Adrenal masses: quantification of fat content with double-echo chemical shift in-phase and opposed-phase FLASH MR images for differentiation of adrenal adenomas

PURPOSE

To quantify fat content in adrenal lesions with double-echo chemical shift magnetic resonance (MR) imaging in a phantom study and to differentiate adrenal adenomas from other adrenal masses by assessing fat content in a clinical study.

MATERIALS AND METHODS

The study consisted of two parts: a phantom study and a clinical study. To explore the effect of the T1 value on in- and opposed-phase MR images of fat-containing tissues, phantom models with various proportions of fat and gadopentetate dimeglumine concentrations were implemented. Signal intensity (SI) indexes ([SI in-phase - SI opposed-phase]/SI in-phase) were calculated with double-echo fast low-angle shot (FLASH) MR imaging. In the clinical study, 23 patients with 28 adrenal masses (16 adrenal adenomas, nine adrenal metastases, and three pheochromocytomas) underwent double-echo FLASH MR imaging, and SI indexes were calculated.

RESULTS

SI index reached a maximum of 0.87 at 53% fat fraction for gadopentetate dimeglumine concentration at 0.5 mmol/L as the simulated T1 of the adrenal mass. The SI indexes of the adrenal adenomas, adrenal metastases, and pheochromocytomas, respectively, were 0.36, -0.15, and -0.07, and estimated fat fraction from the phantom study was 26.5%, 0%, and 0%. All adrenal adenomas contained fat on double-echo FLASH images. There was no overlap in SI index between adenomas and other tumors.

CONCLUSION

Preliminary experience indicates that quantitative measurement of the fat fraction of adrenal masses is possible with the double-echo chemical shift FLASH technique and allows for differentiating adrenal adenomas from other adrenal masses.

Diagnostic accuracy of helical CT arterial portography and CT hepatic arteriography for hypervascular hepatocellular carcinoma in chronic liver damage. An ROC analysis

PURPOSE

To evaluate the detectability of hypervascular hepatocellular carcinomas (HCCs) in chronic liver damage with helical CT arterial portography (CTAP) and CT hepatic arteriography (CTHA).

MATERIAL AND METHODS

Thirty-nine HCC patients who underwent CTAP and CTHA were studied. Diagnostic abilities of CTAP alone, CTHA alone, or combined CTAP and CTHA were evaluated by receiver operating characteristic (ROC) analysis. Fifty-three images with 53 HCC nodules were evaluated. Tumor size ranged from 5 to 90 mm (mean 22.8 mm). Sensitivities and specificities for all techniques were calculated.

RESULTS

ROC analysis showed the diagnostic ability significantly better with combined CTAP and CTHA (mean area under the ROC curve (Az)=0.95), or CTHA alone (Az=0.93) than CTAP alone (Az=0.87) (p<0.01). Combined CTAP and CTHA showed the best sensitivity (95.0%), followed by CTHA alone (88.1%) and CTAP alone (85.5%). The specificities of all three imaging techniques were relatively low (54.1% for combined CTAP and CTHA, 71.1% for CTHA alone, and 54.1% for CTAP alone) because of perfusion abnormalities of the liver parenchyma.

CONCLUSION

The combination of CTAP and CTHA is superior to CTAP alone for detection of hypervascular HCCs. However, its specificity was relatively low in chronic liver damage.

Diffuse perfusion abnormality of the liver parenchyma on angiography-assisted helical CT in relation to cirrhosis and previous treatments: a potential diagnostic pitfall for detecting hepatocellular carcinoma

We evaluated diffuse perfusion abnormality of the liver parenchyma in relation to cirrhosis and previous treatments and estimated its potential limitation in detecting hepatocellular carcinomas (HCCs) on CT arterial portography (CTAP) and CT hepatic arteriography (CTHA). Sixty-one patients of liver cirrhosis with or without HCC received both CTAP and CTHA. Irregular defects of enhancement of the liver parenchyma on CTAP were noted in 37 of 61 patients (60.7%) and compensatory arterial perfusion in these defects on CTHA was noted in 30 of 37 patients (81.1%). Most patients had segmental or mixed patterns of enhancement. In patients with severe cirrhosis, irregular enhancement was often noted. The irregularity was also more often in patients who had had previous treatments. Four of 40 HCC nodules in 18 patients with severe irregular perfusion were not detected on CTAP and CTHA. Diffuse perfusion abnormalities of the liver parenchyma on CTAP and CTHA would decrease the accuracy of tumor detection in HCC patients.

