Cross-sectional imaging work-up of adrenal masses

Advances in medical imaging with current cross-section modalities enable non-invasive characterization of adrenal lesions. Computed tomography (CT) provides characterization with its non-contrast and wash-out features. Magnetic resonance imaging (MRI) is helpful in further characterization using chemical shift imaging (CSI) and MR spectroscopy. For differentiating between benign and malignant masses, positron emission tomography (PET) imaging is useful with its qualitative analysis, as well as its ability to detect the presence of extra-adrenal metastases in cancer patients. The work-up for an indeterminate adrenal mass includes evaluation with a non-contrast CT. If a lesion is less than 10 Hounsfield Units on a non-contrast CT, it is a benign lipid-rich adenoma and no further work-up is required. For the indeterminate adrenal masses, a lipid-poor adenoma can be differentiated from a metastasis utilizing CT wash-out features. Also, MRI is beneficial with CSI and MR spectroscopy. If a mass remains indeterminate, PET imaging may be of use, in which benign lesions demonstrate low or no fluorodeoxyglucose activity. In the few cases in which adrenal lesions remain indeterminate, surgical sampling such as percutaneous biopsy can be performed.     

Comparison of delayed enhanced CT and chemical shift MR for evaluating hyperattenuating incidental adrenal masses

PURPOSE: To retrospectively compare the accuracy of delayed enhanced computed tomography (CT) and chemical shift magnetic resonance (MR) imaging for characterizing hyperattenuating adrenal masses at CT, with either follow-up imaging or pathologic review as the reference standard. MATERIALS AND METHODS: The institutional review board approved this retrospective study with a waiver of patient informed consent. Forty-three hyperattenuating adrenal masses (>10 HU) on unenhanced CT images were found in 34 patients (23 men and 11 women; mean age, 52.7 years) by reviewing radiologic reports. These lesions were retrospectively analyzed with delayed enhanced CT and chemical shift MR. The diagnostic accuracy of CT by using absolute percentage loss of enhancement (PLE) and relative PLE and of chemical shift MR by using adrenal-to-spleen ratio (ASR) or signal intensity index (SII) were obtained to determine which modality was more accurate for lipid-poor adenoma. For CT, an adenoma was diagnosed if a mass had an absolute PLE greater than 60% and a relative PLE greater than 40%. For MR, an adenoma was diagnosed if a mass had an ASR of 0.71 or an SII greater than 16.5%. McNemar test was used to compare diagnostic performance of CT and MR. RESULTS: Hyperattenuating adrenal masses included 37 adenomas and six nonadenomas. The sensitivity, specificity, and accuracy for adenoma at CT were 97% (36 of 37), 100% (six of six), and 98% (42 of 43), respectively, and at MR were 86% (32 of 37), 50% (three of six), and 49% (21 of 43), respectively. CT helped confirm five more adenomas and three more metastatic tumors than did MR. However, there was no significant difference for diagnostic accuracy between these two imaging modalities (P>.05) CONCLUSION: Delayed enhanced CT can characterize additional hyperattenuating adrenal masses that cannot be characterized with chemical shift MR.     

Evaluation of adrenal masses in oncologic patients: dynamic contrast-enhanced MR vs CT

The CT examinations, precontrast gradient echo MR images, and fast contrast enhanced dynamic MR studies were evaluated in 44 patients with 52 adrenal masses and known malignant disease of different origin. Morphologic features (size, shape, attenuation, contour, and enhancement) on CT scans, signal intensity on T2-weighted MR images, and patterns of enhancement on Gd-DTPA enhanced dynamic MR studies were analyzed in all patients. With dynamic contrast enhanced studies with prolonged imaging up to 15 min after Gd-DTPA, masses with moderate enhancement and complete washout after 10 min were considered as adenomas. Computed tomography and plain MR had a sensitivity of 0.71 and 0.96, a specificity of 0.75 and 0.88, and overall accuracy of 0.56 and 0.71, respectively. Simultaneous use of precontrast MR and dynamic contrast enhanced studies led to an accurate diagnosis in 88% (sensitivity = 1.0, specificity = 0.91) and thus should be considered in oncologic patients with undetermined adrenal masses.     

