Differentiation of adrenal adenomas from nonadenomas using CT histogram analysis method: A prospective study

Objective

The objective of our study was to prospectively evaluate the effectiveness of computed tomography (CT) histogram analysis method in the differentiation of benign and malignant adrenal masses.

Materials and Methods

Between March 2007 and June 2008, 94 patients (46 males, 48 females, age range: 30-79 years, mean age: 57.7 years) with 113 adrenal masses (mean diameter: 3.03 cm, range: 1.07-8.02 cm) were prospectively evaluated. These included 66 adenomas, 45 metastases and 2 pheochromocytomas. Histogram analysis method was performed using a circular region of interest (ROI) and mean attenuation, total number of pixels, number of negative pixels and subsequent percentage of negative pixels were detected on both unenhanced and delayed contrast-enhanced CT images for each adrenal mass. A mean attenuation threshold of 10 Hounsfield unit (HU) for unenhanced CT and 5% and 10% negative pixel thresholds for both unenhanced and delayed contrast-enhanced CT were calculated by a consensus of at least two reviewers and the correlation between mean attenuation and percentage of negative pixels was determined. Final diagnoses were based on imaging follow-up of minimum 6 months, biopsy, surgery and adrenal washout study.

Results

51 of 66 adenomas (77.3%) showed attenuation values of ≤10 HU and 15 (22.7%) adenomas showed more than 10 HU on unenhanced CT. All of these adenomas contained negative pixels on unenhanced CT. Eight of 66 (12.1%) adenomas showed a mean attenuation value of ≤10 HU on delayed contrast-enhanced scans and 45 adenomas (68.2%) persisted on containing negative pixels. All metastases had an attenuation value of greater than 10 HU on unenhanced CT images. 21 of 45 (46.6%) metastases contained negative pixels on unenhanced images but only seven metastases (15.5%) had negative pixels on delayed contrast-enhanced images. Two pheochromocytomas had negative pixels on both unenhanced and delayed contrast-enhanced CT images. Increase in the percentage of negative pixels yielded high correlation with mean attenuation decreases, both on unenhanced and delayed contrast-enhanced CT. Our sensitivity was 90.9% for the 10% negative pixel percentage threshold compared to 77.2% sensitivity for ≤10 HU mean attenuation threshold for unenhanced CT. Both methods gave a 100% specificity for the diagnosis of adenoma. We also obtained a 37.9% sensitivity for 5% negative pixel threshold and a slightly lower sensitivity of 28.8% for 10% negative pixel threshold compared to the 12.1% sensitivity of ≤10 HU mean attenuation threshold while maintaining 100% specificity for contrast-enhanced CT.

Conclusion

The CT histogram analysis is a simple and easily applicable method which provides higher sensitivity than the commonly used 10 HU threshold mean attenuation method of unenhanced CT and can replace it for the diagnosis of an adenoma. But with contrast-enhanced CT, although 100% specificity is being maintained, the sensitivities obtained are very poor for each method and is therefore likely to limit CT histogram analysis to be used as a clinically useful adjunct in the diagnosis of adenoma.     

Low-density pheochromocytoma on CT: a mimicker of adrenal adenoma

OBJECTIVE: Attenuation values on CT of less than 10 H are considered characteristic of adrenal adenomas. Adrenal pheochromocytomas can infrequently contain fat that could result in low attenuation on CT. The purpose of our study was to determine if pheochromocytomas could be confused with adenomas by virtue of their attenuation values on unenhanced CT. MATERIALS AND METHODS: CT attenuation and size of nine adrenal nodules producing pheochromocytoma syndrome were measured on unenhanced CT in nine patients. For five patients who received IV contrast material, washout profiles were also calculated. RESULTS: Two of the nine patients had adrenal lesions with attenuation values of less than 10 H; one had a pheochromocytoma with an attentuation of 9.0 H, and the other had a medullary hyperplasia with an attenuation of 1.8 H. These two nodules showed evidence of microscopic fat at histologic examination. No macroscopic fat was seen on the CT scans. The remaining seven patients had lesions with attenuation values exceeding 10 H (mean value, 25.6 H; range, 1.8-41 H). Mean diameter of the nine tumors (including the hyperplastic nodule) was 3.2 cm (range, 0.8-6.7 cm; SD, +/- 2.3 cm). The two low-attenuation lesions also mimicked adenomas by displaying more than 60% contrast washout on 10-min-delayed contrast-enhanced scans, unlike the other three pheochromocytomas for which we had washout data. CONCLUSION: On CT, pheochromocytomas may have attenuation values less than 10 H and also may display more than 60% washout of contrast agents on delayed scanning. Adrenal pheochromocytomas should be included with adenomas in the differential diagnosis both for masses with low attenuation on unenhanced CT and for lesions exhibiting a high percentage of contrast washout.     

