focal area of increased uptake in the thyroid bed that demonstrates progressive intensity over time?

Parathyroid adenoma Signup and view all the answers

What role does dual-isotope imaging play in the evaluation of prostate cancer with Indium-111–capromab pendetide?

It ensures accurate registration of image sets Signup and view all the answers

Which critical organ is affected by the effective dose equivalent of a 5-mCi dose of Indium-111–capromab pendetide?

Liver Signup and view all the answers

What is one of the imaging methods recommended for prostate cancer to enhance visualization of the pelvic region?

Bladder irrigation Signup and view all the answers

What is the typical timeline for commencing imaging following the injection of a radiopharmaceutical for parathyroid studies?

15 to 20 minutes after injection Signup and view all the answers

In colorectal cancer, what component of the 99mTc-arcitumomab is significant for identifying recurrent or metastatic conditions?

Antibody fragment (Fab) Signup and view all the answers

What imaging property is critical for optimizing SPECT acquisition parameters in prostate cancer imaging?

Matrix size and sampling rate Signup and view all the answers

What ensures the effective use of imaging in colorectal cancer evaluation?

Accurate mapping of blood-pool activity Signup and view all the answers

Which cancer is noted to be the second leading cause of cancer death in men?

Prostate cancer Signup and view all the answers

What is the effect of a slow infusion during the administration of Indium-111–capromab pendetide?

Minimizes adverse events Signup and view all the answers

Study Notes

Tumor Imaging

Parathyroid imaging uses 99mTc-sestamibi
- Average adult dose: 20 mCi (740 MBq)
- Flow study is acquired immediately after injection
- First (thyroid phase) begins 15 to 20 minutes after injection
- Second (parathyroid phase) is acquired 2 hours after injection

Prostate Cancer

Indium-111–capromab pendetide (ProstaScint) is used for prostate cancer 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 infused over 3 to 5 minutes
- Blood pool activity can be imaged 30 minutes to 4 hours after injection.
- Imaging should be performed after 96 to 120 hours to achieve optimal targeting and minimize blood pool activity.

Colorectal Cancer

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

Neuroendocrine Tumors

Indium-111-pentetreotide (OctreoScan) is used to visualize primary neuroendocrine tumors and their metastasis.
- Dose: 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 after injection.

Pheochromocytoma and Neuroblastoma

Pheochromocytoma are catecholamine-secreting tumors from the adrenal medulla
Neuroblastoma are malignant tumors of the sympathetic nervous system; they are most common in infants and children.

Breast Scintigraphy

Breast scintigraphy is used to evaluate breast cancer in patients where mammography is nondiagnostic, equivocal, or difficult to interpret.
Prior mammograms, ultrasounds, and MRIs should be available.
Patients should be informed of any known hypersensitivity to 99mTc-sestamibi.
An intravenous injection of 740-1,110 MBq (20-30 mCi) 99mTc-sestamibi is administered 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, followed by 10 cc of saline to flush the vein.
Normal distribution of the radiopharmaceutical includes the salivary and thyroid glands, myocardium, liver, gallbladder, small and large intestine, kidneys, bladder, and skeletal muscles.
Images are acquired 5-10 minutes after administration of the radiopharmaceutical.
- Planar images are acquired for 10 minutes each, using a 128 × 128 or larger matrix.
- The following images should be acquired:
  - Prone lateral image of the breast with the suspected abnormality.
  - Anterior image may be acquired with the patient supine or upright.
Suspicious features of breast malignancy include:
- Focal increased uptake.
- Relatively well-delineated contours.
- Mild-to-intense radiotracer uptake.
- Focal increased uptake (1 or more foci) in the ipsilateral axilla, in the presence of a primary lesion in the breast, is strongly suggestive of axillary lymph node metastatic involvement.
Benign features of breast disease include:
- Diffuse or patchy radiotracer uptake of mild to moderate intensity.
- Bilateral uptake.
- Edges are not visually well defined.
The interpretation of the images should be done from the computer monitor whenever possible.
- A logarithmic scale is preferable for image display.
- Grayscale is preferable to color for interpretation.
Masking of the high-activity chest and abdominal organs, such as the myocardium and liver, from the final images will improve visualization of breast tissue.
Sources of error include:
- 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.
The sensitivity, specificity, and accuracy of this test depend upon several factors, including the size of the breast tumor being imaged. The sensitivity of breast scintigraphy for tumors smaller than 1 cm in diameter is very low with nuclear medicine cameras in current use.