Major salivary gland masses: comparison of MR imaging and CT

Computed tomography (CT) and magnetic resonance (MR) imaging studies were done prospectively in 21 unselected patients in whom 28 major salivary glands had pathologic changes. Blinded and final readings were used to establish the relationship of the lesion to the plane of the facial nerve (parotid masses), whether the lesion was intrinsic to the gland, and whether the lesion was aggressive. In the blinded reading, CT was superior to MR imaging in eight instances; in the final reading, however, with clinical information available, CT was superior in four cases of inflammatory salivary gland "masses." CT and MR imaging provided the same diagnostic information in all cases of salivary gland neoplasms. T1- and T2-weighted images proved of equal value in detection of salivary gland lesions, and use of both provided no additional specificity. In most cases, T1-weighted images alone provided the information necessary for surgical management. MR imaging is a reasonable first choice if a neoplasm is likely; the potential for improved tissue contrast at the margins of a tumor may be particularly useful. If a mass may be of inflammatory origin, contrast material-enhanced CT is a more reasonable first choice.     

Radiologisches Staging des Nierenzellkarzinoms

The routine staging work-up for renal cancer includes a contrast-enhanced multiphasic spiral CT and a chest radiograph. If there is doubt regarding the presence and extent of (supradiaphragmatic) IVC thrombus, MR imaging should be performed. Dynamic contrast-enhanced MR imaging should be used in place of CT in any patient with severe renal dysfunction, symptomatic polycystic kidney disease, or a history of allergy to iodinated contrast media. Cavography is no longer needed in the era of (adaptive array detector) spiral CT and MR venography.     

Evaluation of adrenal masses with gadolinium enhancement and fat-suppressed MR imaging

A study was undertaken to determine the ability to characterize benign and malignant masses with unenhanced and contrast material-enhanced fast lowangle shot and fat-suppressed spin-echo magnetic resonance (MR) imaging. Thirty patients with adrenal masses detected at computed tomography (CT) underwent MR imaging within 14 days after CT. CT and MR images were interpreted in a prospective, blinded fashion. Sixteen patients had 20 benign adrenal masses, and 14 patients had 18 malignant masses. Quantitative measurements included percentage of contrast enhancement on immediate postcontrast dynamic images and periphery - center signal-to-noise ratio (S/N) on gadolinium-enhanced fat-suppressed images. Qualitative evaluation included determination of the regularity of lesion margins, homogeneity of signal intensity, and local extension. MR imaging depicted all adrenal masses discovered at CT examinations. Lesions ranged in diameter from 1 to 15 (mean, 4.4) cm. No significant difference was observed in percentage of contrast enhancement between benign (90.5% ± 59.0 [standard deviation]) and malignant (110.5% ± 116.4) masses. A difference was observed between periphery - center S/N for benign (?.05 ± 1.5) and malignant (7.7 ± 9.8) masses; overlap between the two, however, occurred. Qualitative evaluation allowed correct characterization of 32 of 38 masses, comparing favorably with CT, which allowed characterization of 30 lesions.     

Diagnostic performance of CT versus MR in detecting aldosterone-producing adenoma in primary hyperaldosteronism (Conn’s syndrome)

