Nuclear Medicine Imaging Techniques

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Questions and Answers

What is the primary purpose of calibration in CT imaging systems?

To evaluate the accuracy of Hounsfield units within 5 units (correct)

To perform quality checks on patient imaging

To adjust system configurations based on user preference

To ensure uniform response throughout the field of view

Which component is NOT typically included in the quality control of a combined SPECT/CT system?

Daily sensitivity monitoring (correct)

Calibration checks for accuracy

Attenuation correction accuracy

Registration for spatial alignment

Which radionuclide parent-daughter system is mentioned in the context of PET/CT generators?

Iodine-131 / Xenon-133

Technetium-99m / Molybdenum-99

Gallium-67 / Gallium-68

Strontium-82 / Rubidium-82 (correct)

What quality control test is recommended to be performed annually for PET imaging?

Transverse resolution Signup and view all the answers

In the context of PET/CT imaging quality control, what aspect needs to be ensured regarding the CT portion?

It includes additional registration and attenuation correction accuracy tests Signup and view all the answers

Which collimator type is recommended for planar imaging with 201Tl?

Low-energy, medium-resolution collimator Signup and view all the answers

What is the standard energy window percentage when using 99mTc?

20% Signup and view all the answers

In SPECT imaging, what is the preferred detector separation for a 180° orbit?

90° Signup and view all the answers

Which is NOT a commonly used crystal type in PET cameras?

Gadolinium Calcium Silicate (GCS) Signup and view all the answers

What effect does adding additional detectors in SPECT imaging have on acquired counts?

Doubles acquired counts Signup and view all the answers

What is the benefit of using an elliptical orbit in SPECT imaging?

Improves spatial resolution Signup and view all the answers

Which type of attenuation correction do PET scanners rely on primarily?

Computed tomography (CT) Signup and view all the answers

What is a critical factor in determining the suitability of a collimator in nuclear cardiology?

The energy range of the radiopharmaceutical Signup and view all the answers

Which of the following stress testing protocols is considered most effective for myocardial perfusion imaging?

Dipyridamole infusion with immediate imaging Signup and view all the answers

What image processing method is commonly used in nuclear cardiology for enhancing image quality?

Convolution Filtering Signup and view all the answers

In nuclear cardiology, which gating technique is primarily used to synchronize imaging with the cardiac cycle?

Phase Analysis Gating Signup and view all the answers

In calculating ejection fraction using gated SPECT imaging, which phase of the cardiac cycle is most critical?

End-diastolic phase Signup and view all the answers

Which type of collimator is typically recommended for high-resolution planar imaging in nuclear cardiology?

Parallel-hole collimator Signup and view all the answers

What is the primary objective of using a stress testing protocol in nuclear cardiology?

To provoke ischemia for diagnosis Signup and view all the answers

What specific attribute does pixel spacing influence in SPECT myocardial perfusion imaging?

Resolution of the final image Signup and view all the answers

Which of the following factors is NOT considered when performing quality assurance for imaging equipment in nuclear cardiology?

Evaluating patient compliance during imaging Signup and view all the answers

Which of the following radiopharmaceuticals is primarily used in MIBG imaging?

Iodine-123 Signup and view all the answers

Which of the following practices is recommended to reduce scatter counts during dose calibration for 123I-MIBG?

Using a commercial copper sleeve or tube Signup and view all the answers

What specific characteristic of the dose calibrator is crucial for accurate measurement of 123I-MIBG?

A specific setting for 123I and a correction factor Signup and view all the answers

In the context of myocardial perfusion imaging, which imaging acquisition method is typically employed to ensure adequate counting statistics?

10-minute anterior acquisition in a 128 x 128 x 16 matrix Signup and view all the answers

Which condition should be monitored when administering 123I-MIBG to ensure patient safety and efficacy?

Potential interactions with prescribed thyroid medications Signup and view all the answers

Which technique is crucial when setting up imaging sequences before the day of administering 123I-MIBG to enhance the precision of acquired images?

Testing and configuring the imaging sequence in advance Signup and view all the answers

What is the correct storage temperature range for 123I-MIBG after calibration?

68°F to 77°F Signup and view all the answers

Which of the following is an essential component of the aseptic technique during 123I-MIBG injection?

