Imaging of the adrenal glands

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  • 1. IMAGING OF THE ADRENAL GLANDS

2. ANATOMY Normal size: 2-4 cm CC, smooth limbs without nodularity, max thickness 10 mm. Inverted Y, V or L configuration. 3. Lambda-shaped body and 2 limbs. Inverted Y-shaped body with 2 limbs that point posteriorly. Normal CT appearance 4. NORMAL ADRENALNORMAL ADRENAL Right Suprarenal Posterior to IVC Lateral to right crus Medial to right lobe of the liver Left Lateral to left crus and aorta Posterior to pancreas and splenic vessels 5. II. Imaging characterization of adrenal masses II. Imaging characterization of adrenal masses 6. The Hormonally Active Mass Cortex: Functional adenomas (Cushing syndrome, Conn syndrome, or hyperandrogenism). Carcinomas ( Majority Cushings syndrome). Medulla: Pheochromocytomas (hypersecretes cathecolamines) 7. The Hormonally Active Mass The work-up of a suspected hyperfunctioning adrenal mass (pheochromocytoma and aldosteronoma) should start with appropriate biochemical screening tests followed by thin- collimation computed tomography (CT). Unilateral mass Conns syndrome (aldosterolonoma), Pheochromocytoma. Bilateral masses Hyperplasia (Cushings diseasePituitary adenoma) 8. CT has become the study of choice to differentiate a benign adenoma from a metastasis in the oncology patient. The oncology patient with an adrenal mass 9. NCCT HU < 10 Benign HU > 10 Delayed CECT (10 min) Washout > 50% HU < 30 Benign Washout < 50% HU > 30 Chemical Shift MRI Signal drop-out Benign No signal drop-out PET Biopsy 10. Incidentalomas: Two main concerns exist with incidentalomas: The first is whether it is hormonally active, and the second is whether it is malignant. The treatment for a hormonally active adrenal tumor is surgery. The treatment for a malignancy depends on the cell type, spread, and location of the primary tumor. 11. From: eMedicine.com, Inc. 12. Adrenal mass characterization- MRI In phase and out of phase gradient echo MR sequences are used to diagnose adrenal adenomas. The signal intensity of the adrenal adenoma decreases on out of phase imaging. Precession frequencies of protons found in intracellular fat and protons in water cancel out each other's signal at the time the echo is acquired. The signal intensity of the adenoma follows that of the of bone marrow, because bone marrow also contains small amounts of adipose tissue. The spleen is used as organ of reference on OP images for subjective evaluation. ***Lipid-poor adenomas if an adrenal mass fails to exhibit signal drop out on out of phase imaging it could still be an adenoma. 13. Adrenal mass characterization On the chemical shift imaging, signal intensity index, calculated as: Signal intensity (SI) indexes (D)= [SI in-phase - SI opposed-phase] x 100 (SI in-phase) A signal intensity index defined as D superior to 25% is used as positive diagnosis criteria for adenoma. 14. 1.5 T Chemical shift Imaging (CSI) Schematic shows lipid and water protons precessing in and out of phase with respect to each other over time at 1.5 T. The sine wave depicts the signal intensity within a voxel over time as the water and lipid protons oscillate between in phase and out of phase after the radio-frequency excitation pulse is delivered. 15. Adrenomedullary tumors : Pheochromocytoma Ganglioneuroblastoma Neuroblastoma Neuroendocrine carcinoma Adrenocortical carcinomas: -Functional -Nonfunctional -Well differentiated -Intermediate -Poorly differentiated to anaplastic Adrenocortical adenomas: -Functional- Cortisol, aldosterone,androgens -Non-functional Primary neoplasms 16. From: eMedicine.com, Inc. 17. Adenomas The prevalence of adrenal adenoma is age related. 0.14%for patients aged 2029 years and 7% in those older than 70 years The majority of lesions are not functioning the presence of contralateral adrenal atrophy suggests that a lesion may be functioning, because ACTH secretion is suppressed by elevated cortisol levels 18. LIPID-RICH ADENOMA 70 % are lipid-rich Clear cells have abundant intracytoplasmic fat CT Low attenuation on nonenhanced CT Threshold of < 10 HU is 71% sens, 98% spec [1] Spec approaches 100% when considering other features (size, shape, stability) < 30 HU on delayed CECT also diagnostic [1] Boland et al. AJR 1998; 171:201-4 19. LIPID-RICH ADENOMA MRI Chemical shift imaging is the most sensitive way to differentiate adenoma Relies on the different resonance frequencies of protons in fat and water molecules Use spleen as internal standard Look for signal drop-off (20%) on out-of-phase images due to intra-voxel signal cancellation of the lipid and water protons 81-100% sens, 94-100% spec 20. LIPID-POOR ADENOMA 30% are lipid-poor and do not have low attenuation on CT Adenomas enhance rapidly and wash out rapidly (independent of lipid content) Reflects physiologic differences in perfusion between adenoma and other lesions 21. The precontrast attenuation varies according to the presence or absence of lipid, with mean attenuation in the range of 2 to 16 HU in lipid-rich adenomas 20 to 25 HU in lipid-poor adenomas 22. ADENOMA -3.0 HU 23. Adenomas Non-functioning adenomas (most common) Incidentalomas. Functional adenomas **15%-20% of all Cushings syndromes cases are caused by adenomas or carcinomas . ** 80% of all Conn syndromes cases are caused by small adenomas (the remaining 20% are caused essentially by adrenal hyperplasia rarely by carcinomas). 