Characterization of non-secreting adrenal nodules (incidentalomas): role of multiphasic spiral computerized tomography

PURPOSE: To evaluate the diagnostic yield of multiphasic helical CT in the characterization of single non functioning adrenal nodules (incidentalomas) less than 50 mm in diameter. Emphasis was given to the possible replacement of unenhanced with delayed scans in cancer patients undergoing staging procedures. MATERIAL AND METHODS: Sixty patients with single adrenal nodules (30 of them neoplastic and 30 non-neoplastic) were examined with thin unenhanced scans (5 mm), early scans after administration of a contrast agent (120 mL at 2.5 mL/s with 60 s delay) and late scans (30 min delay). RESULTS: On both unenhanced and late scans a threshold could be selected on the Hounsfield unit scale which guaranteed absolute specificity in the characterization of adenomas (100% specificity) with very high sensitivity (93% at both scans): this threshold was 19 HU on unenhanced and of 41 HU on late scans. In contrast, at early delayed scanning the threshold which guaranteed 100% specificity was associated with negligible sensitivity (30%). The evaluation of lesion size had no diagnostic value, since the mean diameter of both benign and malignant nodules was of 25 mm. CONCLUSIONS: Late scans have diagnostic yield comparable to unenhanced scans: at the selected delay (30 min), benign lesions nearly always have lower attenuation values than malignant nodules and can be diagnosed with confidence when they exhibit mean attenuation values lower than 41.     

Delayed enhanced CT of lipid-poor adrenal adenomas

OBJECTIVE. Although representing a minority of adrenal adenomas, the lipid-poor variety cannot be accurately identified on unenhanced CT or chemical shift MR imaging. We compared the delayed contrast-enhanced CT features of lipid-poor adenomas with those of lipid-rich adenomas and of adrenal nonadenomas to determine whether there were differences in the washout features between these groups of lesions. SUBJECTS AND METHODS. Eighteen proven lipid-poor adenomas, 56 lipid-rich adenomas, and 40 adrenal nonadenomas underwent CT before, immediately after, and 15 min delay after IV contrast injection. Region-of-interest measurements were made of all adrenal lesions at the three time points. The degree of enhancement, enhancement washout, percentage enhancement washout, and relative percentage enhancement washout were calculated for each adrenal mass. Pooled data were analyzed statistically. Optimal threshold values for diagnosing adrenal adenomas were also determined. RESULTS. The mean CT attenuation of lipid-poor adenomas was significantly higher than that of lipid-rich adenomas at all three phases but not significantly different from that of nonadenomas. The mean percentage enhancement washout on images obtained 15 min after administration of contrast material was similar for lipid-rich and lipid-poor adenomas but was significantly higher than that of nonadenomas. The mean relative percentage enhancement washout was significantly different among all three groups. CONCLUSION. Lipid-poor adenomas cannot be differentiated from adrenal nonadenomas on the basis of a single mean attenuation value. However, 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%.     

Adrenal lesions: characterization with fused PET/CT image in patients with proved or suspected malignancy--initial experience