Flushing the intravenous line with saline Signup and view all the answers

How does kidney disease potentially impact the administration of 123I-MIBG?

It can cause increased radiation exposure to healthy tissues. Signup and view all the answers

Which factor is crucial to verify before injecting 123I-MIBG into a patient?

The timing of the calibration Signup and view all the answers

What procedure should be followed for radiation safety regarding the 123I-MIBG dose after its calibration time?

It should be discarded after 36 hours. Signup and view all the answers

What is the recommended method to draw 123I-MIBG for administration to the patient?

Employing a shielded syringe and aseptic technique. Signup and view all the answers

What potential risk is associated with administering 123I-MIBG to patients with a history of thyroid cancer?

Risk of metastasis to other areas due to iodine. Signup and view all the answers

What is a primary consideration when administering 123I-MIBG to patients with renal insufficiency?

Potential for impaired clearance of the drug Signup and view all the answers

Which practice is recommended to mitigate thyroid cancer risk during 123I-MIBG administration?

Pretreatment with potassium iodide Signup and view all the answers

What specific action should be taken to ensure patient safety during the administration of 123I-MIBG?

Ensure the patient is well informed about the procedure Signup and view all the answers

How is radiation dosimetry relevant in the context of 123I-MIBG testing?

It informs about the radiation dose received by the patient Signup and view all the answers

What timing is critical for the acquisition of images after the administration of 123I-MIBG?

15 minutes after injection for early imaging Signup and view all the answers

Which patients may be considered for potassium iodide pretreatment before 123I-MIBG administration?

Patients at increased risk for thyroid cancer Signup and view all the answers

Why is hydration important before the 123I-MIBG test, especially for certain patients?

To prevent dehydration-related complications in those with heart failure Signup and view all the answers

What should be monitored in patients during and after the administration of 123I-MIBG?

Presence of adverse reactions to the medication Signup and view all the answers

What is the consequence of not ensuring the camera is unoccupied before administering 123I-MIBG?

Exposure of the staff to unnecessary radiation Signup and view all the answers

What timing interval follows the late imaging session after 123I-MIBG injection?

3 hours and 50 minutes post-injection Signup and view all the answers

What imaging characteristic distinguishes 99mTc-HMDP and 99mTc-DPD from 99mTc-pyrophosphate?

They demonstrate soft-tissue uptake. Signup and view all the answers

Which imaging method is best for calculating the heart-to-contralateral-lung ratio?

SPECT imaging with a focus on the ribcage. Signup and view all the answers

What positioning should patients maintain during imaging to visualize the entire ribcage?

Supine with arms overhead. Signup and view all the answers

What is a notable feature of the imaging parameters used in different camera systems?

Variability exists, but general recommendations can guide most systems. Signup and view all the answers

In the context of 99mTc imaging, which of the following aspects should not be a concern for patient preparation?

Collecting serum and urine samples prior to imaging. Signup and view all the answers

What is the primary reason for using 99mTc-pyrophosphate in the United States instead of other radiopharmaceuticals?

Other alternatives are not FDA approved. Signup and view all the answers

Which imaging technique is typically used to obtain images of a patient's chest after administering 99mTc-pyrophosphate?

Planar and SPECT imaging Signup and view all the answers

What is the typical dose range for administering 99mTc-pyrophosphate intravenously?

370–740 MBq Signup and view all the answers

What is the approximate radiation exposure from a 555-MBq dose of 99mTc-pyrophosphate?

3 mSv Signup and view all the answers

Why is 99mTc-methylene diphosphonate not recommended for cardiac amyloid imaging?

It has significantly lower sensitivity. Signup and view all the answers

What imaging configuration is typically utilized when obtaining images after the administration of 99mTc-pyrophosphate?

Standard dual-head g-camera with 90° configuration Signup and view all the answers

What process occurs three hours after the intravenous injection of 99mTc-pyrophosphate?

Imaging of the chest Signup and view all the answers

Which condition can 99mTc-pyrophosphate imaging help differentiate in patients with a family history of amyloidosis?

Variant cardiac ATTR Signup and view all the answers

What is an essential indication for 99mTc-pyrophosphate imaging in cardiac amyloidosis?

Patients with negative serum and urine studies for AL Signup and view all the answers

Which of the following radiopharmaceuticals is associated with nuclear medicine imaging for cardiac amyloidosis?