MRI of arachnoid granulations within the dural sinuses using a FLAIR pulse sequence

The purpose of the study was to assess the signal intensities of arachnoid granulations within the dural sinuses using the FLAIR sequence for differentiation of space-occupying lesions in and adjacent to the dural sinuses. We retrospectively reviewed MR images of the brain of 1118 consecutive subjects, ranging in age from 0 to 93 years (mean 57.2 years). Nodules within the dural sinuses with signal intensities similar to that of cerebrospinal fluid (CSF) on both T1 and T2 weighted images were defined as arachnoid granulations. The location, signal intensity on T1 weighted spin echo (SE), T2 weighted fast SE and FLAIR images, the impression on the inner table of the skull, and the size of the lesion were assessed. 112 subjects (10.0%), age range 4-89 years old (mean 58.9 years), were found to have 134 arachnoid granulations. The commonest location was the transverse sinus, with 115 granulations (85.8%). The prevalence of the granulations showed a peak in the sixth decade of age. All granulations were isointense relative to CSF on T2 weighted images and almost all lesions were isointense relative to CSF on T1 weighted images. On FLAIR images, 90.3% of the granulations were isointense relative to CSF and the other 9.7% granulations were slightly hyperintense compared with the CSF. 21 (15.7%) subjects showed impressions on the inner table; one case involved the outer table. In conclusion, arachnoid granulations were isointense or slightly hyperintense relative to CSF on FLAIR. FLAIR images are helpful in differentiating arachnoid granulations from other dural sinus lesions or skull lesions which have an intensity similar to that of CSF on T1 weighted and T2 weighted images.

Intraarterial catheter thrombolytic therapy for acute peripheral arterial occlusions

Intraarterial thrombolytic therapy was performed in 36 patients with acute arterial occlusions of the extremities. Intraarterial thrombolytic therapy was effective in 19 of 24 patients (79.2%) with embolic occlusions. However, the results were poor in patients who had multiple arterial occlusions including those at sites other than the extremities. Only four of 12 patients (33.3%) with thrombotic occlusions had good initial technical results. Six patients died shortly after the thrombolytic procedure, and seven patients underwent amputation. The long-term patency rate of 21 patients who were treated successfully was 92.7% after one year and 74.6% after five years. Intraarterial catheter thrombolytic therapy was effective for embolic occlusion even when more than six hours had elapsed from the onset of symptoms. The indications for thrombotic occlusions may be limited, since associated marked atherosclerotic change was often present.

MR imaging of Tornwaldt's cysts

OBJECTIVE

The purpose of this study was to assess the characteristics of Tornwaldt's cysts as revealed by routine MR studies.

MATERIALS AND METHODS

We retrospectively reviewed MR images of the brain in 1208 consecutive subjects who ranged in age from 3 weeks to 93 years (mean, 57.1 years). The signal intensity, shape, and size of Tornwaldt's cysts were assessed. Patients with Tornwaldt's cysts were then questioned about the presence of persistent nasal discharge, occipital headaches, and halitosis and an unpleasant taste in the mouth and about a history of adenoidectomy.

RESULTS

Tornwaldt's cysts were found in 23 patients (1.9%) who ranged in age from 39 to 78 years (mean, 57.3 years). Of the 23 Tornwaldt's cysts, all were isointense to CSF on T2-weighted images and hyperintense to gray matter on the fluid-attenuated inversion-recovery images. The cysts showed high signal intensity compared with muscle on T1-weighted images. Nineteen cysts were round and four were oval. The mean size of the lesions was 6.0 mm in the major axis and 5.5 mm in the minor axis. Two patients with Tornwaldt's cysts had persistent nasal discharge and occipital headaches, and another patient had occipital headaches alone. None of the patients had undergone an adenoidectomy.

CONCLUSION

Lesions consistent with Tornwaldt's cysts were found in 1.9% of the routine MR studies of the brain. The cysts had high signal intensity on T1-weighted, T2-weighted, and fluid-attenuated inversion-recovery images.