Areas Requiring Further Study

Further study is needed to determine the characteristics of the population most likely to benefit from breast scintigraphy.
There is no consensus regarding the efficacy of routine SPECT imaging.
The usefulness of other radiopharmaceuticals for breast scintigraphy has not been established.
The usefulness of breast scintigraphy for all indications included here requires further study.

Sentinel Lymph Node (SLN) Procedure in Melanoma

SLN procedure: A sequence of procedures involving nuclear medicine, radiology, surgery, and pathology.
Goal: Provide general information about SLN procedure and protocols routinely used in melanoma patients.
Purpose of guidelines: To optimize nuclear medicine imaging before SLNB to improve diagnosis and staging.
Melanoma: A global health issue with rising incidence; risk factors include sunburn, UV exposure, red/blond hair, family history.
Prognosis: Generally good for localized melanoma but worsens with regional or distant metastases.
SLN imaging:
- Preoperative lymphoscintigraphy: Using radiopharmaceuticals to identify SLNs.
- Gamma probe:
  - Used for in vivo and ex vivo measurement.
  - Guides the surgeon towards SLN location in surgical bed.
Static Images:
- Acquired 3-5 minutes after tracer injection (1-3 hours post-injection).
- Used to identify all relevant SLNs.
- Image location depends on melanoma site (see Table 2 for recommendations).
SPECT/CT:
- Can be used for SLN procedure.
- Should be used with caution due to increased radiation dose.
Radioactive waste: Requires safe collection and handling following local guidelines.
Histopathology: Plays a key role in confirming SLN status.
Staff dosimetry:
- EU directives on radiation protection apply.
- Justification, optimization, and limitation of exposures are crucial.
- All staff involved in SLNB must be trained and competent.
Pregnancy: SLNB can be offered after careful counselling regarding risks and benefits.
Disclaimer: These guidelines are not intended for litigation purposes.

Systemic Lymphatic Mapping (SLN)

SLN Biopsy: A minimally invasive procedure used to detect the spread of breast cancer to lymph nodes.
Controversial Indications: There are specific situations where the use of SLN biopsy is debated due to limited evidence or lack of universal agreement.
SLN Biopsy Advantages: Compared to axillary lymph node dissection, SLN Biopsy has lower morbidity (complications) and similar nodal relapse rates (cancer returning to the lymph nodes)
SLN Biopsy and DCIS (Ductal Carcinoma in Situ): SLN Biopsy is controversial for DCIS, as the evidence for its benefit in this specific scenario is not conclusive.

Precautions

Pregnancy: SLN Biopsy is not contraindicated during pregnancy.
- Blue Dye: Used sparingly due to potential harm to the fetus.
- Radiotracers: Low doses are used, resulting in minimal fetal exposure.
Lactation: SLN Biopsy is justified due to the low risks compared to the potential dangers of axillary dissection.
- Nursing: Should be suspended for 24 hours following radiopharmaceutical administration.

Lymphoscintigraphic Mapping

Imaging Goals: To identify SLNs and potentially stage lymph nodes beyond the armpit (axilla).
Tracers:
- Superficial Injection (Periareolar, Subareolar, Subdermal, Intradermal): Preferred for axillary staging.
- Deep Injection (Peritumoral, Intratumoral): Preferred for staging lymph nodes beyond the axilla.
- Dual Injection (Superficial + Deep): Captures the advantages of both techniques and reduces false-negative results.
Positioning:
- Breast with Cancer: Should be positioned dependent towards the midline of the patient's body.
- Arm: The arm on the side of the cancer should be positioned above the head.
- Camera Positioning: Directly above the patient to reduce signal attenuation.
- Lateral Views: Patient might be rotated 90° to the side opposite the cancer, with the involved breast facing away from the axilla.
- 45° Anterior Oblique Imaging: If possible, the breast should be held towards the midline to allow for better imaging of the axilla.

