John E. Freitas

Radionuclide diagnosis and therapy of thyroid cancer: current status report

Thyroid cancer is uncommon, with an incidence of 10,300 new patients each year and a mortality of 1,100 patients each year. Patient survival correlates with many factors, including tumor pathology, age, primary lesion size, distant metastases, extent of surgery, and radioiodine therapy. Deaths from thyroid cancer may occur many years after diagnosis, and such an indolent course has hampered the analysis of the multiple treatment programs advocated. Thyroid imaging continues to play an important role in the initial detection and follow-up management of thyroid cancer, but the search for a specific tracer for the primary lesion continues. The complementary role of serum thyroglobulin and radioiodine in the follow-up of the thyroidectomized patient is discussed. Radioiodine therapy has proven effectiveness in those patients with radioiodine-avid distant metastases and/or regional metastases. Whether radioiodine ablation of residual thyroid bed activity is beneficial remains controversial.

Scintigraphic localization of adrenal lesions in primary aldosteronism.

Dexamethasone suppression adrenal cortical scintiscanning was performed in 87 patients with primary aldosteronism. Fifty patients had adrenal cortical adenomas and 37 had bilateral adrenal hyperplasia. The diagnosis of adrenal cortical adenoma was confirmed by surgery in 49 of 50, and bilateral adrenal hyperplasia was confirmed by adrenal vein aldosterone sampling in 33 and at operation in four. Dexamethasone suppression adrenal scintigraphy correctly identified the lesion(s) in 82 of the 87 patients. There were three false-negative and two false-positive adrenal cortical scintiscanning results. Computed tomography was performed in 33 patients and correctly identified 14 of 23 patients with adrenal cortical adenomas and two of 10 patients with bilateral adrenal hyperplasia and bilateral enlarged adrenals, whereas the remaining eight were considered to have normal findings. These data indicate that, when properly performed, adrenal cortical scintigraphy is an accurate and efficacious modality for the localization of adrenal cortical adenomas and in the differentiation of adrenal cortical adenoma from bilateral adrenal hyperplasia in primary aldosteronism.

Cholescintigraphy in acute and chronic cholecystitis

Since the introduction of technetium-99m-labeled cholescintigraphic agents in the mid-1970s, there has been extensive investigation of their role in the evaluation of biliary tract disorders. These agents accurately assess the patency of the cystic and common bile ducts, and to date, their greatest impact has been on the diagnostic evaluation of suspected acute cholecystitis. This article reviews the use of 99mTc-iminodiacetic acid (IDA) derivatives in acute and chronic cholecystitis. Since acute cholecystitis is characterized by cystic duct obstruction, failure of the gallbladder to visualize following 99mTc-IDA administration is indicative of cystic duct obstruction and acute cholecystitis. Using this approach, cholescintigraphy has been shown to be highly sensitive, specific, and efficacious in the diagnosis of acute cholecystitis. Cholescintigraphy is now the procedure of choice for the detection of acute cholecystitis. Unlike its successful applications in acute cholecystitis, cholescintigraphy appears of limited value in chronic cholecystitis. Certain circumstances where cholescintigraphy is of value in chronic cholecystitis are discussed. Whether or not cholescintigraphy may play a greater role in the future in elucidating the pathogenesis of chronic cholecystitis by assessment of biliary kinetics remains unanswered.

Adrenal localization in the adrenocorticotropic hormone-independent Cushing syndrome.

