Characterization Of Adrenal Masses Research Articles

Current concepts in imaging of adrenal masses.

Adrenal masses are a common entity. With the advent of improved cross-sectional imaging techniques the detection and characterization of adrenal masses has improved dramatically. We review the imaging features of benign and malignant adrenal masses and other entities that may cause mass-like enlargement of the adrenal glands.

Diagnosis of adrenal adenoma: Value of central spot of high‐intensity hyperintense rim sign and homogeneous isointensity to liver on gadolinium‐enhanced fat‐suppressed spin‐echo MR images

Eighty-nine patients with 108 adrenal masses, either adenomas (n = 88) or malignant lesions (n = 20), underwent magnetic resonance imaging (MRI) of the abdomen at 0.5 T for the purpose of determining whether adrenal adenomas could be differentiated from malignant lesions on gadolinium-enhanced fat-suppressed T1-weighted spin-echo (SE) images (Gd-E FS T1WI) and on T2-weighted SE images. The imaging protocol included conventional unenhanced SE T1- and T2-weighted sequences and Gd-E FS T1WI. Three observers independently evaluated signal intensity on unenhanced and enhanced images and also the presence of structures of high signal intensity in the outer margin [hyperintense rim sign (HRS)] or in the center [hyperintense central spot (HCS)] of the adrenal masses. Forty-one (46.5%) of 88 adenomas were homogeneously isointense to liver in unenhanced and enhanced T1-weighted sequences and in T2WI. HCS and HRS were observed in 33/88 (37.5%) and 15/88 (17%) adenomas, respectively, on Gd-E FS T1WI; in contrast, these signs were never revealed in any case of malignant lesions. Sensitivity, specificity, positive predictive value, negative predictive value, and overall accuracy in classifying lesions as suggestive of adenoma were 93%, 90%, 98%, 75%, and 93%, respectively. Visual evaluation of details of tumor structures on Gd-E FS T1WI allows good characterization of adrenal masses. HCS, HRS, and homogeneous isointensity to liver are characteristic signs of adrenal adenomas. J. Magn. Reson. Imaging 1999; 9:304–310. © 1999 Wiley-Liss, Inc.

Diagnosis of adrenal adenoma: value of central spot of high-intensity hyperintense rim sign and homogeneous isointensity to liver on gadolinium-enhanced fat-suppressed spin-echo MR images.

Eighty-nine patients with 108 adrenal masses, either adenomas (n = 88) or malignant lesions (n = 20), underwent magnetic resonance imaging (MRI) of the abdomen at 0.5 T for the purpose of determining whether adrenal adenomas could be differentiated from malignant lesions on gadolinium-enhanced fat-suppressed T1-weighted spin-echo (SE) images (Gd-E FS T1WI) and on T2-weighted SE images. The imaging protocol included conventional unenhanced SE T1- and T2-weighted sequences and Gd-E FS T1WI. Three observers independently evaluated signal intensity on unenhanced and enhanced images and also the presence of structures of high signal intensity in the outer margin [hyperintense rim sign (HRS)] or in the center [hyperintense central spot (HCS)] of the adrenal masses. Forty-one (46.5%) of 88 adenomas were homogeneously isointense to liver in unenhanced and enhanced T1-weighted sequences and in T2WI. HCS and HRS were observed in 33/88 (37.5%) and 15/88 (17%) adenomas, respectively, on Gd-E FS T1WI; in contrast, these signs were never revealed in any case of malignant lesions. Sensitivity, specificity, positive predictive value, negative predictive value, and overall accuracy in classifying lesions as suggestive of adenoma were 93%, 90%, 98%, 75%, and 93%, respectively. Visual evaluation of details of tumor structures on Gd-E FS T1WI allows good characterization of adrenal masses. HCS, HRS, and homogeneous isointensity to liver are characteristic signs of adrenal adenomas.

Characterization of Adrenal Masses Using Unenhanced CT

Characterization of Adrenal Masses Using Unenhanced CT

Characterization of Adrenal Masses Using Unenhanced CT: An Analysis of the CT Literature

Unenhanced CT scanning can reliably characterize incidentally detected adrenal masses when observers use density measurements of the adrenal gland. However, controversy exists as to the optimal density threshold required to differentiate benign from malignant lesions. This study attempts to establish a consensus by performing a pooled analysis of data found in the CT literature.Ten CT reports were analyzed, from which individual adrenal lesion density measurements were obtained for 495 adrenal lesions (272 benign lesions and 223 malignant lesions). Threshold analysis generated a range of sensitivities and specificities for lesion characterization at different density thresholds.Sensitivity for characterizing a lesion as benign ranged from 47% at a threshold of 2 H to 88% at a threshold of 20 H. Similarly, specificity varied from 100% at a threshold of 2 H to 84% at a threshold of 20 H.The attempt to be absolutely certain that an adrenal lesion is benign may lead to an unacceptably low sensitivity for lesi...