PURPOSE: To retrospectively evaluate the accuracy of the fused positron emission tomographic (PET)/computed tomographic (CT) image for characterization of adrenal lesions in patients who have proved malignancy or are suspected of having malignancy. MATERIALS AND METHODS: Institutional review board approval was received for this retrospective HIPAA-compliant study, and informed consent was waived. Forty-one adrenal lesions in 38 patients (21 men, 17 women; mean age, 66 years; range, 37-86 years) were evaluated with PET/CT. Of the 41 lesions, nine were assumed to be malignant with documentation of enlargement (n = 8) or reduction in size in response to treatment (n = 1), and 32 were assumed to be benign with documentation of stability for 6 months (n = 31) or with confirmation with biopsy results (n = 1). The PET examination findings were positive when adrenal lesion maximum standardized uptake values (SUVs) exceeded hepatic maximum SUVs. CT contrast medium washout analysis was used to further characterize two lesions with PET findings positive for malignancy. The t test was used to assess significant (P < .05) differences between fluorine 18 fluorodeoxyglucose (FDG) uptake of benign lesions and that of malignant lesions. RESULTS: At PET/CT, findings for all malignant lesions were positive (mean adrenal lesion-liver activity ratio, 4.04; range, 1.53-17.08). Of the 32 benign lesions, most (30 of 32) had activity less than that of the liver (mean ratio, 0.66; range, 0.22-0.94). PET/CT demonstrated sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of 100%, 93.8%, 81.8%, 100%, and 95.1%, respectively. Incorporating contrast material-enhanced CT with delayed imaging increased specificity to 100% because two lesions with PET findings positive for malignancy were characterized as benign. There was a significant difference between maximum SUV (P < .05) and the ratio of adrenal lesion-liver FDG activity (P < .001) in benign versus malignant adrenal lesions. CONCLUSION: PET/CT provides a powerful combination of functional and attenuation information for adrenal lesion characterization. All malignant lesions were detected at PET/CT, with no false-negative results.     

State-of-the-art adrenal imaging.

The adrenal gland is a common site of disease, and detection of adrenal masses has increased with the expanding use of cross-sectional imaging. Radiology is playing a critical role in not only the detection of adrenal abnormalities but in characterizing them as benign or malignant. The purpose of the article is to illustrate and describe the appropriate radiologic work-up for diseases affecting the adrenal gland. 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). If results of CT are not diagnostic, magnetic resonance (MR) and nuclear medicine imaging examinations should be performed. CT has become the study of choice to differentiate a benign adenoma from a metastasis in the oncology patient. If the attenuation of the adrenal gland is over 10 HU at nonenhanced CT, contrast material-enhanced CT should be performed and washout calculated. Over 50% washout of contrast material on a 10-minute delayed CT scan is diagnostic of an adenoma. For adrenal lesions that are indeterminate at CT in the oncology patient, chemical shift MR imaging or adrenal biopsy should be performed. Certain features can be used by the radiologist to establish a definitive diagnosis for most adrenal masses (including carcinoma, infections, and hemorrhage) based on imaging findings alone.     

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。     

Distinguishing benign from malignant adrenal masses: multi-detector row CT protocol with 10-minute delay

PURPOSE: To retrospectively evaluate the accuracy of precontrast attenuation, relative percentage washout (RPW), and absolute percentage washout (APW) in distinguishing benign from malignant adrenal masses at multi-detector row computed tomography (CT). MATERIALS AND METHODS: This HIPAA-compliant retrospective study had institutional review board approval; the need for informed consent was waived. One hundred twenty-two adrenal masses were evaluated in 99 patients (51 men, 48 women; age range, 37-86 years) who had undergone CT performed according to the study protocol and who either were given a pathologic diagnosis or underwent follow-up imaging. Unenhanced images were obtained before administration of 120 mL of an intravenous contrast agent with a 75-second scan delay. Delayed images were obtained after 10 minutes. RPW and APW were computed. Receiver operating characteristic (ROC) analysis was performed to compare mean attenuation and both RPW and APW. Analysis was first performed with the exclusion of pheochromocytomas, myelolipomas, and cysts. Precontrast attenuation criteria specific for benignity or malignancy were determined, and ROC analysis of results for the entire nonpheochromocytoma group was then performed. RESULTS: By using an RPW of 37.5% and excluding cysts and myelolipomas, all malignant lesions were detected with a sensitivity of 100% (17 of 17 lesions) and a specificity of 95% (90 of 95 lesions). Area under the binomial ROC curve (A(z)) values were 0.912, 0.985, and 0.892 for precontrast attenuation, RPW, and APW, respectively. Precontrast attenuation of less than 0 or more than 43 HU indicated benign and malignant entities, respectively. Incorporation of these criteria into the APW analysis yielded a sensitivity of 100% (17 of 17 lesions) and a specificity of 98% (93 of 95 lesions) for a threshold washout value of 52.0%. This attenuation-corrected APW generated the greatest A(z) value (ie, 0.988). Combining all the information available from the protocol yielded a sensitivity of 100% (17 of 17 lesions) and a specificity of 98% (98 of 100 lesions) for differentiating benign from malignant masses. CONCLUSION: Precontrast attenuation of less than 0 HU supercedes the washout profile in the evaluation of an individual adrenal mass. Noncalcified, nonhemorrhagic adrenal lesions with precontrast attenuation of more than 43 HU should be considered suspicious for malignancy.     