CT differentiation between necrotic and nonnecrotic small bowel in closed loop and strangulating obstruction

BACKGROUND

The purpose of this study was to evaluate computed tomographic (CT) findings for predicting the presence of intestinal necrosis in patients with closed loop and strangulating obstruction of the small bowel.

METHODS

Twenty-five patients with surgically confirmed closed loop and strangulating obstruction were divided into two groups with (n = 16) and without (n = 9) intestinal necrosis. By using univariate and multivariate statistical procedures, we evaluated the differences in CT findings between the two groups on the basis of the following six findings: bowel dilatation of strangulated loops (bowel dilatation), wall thickening of strangulated intestines (wall thickening), ascites, vascular dilatation of affected mesenteries (vascular dilatation), elevation of mesenteric attenuation (mesenteric attenuation), and radial distribution of the mesenteric vessels (radial distribution).

RESULTS

Of the six findings, ascites, vascular dilatation, mesenteric attenuation, and radial distribution provided significant discriminating findings between the two groups on univariate analysis. On multivariate analysis, mesenteric attenuation was the most important discriminative factor, followed by radial distribution and ascites. Using these three parameters, the CT was correlated with the surgical findings in 15 of the 16 patients in the necrosis group (sensitivity = 93.8%) and in eight of the nine patients in the nonnecrosis group (specificity = 88.9%). The overall accuracy was 92.0%.

CONCLUSIONS

Mesenteric attenuation, radial distribution, and ascites, depicted on CT differentiate well between necrosis and nonnecrosis of the small bowel in patients with closed loop and strangulating obstruction.

Embolization for ruptured superior mesenteric artery aneurysms

Superior mesenteric artery (SMA) aneurysms are very uncommon. They are difficult to detect until they rupture and cause hypovolaemic shock. We performed embolization in four cases of aneurysm of branches of the superior mesenteric artery, succeeding in three cases without the need for surgical treatment. In the first case, the aneurysm was excised because of migration of a microcoil into the left hepatic artery. It was not retrieved because sufficient blood flow to the liver was shown on angiography after migration and no ischaemic change of liver was detected on laparotomy. In the second case, the aneurysm arose from the anterior pancreaticoduodenal artery. In the third case, the patient had two SMA aneurysms; one had been resected at surgery, another was revealed on follow-up angiography and embolized with microcoils. The fourth patient had a jejunal artery aneurysm with extravasation; haemostasis was achieved by packing it. In all four cases, no major complications were observed in the clinical course after embolization. Microcoils were considered to be the desirable embolic material, in order to prevent post-therapeutic ischaemic change. Embolization should be the treatment of choice for SMA aneurysms, because it is less invasive and takes less time than surgical treatment.

Hyperechoic renal tumors: anechoic rim and intratumoral cysts in US differentiation of renal cell carcinoma from angiomyolipoma

To determine whether angiomyolipomas (AMLs) and renal cell carcinomas (RCCs) can be differentiated at ultrasonography (US), the authors retrospectively evaluated the sonographic appearances of 31 AMLs and 38 RCCs. Sonograms were evaluated by three radiologists without knowledge of histologic findings, with respect to the echogenicity of the tumor, predominant echotexture, and whether an anechoic rim was present. All patients had also undergone computed tomography (CT) to check for tumoral fat. Intratumoral fat was evident at CT in 28 of the 31 AMLs. RCCs had no fat at CT or histologic evaluation. An anechoic rim was evident in 32 of 38 (84%) RCCs, and 10 RCCs had small anechoic areas with back echo enhancement, which corresponded to intratumoral cysts or cystic necrosis at histologic evaluation. The anechoic rim and areas indicative of cysts were not found in AMLs. Demonstration of an anechoic rim and/or intratumoral cysts in a hyperechoic mass at US suggests that the tumor is an RCC.

[Diagnosis of the pelvic fracture which requires TAE on plain pelvic radiograph]

We reviewed the initial emergency-room plain pelvic radiographs of 75 patients with pelvic fracture. In thirty-six patients transcatheter arterial embolization (TAE) was performed for retroperitoneal hemorrhage associated with pelvic fracture (TAE group) and in 39 patients (non-shock group) TAE was not required. In TAE group, fractures involving iliosacral region and pubic symphysis were more dominant than in non-shock group. Specific soft tissue abnormal shadow of TAE group was not present. It may be impossible to determine the necessity of TAE in pelvic fracture on the basis of plain pelvic radiograph.