The aim of the present study is to compare the diagnostic performance of CT and MR imaging in detecting aldosterone-producing adenoma and to compare the interobserver variability in the detection of an aldosterone-producing adenoma on CT and MR. A retrospective study of 34 patients with primary hyperaldosteronism was performed. A total of 17 cases of aldosterone-producing adenoma and 17 cases of bilateral adrenal hyperplasia were included. The final diagnosis of an adenoma was made by surgery with histological confirmation, whereas that of bilateral adrenal hyperplasia was made on adrenal venous sampling or a good biochemical and clinical response following medical treatment alone and in the absence of a unilateral radiological abnormality. The CT (n=30) and MR (n=24) scans were reviewed independently by two radiologists experienced in adrenal imaging, who were unaware of the cause of the primary hyperaldosteronism. The diagnostic performances of both observers in detecting an aldosterone-producing adenoma on CT and MR imaging were compared. The 16 adenomatous nodules that were detected on imaging ranged from 1 to 4.75 cm in diameter. The calculated sensitivity and specificity for detecting aldosterone-producing adenoma were 87 and 93% for one observer and 85 and 82% for the other observer on CT, and 83 and 83% for one observer and 92 and 92% for the other observer on MR, respectively. Receptor operating characteristics curve analysis showed similar performances of both observers in detecting an aldosterone-producing adenoma on CT and MR imaging. There was good interobserver agreement on CT (k=0.71) and on MR (k=0.67). We have demonstrated comparable diagnostic performance and good interobserver agreement on CT and MR imaging for the detection of aldosterone-producing adenoma.     

Overview of adrenal imaging/adrenal CT

CT is the imaging procedure of choice for the detection of most suspected adrenal masses. But except for some patients with acute adrenal hemorrhage or fat-containing myelolipoma, the precise histologic nature of an adrenal mass is not apparent from the CT image. MIBG radionuclide scanning is useful in some patients with pheochromocytoma, whereas bilateral adrenal venous sampling for hormone assay is necessary for correct lateralization in some patients with a small aldosterone-producing adenoma. The potential value of MR imaging in the characterization of adrenal masses, especially to distinguish benign adrenal cortical adenomas from metastatic disease, is now under investigation. Currently percutaneous aspiration biopsy is still necessary to make this distinction in patients with an adrenal mass and a known extra-adrenal primary neoplasm.     

Overview of adrenal imaging/adrenal CT

CT is the imaging procedure of choice for the detection of most suspected adrenal masses. But except for some patients with acute adrenal hemorrhage or fat-containing myelolipoma, the precise histologic nature of an adrenal mass is not apparent from the CT image. MIBG radionuclide scanning is useful in some patients with pheochromocytoma, whereas bilateral adrenal venous sampling for hormone assay is necessary for correct lateralization in some patients with a small aldosterone-producing adenoma. The potential value of MR imaging in the characterization of adrenal masses, especially to distinguish benign adrenal cortical adenomas from metastatic disease, is now under investigation. Currently percutaneous aspiration biopsy is still necessary to make this distinction in patients with an adrenal mass and a known extraadrenal primary neoplasm.     

Scintigraphy of incidentally discovered bilateral adrenal masses

The purpose of this study was to determine the patterns of iodine-131 6-iodomethylnorcholesterol (NP-59) imaging and the correlation with computed tomography (CT)-guided adrenal biopsy and follow-up in patients with bilateral adrenal masses. To this end we investigated a consecutive sample of 29 euadrenal patients with bilateral adrenal masses discovered on CT for reasons other than suspected adrenal disease. Adrenal scintigraphy was performed using 1 mCi of NP-59 injected intravenously, with gamma camera imaging 5–7 days later. In 13 of the 29 patients bilateral adrenal masses were the result of metastatic involvement from lung carcinoma (5), lymphoma (3), adrenocarcinoma of the colon (3), squamous cell carcinoma of the larynx (1), and anaplastic carcinoma of unknown primary (1). Among these cases the NP-59 scan demonstrated either bilaterally absent tracer accumulation (in eight, all with bilateral metastases proven by CT guided biopsy or progression on follow-up CT) or marked asymmetry of adrenocortical NP-59 uptake (in five). Biopsy of the adrenal demonstrating the least NP-59 uptake documented malignant involvement of that gland in five of five patients. In two patients an adenoma was found simultaneously in one adrenal with a contralateral malignant adrenal mass. In each of these cases, the adenoma demonstrated the greatest NP-59 uptake. In 16 patients diagnosis of adenoma was made on the basis of (a) CT guided adrenal biopsy of the gland with the greatest NP-59 uptake of the pair (n=4), or (b) adrenalectomy (n=2), or (c) absence of change in the size of the adrenal mass on follow-up CT scanning performed 6 months to 3 years later (n=10). It is concluded that differential in vivo functional information provided by NP-59 scintigraphy complements that derived from anatomic imaging and can be used in patients with bilateral adrenal masses to select which gland would be the best choice for further diagnostic invasive evaluation (e.g., adrenal biopsy) or may suggest the presence of bilateral adrenal metastases in patients with incidentally discovered, bilateral adrenal masses.     