Solitary pulmonary nodule: characterization with combined wash-in and washout features at dynamic multi-detector row CT

PURPOSE: To prospectively assess the accuracy of combined wash-in and washout characteristics at dynamic contrast material-enhanced multi-detector row computed tomography (CT) in distinguishing benign from malignant solitary pulmonary nodules. MATERIALS AND METHODS: Institutional review board approval and informed consent were obtained. The study included 107 patients (62 men, 45 women; mean age, 55 years; range, 22-81 years) with a solitary pulmonary nodule. After unenhanced CT (2.5-mm collimation) scans were obtained, dynamic CT was performed by using a helical technique (series of images obtained throughout the nodule, with 2.5-mm collimation, at 30, 60, 90, and 120 seconds and 4, 5, 9, 12, and 15 minutes) after intravenous injection of contrast medium (120 mL). Tissue diagnosis was made in 70 nodules, and follow-up images showed benignancy in the remaining 37 (no change in size, n = 32; decrease in size, n = 5). CT findings were analyzed in terms of wash-in and washout of contrast medium. Sensitivity, specificity, and accuracy for malignant nodules were calculated by considering both the wash-in and washout characteristics at dynamic CT. RESULTS: There were 49 malignant and 58 benign nodules. When diagnostic criteria for malignancy of both wash-in of 25 HU or greater and washout of 5-31 HU were applied, sensitivity, specificity, and accuracy for malignancy were 94% (46 of 49 nodules), 90% (52 of 58 nodules), and 92% (98 of 107 nodules), respectively. Of 58 benign nodules, 27 showed less than 25 HU wash-in, 14 showed persistent contrast enhancement without washout and with wash-in of 25 HU or greater, and 11 showed washout greater than 31 HU and wash-in of 25 HU or greater. CONCLUSION: Evaluation of solitary pulmonary nodules by analyzing combined wash-in and washout characteristics at dynamic contrast-enhanced multi-detector row CT showed 92% accuracy for distinguishing benign nodules from malignant nodules.     

Adrenocortical carcinoma: contrast washout characteristics on CT

OBJECTIVE: The purpose of this study was to characterize pathologically proven adrenocortical carcinoma by examination of washout attenuation characteristics on contrast-enhanced CT images. CONCLUSION: Adrenocortical carcinoma has relative contrast retention on delayed contrast-enhanced CT. All tumors in this series had a relative percentage washout less than 40%, a finding consistent with malignant disease.     

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.     

Soft-tissue tumors: value of static and dynamic gadopentetate dimeglumine-enhanced MR imaging in prediction of malignancy

PURPOSE: To prospectively evaluate static and dynamic gadopentetate dimeglumine-enhanced magnetic resonance (MR) imaging relative to nonenhanced MR imaging in differentiation of benign from malignant soft-tissue lesions and to evaluate which MR imaging parameters are most predictive of malignancy, with associated interobserver variability. MATERIALS AND METHODS: One hundred forty consecutive patients (78 male patients [median age, 51 years], 62 female patients [median age, 53 years]) with a soft-tissue mass underwent nonenhanced static and dynamic contrast material-enhanced MR imaging. Diagnosis was based on histologic findings in surgical specimens (86 of 140), findings at core-needle biopsy (43 of 140), or results of all imaging procedures with clinical follow-up (11 of 140). Multivariate logistic regression analysis was used to identify the best combination of MR imaging parameters that might be predictive of malignancy. Subjective overall performance of two observers was evaluated with receiver operating characteristic analysis. RESULTS: For subjective overall diagnosis, area under the receiver operating characteristic curve, a measure for diagnostic accuracy, was significantly larger for combined nonenhanced and contrast-enhanced MR imaging than it was for nonenhanced MR imaging alone, with no significant difference between observers. Multivariate analysis of all lesions revealed that combined nonenhanced static and dynamic contrast-enhanced MR imaging parameters were significantly superior to nonenhanced MR imaging parameters alone and to nonenhanced MR imaging parameters combined with static contrast-enhanced MR imaging parameters in prediction of malignancy. The most discriminating parameters were presence of liquefaction, start of dynamic enhancement (time interval between start of arterial and tumor enhancement), and lesion size (diameter). Results for extremity lesions were the same, with one exception: With dynamic contrast-enhanced MR imaging parameters, diagnostic performance of one observer did not improve. CONCLUSION: Static and dynamic contrast-enhanced MR imaging, when added to nonenhanced MR imaging, improved differentiation between benign and malignant soft-tissue lesions.     