Characterization of adrenal masses using unenhanced CT: an analysis of the CT literature.

Unenhanced CT scanning can reliably characterize incidentally detected adrenal masses when observers use density measurements of the adrenal gland. However, controversy exists as to the optimal density threshold required to differentiate benign from malignant lesions. This study attempts to establish a consensus by performing a pooled analysis of data found in the CT literature. Ten CT reports were analyzed, from which individual adrenal lesion density measurements were obtained for 495 adrenal lesions (272 benign lesions and 223 malignant lesions). Threshold analysis generated a range of sensitivities and specificities for lesion characterization at different density thresholds. Sensitivity for characterizing a lesion as benign ranged from 47% at a threshold of 2 H to 88% at a threshold of 20 H. Similarly, specificity varied from 100% at a threshold of 2 H to 84% at a threshold of 20 H. The attempt to be absolutely certain that an adrenal lesion is benign may lead to an unacceptably low sensitivity for lesion characterization. The threshold chosen will depend on the patient population and the cost-benefit approach to patient care.

Adrenal masses: characterization with delayed contrast-enhanced CT.

To evaluate the use of attenuation measurements from early delayed computed tomographic (CT) scans to differentiate benign from malignant lesions of the adrenal glands. Forty-four patients (19 men, 25 women; age range, 21-88 years; mean age, 63 years) with 46 adrenal masses underwent dynamic contrast material-enhanced CT and early delayed CT (range, 12-18 minutes; mean delay, 14 minutes) with similar scanning parameters. Each patient also underwent non-contrast-enhanced CT within 3 months of the contrast-enhanced examination. Attenuation of adrenal masses on each type of scan was measured, and receiver operating characteristic analysis was performed. An attenuation threshold of 24 HU was selected; thus, all lesions with attenuation values of 24 HU or less were considered benign. When this threshold was applied to the results, the sensitivity of characterization of adrenal masses on early delayed scans was 96%, and the specificity was 96%. Adrenal masses detected with contrast-enhanced CT can be characterized as benign or malignant on early delayed scans of the adrenal glands.

Magnetic resonance imaging differentiation of adrenal masses at 1.5 t: t2-weighted images, chemical shift imaging, and gd-dtpa dynamic studies

The purpose of our study was to assess the potential role of spin-echo (SE), chemical shift, and gadolinium-enhanced magnetic resonance imaging (MRI) in the differentiation of adrenal masses. Seventy-two adrenal masses (26 nonhyperfunctioning adenomas, 16 aldosterone-secreting adenomas and 6 other different benign cortical masses, 18 pheochromocytomas, and 6 malignant masses) in 63 patients were evaluated with spin-echo sequences, chemical shift imaging (CSI) and gadolinium diethylenetriamine penta-acetic acid (Gd-DTPA) dynamic studies. Ratios and indices of signal intensity for all examined MRI methods were calculated and examined for significance of difference between different types of adrenal masses. Quantitative magnetic resonance evaluation of adrenal masses showed significant differences (at least alpha < 0.01) between nonhyperfunctioning adenomas vs. pheochromocytomas or vs. malignant lesions or vs. aldosterone-secreting adenomas and between pheochromocytomas vs. malignant lesions. The most specific indicators of adrenal mass character proved to be the CSI ratio based on opposed-phase and in-phase two-dimensional fast low-angle shot (FLASH) images, reflecting lipid content in the lesion, and Gd-DTPA dynamic studies ratios reflecting contrast agent inflow and washout in the lesion: WoMAX/LAST and Dyn1.2-3.2. There was no overlap of CSI ratio between adenomas and pheochromocytomas. The overlap of ranges of CSI ratio between nonhyperfunctioning adenomas and aldosterone-secreting adenomas was only 18.5%. There was no overlap of WoMAX/LAST ratio between adenomas and pheochromocytomas, or adenomas and malignant lesions. The overlap of ranges of Dyn1.2-3.2 ratio between pheochromocytomas and malignant lesions was only 17.6%. MRI enables good visualization and specific characterization of adrenal masses. The optimal MRI protocol for the adrenal region is presented.

An imaging algorithm for the differential diagnosis of adrenal adenomas and metastases.