Differentiation between small benign and malignant adrenal masses with dynamic incremented CT

Contrast-enhanced dynamic incremented CT scans in 37 patients with 44 small adrenal masses (28 benign and 16 malignant) were reviewed by two observers unaware of the histologic diagnosis to determine if applying morphologic criteria could help differentiate small benign adrenal masses from malignant adrenal masses. Only lesions smaller than 5 cm with diagnoses confirmed by histology (12 masses) or follow-up (32 masses) were included. Features evaluated to suggest a benign diagnosis were homogeneous low attenuation, possibly with punctate contrast enhancement; an enlarged gland (adrenal configuration maintained); a thin or absent rim; round or oval shape with sharp margins; and diffusely homogeneous attenuation about equal to or greater than that of muscle. Features studied to suggest a malignant diagnosis were a thick enhancing rim, invasion of adjacent structures, irregular or poorly defined margins, and inhomogeneous attenuation. Both observers' diagnoses of benign vs malignant lesions with CT criteria were highly statistically significant. The positive predictive value of a benign diagnosis was 100% for both observers and of a malignant diagnosis was 82% and 62% for the two observers. Evaluated singly, all but three diagnostic criteria were statistically significant in differentiating lesions for both observers; the other three criteria were present in a smaller percentage of patients, but nevertheless had positive predictive values for benignancy of 89-100%. We conclude that experienced observers who use CT criteria can often discriminate accurately between benign and malignant small adrenal masses and, in particular, minimize the number of false-negative diagnoses of adrenal metastases. If these results are confirmed and refined by prospective studies, aggressive diagnostic evaluation can be eliminated in some patients with benign adrenal lesions.     

Adrenal masses: characterization with combined unenhanced and delayed enhanced CT

PURPOSE: To assess the accuracy of a dedicated adrenal computed tomographic (CT) protocol. MATERIALS AND METHODS: One hundred sixty-six adrenal masses were evaluated with a protocol consisting of unenhanced CT, and, for those with attenuation values greater than 10 HU, contrast material-enhanced and delayed enhanced CT. Attenuation values and enhancement washout calculations were obtained. An adenoma was diagnosed if a mass had an attenuation value of 10 HU or less at unenhanced CT or a percentage enhancement washout value of 60% or higher. RESULTS: The final diagnosis was adenoma in 127 masses and non-adenoma in 39. Masses measuring more than 10 HU on unenhanced CT scans were confirmed at biopsy (n = 28) or were examined for stability or change in size at follow-up CT performed at a minimum interval of 6 months (n = 33). Thirty-six (92%) of 39 non-adenomas and 124 (98%) of 127 adenomas were correctly characterized. The sensitivity and specificity of this protocol were 98% and 92%, respectively. This protocol correctly characterized 160 (96%) of 166 masses. CONCLUSION: With a combination of unenhanced and delayed enhanced CT, nearly all adrenal masses can be correctly categorized as adenomas or non-adenomas.     

Imaging findings of primary adrenal tumors in pediatric patients

Apart from neuroblastomas, adrenal tumors are rarely seen in children. The most common adrenal tumors are adrenocortical carcinoma and pheochromocytoma. Adrenocortical carcinoma is usually a large heterogeneous, well-marginated mass with solid/cystic areas and calcifications, with poor prognosis. Most of the pheochromocytomas are benign tumors and usually show intense contrast enhancement, the pattern of which may be diffuse, mottled, or peripheral on computed tomography and magnetic resonance imaging. The purpose of this article is to evaluate primary nonneurogenic adrenal tumors.