99mTc-pyrophosphate Signup and view all the answers

What is a contraindication for cardiac MRI that makes patients candidates for 99mTc-pyrophosphate imaging?

Presence of an implantable device Signup and view all the answers

Which of the following patient preparation protocols is necessary before undergoing 99mTc-pyrophosphate imaging?

No specific restrictions on diet or medications Signup and view all the answers

What is the primary utility of the serum free light-chain ratio in the diagnostic process?

To rule out cardiac ATTR Signup and view all the answers

What aspect of the 99mTc-pyrophosphate imaging process presents no specific contraindications?

General nuclear medicine procedure cautions Signup and view all the answers

In terms of imaging results, what indicates strong myocardial uptake in 99mTc-pyrophosphate scans?

Diffuse myocardial uptake Signup and view all the answers

Which imaging technique is considered diagnostic of ATTR cardiomyopathy upon meeting specific criteria?

99mTc-pyrophosphate imaging with negative serum and urine studies for AL Signup and view all the answers

What types of examinations can 99mTc-pyrophosphate imaging replace for patients with specific contraindications?

Cardiac MRIs Signup and view all the answers

What is the radiopharmaceutical used for adrenal imaging that is taken up by chromaffin cells?

Metaiodobenzylguanidine (MIBG) Signup and view all the answers

What is the main challenge in differentiating metastatic adrenal masses from benign lesions using PET/CT?

False negatives due to small lesions Signup and view all the answers

What is the standardized uptake value (SUV) threshold indicating positive adrenal uptake?

Greater than or equal to 3.1 Signup and view all the answers

In imaging suspected pheochromocytomas, what is the sensitivity and specificity of MIBG?

90% sensitivity, 90% specificity Signup and view all the answers

What is a notable characteristic of the uptake pattern of radioiodinated MIBG in normal tissues?

Faint activity in the heart and thyroid gland Signup and view all the answers

What percentage of adrenal adenomas are classified as hypermetabolic?

5% Signup and view all the answers

What is the typical method of excretion for MIBG after administration?

Mostly excreted unchanged by the kidneys Signup and view all the answers

What is generally observed in patients with nonprimary adrenal malignancies regarding adrenal masses?

Up to 50% may be benign Signup and view all the answers

What is the primary rationale for using a specific radiopharmaceutical labeled with iodine-123 in MIBG imaging?

High radioactivity and short half-life Signup and view all the answers

Which other neuroendocrine tumors may be localized to a lesser degree by MIBG apart from pheochromocytoma?

Medullary thyroid carcinoma Signup and view all the answers

What percentage of patients may visualize the normal adrenal medulla on delayed images?

30% to 50% Signup and view all the answers

Pheochromocytomas are often referred to as 'ten-percent tumors' for several reasons. Which of the following is NOT one of those reasons?

Approximately 10% are ectopic. Signup and view all the answers

What is the primary imaging method of choice for detecting pheochromocytomas?

Whole-body imaging with SPECT or SPECT/CT with 123I-MIBG Signup and view all the answers

Which substance may interfere with the localization of radioiodinated MIBG and should be withheld before imaging?

Antidepressants Signup and view all the answers

What is the sensitivity of MIBG in detecting adrenal neuroblastoma and its metastases in affected neonates and children?

More than 90% Signup and view all the answers

Which form of imaging is often utilized to visualize skeletal and marrow metastases associated with neuroblastomas?

Whole-body imaging at 24 and 48 hours post-injection Signup and view all the answers

What potential effect does aggressive chemotherapy have on imaging for metastases in neuroblastoma?

Reduces radiopharmaceutical uptake Signup and view all the answers

Which type of neuroendocrine tumors may result in excessive catecholamine production without secretion into circulation?

Paragangliomas Signup and view all the answers

How is the adrenal medullary tissue typically characterized in size compared to the adrenal cortex?

Small and relatively less extensive Signup and view all the answers

What imaging technique is particularly sensitive in detecting ectopic lesions in pheochromocytomas?

Whole-body planar imaging Signup and view all the answers

What is the primary advantage of using 123I-MIBG over 131I-MIBG in clinical settings?

Commercial availability makes it easier to obtain Signup and view all the answers

Which of the following conditions is least likely to influence the administration of 123I-MIBG?

