Whole-Body 1-131 Metastatic Survey
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Questions and Answers

What is one of the primary purposes of a whole-body 1-131 metastatic survey?

  • To assess the necessity for surgical interventions
  • To prescribe therapeutic doses of chemotherapy
  • To determine the extent of metastases and tumor uptake (correct)
  • To provide a definitive treatment plan for all patients

    • Why is it beneficial to perform periodic whole-body scans after radioiodine therapy?

  • They guarantee the complete regression of thyroid cancer
  • They ensure that no further scans are needed for future management
  • They evaluate the effectiveness of the initial treatment (correct)
  • They allow the immediate administration of additional medications

    • What is the significance of using a dual-probe rectilinear scanner in the study?

  • It enhances the resolution of background images
  • It allows for only one imaging technique to be used
  • It helps detect metastatic and focal thyroid cancer more effectively (correct)
  • It reduces the time required for imaging significantly

    • What crucial benefit does surgery provide before radioiodine therapy?

    <p>A large specimen for detailed pathological examination</p> Signup and view all the answers

    What is presumed about remaining thyroid tissue regarding radioiodine uptake?

    <p>It will have little or no accumulation of radioiodine</p> Signup and view all the answers

    What are the advantages of a whole-body 1-131 metastatic survey in terms of patient scheduling?

    <p>The survey usually takes only 3-5 minutes to acquire images, resulting in minimal disruption of patient scheduling.</p> Signup and view all the answers

    How does the timing of a whole-body scan after surgery enhance the evaluation of residual thyroid tissue?

    <p>Conducting the scan 48 to 72 hours post-surgery allows for some radioiodine to be excreted, reducing body background and improving detection.</p> Signup and view all the answers

    Explain the role of pathology in determining the appropriateness of subsequent radioiodine therapy post-surgery?

    <p>The surgical specimen provides crucial pathological evidence to identify cancerous tissue, influencing the decision for radioiodine therapy.</p> Signup and view all the answers

    In what way does the dual-probe rectilinear scanner contribute to the detection of metastatic thyroid cancer?

    <p>The scanner, supplemented by scintillation camera images, enhances sensitivity in identifying both metastatic and focal thyroid cancer.</p> Signup and view all the answers

    What assumption underlies the studies involving radioiodine uptake by residual thyroid tissue in patients?

    <p>It is assumed that remaining thyroid tissue will have minimal accumulation of radioiodine due to effective surgical removal.</p> Signup and view all the answers

    What are the time intervals typically used for performing whole-body scans after oral administration of sodium iodide?

    <p>48 or 72 hours</p> Signup and view all the answers

    What type of collimators are used for recording images during a whole-body scan?

    <p>Medium energy collimators</p> Signup and view all the answers

    Which method is employed to avoid detection errors during a whole-body scan?

    <p>Detection of all radioiodine concentration areas</p> Signup and view all the answers

    What is the elapsed time for completing a typical whole-body scan procedure?

    <p>40 minutes</p> Signup and view all the answers

    What aspect of the patient's lower extremities is addressed during the scanning process?

    <p>They are excluded from the scan</p> Signup and view all the answers

    What type of camera is utilized when additional images are requested during the scanning process?

    <p>Scintillation camera</p> Signup and view all the answers

    What scanning speed is maintained during the whole-body scan procedure?

    <p>700 cm/min</p> Signup and view all the answers

    What is a key factor that enhances the accuracy of whole-body scans in detecting thyroid metastases?

    <p>Low background from radioiodine excretion</p> Signup and view all the answers

    How does the removal of thyroid tissue impact the uptake of radioiodine in remaining cancerous tissue?

    <p>It allows for increased uptake of radioiodine</p> Signup and view all the answers

    What is an essential reason for performing a 48- or 72-hour study after administering radioiodine?

    <p>To allow for the excretion of some radioiodine and reduce background</p> Signup and view all the answers

    What is the purpose of employing scintillation camera images in conjunction with the whole-body scans?