In children, neoplastic and non-neoplastic lesions might be seen in the adrenal region. Pediatric adrenal lesions may be found incidentally, can be suspected in children that suffer endocrine, metabolic, neurological problems or with an abdominal mass. In fetal life, adrenal glands are much larger than in adults because of the existence of a prominent fetal cortex. Their prominent fetal size is also seen in early neonatal life. Ultrasonography (US) is the initial imaging technique to examine the adrenal glands in newborns. In older children, due to the physiologic atrophy of the fetal adrenal cortex, adrenal limbs are thinner than the adjacent crura of the diaphragm. Consequently, they are much more difficult to specify with US, but can be easily identified on computed tomography (CT) or magnetic resonance imaging (MRI). US is the primary modality for imaging the pediatric abdomen. CT or MRI are used as a problem-solving tool for lesion characterization, to determine the relationship to adjacent tissues, and to differentiate benign from malignant masses after initial US evaluation (1). In older children MRI should be preferred rather than CT examination. In adults, abdominal CT examinations assess tumor washout of contrast material based upon multi-phase CT, which is necessary to characterize adrenocortical masses (especially adenomas). However, pediatric CT examinations should be done in single portal venous phase to comply with “Image Gently” and “as low as reasonably achievable” (ALARA) principles.Primary adrenal tumors are classified according to their origin and function. They might originate from the medulla or cortex, and they are hyperfunctioning or nonfunctioning. Primary medullary tumors encompass a spectrum of sympathetic neuroectodermal tumors, which are neuroblastoma, ganglioneuroblastoma, ganglioneuroma, and pheochromocytoma, all of which stem from the neural crest and may take place anywhere along the sympathetic chain aside from the adrenal gland itself. Neoplasms arising from the adrenal cortex are adrenocortical carcinoma and adenoma.In the literature, few studies have reported imaging findings of pediatric adrenal tumors, including all types of involvement (i.e., benign, malignant, and metastatic) (1–3). The aim of this article is to describe the imaging findings of primary nonneurogenic adrenal tumors.     

动态增强CT检查对肾上腺腺瘤与非腺瘤的鉴别诊断价值

目的探讨动态增强CT检查技术对肾上腺腺瘤与非腺瘤的鉴别诊断价值并优选出有意义的参数，以进一步明确两者的鉴别诊断标准。资料与方法对44例共49个肾上腺肿瘤先平扫再行动态增强CT检查，观察以肿瘤的CT绝对值、绝对开始廓清率及相对开始廓清率作为标准鉴别肾上腺腺瘤与非腺瘤的诊断价值。结果延时3min，以36％的绝对开始廓清率或35％的相对开始廓清率分别与CT绝对值58HU相结合作为标准，对腺瘤有较高的诊断价值，对于腺瘤中的乏脂质性腺瘤与非腺瘤的鉴别诊断也具有同样的价值。结论以肿瘤的廓清率与延时增强后的CT绝对值作为联合标准，能明显提高腺瘤的诊断价值。     

Value of various imaging modalities for diagnostic work-up of tumors of the adrenal gland

OBJECTIVE: This paper describes the value of various imaging modalities for diagnostic work-up of tumors of the adrenal gland. METHODS: Results of the literature are reviewed. An optimized examination protocol for computed tomography (CT) and magnetic resonance imaging (MRI) is shown for assessment and differentiation of unclear lesions of the adrenal gland. RESULTS: Measurements of attenuation in the native examination as well as delayed enhancement are the cornerstones in the CT diagnostics of tumors of the adrenal gland. In MRI, chemical-shift imaging and evaluation of signal characteristics in T1- and T2-weighted images are most important for characterization even in unclear cases. CONCLUSION: CT and MRI play the major role in imaging of adrenal gland tumors.Whereas CT is less expensive and widely available,MRI provides advantages in unclear cases because of the excellent tissue contrast and the superior characterization.     