Patient's weight and height measurements Signup and view all the answers

Which imaging method is most suitable for distinguishing between neuroendocrine tumors during diagnostic evaluations?

Iodine-123–metaiodobenzylguanidine (MIBG) Signup and view all the answers

In preparing a patient for an MIBG scan, which of the following is a mandatory intervention?

Initiation of potassium iodide or Lugol solution Signup and view all the answers

What is the key reason MIBG is incorporated into presynaptic adrenergic storage granules?

Its chemical structure is similar to norepinephrine. Signup and view all the answers

Which imaging parameter is pivotal when acquiring static images for MIBG?

Acquiring pelvic images before bladder filling Signup and view all the answers

What is a common misconception about the pharmacological effects of MIBG?

It has little or no pharmacological effect. Signup and view all the answers

For what purpose is SPECT imaging primarily used in conjunction with MIBG?

To provide clarification of whole-body and static images Signup and view all the answers

What is the expected imaging speed during a whole-body MIBG scan?

5 cm/s Signup and view all the answers

What is the main limitation of using 131I-MIBG compared to its counterpart?

Its gamma emission is of higher energy and less manageable. Signup and view all the answers

What is the purpose of 99mTc sestamibi in breast tumor imaging?

Imaging without uptake in normal breast tissue Signup and view all the answers

Which of the following is NOT true regarding the characteristics of 111In pentetreotide?

It interacts poorly with human antibodies Signup and view all the answers

Which statement about HAMA response is accurate?

It is linked to the immunogenicity of mouse-derived monoclonal antibodies Signup and view all the answers

Regarding the use of 67Ga citrate, what is the optimal scanning time for accurate neoplasm imaging?

24 hours after administration Signup and view all the answers

What is a key advantage of using 201Tl chloride compared to 67Ga citrate?

Lower sensitivity to inflammatory conditions Signup and view all the answers

How should 99mTc sestamibi be administered when used for breast tumor imaging? Select all

(c ) Via intravenous injection in the arm contralateral to involved breast Signup and view all the answers

Lymphoscintigraphy is used to:

All of the above Signup and view all the answers

111In pentetreotide is a:

Somatostatin analog Signup and view all the answers

A HAMA response occurs because:

Monoclonal antibodies are produced from mouse cells which the human body recognizes as a foreign protein. Signup and view all the answers

Advantages of 201Tl chloride over 67Ga citrate include:

All of the above. Signup and view all the answers

It is possible to use 99mTc sestamibi for breast tumor imaging because there is no uptake of sestamibi in the normal breast.

False Signup and view all the answers

A monoclonal antibody is developed which displays cross- reaction. This means:

The antibody will bind antigens other than the one it was formed with. Signup and view all the answers

Examples of neuroendocrine tumor include:

All of the above Signup and view all the answers

Visualization of kidneys at 48 h is _on a scan using 111In pentetreotide and _on a 67Ga citrate scan.

Normal, abnormal Signup and view all the answers

18FDG can be used to image tumors because the glycolyticrate is higher in tumor than in normal tissues.

True Signup and view all the answers

Which of the following are true regarding 18FDG tumor imaging?

PET scanning is required. Signup and view all the answers

Pheochromocytomas are imaged using:

131I MIBG Signup and view all the answers

The use of PET imaging in oncology takes advantage of the _____differences between normal and neoplastic tissue.

Metabolic Signup and view all the answers

Hodgkin’s disease is a type of:

Lymphoma Signup and view all the answers

F-18 fluciclovine is currently an FDA-approved imaging agent for what type of cancer?

Prostate Cancer Signup and view all the answers

Recommended dose for imaging with Ga-68 dotatate?

0.054 mCi/kg up to 5.4 mCi Signup and view all the answers

Gallium-68 is:

Generator Produced Signup and view all the answers

Gallium-68 dotatate is indicated for imaging what type of can- cers utilizing PET?

Neuroendocrine Tumors Signup and view all the answers

Recommended dose for imaging with F-18 fluciclovine?

10 mCi Signup and view all the answers

Thyrotropin is also known as:

TSH Signup and view all the answers

Most people have four parathyroid glands.

True Signup and view all the answers

The salivary glands include:

Sublingual salivary glands Signup and view all the answers

Which of the following are used to image the parathyroid?