    <p>To enhance the detection capability for metastatic thyroid cancer</p> Signup and view all the answers

    What can be inferred about the effectiveness of radioiodine therapy based on imaging results?

    <p>Periodic scans can indicate the necessity for retreatment</p> Signup and view all the answers

    What role does the pathological examination of thyroid tissues play before radioiodine therapy?

    <p>It helps in understanding tumor characteristics</p> Signup and view all the answers

    What assumption is made regarding the uptake of 1-131 in remaining thyroid tissues after surgery?

    <p>There will be little or no accumulation in remaining tissues</p> Signup and view all the answers

    Why is surgery considered the best treatment for thyroid carcinoma before radioiodine therapy?

    <p>It provides a large specimen for pathological examination</p> Signup and view all the answers

    Which imaging technique is noted for its high sensitivity in assessing neuroendocrine tumors?

    <p>Gallium-68 DOTATATE</p> Signup and view all the answers

    What is the typical use case for octreotide scans in the diagnosis of neuroendocrine tumors?

    <p>Initial tumor screening</p> Signup and view all the answers

    What challenge is associated with advanced imaging techniques for neuroendocrine tumors?

    <p>Insurance coverage limitations</p> Signup and view all the answers

    Which technique is utilized for the standard evaluation of tumors in neuroendocrine tumors?

    <p>CT/MRI</p> Signup and view all the answers

    In the context of imaging techniques, which statement about gallium-68 DOTATATE is accurate?

    <p>It enhances detection and has high sensitivity for staging.</p> Signup and view all the answers

    Why is it important for patients and clinicians to stay informed about advancements in imaging techniques for neuroendocrine tumors?

    <p>To ensure access to the latest diagnostic tools.</p> Signup and view all the answers

    What is one of the promises of emerging imaging techniques for neuroendocrine tumors?

    <p>Significant improvement in diagnostic accuracy.</p> Signup and view all the answers

    What aspect of gallium-68 DOTATATE PET scans improves patient outcomes?

    <p>Enhanced detection capabilities.</p> Signup and view all the answers

    What is a key consideration to maximize the benefits of advanced imaging technologies for neuroendocrine tumors?

    <p>Collaborative research for regulatory approvals.</p> Signup and view all the answers

    What percentage of neuroendocrine tumors (NETs) can traditional imaging methods like CT and MRI miss?

    <p>20-80%</p> Signup and view all the answers

    Which peptide-based therapy has shown a significant reduction in the risk of death in advanced neuroendocrine tumors?

    <p>PRRT with lutetium-177 DOTATATE</p> Signup and view all the answers

    What imaging technique is recognized for its superior detection capabilities in neuroendocrine tumors?

    <p>Gallium-68 DOTATATE PET scans</p> Signup and view all the answers

    In clinical trials, what was the partial response rate associated with PRRT compared to standard therapies?

    <p>17%</p> Signup and view all the answers

    What is a notable characteristic of traditional imaging methods in the context of neuroendocrine tumors?

    <p>They often miss the more aggressive types of NETs.</p> Signup and view all the answers

    What critical advancement was made in imaging for neuroendocrine tumors in 2016?

    <p>Approval of Gallium-68 DOTATATE</p> Signup and view all the answers

    What challenge remains in the therapeutic approach to neuroendocrine tumors despite advancements?

    <p>Improved clarity in insurance coverage and reimbursement</p> Signup and view all the answers

    What is a limitation of the first radio-labeled peptide used for NET imaging?

    <p>Still misses many tumors</p> Signup and view all the answers

    What major benefit does PRRT using lutetium-177 DOTATATE provide over the previous standard therapies?

    <p>Significant improvement in patient outcomes</p> Signup and view all the answers

    What key aspect of CT and MRI imaging is highlighted as a limitation in diagnosing neuroendocrine tumors?