STUDY OBJECTIVE To assess the efficacy of 131I-6-beta-iodomethylnorcholesterol scintigraphy in the adrenocorticotropic hormone-independent Cushing syndrome and to compare this with computed tomography. DESIGN Retrospective analysis of case series from 1977 to 1987. SETTING Referral to the Division of Nuclear Medicine at a tertiary-care university medical center. PATIENTS Twenty-four patients with a pathologically-confirmed diagnosis of the adrenocorticotropic hormone-independent Cushing syndrome had 131I-6-beta-iodomethylnorcholesterol scintigraphy and, in most cases, computed tomography. MEASUREMENTS AND MAIN RESULTS Using 131I-6-beta-iodomethylnorcholesterol scintigraphy, adenomas were accurately seen as focal, unilateral tracer uptake in 14 of 14 patients. In carcinoma, the classic scintigraphic pattern of bilateral nonvisualization was observed in 3 of 4 patients, with ipsilateral uptake of tracer in 1 patient with a histologically well-differentiated malignancy. Computed tomography done during the same interval depicted abnormal adrenals in all cases of adenoma and carcinoma. In cortical nodular hyperplasia, however, computed tomography identified abnormal pairs of adrenals in only one of four cases studied, whereas scintigraphy showed typical patterns of bilateral increased uptake in all of the cases. CONCLUSION 131I-6-beta-iodomethylnorcholesterol scintigraphy accurately shows the location and nature of adrenal dysfunction in the adrenocorticotropic hormone-independent Cushing syndrome and may be particularly useful in identifying the bilateral adrenal involvement in cortical nodular hyperplasia.

Adrenal cortical and medullary imaging

Adrenal disease can be manifested by endocrine dysfunction or anatomic abnormalities detected by cross-sectional imaging modalities. With the advent of newer and more reliable in vitro assays and a better understanding of the spectrum of adrenal pathology, the physician can now adopt a more accurate and cost-effective approach to the diagnosis of adrenal disease. Both functional and anatomic imaging modalities can play an important role in the evaluation of the incidental adrenal mass, the early detection of adrenal metastases, differentiation of the various causes of Cushingss syndrome, selection of patients for potentially curative surgery in primary aldosteronism and adrenal hyperandrogenism, and localization of pheochromocytomas and neuroblastomas. The usefulness of the adrenal cortical radiopharmaceutical, 131I-6-beta-iodomethylnorcholesterol (NP-59), and the adrenal medullary radiopharmaceuticals, 131I and 123I-metaiodobenzylguanidine (MIBG), is detailed for these various clinical settings and the role of NP-59 and MIBG is contrasted to that of the cross-sectional modalities, computed tomography and magnetic resonance imaging (MRI). Incidental adrenal masses are common, but malignancies are few. Imaging studies select those patients who require a further evaluation by biopsy examination or adrenalectomy. In the hyperfunctioning endocrine states, such as Cushings syndrome, primary aldosteronism, adrenal androgenism, and pheochromocytoma, correlation of biochemical findings with both functional and anatomic imaging is necessary to avoid inappropriate and ineffective surgical intervention, yet not miss an opportunity for curative resection. Lastly, MIBG and MRI are complementary in the detection and staging of neuroblastoma.

Suspected acute cholecystitis. Comparison of hepatobiliary scintigraphy versus ultrasonography

One hundred ninety-fine patients with suspected acute cholecystitis (AC) underwent both hepatobiliary scintigraphy (HBS) and static gray-scale ultrasonography (US) to assess the relative value of each imaging modality in this clinical setting. HBS was performed after the intravenous injection of 5 mCi Tc-99m iprofenin. Abnormal HBS indicative of AC visualized the common bile duct, but not the gallbladder, within 1 to 4 hours after tracer administration. Abnormal US indicative of AC demonstrated cholelithiasis and/or gallbladder wall edema. In this series, HBS surpassed US in sensitivity (98.3% versus 81.4%), specificity (90.2% versus 60.2%), predictive value of an abnormal test (91.4% versus 51.6%), and predictive value of a normal test (100% versus 92%), HBS should be the procedure of choice for the rapid detection of AC.

The relationship of I-131 6 beta-iodomethyl-19-norcholesterol (NP-59) adrenal cortical uptake to indices of androgen secretion in women with hyperandrogenism.