Tc99 Sestamibi Signup and view all the answers

Study Notes

Energy Windows

Energy windows around the photopeak should be symmetric.
Energy peak and window settings are camera-specific and should be established for each individual camera.
A 20% window is standard when using 99mTc.
For 201Tl a 30% window around the 70 keV peak and a 15% window around the 167 keV peak are sufficient.

Collimation

It is recommended that a parallel-hole collimator be used for planar imaging.
For 99mTc, the low-energy, high-resolution collimator is usually best.
When using 201Tl, a low-energy, medium-resolution (all-purpose) collimator is best since the counting statistics become limited with a high-resolution collimator.

SPECT Imaging

Single-head cameras are widely used.
Adding additional detectors doubles the acquired counts, reducing acquisition time.
Traditional orbits include circular, step-and-shoot motion using a rotational range of 180° or 360°.
For a 180° orbit, two detectors separated by 90° are ideal.
A 360° orbit ideally uses three detectors separated by 120°.
Elliptical orbits, common in modern SPECT systems, improve spatial resolution.
SPECT and CT integration offers potential benefits.
SPECT apparatus typically has a large FOV and dual detectors.
CT apparatus provides anatomical location, attenuation correction, and may include multi-slice units for standalone diagnostic scans.

Positron Emission Tomography (PET) Imaging

Most dedicated PET cameras consist of rings of small detectors.
Commonly used crystal types include bismuth germinate (BGO), gadolinium oxyorthosilicate (GSO), lutetium oxyorthosilicate (LSO), and lutetium yttrium orthosilicate (LYSO).
PET scanners rely mainly on CT scans for attenuation correction, but can also use rotating-rod sources of germanium-68/gallium-68.

Nuclear Cardiology

It has become a major component of nuclear medicine.
Technologists focused solely on performing cardiac studies may be eligible to sit for the nuclear cardiology specialty board exam.
It is essential to review topics such as instrumentation, quality control, patient care, the cardiovascular system, pathology, electrocardiogram (ECG), emergency care, radiopharmaceuticals, and interventional drugs.

Planar Imaging

While no longer the standard approach for myocardial perfusion imaging, it can be an alternative for patients unable to have SPECT imaging due to body habitus or inability to remain in position.
A small field of view scintillation camera is practical for cardiac imaging.
Using a 10 in. field of view (FOV) with a matrix of 128 x 128 results in about 2 mm of pixel spacing.
A 15 in. FOV camera should be zoomed using a magnification of 1.2-1.5 to achieve pixel size close to 2 mm.

Combined SPECT/CT Quality Control

Includes all SPECT and CT imaging quality control tests.
The CT portion must additionally perform registration, attenuation correction accuracy, and mis-registration consequences.

Dedicated PET Imaging Quality Control

Suggested quality controls include acceptance testing, sensitivity, transverse resolution, scatter fraction, accuracy of attenuation correction, and any other test recommended by the manufacturer.
Sensitivity should be performed daily or at least weekly.
Transverse resolution should be performed annually using a point source or rod source.
It is also recommended that scatter fraction and accuracy of attenuation correction be performed annually.

PET/CT Imaging Quality Control

The quality control of the PET portion of PET/CT includes all of the suggested quality controls for PET imaging.
The quality control of the CT portion of PET/CT also includes calibration and feild uniformity.

Combined PET/CT Quality Control

Includes individual PET and CT portions as mentioned above, as well as registration and attenuation correction accuracy.

Radionuclide PET/CT Generator

Radionuclide generators provide a convenient source of short-lived radionuclides.
In a radionuclide generator, a longer-lived radionuclide (parent) decays to a shorter-lived radionuclide (daughter).
The daughter can be removed periodically since it is replenished by decay of the parent.
Examples of parent-daughter systems used in radionuclide PET/CT generators are strontium-82 (82Sr)/rubidium-82 (82Rb).
These systems are commercially available as sterile, shielded, automatically operated devices.

99mTc-Pyrophosphate

99mTc-Pyrophosphate is used for cardiac amyloid imaging in Europe due to unavailability of other, more readily accessible radiopharmaceuticals like 99mTc-DPD
In the United States, 99mTc-methylene diphosphonate (99mTc-HMDP) is widely available but has lower sensitivity and is not recommended for cardiac amyloid imaging.