    <p>Limited biological information about tumor characteristics</p> Signup and view all the answers

    What percentage of neuroendocrine tumors can traditional imaging methods like CT and MRI miss?

    <p>20-80%</p> Signup and view all the answers

    What was the reduction in the risk of death associated with PRRT therapy in advanced neuroendocrine tumors?

    <p>46%</p> Signup and view all the answers

    How does the sensitivity of gallium-68 DOTATATE PET scans compare to traditional imaging modalities?

    <p>It provides a three-fold better detection rate.</p> Signup and view all the answers

    What is one major challenge remaining in the therapeutic approach to neuroendocrine tumors despite advancements in therapies?

    <p>Improved clarity in insurance coverage and reimbursement processes.</p> Signup and view all the answers

    What were the partial response rates of PRRT compared to the control groups receiving standard somatostatin analogs?

    <p>17%</p> Signup and view all the answers

    What key challenges persist regarding gallium-68 DOTATATE PET scans and insurance coverage?

    <p>Challenges include limited insurance coverage and the need for patients and clinicians to advocate for access to these scans.</p> Signup and view all the answers

    How do tumor imaging techniques differ in sensitivity, particularly between traditional methods and gallium-68 DOTATATE?

    <p>Traditional methods like CT and MRI have low to moderate sensitivity, while gallium-68 DOTATATE features high sensitivity for neuroendocrine tumor assessment.</p> Signup and view all the answers

    What is the role of lutetium-177 DOTATATE in the treatment of advanced neuroendocrine tumors?

    <p>Lutetium-177 DOTATATE significantly improves patient outcomes by targeting neuroendocrine tumors directly.</p> Signup and view all the answers

    In what ways do emerging imaging techniques for neuroendocrine tumors promise improved diagnostic accuracy?

    <p>These techniques, such as gallium-68 DOTATATE, offer enhanced detection capabilities, allowing for comprehensive assessment and staging of tumors.</p> Signup and view all the answers

    Why is it essential for both patients and clinicians to remain informed about advancements in neuroendocrine tumor imaging techniques?

    <p>Staying informed is crucial for advocating access to innovative treatments and ensuring optimal patient outcomes with the latest technologies.</p> Signup and view all the answers

    What are the clinical presentations associated with adrenal lesions?

    <p>Adrenal lesions may present with signs of endocrine hyperfunction or as masses or adrenal enlargement on imaging.</p> Signup and view all the answers

    What percentage of adrenal masses are benign in patients with non-primary adrenal malignancies?

    <p>Up to 50% of adrenal masses in these patients may be benign.</p> Signup and view all the answers

    What is the significance of the standardized uptake value (SUV) in adrenal imaging?

    <p>A standardized uptake value (SUV) of greater than or equal to 3.1 is considered positive for adrenal uptake on PET/CT.</p> Signup and view all the answers

    What is the accuracy of PET/CT in differentiating metastatic adrenal masses from benign lesions?

    <p>The accuracy is about 90%, but false negatives can occur due to various factors.</p> Signup and view all the answers

    How does FDG accumulation differ in normal adrenal glands compared to adrenal masses?

    <p>FDG is poorly accumulated in normal adrenal glands, making imaging more effective in assessing lesions with increased activity.</p> Signup and view all the answers

    What imaging techniques are commonly used to evaluate incidental adrenal masses?

    <p>CT or MRI are commonly used, with nuclear medicine studies available for further evaluation when warranted.</p> Signup and view all the answers

    What role do nuclear medicine studies play in the management of adrenal lesions?

    <p>They allow for the selection of patients for biopsy or surgical intervention based on imaging results.</p> Signup and view all the answers

    What common conditions can cause adrenal lesions as seen on imaging studies?

    <p>Conditions such as adrenal tumors, hyperplasia, and incidentalomas may all present as adrenal lesions.</p> Signup and view all the answers

    What imaging patterns indicate acute tubular necrosis in renal transplant evaluations?