Three-phase dynamic breast magnetic resonance imaging with two-way subtraction

OBJECTIVE: This study was undertaken to introduce a new breast magnetic resonance (MR) imaging technique, 3-phase dynamic MR imaging with 2-way subtraction, and to examine the morphologic and kinetic features of malignant and benign breast lesions using this technique. METHODS: In 99 breasts from 89 consecutive women with suspicious breast lesions (age range: 32-72 years, mean = 48.2 years), MR imaging was performed using a fat-saturated, sagittal, gradient-echo sequence in 3 phases (1 precontrast and 2 postcontrast scans). Two-way subtraction was performed: standard subtraction (early postcontrast minus precontrast scans) and reverse subtraction (early postcontrast minus late postcontrast scans). A radiologist interpreted all the images, described the breast lesions (using the Breast Imaging Reporting and Data System MR lexicon), and assessed the lesions prospectively as being benign or malignant. The lesions with at least 1 malignant feature were classified as malignant. The MR classifications were compared with the biopsy or follow-up results. RESULTS: Sixty-five (65.7%) breast lesions were malignant, and 34 (34.3%) were benign. Forty-two (97.7%) of the 43 cases of microinvasive or invasive ductal cancer showed malignant morphologic features, and 38 (88.4%) showed washout kinetics. Eighteen (81.8%) of the 22 cases of ductal carcinoma in situ showed malignant morphologic features, and 11 (50.0%) showed washout kinetics. Twenty-nine (85.3%) of the 34 benign lesions showed neither malignant morphologic features nor washout kinetics. The sensitivity and specificity were 92.3% and 91.2% by morphologic analysis and 93.8% and 85.3% by the combined method (morphology plus kinetic analysis), respectively. CONCLUSIONS: This study demonstrated that 3-phase dynamic breast MR imaging with 2-way subtraction and a maximum intensity projection (MIP) image is a simple and useful technique for identifying breast lesions. Although the addition of the kinetic criteria enhanced the sensitivity at the cost of specificity, radiologists can diagnose a malignant lesion showing non-mass-like enhancement more confidently using reverse subtraction imaging. Therefore, this study proposes 3-phase dynamic imaging with 2-way subtraction and an MIP image as one of the standard protocols of breast MR imaging.     

Re-evaluation of pheochromocytomas on delayed contrast-enhanced CT: washout enhancement and other imaging features

The purpose of this study was to retrospectively evaluate the enhancement washout and other imaging features of pheochromocytomas on delayed contrast-enhanced CT. Twenty-four patients with 31 pathologically confirmed pheochromocytomas were examined using unenhanced, early and delayed contrast-enhanced CT. The range of their APEW (absolute percentage of enhancement washout) or RPEW (relative PEW) values was analyzed. The other CT features including cystic or necrotic change, calcification, and hemorrhage were also determined by a pathologic correlation. Of the 31 pheochromocytomas, 10 (32%) had APEW values of 60% or less and RPEW values of 40% or less. Fourteen (45%) had APEW values >60% and RPEW values >40%. CT showed cystic or necrotic changes in 11 pheochromocytomas (35%) and calcification (10%) in 3. Nineteen pheochromocytomas showed cystic or necrotic changes on early contrast-enhanced CT, but eight of these lesions showed late enhancement on delayed contrast-enhanced CT, which pathologically corresponded to myxoid degeneration. The unenhanced CT showed hemorrhage in 23 pheochromocytomas, but the pathology examinations showed hemorrhage in 15 lesions. Many pheochromocytomas can be misdiagnosed as adenomas on CT due to the high enhancement washout values. Delayed contrast-enhanced CT can detect myxoid degeneration with late enhancement, which is seen as a cystic or necrotic change on early contrast-enhanced CT.     