Administration and Imaging

Recommended dose: 370-740 MBq (10-20 mCi) administered intravenously
Total radiation exposure from 555-MBq (15-mCi) dose: approximately 3 mSv
Imaging is performed 3 hours after intravenous injection, using planar and SPECT images of the patient's chest
Imaging typically utilizes a standard dual-head gamma camera with a 90" detector configuration
Recent research suggests feasibility of semiquantitative analysis of 3-dimensional images using cadmium-zinc-telluride cameras

Indications

99mTc-Pyrophosphate imaging is used to differentiate variant from wild-type cardiac ATTR in patients with suspected or known family history of amyloidosis
Also indicated for patients suspected of cardiac ATTR but with contraindications to cardiac MRI, such as implantable devices or renal insufficiency
In such cases, a negative serum and urine study for AL amyloidosis supports a diagnosis of ATTR cardiomyopathy

Contraindications

No known specific contraindications other than general nuclear medicine procedure cautions regarding pregnancy, breastfeeding, and recent nuclear medicine scans

Patient Preparation

No specific patient restrictions before 99mTc-pyrophosphate imaging
Patients can eat, drink, and take medications as usual
Patients are imaged supine with arms above their head, ensuring the entire ribcage is visualized

Imaging Parameters

Planar images include anterior and left lateral projections
Imaging parameters vary among equipment but the parameters outlined in the 2021 addendum to the recommendations generally work well for most camera systems.

Whole-Body Imaging

Whole-body imaging is not useful for 99mTc-pyrophosphate
However, whole-body imaging with 99mTc-HMDP or 99mTc-DPD demonstrates soft-tissue uptake
This is because the heart-to-contralateral-lung ratio is calculated to assess cardiac uptake
The camera should be large enough to image the complete chest to visualize rib uptake and enable this calculation

Adrenal Gland Imaging

Adrenal lesions can have clinical signs and symptoms of endocrine hyperfunction or be discovered as masses or adrenal enlargement on cross-sectional imaging.
Incidental adrenal masses found on CT or MRI are common.
Nuclear medicine studies allow for selection of patients needing biopsy or surgical intervention, when clinically necessary.
FDG is poorly accumulated in normal adrenal glands, making PET/CT helpful in assessing and characterizing adrenal masses with increased activity.
This includes cancer patients and those with "incidentalomas" found on 5% of CT scans done for other reasons.
Up to 50% of adrenal masses in patients with a nonprimary adrenal malignancy may be benign.
Adrenal uptake is usually considered positive if it's greater than or equal to that in the liver or has a standardized uptake value (SUV) greater than 3.1.
PET/CT has about 90% accuracy in differentiating metastatic adrenal masses from benign lesions.
False negatives can occur due to small lesions, hemorrhage, and necrosis.
Approximately 5% of adrenal adenomas are hypermetabolic.

Adrenal Medullary Imaging

Metaiodobenzylguanidine (MIBG) is a guanethidine analog similar to norepinephrine.
It's taken up by chromaffin cells, making it useful for imaging normal and abnormal sympathetic adrenergic tissue, especially pheochromocytomas and neuroblastomas.
MIBG is localized in other neuroendocrine tumors, including carcinoid, medullary thyroid carcinoma, and paraganglioma, but to a lesser degree.
In cases of pheochromocytoma and neuroblastoma, MIBG has high sensitivity and specificity, approaching 90%.
The specific radiopharmaceutical used is radioiodinated MIBG labeled with 3 to 10 mCi (81 to 370 MBq) of iodine-123 (123I).
Iodinated MIBG is slowly metabolized, with 75% to 90% excreted by the kidneys as unaltered MIBG.
Whole-body planar images or selected spot images of the regions of interest are obtained serially over 24 to 72 hours, depending on the suspected pathology.
Radioiodinated MIBG appears normally in the salivary glands and liver, with faint activity in the heart and thyroid gland.
Due to renal excretion, there is renal and bladder activity.
Nasal, neck muscle, diffuse lung activity, and bowel activity can be noted in some patients.
Normal adrenal medulla is visualized on delayed images in about 30% to 50% of patients, which can lead to false-positive results.
However, the intensity is usually less than the adjacent liver and needs to be distinguished from the more intense abnormal accumulation seen in pheochromocytoma or neuroblastoma, which is greater than the liver in 80% to 90% of patients.