    <p>Increasing parenchymal activity on renogram images over time suggests acute tubular necrosis.</p> Signup and view all the answers

    Why is the distinction between benign and malignant adrenal masses critical in clinical practice?

    <p>Correctly identifying the nature of adrenal masses influences treatment decisions and prognosis significantly.</p> Signup and view all the answers

    What is the main function of the adrenal medulla in the body?

    <p>The adrenal medulla synthesizes and secretes catecholamines such as epinephrine and norepinephrine, which regulate stress responses and physiological functions.</p> Signup and view all the answers

    How do pheochromocytomas affect the body's catecholamine levels?

    <p>Pheochromocytomas may secrete excessive amounts of catecholamines, leading to symptoms like hypertension.</p> Signup and view all the answers

    Distinguish between pheochromocytomas and paragangliomas in terms of hormone secretion.

    <p>Pheochromocytomas generally secrete catecholamines, whereas paragangliomas may elaborate excess catecholamines without releasing them into the bloodstream.</p> Signup and view all the answers

    What anatomical feature distinguishes the right adrenal gland from the left?

    <p>The right adrenal gland is triangular and higher, while the left adrenal gland is crescent-shaped and lies anteromedial to the left kidney.</p> Signup and view all the answers

    What is a common consequence of excessive catecholamine production in the body?

    <p>Common consequences include hypertension and increased smooth muscle tone, resulting from elevated epinephrine and norepinephrine levels.</p> Signup and view all the answers

    What complicates the diagnosis of pheochromocytoma via CT and MRI?

    <p>The small size of the adrenal medullary tissue and its propensity for ectopic locations make diagnosis unreliable.</p> Signup and view all the answers

    What is the role of 131I-MIBG in diagnosing neuroendocrine tumors?

    <p>131I-MIBG is used as a diagnostic imaging agent to identify normal, ectopic, or hyperfunctioning adrenal medullary tissue.</p> Signup and view all the answers

    Which MIBG isotope is currently commercially available for routine use, and what is its significance?

    <p>123I-MIBG is currently commercially available, significant for its shorter half-life and improved imaging efficiency.</p> Signup and view all the answers

    How does MIBG accumulate in presynaptic tissue?

    <p>MIBG accumulates in presynaptic tissue due to its structural similarities to norepinephrine, allowing reuptake into granules.</p> Signup and view all the answers

    What advantage does SPECT/CT imaging provide in the evaluation of pheochromocytomas?

    <p>SPECT/CT imaging improves detection of malignant adrenergic tumors and enhances specificity in identifying tumor accumulations.</p> Signup and view all the answers

    What is the preferred imaging agent for detecting pheochromocytomas?

    <p>123I-MIBG</p> Signup and view all the answers

    What is the significance of administering Lugol solution before MIBG administration?

    <p>To block thyroid uptake of released iodine</p> Signup and view all the answers

    Which factor contributes to the quality of 123I-MIBG imaging compared to 131I-MIBG?

    <p>Better target-to-background contrast</p> Signup and view all the answers

    Which medications should be discontinued prior to 123I-MIBG imaging?

    <p>Tricyclic antidepressants</p> Signup and view all the answers

    What is the normal distribution pattern of 131I-MIBG in the human body?

    <p>Heart, liver, spleen, salivary glands, and bladder</p> Signup and view all the answers

    What is the approximate ratio of the area of the adrenal cortex to the adrenal medulla?

    <p>10:1</p> Signup and view all the answers

    Which of the following hormones is primarily secreted by the adrenal medulla?

    <p>Epinephrine</p> Signup and view all the answers

    What distinguishes a paraganglioma from a pheochromocytoma?

    <p>Secretion of catecholamines</p> Signup and view all the answers

    What type of tumors are classified as hyperplastic nodules of 1 cm or larger within the adrenal medulla?

    <p>Pheochromocytomas</p> Signup and view all the answers

    Which hereditary syndrome is frequently associated with pheochromocytomas?