Magnetic resonance tomography of adrenal gland tumors. Detection and differentiation using fast gradient echo sequences and dynamic contrast media studies

The use of fast gradient echo sequences enable reduction of the acquisition times in MR imaging, allowing examinations during suspended respiration. Furthermore, repeated single slices in the same position after administration of a paramagnetic contrast agent provide dynamic evaluation of tissue perfusion. These new diagnostic modalities were applied for imaging normal adrenal glands in 128 cases and for differentiation of 83 adrenal tumors in 74 patients. CT remains the imaging method of choice for the detection of adrenal masses, due to the higher spatial resolution. Fast gradient echo MRI offers the possibility of differentiation between benign and malignant adrenal lesions. The 70% accuracy reached with precontrast scans can be augmented to 90% using dynamic contrast-enhanced studies.     

Incidental Bilateral Renal Oncocytoma in a Patient with Metastatic Carcinoma of Unknown Primary: a Pitfall on 18F-FDG PET/CT

Bilateral renal masses are uncommon but can raise a strong suspicion of primary or secondary malignancy, especially during the initial work-up of an oncology patient. Renal oncocytomas are benign renal tumors that are commonly discovered incidentally on diagnostic imaging with a small percentage occurring bilaterally. Although ¹⁸F-FDG uptake in renal oncocytomas has been described, a case of a bilateral ¹⁸F-FDG-avid renal oncocytoma has not been previously reported in the literature. A variety of malignant causes of bilateral ¹⁸F-FDG positive renal masses are known, however it is important to include this benign etiology in the differential diagnosis. We report an unusual case of an incidental bilateral renal oncocytoma evaluated with contrast enhanced CT and ¹⁸F-FDG PET/CT.     

Paraovarian adrenal rest with MRI features characteristic of an adrenal adenoma

We report MR and sonographic imaging features of an incidentally detected paraovarian adrenal rest in a 44-year-old woman who was being evaluated for menorrhagia. This is the first report of chemical shift imaging identifying the presence of lipid within an adrenal rest as well as rapid washout of contrast. Both of these MR characteristics are typically seen with an adrenal adenoma.     

Diagnostic radiology of liver tumors. Part 1: General disease aspects and radiological procedures

Besides malignant disease, focal liver lesions can also represent benign changes. Among the malignant lesions, in addition to hepatocellular carcinoma, liver metastases should be mentioned. In contrast, benign lesions such as focal nodular hyperplasia and hepatocellular adenoma are rarely encountered. Various radiological procedures are employed for the (differential) diagnosis. The transabdominal ultrasound examination is supplemented by color Doppler procedures, contrast-enhanced or intraoperative ultrasound. Computed tomography (CT) should be performed with native images as well as after using modern nonionic, iodine-containing water-soluble contrast agents; multidetector spiral CT is today's standard. If comparable optimal technology is available on-site, (contrast-enhanced) MRI is preferable. Intra-arterial selective angiography has become less important for detecting and characterizing focal liver changes with the advent of tomographic procedures. The question of whether sonography- or CT-guided biopsy of the liver is needed for further diagnostic work-up, whether a wait-and-see approach is justified, or whether surgery is required to clarify the diagnosis should always be answered on a case-by-case basis.     

Radiologische Diagnostik von Lebertumoren

Besides malignant disease, focal liver lesions can also represent benign changes. Among the malignant lesions, in addition to hepatocellular carcinoma, liver metastases should be mentioned. In contrast, benign lesions such as focal nodular hyperplasia and hepatocellular adenoma are rarely encountered. Various radiological procedures are employed for the (differential) diagnosis. The transabdominal ultrasound examination is supplemented by color Doppler procedures, contrast-enhanced or intraoperative ultrasound. Computed tomography (CT) should be performed with native images as well as after using modern nonionic, iodine-containing water-soluble contrast agents; multidetector spiral CT is today’s standard. If comparable optimal technology is available on-site, (contrast-enhanced) MRI is preferable. Intra-arterial selective angiography has become less important for detecting and characterizing focal liver changes with the advent of tomographic procedures. The question of whether sonography- or CT-guided biopsy of the liver is needed for further diagnostic work-up, whether a wait-and-see approach is justified, or whether surgery is required to clarify the diagnosis should always be answered on a case-by-case basis.