Clinical Applications

Pheochromocytomas are known as the "ten-percent tumors" because approximately 10% are bilateral, 10% occur in children, 10% are extraadrenal, and 10% are malignant.
Whole-body imaging augmented by SPECT or SPECT/CT with 123I-MIBG has been the method of choice for pheochromocytomas.
18FDG and 68Ga DOTATATE PET/CT are also useful.
MIBG scans for pheochromocytomas are especially helpful in diseases with a high incidence of neoplasm, including multiple endocrine neoplasms types 2A and 2B, neurofibromatosis, von Hippel-Lindau disease, Carney triad, and familial pheochromocytoma.
The technique is sensitive in both adults and children.
Posterior adrenal images are obtained at 24, 48, or 72 hours, as needed.
Whole-body planar imaging is useful if ectopic lesions are suspected.
Pheochromocytomas imaged with radioiodinated MIBG present as focally increased activity, whether the tumor is located in the adrenal medulla or ectopically.
Radiopharmaceutical uptake is greater in well-differentiated tumors than in less well-differentiated tumors.
Occasionally, some large tumors are not visualized due to extensive tumor necrosis.
Imipramine, insulin, reserpine, tricyclic antidepressants, and amphetamine-like drugs may inhibit localization of radioiodinated MIBG, interfering with tumor imaging.
These should be withheld before imaging when practical.

Neuroblastoma

MIBG can be used to detect adrenal medullary neuroblastoma and its metastases in more than 90% of affected neonates and children.
Whole-body imaging with or without SPECT or SPECT/CT is performed 24 and 48 hours after administration.
In normal subjects, the adrenal medulla can be seen on more delayed images, and diffuse lung and gut activity can be prominent.
Neuroblastomas & any metastases detected with MIBG present as foci of increased activity.
Skeletal and marrow metastases are usually best seen on 48-hour images.
Aggressive chemotherapy may hinder the detection of some metastases.
Imaging of neuroblastomas and pheochromocytomas using 111In-pentetreotide (a radiolabeled somatostatin analog) and 18F-FDG is discussed elsewhere.
111In-pentetreotide may be limited for detecting adrenal lesions due to intense normal activity in nearby kidneys.

Adrenal Glands

The adrenal glands consist of an outer adrenal cortex and an interior neurosecretory adrenal medulla.
Located in the retroperitoneum, superior to the kidneys (suprarenal), they lie approximately below the eleventh rib.
The right adrenal gland is higher and more posterior than the left, even though the left kidney is often higher than the right.
The right adrenal gland is triangular, sitting astride the upper pole of the right kidney.
The left adrenal gland is more crescent shaped and lies anteromedial to the upper pole of the left kidney.

Adrenal Medulla

The adrenal medulla is typically located within the adrenal gland surrounded by the adrenal cortex.
Medullary tissue is quite small, with a cortex-to-medulla area ratio of approximately 10:1.
The adrenal medulla tissue synthesizes and secretes the catecholamines epinephrine and norepinephrine.
These hormones maintain (or increase) smooth muscle tone, heart rate and force of contraction, and other physiological responses associated with stress.

Adrenal Medulla Clinical Aspects

Benign or malignant functioning tumors of adrenal medulla tissue are known as pheochromocytomas, which are hyperplastic nodules 1 cm in diameter or larger.
Smaller tumors are considered macronodular hyperplasia.
Despite their small size, these tumors can produce excessive amounts of epinephrine or norepinephrine, leading to undesirable symptoms.
These symptoms typically include hypertension and other consequences of excessive catecholamine production.
Pheochromocytomas can occur as apparently spontaneous benign or malignant tumors, but they may arise from any site of autonomic nervous tissue.
These tumors are frequent components of the hereditary syndrome multiple endocrine neoplasia (MEN) types IIa and IIb.
While advances in clinical chemistry have made direct assay of catecholamines and even specific assays of plasma and urinary epinephrine and norepinephrine more readily available, the disease is often a clinical enigma, frequently not diagnosed until postmortem examination.
Some tumors produce excessive amounts of catecholamines, but they do not secrete these products into the circulation, so patients may not present with typical clinical symptoms.
These nonsecretory tumors are called paragangliomas.
They can become malignant, invading surrounding tissue, metastasizing throughout the body, or both.
The small size of the adrenal medullary tissue and a propensity for ectopic sites make diagnosis even by CT and MRI unreliable.
24 of 107 pheochromocytomas were found outside the adrenal glands in one large surgical series.