    <p>Multiple endocrine neoplasia (MEN) type II</p> Signup and view all the answers

    What potential complication can arise from malignant paragangliomas?

    <p>Invasion of surrounding tissue</p> Signup and view all the answers

    Which type of adrenal tumor may elaborate excessive amounts of catecholamines without causing typical clinical symptoms?

    <p>Paraganglioma</p> Signup and view all the answers

    What is the primary use of 131I-MIBG in clinical settings?

    <p>As a diagnostic imaging agent for adrenal medullary tissue</p> Signup and view all the answers

    What indicates a benzodiazepine-like effect from MIBG in imaging?

    <p>Its incorporation in presynaptic storage granules</p> Signup and view all the answers

    Where were ectopic pheochromocytomas primarily located according to the data presented?

    <p>Along the distribution of para-aortic tissue</p> Signup and view all the answers

    What major benefit does SPECT/CT provide in imaging?

    <p>Fuses images that improve interpretation of tumors</p> Signup and view all the answers

    What is a key consideration when preparing a patient for MIBG imaging?

    <p>Confirm the use of thyroid protection with Lugol solution</p> Signup and view all the answers

    What distinguishes 123I-MIBG from 131I-MIBG for clinical use?

    <p>Shorter half-life limiting its availability</p> Signup and view all the answers

    In a study of pheochromocytomas, how many patients were found with ectopic tumors?

    <p>24 out of 107 patients</p> Signup and view all the answers

    What imaging equipment is suggested for MIBG studies?

    <p>Gamma camera with medium- or low-energy collimators</p> Signup and view all the answers

    What is the recommended dose of iodine-123–metaiodobenzylguanidine for administration?

    <p>10 mCi</p> Signup and view all the answers

    Study Notes

    Whole-Body 1-131 Metastatic Survey

    • Purpose: To determine the extent of metastases, quality of tumor uptake, and whether the patient will benefit from therapeutic doses of radioiodine.
    • Frequency: Periodic whole-body scans are helpful in evaluating the success of radioiodine therapy or the necessity to repeat therapeutic treatments.
    • Methodology:
      • 48 or 72 hours following the oral administration of 1-3 mCi of sodium iodide
      • Images are recorded by an Ohio-Nuclear model 84 dual-probe rectilinear scanner
      • 38-M medium energy collimators
      • Minified scans are obtained using a 5:1 ratio and 5:1 light apertures with a 1/8-in. line spacing
      • Neither background erase nor contrast enhancement is used
    • Procedure:
      • Scan duration is approximately 40 minutes.
      • The lower distal extremities are excluded from scanning.
    • Post-Procedure:
      • Patients remain in the department until the images are reviewed by a nuclear medicine physician.
      • Additional images of abnormal areas of radioiodine accumulation may be requested with pinhole or medium energy collimators attached to a scintillation camera.

    Treatment of Thyroid Carcinoma

    • Surgery is the best available treatment for carcinoma of the thyroid.
    • Reasons for Surgery Preceding Radioiodine Therapy:
      • A large specimen of the tumor is provided for pathological examination.
      • Uptake of the remaining cancerous tissue is increased when part or all of the gland is removed.
    • Post-Surgery:
      • Depending on the outcome of the pathological examination, various treatment paths may be taken.

    Benefits of Whole-Body 1-131 Metastatic Survey

    • Short scan time (3-5 minutes) minimizes disruption in patient scheduling.
    • Performs 48- or 72-hr scans to allow for radioiodine excretion by the urinary system, decreasing body background.
    • Detects metastatic and focal thyroid cancer.
    • Benefits from the readily available scanner for the next patient.

    Whole-Body Scan Rationale

    • Whole-body scans are used to determine the extent of metastases, evaluate tumor uptake, and assess benefit from radioiodine therapy.
    • Periodic whole-body scans monitor radioiodine therapy effectiveness and identify the need for repeat treatments.