The purpose of this study was to develop an algorithm using CT and chemical-shift MR imaging for the characterization of adrenal masses in patients with a primary cancer and no other evidence of metastatic disease. Thirty-three patients with 37 adrenal masses (19 metastases, 18 adenomas), all of whom had a known primary cancer, were studied with noncontrast CT and chemical-shift MR imaging (1.5 T). Lesion size and density in Hounsfield units (H) were determined by CT. Adrenal signal intensity normalized to that of spleen was used to calculate adrenal-spleen ratio (ASR), defined as the percentage of signal remaining in the opposed-phase image relative to the in-phase image. Lesions less than or equal to 0 H were classified as benign, lesions greater than 20 H were regarded as malignant, and lesions between 0 and 20 H were regarded as indeterminate. Diagnoses were confirmed by biopsy (for 19 lesions) or by follow-up imaging (for 18 lesions). An imaging algorithm was derived by determining the relative value of CT and MR imaging for diagnosing the lesions. The reimbursement rates for CT-guided biopsy and MR imaging of the abdomen were obtained from Medicare. All 13 lesions of 0 or less H were correctly classified as benign by CT. ASR was less than 70 in 10 of these 13. In another 13 lesions, H was greater than 20; all were malignant and all had an ASR greater than 80. Of 11 CT-indeterminate lesions, four of five adenomas had an ASR less than 70, and four of six metastases had an ASR greater than 80. Two malignant lesions had ASRs between 70 and 80 and were diagnosed by biopsy findings. One CT-indeterminate adenoma had an ASR of 84 and was diagnosed by biopsy findings. The reimbursement rate by Medicare is similar for CT-guided biopsy with pathologic interpretation and for MR imaging of the abdomen. An algorithm was developed for diagnosis of adrenal lesions that uses the density reading on noncontrast CT as the first step, with chemical-shift MR imaging for CT-indeterminate lesions. In this algorithm, lesions of 0 H or less may be regarded as benign and further work-up is not required. Lesions with a density greater than 20 H are likely malignant and should be biopsied when the result will influence management. For CT-indeterminate lesions, we recommend chemical-shift MR imaging. An ASR threshold of 70 indicates a benign lesion, and no further workup is required in these patients. Lesions with an ASR greater than 70 should have a biopsy performed, depending on the clinical situation. The above algorithm is cost-effective and reduces the number of biopsies required without reducing the sensitivity of detecting malignant lesions.

Characterization of adrenal masses with chemical shift MR imaging: how to select echo times.

Characterization of adrenal masses with chemical shift MR imaging: how to select echo times.

Echoplanar MR imaging for characterization of adrenal masses in patients with malignant neoplasms: preliminary evaluation of calculated T2 relaxation values.

We undertook this study to assess the utility of echoplanar MR imaging for distinguishing benign from malignant adrenal masses in patients with known malignant neoplasms. Thirty consecutive patients with 31 adrenal masses and a known malignant neoplasm underwent breath-hold echoplanar MR imaging with a repetition time of 6000 msec and four echo times (40, 80, 120, 160 msec) on a 1.5-T unit before biopsy. Subsequently, 10 masses were shown to be malignant at histologic examination, 12 masses were benign at histologic examination, and nine were thought to be benign because they had not changed in size at follow-up imaging. Mean lesion size was 2.4 +/- 2.1 cm. T2 calculations using regions of interest in the liver and adrenal mass were performed in each patient. The mean calculated T2 value of benign adrenal masses was 70.3 msec (SD, 11.6 msec) versus 104.6 msec (SD, 35.2 msec) for malignant adrenal masses (p = .013). Using a cutoff T2 value of 84 msec, 19 (90%) of 21 benign masses and nine (90%) of 10 malignant masses were correctly classified. The mean adrenal/liver T2 ratio was 1.4 (SD, 0.25) for benign lesions, and 2.1 (SD, 0.78) for malignant lesions (p = .017). Using a cutoff ratio of 1.60, 19 (90%) of 21 benign lesions and eight (80%) of 10 malignant lesions would have been correctly classified. This preliminary work suggests that obtaining T2 calculations from echoplanar MR images of adrenal masses is a useful technique for distinguishing benign from malignant adrenal masses in patients at risk for adrenal metastasis.

MR IMAGING OF THE ADRENAL GLANDS

MR imaging provides an excellent morphologic depiction of normal and abnormal adrenal glands. Although CT scanning remains the primary imaging technique for detecting adrenal lesions, MR imaging is being used increasingly for characterization of adrenal masses. Chemical shift imaging is the most recent MR technique to be evaluated for distinguishing benign from malignant masses, and it appears to be the most reliable; however, further validation of this technique is necessary. In most clinical situations, adrenal lesions thought to be malignant on the basis of MR criteria should still be biopsied. MR imaging is also a useful problem-solving technique after equivocal CT scanning or sonography.

Adrenal masses: differentiation with chemical shift, fast low-angle shot MR imaging.