24. ADENOMA T1W OPT1W IP 25. ADENOMA T2W T1W IP T1W OP 26. ADENOMA 27. The lipid-poor adenoma Although representing a minority of adrenal adenomas (30%) the lipid-poor variety cannot be accurately identified on unenhanced CT or chemical shift MR imaging. ..lipid-poor adrenal adenomas show enhancement and enhancement washout features nearly identical to lipid-rich adenomas and can be distinguished from nonadenomas on the basis of a percentage washout threshold value of 60% and a relative percentage washout of 40%. AJR Am J Roentgenol. 2000 Nov;175(5):1411-5. 28. Percentage of enhancement washout [E-D/E-U] x 100 = % ICM washout after 10 min. E= enhanced attenuation value U= Unenhanced attn value D= Delayed enhanced value (15 min) E= 90 HU U= 40 HU D= 50 HU [90-50/90-40] x 100 = 80% washout 29. Relative % washout If unenhanced CT has not been performed: (E-D) / E x 100 Optimal threshold 40% washout (sens 96%, Spec 100%) if threshold used is 50% then sens and spec= 100% 30. 40 HU 114 HU 65 HU [114-65/114-40] x 100 = 49/74 x 100 = 66% washout (>60 %) Lipid poor adenoma AJR:179, September 2002 [E-D/E-U] x 100 U E D 31. 32 HU 83 HU 57 HU [83-57/83-32] x 100 = 26/51x 100 = 50% washout ( 10 Delayed CECT (10 min) Washout > 50% HU < 30 Benign Washout < 50% HU > 30 Chemical Shift MRI Signal drop-out Benign No signal drop-out PET Biopsy 35. METASTASESMETASTASES Common site for mets Variable appearance Any size Round or lobulated Homogeneous or inhomogeneous Calcified Necrotic Even in pt with known malignancy, 50% of adrenal masses may be adenomas 36. METASTASESMETASTASES Features that favor mets include: Size > 3 cm Poorly defined margins Thick, enhancing rim Inhomogeneous Invasion of adjacent structures Mets elsewhere 37. METASTASES Metastatic adrenal tumors - Most common potential primaries include the following: Lung Breast Melanoma Renal cell carcinoma Extra-adrenal lymphoma Leukemias Pancreatic carcinoma Colonic carcinoma Ovarian carcinoma 38. METASTASES 39. METASTASES [E-D/E-U] x 100 33% washout 40. METASTASES 41. METASTASES PET CT FDG FDG 42. METASTASES Melanoma T1W T2W FS 43. ADRENAL CARCINOMAADRENAL CARCINOMA Rare Cortex 10% bilateral 50% functional Usually large at presentation (4-10 cm) 44. ADRENAL CARCINOMAADRENAL CARCINOMA Heterogeneous, irregular contour Calcification in 30% Large areas of internal hemorrhage and necrosis in most 45. ADRENAL CARCINOMAADRENAL CARCINOMA Look for invasion of adjacent organs and veins 46. Adrenocortical carcinomas 47. Adrenocortical carcinomasAdrenocortical carcinomas Left renal vein 48. Adrenocortical carcinoma 68-year-old woman with right upper quadrant palpable mass. 49. Precocious puberty in a child. Adrenocortical carcinoma 50. PHEOCHROMOCYTOMAPHEOCHROMOCYTOMA Neoplasm of chromafin cells in medulla (10% extra adrenal) Capacity to store and release catecholamines 0.1% of causes of HTN 51. PheochromocytomaPheochromocytoma "10-percent rule" 10% bilateral 10% malignant 10% extra-adrenal associated syndromes: neurofibromatosis von-Hippel-Lindau multiple endrocine neoplasia: MEN-2 and MEN- 1 extra-adrenal sites: detected with MIBG ( I 131-MIBG-NE analog) Organ of Zuckerkandl (most common) 52. PHEOCHROMOCYTOMAPHEOCHROMOCYTOMA Size determines imaging features < 4 cm Well defined and homogeneous Larger tumors more likely to have central necrosis 53. PHEOCHROMOCYTOMAPHEOCHROMOCYTOMA Classically hyperintense on T2 Enhance avidly 54. Pheochromocytoma 55. Pheochromocytoma 56. Pheochromocytoma 57. Pheochromocytoma T1W T2W 58. T1W T2W T1W POSTGAD Pheochromocytoma 59. Paragangliomas Extra-adrenal paragangliomas, as the name implies, can occur anywhere along the paraganglionic chain, but are most commonly found in the superior para- aortic region. between the diaphragm and the lower poles of the kidneys. Patients often present with headaches, palpitations, sweating, and hypertension. Clinical suspicion for extra-adrenal paraganglioma is usually confirmed by elevated urinary catecholamines and their metabolites. 60. Paraganglioma of the Organ of Zuckerkandl 61. Von-Hippel-Lindau VHL- pheochromocytoma, carotid body tumor and islet cell tumor of the pancreas. T2W 62. MYELOLIPOMAMYELOLIPOMA Rare benign tumor (0.2%) Composed of myeloid, erythroid