    Procedure and Timing

    • Scans are typically performed 48 or 72 hours after oral administration of 1-3 mCi of [131I] sodium iodide.
    • A dual-probe rectilinear scanner with 38-M medium energy collimators is used.
    • Scans are completed in approximately 40 minutes, excluding lower extremities.

    Minimizing Disruption

    • Whole-body scans are efficient, requiring only 3-5 minutes for camera imaging.
    • This minimizes disruption to patient scheduling and allows for swift subsequent patient scanning.

    Radioiodine Excretion

    • A 48- or 72-hour scan permits radioiodine excretion via the urinary system, reducing background noise and enhancing scan clarity.

    Metastatic Thyroid Cancer

    • Following thyroid cancer surgery, radioiodine (sodium iodide) is used for residual functioning tissue evaluation.
    • Imaging, 1-131-PBI conversion rates, and excretion studies are employed.
    • The presence of metastases and significant iodine concentration in the lesion are essential indicators for radioiodine therapy selection.

    Surgical Precedence

    • Surgery is the primary treatment for thyroid carcinoma.
    • Surgery precedes radioiodine therapy because it provides a larger tumor specimen for pathological examination and enhances uptake by remaining cancerous tissue.

    Pathological Examination

    • The pathological examination guides post-surgical treatment pathways, including potential radioiodine therapy.

    Neuroendocrine Tumors (NETs)

    • NETs arise from neuroendocrine cells
    • Can be difficult to diagnose due to varied symptoms and behaviors
    • Advances in imaging and therapy are significantly improving patient outcomes

    Standard Imaging Limitations

    • CT and MRI can miss a significant portion (20-80%) of NETs especially aggressive types.
    • These traditional methods provide limited information on tumor characteristics.

    Advancements in Imaging

    • Octreotide Scans: Used since 1994, detected many tumors but still missed some.
    • Gallium-68 DOTATATE PET Scans: Approved in 2016 and revolutionized NET imaging:
      • Shows a 3-fold increase in detection compared to CT/MRI.
      • Provides superior sensitivity for detecting tumors.

    Peptide-Based Therapies

    • Peptide Receptor Radionuclide Therapy (PRRT): Uses radiolabeled drugs like lutetium-177 DOTATATE.
    • Significant clinical trial findings:
      • Therapy yielded partial responses in 17% of patients compared to control groups.
      • Reduced death risk by 46% in patients using this therapy.

    Imaging Technique Comparison

    • CT/MRI: Low to Moderate Sensitivity, typically used for standard tumor evaluations.
    • Octreotide Scan: Moderate Sensitivity, used for initial tumor screening.
    • Gallium-68 DOTATATE: High Sensitivity, used for comprehensive assessment and staging of NETs.

    Conclusion

    • New imaging and therapeutic techniques, such as gallium-68 DOTATATE PET scans and lutetium-177 DOTATATE therapy, significantly improve outcomes for NET patients.
    • Current challenges include insurance coverage and reimbursement for these advanced technologies.
    • Continued research is necessary for streamlined integration into clinical practice and broader access to these beneficial treatments.

    Neuroendocrine Tumor (NET) Diagnosis and Therapy Advancements

    • NETs are complex tumors with varied behavior.
    • Effective diagnosis and treatment are crucial for optimal patient outcomes.
    • Imaging techniques are playing a significant role.

    Imaging Limitations

    • Traditional CT and MRI miss 20-80% of NETs, especially aggressive types.
    • These methods lack detailed biological information about the tumor.

    Alternative Imaging Agents

    • Octreotide scans were first introduced in 1994, but still missed many tumors.
    • Gallium-68 DOTATATE (approved in 2016) is superior for NET detection, leading to a revolution in NET imaging.