Radionuclides

After many years of research, 131I-MIBG was approved by the FDA in the 1970s for clinical use as a diagnostic imaging agent.
Although cumbersome to work with, 131I-MIBG became the imaging agent of choice to identify normal, ectopic, or hyperfunctioning adrenal medullary tissue.
Subsequently, 123I-MIBG was synthesized, but the short half-life of 123I initially limited availability.
123I-MIBG is now commercially accessible for routine use in nuclear medicine departments.
MIBG labeled with 123I or 131I can identify the extent of disease in patients with neuroblastoma, a malignant tumor of childhood that can be widely disseminated in the abdomen and bone marrow.
After secretion at the synapse, a portion of the norepinephrine is reabsorbed and stored in granules at the presynaptic site through a presynaptic reuptake mechanism.
MIBG has little or no pharmacological effect and does not significantly bind at postsynaptic receptors.
It's incorporated into the presynaptic adrenergic storage granules due to structural similarities to norepinephrine, providing the basis for visualization of adrenergic tissue in general and pheochromocytomas and paragangliomas in particular.

99mTc Sestamibi for Breast Tumor Imaging

Administration: Intravenous injection in the arm contralateral to the involved breast
Reason for contralateral arm: To avoid potential radiation exposure to normal breast tissue

Optimal Scanning Time for Neoplasm with 67Ga Citrate

Optimal time for 67Ga citrate imaging: 24 hours after injection

Lymphoscintigraphy

Purpose: Mapping lymphatic channels, determining drainage pathways from malignant neoplasms, identifying the sentinel node

111In Pentetreotide

Type: Somatostatin analog

HAMA Response

Cause: Occurs when monoclonal antibodies, which are produced from mouse cells, are recognized as foreign proteins by the human body, triggering an immune response.

111In Satumomab Pendetide Administration

Pre-Injection: Should be shielded and assayed

111In Satumomab Pendetide Use

Target: Imaging of extrahepatic metastases from colorectal and ovarian cancer

Advantages of 201Tl Chloride over 67Ga Citrate

Shorter half-life: Allows for imaging to be performed sooner
Less uptake in inflammatory processes: Improved specificity for detecting tumor

99mTc Sestamibi for Breast Tumor Imaging

Specificity: Sestamibi has preferential uptake in breast tumors, allowing for distinct imaging

Cross-Reaction with Monoclonal Antibodies

Definition: Monoclonal antibody binds to antigens other than the one it was originally designed for which can lead to off-target effects

Neuroendocrine Tumor Examples

Examples: Pituitary adenomas, small-cell lung cancer, neuroblastomas

Kidney Visualization with 111In Pentetreotide and 67Ga Citrate

111In pentetreotide: Normal kidney visualization at 48 hours
67Ga citrate: Abnormal kidney visualization at 48 hours

18FDG for Tumor Imaging

Mechanism: 18FDG utilizes the higher glycolytic rate in tumors compared to normal tissues for imaging

18FDG Tumor Imaging Considerations

Requirements: PET scanning, patient fasting prior to the exam
Target: 18FDG can detect a wide variety of tumors, not just brain tumors

Pheochromocytomas

Imaging agent: 131I MIBG

PET Imaging in Oncology

Advantage: Exploits metabolic differences between normal and neoplastic tissue

Hodgkin's Disease

Type: Lymphoma

Normal 67Ga Citrate Uptake Sites

Uptake locations: Intestinal mucosa, liver
Excluded location: Parathyroid glands

F-18 Fluciclovine

FDA-approved indication: Imaging of prostate cancer

Ga-68 Dotatate

Half-life: 68 minutes
Recommended dose: 0.054 mCi/kg up to 5.4 mCi
Production method: Cyclotron
Target: Neuroendocrine tumors

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Description

This quiz covers essential concepts in nuclear medicine imaging, focusing specifically on energy windows, collimation, and SPECT imaging. Understand the camera-specific settings for energy peaks and window sizes as well as the recommended collimators for different isotopes like 99mTc and 201Tl. Test your knowledge on the methodologies used in SPECT imaging.