Dexamethasone suppression (DS) adrenal cortical scintigraphy has been shown to be useful in the detection of the adrenal pathology in women with hyperandrogenism. However, a relationship between adrenal cortical uptake of 1-131 6β-iodomethylnorcholesterol (NP-59) and the level of adrenal androgen secretion has not been established. A retrospective analysis of DS adrenal scintiscans has been performed on 39 women with hirsutism and hyperandrogenism. In 14 patients with normal patterns of imaging, in vivo adrenal gland iodocholesterol uptake, calculated using a semioperator-independent-computer algorithm, did not correlate with the excretion of urinary 17-ketosteroids (17-KS). In contrast, in 20 patients demonstrating abnormal bilateral early imaging patterns, adrenal gland NP-59 uptake correlated significantly with the level of urinary 17-KS excretion (r = 0.65, P < 0.05). To date seven of these 20 patients have had confirmatory procedures documenting the adrenal glands as contributing sites of androgen secretion. A similar correlation with urinary 17-KS excretion was seen in five other patients with unilateral imaging patterns (r = 0.94, P < 0.005), due to androgen-secreting adrenal cortical adenomas. No correlation between adrenal NP-59 uptake and plasma testosterone or dehydroepiandrosterone sulphate levels was observed in any of the groups. Thus, adrenal gland uptake of NP-59 under DS reflects a measure of androgen secretion in women with androgen excess.

Interference by spironolactone on adrenocortical scintigraphy and other pitfalls in the location of adrenal abnormalities in primary aldosteronism.

A case of primary aldosteronism is presented in which the CT scan was initially misleading, adrenocortical scintigraphy was rendered inaccurate by pharmacological interference of spironolactone, and selective adrenal venous sampling of aldosterone was technically difficult. When dexamethasone suppression adrenocortical scintigraphy was performed with attention to technical detail and exclusion of interference by spironolactone, the causative lesion was scintigraphically demonstrated. This finding was confirmed by the results of venous sampling and the correctly located tumor removed.

Surgical treatment of thyrotoxicosis in children and adolescents

Forty-one children and adolescents had thyroidectomies for Grave’s disease during an 8 yr period. Twenty patients became euthyroid within a short period after treatment with antithyroid drugs and had operations with minimal ditruption of their lives. Antithyroid drugs were administered to 20 patients for a longer period of time as a primary form of treatment for Grave’s disease. Complications resulting from drug toxicity, poor cooperation by patients, and persistent goiters were indications for thyroidectomier in this group. Permanent remissions, after prolonged antithyroid drug therapy, are rare in children. Because the treatment is associated with significant morbidity, this form of therapy is unacceptable in most cases. Iodine-131 was given to 30 children or adolescents for Grave’s disease during the same time period. Iodine-131 is primarily indicated for patients who are resistant or allergic to antithyroid drugs, I7 ORTY-FIVE CHILDREN, 13 yr who have serious systemic diseases, or who have had previous thyroid opemtions. Hypothyroidism is an inevitable result of effective “‘I treatment of Grave’s disey;; in children. Serious consequences from I therapy were not observed during the short period of follow-up. Subtotal thyroidectomy continues to be the preferred primary treatment for most patients with Grave’s disease in childhood. Total thyroidectomy may be indicated for patients in the first decade of life. Hypothyroidism, which is easily managed in this age group, is the price paid for the prevention of recurrent Grave’s disease. Early detection and treatment of hypothyroidism can be achieved only by a careful follow-up of all patients treated by less than total thyroidectomy for Grave’s disease.

Adrenal hyperandrogenism: detection by adrenal scintigraphy

Hyperandrogenism Is a common endocrinopathy in women. Localization of the source of excess androgen production is mandatory for proper management. Ovarian hyperandrogenism has been implicated in the majority of patients studied, though the true prevalence of adrenal hyperandrogenism is not yet known. Adrenal scintigraphy is a simple non-invasive technique which detects adrenal functional abnormalities. The detection of adrenal hyperandrogenism by adrenal scintigraphy in three women with mild hirsutism is discussed.