    Peptide-Based Therapies

    • Peptide Receptor Radionuclide Therapy (PRRT) uses radiolabeled drugs like lutetium-177 DOTATATE.
    • Clinical trials show promising results with PRRT:
      • Partial response rates of 17% compared to standard treatment.
      • Reduced risk of death by 46% with PRRT.

    Imaging Techniques Comparison

    • CT/MRI: Low to moderate sensitivity, standard evaluation of tumors.
    • Octreotide Scan: Moderate sensitivity, initial tumor screening.
    • Gallium-68 DOTATATE: High sensitivity, comprehensive assessment and staging.

    Conclusion

    • New imaging and therapies for NETs offer improved diagnostic accuracy and treatment efficacy.
    • Gallium-68 DOTATATE PET scans provide exceptional detection, and lutetium-177 DOTATATE improves patient outcomes.
    • Insurance coverage for these advancements presents a challenge.
    • Patients and clinicians need to stay informed and advocate for access to innovative treatments.
    • Continued research aims for streamlined approvals and broader integration of these technologies into clinical practice.

    Adrenal Lesions and Imaging

    • Adrenal lesions can present with symptoms of endocrine hyperfunction, masses, or adrenal enlargement on imaging.
    • Incidental adrenal masses are common findings on CT or MRI scans.
    • Nuclear medicine studies can help select patients for biopsy or surgery when clinically indicated.
    • FDG-PET/CT is useful for assessing and characterizing adrenal masses with increased activity, which may indicate malignancy, even in cancer patients presenting with "incidentalomas".
    • Up to 50% of adrenal masses in patients with non-primary adrenal malignancy may be benign.
    • Adrenal uptake is considered positive if it's greater than or equal to that of the liver or has a standardized uptake value (SUV) greater than 3.1.
    • PET/CT has an accuracy of approximately 90% in differentiating metastatic adrenal masses from benign lesions.
    • False negatives in PET/CT can occur with small lesions, hemorrhage, or necrosis.
    • About 5% of adrenal adenomas can be hypermetabolic.

    Adrenal Gland Anatomy

    • The adrenal glands are located superior to the kidneys in the retroperitoneum.
    • The right adrenal gland is triangular and higher than the left.
    • The left adrenal gland is crescent-shaped and anterior to the left kidney.

    Adrenal Medulla

    • The inner layer of the adrenal gland, tissue synthesizes and secretes epinephrine and norepinephrine.
    • Catecholamines regulate smooth muscle tone, heart rate, and other stress responses.

    Pheochromocytoma

    • Benign or malignant tumors of the adrenal medulla, typically hyperplastic nodules over 1 cm in diameter.
    • Smaller tumors are classified as macronodular hyperplasia.
    • Cause excessive catecholamine secretion, leading to symptoms like hypertension.
    • Can occur in any autonomic nervous tissue and are often found in multiple endocrine neoplasia (MEN) types IIa and IIb.
    • Can be difficult to diagnose and often go undetected until autopsy.

    Paraganglioma

    • Non-secretory tumors of adrenal medulla, may become malignant and spread to surrounding tissues or metastasize.
    • Small size and ectopic locations make diagnosis challenging, even with CT and MRI.

    Imaging with MIBG

    • 131I-MIBG (metaiodobenzylguanidine) is a radioactive tracer used to image adrenal medullary tissue, including normal, ectopic, and hyperfunctioning tissue.
    • Provides a means to identify the extent of disease in neuroblastoma, a malignant tumor of childhood.
    • 123I-MIBG, a shorter-lived isotope, is preferred for imaging due to convenience and better image quality.
    • MIBG is taken up by adrenergic storage granules due to its structural similarity to norepinephrine.

    123I-MIBG Imaging Procedure

    • Administered intravenously, images are acquired at 4 hours and 24 hours after injection.
    • Whole-body anterior and posterior images are acquired at a speed of 5 cm/s.
    • Static images can be acquired for further clarification.
    • SPECT/CT imaging provides fused images to improve interpretation and tumor identification.