The purpose of this study was to investigate the efficacy of chemical shift, fast low-angle shot (FLASH) imaging at 1.5 T to differentiate adrenal masses. The materials included patients with adrenocortical adenomas (n = 32), metastatic tumors (n = 17), and pheochromocytomas (n = 4). FLASH images were obtained with breath holding at 100/11 (repetition time msec/echo time msec) (out-of-phase images) and 100/13 (in-phase images) and a flip angle of 20 degrees to differentiate the lipid contents in the adrenal tumors. The signal-intensity (SI) indexes of adrenal masses ([SI on IP - SI on OP]/[SI on IP x 100]), where IP = in-phase image and OP = out-of-phase image, were calculated. All adenomas had SI indexes of more than 5%, while SI indexes of metastatic tumors and pheochromocytomas were less than 5%, with accuracy of 100% in the differentiation between adenoma and nonadenoma. Hyperfunctioning adenoma, however, could not be differentiated from nonhyperfunctioning adenoma. Chemical shift FLASH imaging was superior to the calculated T2 in the characterization of adrenal masses.

Magnetic resonance imaging in the evaluation of lung cancer

MRI is used most efficaciously in the evaluation of patients with bronchogenic carcinoma when employed as a tailored examination designed to answer specific questions relevant to patient management. CT continues to be used more generally in staging lung cancer when imaging beyond conventional chest radiography is required. Specific areas in which MRI can provide important and unique information (which may supplement a CT study) include the following: (1) evaluation of the local extent of superior sulcus tumors, and (2) distinction between stage IIIA (resectable) and stage IIIB (unresectable) tumors. Confirmation of tumor invasion of major mediastinal structures is necessary before depriving a patient of potential curative resection. MRI may contribute important information when CT findings are indefinite, particularly with regard to invasion of major cardiovascular structures (eg, superior vena cava, pulmonary artery, pericardium, and heart); invasion of the tracheal carina or bilateral involvement of main bronchi; and the presence of contralateral mediastinal or hilar lymphadenopathy. MRI should be considered as a primary imaging modality to evaluate central tumors in patients for whom intravenous contrast agents are contraindicated, and as a problem-solving modality when CT is inconclusive in the detection of a possible hilar or mediastinal mass. Other specific applications of MRI include the identification of tumor recurrence in the presence of radiation fibrosis, assessment of the extent of chest wall invasion of peripheral lung tumors, and the noninvasive characterization of adrenal masses. The scope of these MRI applications in patients with lung cancer may expand in the future with refinements in motion suppression techniques, implementation of ultrafast MRI (using variations of the echoplanar method), and further development of MRI spectroscopy and MRI contrast agents.

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.

MR evaluation of adrenal masses at 1.5 T.

We retrospectively studied the value of MR imaging at 1.5 T to distinguish between nonadenomatous (n = 17) and adenomatous (n = 15) adrenal masses on the basis of (1) signal-intensity ratios on T1- and T2-weighted spin-echo images, (2) T2 relaxation times, and (3) T2 relaxation-time ratios. Univariate and then multivariate logistic regression were applied to these quantitative parameters to determine which of these best discriminated nonadenomas from adenomas, and whether or not more than one of these parameters improved the prediction. The adrenal mass/liver signal-intensity ratio on T2-weighted spin-echo images could not be used to differentiate nonadenomas from adenomas. Adrenal mass/fat signal-intensity ratios on T2-weighted spin-echo images, adrenal/liver T2 relaxation-time ratios, and adrenal mass T2 relaxation times were best for distinguishing nonadenomas from adenomas. By using a T2 value of greater than 61 msec, the true-positive ratio/false-positive ratio of differentiating nonadenomas from adenomas was 100%/20%; at greater than 82 msec, it was 64%/0.06%. The adrenal mass/fat signal-intensity ratios on T2-weighted spin-echo images and the adrenal/liver T2 relaxation-time ratios showed similar inherent discriminatory capacity. Overlap remains despite the use of these parameters. On the basis of this preliminary information, we conclude that MR has merit for the characterization of adrenal masses at 1.5 T. T2 relaxation time of the adrenal mass shows the greatest promise for discriminating nonadenomas from adenomas.

MR characterization of adrenal masses: field strength and pulse sequence considerations.

The authors evaluated the ability of magnetic resonance (MR) imaging at 1.5 T to characterize 28 adrenal masses, using several variables: signal intensity ratios (adrenal/liver and adrenal/fat) on T2- and T1-weighted images, and the calculated T2 relaxation time of the adrenal mass. Signal intensity ratios were unreliable in distinguishing adenomas from nonadenomas. The calculated T2 relaxation time was more useful: All 15 adrenal masses with a T2 of less than 60 msec were adenomas. A T2 greater than 60 msec was less specific and included six metastases, two pheochromocytomas, one adrenal carcinoma, two adrenal hemorrhages, and two nonhyper-functioning adenomas. Therefore, T2 values are more accurate than signal intensity ratios for characterization of adrenal masses at 1.5 T. The unsuitability of previously published criteria determined with 0.35- and 0.5-T systems may reflect the change of T1 and T2 relaxation times with field strength, altering the relative T1 and T2 weighting by a given pulse sequence.