Image Acquisition

Dynamic (Flow) Imaging: Used less frequently but can provide useful information for tracking the flow of the radiotracer.
Planar (Static) Imaging:
- Timing: Images should be taken 15-30 min, 1 hour, 2-4 hours, and as needed up to 18-24 hours after tracer injection.
- Views: At least two (anterior, 45° anterior oblique) and ideally all three (anterior, 45° anterior oblique, and lateral) views should be acquired.
SPECT/CT (Single Photon Emission Computed Tomography / Computed Tomography):
- Advantages:
  - Three-dimensional images
  - Better contrast and spatial resolution than planar imaging
  - Allows for correction for attenuation (signal weakening) and scatter (signal spreading).
  - Provides accurate anatomical localization of SLNs.
- Indications:
- Non-visualization of SLN on conventional planar imaging
- Patient obesity
- The presence of extra-axillary SLNs
- Unusual drainage patterns
- Difficult-to-interpret conventional images.
- Acquisition Parameters:
  - Dual-detector SPECT system with LEHR or LEUHR collimators
  - Matrix size: 128 × 128 (4–5 mm pixels)
  - 120 or 128 projections over 360°, with 20–25 s/projection.
- CT:
  - Low-dose CT: 140 kVp, 2.5 mA
  - Conventional CT: 140 kVp, 30–150 mA

Histopathological Assessment

Gold Standard: Histopathological examination of SLNs is the primary method for confirming cancer spread.
Variable Among Centres: Different facilities use different approaches for SLN histopathological assessment.
- Intraoperative Assessment: Performed during surgery using imprint cytology, frozen sectioning, or both.
- Postoperative Assessment: More thorough examination of SLNs after the operation.
- Molecular Methods: Some molecular methods have been used but have limitations in terms of reproducibility and time required for intraoperative assessment.

Radiation Dosimetry

Low Patient Exposure: The doses of radiotracers used in SLN procedures are low and result in minimal radiation exposure to patients.
SLN Procedures in Pregnancy: Exposure is not a contraindication, but caution should be exercised.
Professionals: Professionals working with SLN procedures have very low radiation exposure, below recommended limits.
- Nuclear Medicine, Surgery, and Pathology Professionals: All involved professionals have exposure.
- NRC (United States Nuclear Regulatory Commission): Has determined that exposures to pathologists from radioactive SLN specimens are too low to require specific regulation.
Doses to Organs: Absorbed and equivalent doses to organs have been estimated and are documented in various publications and package inserts.

Nuclear Radiologist

A nuclear radiologist is a radiologist and a nuclear medicine physician.
They are board certified in both specialties.
A nuclear radiologist completes a five-year radiology residency and a one-year nuclear medicine fellowship.

Nuclear Medicine

Nuclear medicine focuses on cell function and receptor activity.
Examples of nuclear medicine include molecular breast imaging (MBI), lymphoscintigraphy, and PET.

Breast Cancer Imaging

Breast density affects the visibility of tumors on mammograms.
Dense breasts make it difficult to detect tumors on mammograms.

Molecular Imaging Technologies

Molecular imaging techniques, such as PEM, MBI, and dedicated breast PET, offer complementary information to mammograms and breast MRIs.
PEM is a comfortable alternative to mammograms with minimal compression.
MBI provides clearer tumor visualizations compared to mammograms.
Dedicated breast PET is similar to breast MRI setup and provides comparable information.

Sentinel Lymph Node

The sentinel lymph node is the first lymph node to drain lymphatic fluid from the breast.
If cancerous cells escape the tumor, they are likely to be detected by the sentinel lymph node first.
Examining the sentinel lymph node helps determine the likelihood of cancer spread to other lymph nodes.

Lymphoscintigraphy

Lymphoscintigraphy uses radioactive tracers to visualize the lymphatic system and identify the sentinel lymph node.
It helps surgeons target the sentinel node for removal during surgery.

Whole-Body Metastatic Disease Imaging

PET scans use radiotracers, such as sugar, to visualize metabolic activity in the body.
Tumors often exhibit high metabolic activity, making them detectable on PET scans.
PET-CT combines PET scans with CT scans to provide detailed anatomical and functional information.
PET can reveal metastatic disease in bone, even when conventional imaging like CT shows no abnormalities.
Estrogen-PET uses estrogen as its radiotracer to detect estrogen receptor-positive tumors.

Molecular Imaging Benefits

Molecular imaging techniques, such as PET, can improve the accuracy of cancer detection, reduce false positives, and accelerate treatment initiation.
Estrogen-PET is particularly useful for visualizing lobular breast cancer, which can be difficult to see on other imaging modalities.