    123I-MIBG Imaging Procedure: Pre-Procedure

    • Potassium iodide or Lugol solution are given for thyroid protection.
    • Medications affecting the adrenergic system (alpha- and beta-blockers, decongestants, calcium channel blockers, and tricyclic antidepressants) should be discontinued.
    • Alpha and beta-blockers do not affect MIBG uptake.

    123I-MIBG Imaging Procedure: Post-Procedure

    • Images should be obtained using medium-energy collimation.
    • Blood pressure and electrocardiographic monitoring are optional.

    123I-MIBG Imaging: Normal Distribution

    • 123I-MIBG accumulates in the heart, liver, spleen, salivary glands, and bladder.
    • Faint uptake in the adrenal medulla is usually considered normal.

    123I-MIBG Imaging: Abnormal Findings

    • Asymmetrical intense tracer uptake in the adrenal bed or other locations suggests a pheochromocytoma or paraganglioma.
    • Persistent or increased bilateral uptake may indicate bilateral pheochromocytoma.
    • Uptake in the liver, bone, lymph nodes, heart, lungs, mediastinum, or other sites could indicate malignant pheochromocytoma metastases.

    131I-MIBG Therapy

    • Used as a therapeutic agent to treat malignant pheochromocytoma, paraganglioma, and some neuroblastomas.
    • Limited to investigational protocols and requires physician-sponsored investigational new drug (IND) approval.

    Adrenal Glands

    • Located in the retroperitoneum, superior to the kidneys
    • Right adrenal gland is higher and more posterior than the left and is triangular shaped
    • Left adrenal gland is more crescent shaped

    Adrenal Medulla

    • Surrounded by the adrenal cortex
    • Synthesizes and secretes the catecholamines epinephrine and norepinephrine

    Pheochromocytomas

    • Benign or malignant functioning tumors of the adrenal medulla
    • Hyperplastic nodules 1 cm in diameter or larger
    • Can elaborate excessive amounts of epinephrine or norepinephrine
    • Can occur as spontaneous tumors, or as part of multiple endocrine neoplasia (MEN) type IIa and IIb.
    • May not necessarily secrete catecholamines into the circulation
    • Can be difficult to diagnose even with CT and MRI

    Paragangliomas

    • Nonsecretory tumors
    • May become malignant, invading surrounding tissue or metastasizing

    Iodine-123–Metaiodobenzylguanidine (123I-MIBG) Imaging

    • Used to identify neuroendocrine tumors
    • Radiopharmaceutical is administered intravenously
    • Images are acquired 24 hours after injection
    • SPECT/CT can be used for further clarification
    • Pelvic images should be acquired before the bladder fills
    • Lugol solution or potassium iodide should be given for thyroid protection
    • Medications that affect the adrenergic system should be discontinued

    Mechanism of 123I-MIBG Uptake

    • MIBG is structurally similar to norepinephrine
    • Accumulates in presynaptic adrenergic storage granules
    • Does not significantly bind to postsynaptic receptors

    Advantages of 123I-MIBG over 131I-MIBG

    • Better image quality
    • Shorter half-life allows for same-day or 24-hour imaging
    • Sufficient photon flux for SPECT imaging

    Normal Distribution of 131I-MIBG

    • Heart
    • Liver
    • Spleen
    • Salivary glands
    • Bladder

    Pheochromocytoma Imaging

    • Asymmetrical intense tracer uptake in the adrenal bed or elsewhere in the abdomen or thorax is suggestive
    • Persistent or increased uptake bilaterally suggests bilateral pheochromocytoma
    • Metastatic pheochromocytomas can be seen in the liver, bone, lymph nodes, heart, lungs, mediastinum

    111In-DTPA-pentetreotide

    • Used for pheochromocytoma imaging, but 123I-MIBG is preferred due to its shorter half-life

    131I-MIBG Therapy

    • Limited to investigational protocols to treat malignant pheochromocytoma, paraganglioma, and neuroblastoma.

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