Benign or malignant?: differentiating breast lesions with computed tomography attenuation values on dynamic computed tomography mammography

OBJECTIVE: To evaluate enhancement effects of breast lesions with dynamic computed tomography (CT) and to determine characteristics to aid in differential diagnosis of benign and malignant lesions. METHODS: One hundred seventy-six women underwent preoperative dynamic CT, in which they were scanned with rapid injection of contrast media (3 mL/s) after 30 seconds and 2 minutes (early and delayed phases, respectively). The CT values and enhancement patterns of malignant lesions (n = 154) were compared with those of benign lesions (n = 22), and the cut point of CT values with the best validity was analyzed. RESULTS: The CT values of malignant lesions were higher than those of benign lesions in both phases (P < 0.0001). The cut point was determined to be 60 Hounsfield units (HU) in the early phase (44% validity, 90% sensitivity). Washout and plateau patterns were more commonly seen in the malignant group (73% specificity). CONCLUSIONS: The analysis of enhancement effects on CT may lead to more appropriate differentiation of benign and malignant lesions.     

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.     

18F-FDG PET/CT in the evaluation of adrenal masses.

Our purpose was to evaluate the performance of (18)F-FDG PET/CT, using data from both the PET and the unenhanced CT portions of the study, in characterizing adrenal masses in oncology patients. METHODS: One hundred seventy-five adrenal masses in 150 patients referred for (18)F-FDG PET/CT were assessed. Final diagnosis was based on histology (n = 6), imaging follow-up (n = 118) of 6-29 mo (mean, 14 mo), or morphologic imaging criteria (n = 51). Each adrenal mass was characterized by its size; its attenuation on CT, expressed by Hounsfield units (HU); and the intensity of (18)F-FDG uptake, expressed as standardized uptake value (SUV). Receiver operating characteristic curves were drawn to determine the optimal cutoff values of HU and SUV that would best discriminate between benign and malignant masses. RESULTS: When malignant lesions were compared with adenomas, PET data alone using an SUV cutoff of 3.1 yielded a sensitivity, specificity, positive predictive value, and negative predictive value of 98.5%, 92%, 89.3%, 98.9%, respectively. For combined PET/CT data, the sensitivity, specificity, positive predictive value, and negative predictive value were 100%, 98%, 97%, 100%, respectively. Specificity was significantly higher for PET/CT (P < 0.01). Fifty-one of the 175 masses were 1.5 cm or less in diameter. When a cutoff SUV of 3.1 was used for this group, (18)F-FDG PET/CT correctly classified all lesions. CONCLUSION: (18)F-FDG PET/CT improves the performance of (18)F-FDG PET alone in discriminating benign from malignant adrenal lesions in oncology patients.     

Thallium-201 scintigraphy in bone and soft-tissue tumors: a comparison of dynamic, early and delayed scans

OBJECTIVE: It has been reported that delayed scan of thallium-201 (201Tl) scintigraphy is useful for differentiating malignant tumors from benign lesions and for evaluating treatment response. However, physiological muscle uptake which usually increases in delayed scans, often makes it difficult to evaluate 201Tl uptake and its washout in bone and soft-tissue tumors. The purpose of this study was to evaluate whether the delayed scan is necessary and whether a dynamic scan is useful in the evaluation of bone and soft-tissue tumors. METHODS: We studied 175 cases of bone and soft-tissue tumors (malignant 45, benign 130). Dynamic scans were acquired every 5 seconds for 10 minutes after 201Tl injection, and time activity curves (TACs) were generated by adaptive smoothing methods. Early and delayed scans were acquired at 10-15 minutes and 2 hours after injection. 201Tl images were visually interpreted and the radioactivity count ratio (T/N) of tumors to normal tissues and washout rate [WR = (early T/N - delayed T/N)/early T/N] were defined. RESULTS: When there were no 201Tl uptake in dynamic (n = 67) and early scans (n = 68), no tumor uptake was also appreciated in delayed scans, and all but two cases of negative scans were benign. In 107 lesions, although there were significant differences in T/Ns between malignant and benign lesions both on early scans (2.84 +/- 1.45 vs. 2.05 +/- 1.13, p < 0.05) and delayed scans (2.17 +/- 1.03 vs. 1.58 +/- 0.64, p < 0.05), there was a substantial overlap. The T/Ns decreased in delayed scans (i.e., WR > 0) in 100 of 107 cases due to increase of surrounding muscle uptake, and there was no difference in WR between malignant tumors and benign lesions (0.21 +/- 0.14 vs. 0.19 +/- 0.14). CONCLUSIONS: For evaluating bone and soft-tissue tumors, delayed scan had little clinical usefulness and it may be time consuming. Dynamic scan would be useful for demonstrating the differences between tumor blood flow and 201Tl uptake in tumors.     

原发性肾脏罕少见良性肿瘤的CT、MRI 表现与临床病理分析

目的：分析和探讨肾脏罕少见良性肿瘤的 CT、MRI 影像学表现及临床病理分析,提高肾脏罕少见良性肿瘤的诊断准确性。方法回顾性分析本院9例经手术及病理证实的肾脏罕少见良性肿瘤的 CT 及 MRI 影像学资料,分析其影像学特点和病理特征。结果入组病例分别为混合型上皮间质肿瘤(MESTK),囊性肾瘤(CN),平滑肌瘤(RL),嗜酸细胞腺瘤(RO)。病变分布情况：6例位于左肾,3例位于右肾。瘤体大小：长径2.5~8.9 cm,平均5.7 cm;短径2.5~8.4 cm,平均4.9 cm。形态：类圆形或椭圆形(n=7),不规则形(n=2)。9例病灶突出于肾轮廓外。MESTK 呈多囊性病变,增强扫描囊性成分未见明确强化,囊壁及粗间隔可见强化。CN 呈囊性病灶,平扫可见斑片状钙化,增强扫描囊性成分未见明确强化,病灶可见强化分隔影。RL 的 CT 和 MRI 平扫密度/信号不均匀,可见斑片状坏死;病灶增强扫描皮质期及髓质期明显强化,延迟期强化程度减退。RO 1例 MRI 平扫 T1 WI 呈不均匀低信号;T2 WI 呈不均匀高信号;CT 病灶密度欠均匀,平扫以等密度为主;增强扫描皮质期、髓质期病变呈明显不均匀强化,排泄期强化程度下降,中心瘢痕可见轻度延迟强化。结论肾脏罕少见良性肿瘤具有一定的 CT、MRI 影像学特点,结合其临床病理特点,可以提高肾脏罕少见恶性肿瘤的诊断和鉴别诊断。     

Hepatic lesion detection and characterization: value of nonenhanced MR imaging, superparamagnetic iron oxide-enhanced MR imaging, and spiral CT-ROC analysis

PURPOSE: To determine the accuracy for detection and characterization of focal hepatic lesions of nonenhanced, superparamagnetic iron oxide (SPIO)-enhanced, or a combination of nonenhanced and SPIO-enhanced MR imaging and contrast-enhanced spiral computed tomography (CT). MATERIALS AND METHODS: Spiral CT and T2-weighted SPIO-enhanced (ferucarbotran-enhanced) MR imaging were performed in 35 patients within 2 weeks before surgery for malignant hepatic lesions. Only malignant lesions with histopathologic proof were considered. A total of 875 images with and 800 images without focal lesions were presented to five readers, who were asked to assess the presence and characterization of lesions by using a five-point confidence scale. Receiver operating characteristic analysis was performed. RESULTS: Nonenhanced and SPIO-enhanced images together and SPIO-enhanced images alone yielded the best performance for lesion detection. No differences were found among all imaging techniques with regard to lesion characterization (benign vs malignant). The combined approach resulted in larger area under the ROC curve (A(z) = 0.9062) and accuracy (85.3%) (P < 0.02), as compared with SPIO-enhanced MR imaging (A(z) = 0.8667; accuracy, 73.1%). CONCLUSION: SPIO-enhanced T2-weighted MR imaging was more accurate than nonenhanced T1-weighted and T2-weighted MR imaging and contrast-enhanced spiral CT for the detection of focal hepatic lesions. The combined analysis of nonenhanced and SPIO-enhanced images was more accurate in the characterization of focal hepatic lesions than was review of SPIO-enhanced images alone.