MR Imaging Findings of Intraosseous Lipoma

PURPOSE: To evaluate the MR imaging findings of intraosseous lipoma. MATERIALS AND METHODS: The MR imaging findings of 12 cases of intraosseous lipoma were retrospectively analyzed with regard to internal signal intensity, enhancement patterns, the presence of calcification and the status of the margin. The findings relating to these last two features were compared with those of plain films and CT. RESULTS: Six tumors were located in the calcaneus, three in the tibia, two in the ilium, and one in the carpal lunate. A fat component was clearly identified in all cases, but no lesion was purely fatty. Cyst formation was noted in four cases, and hyperintense portions different from the cystic area were seen on T2WI in ten. Contrast enhancement was observed in four patients, and although plain film and CT images revealed, in all cases, the presence of calcification, in two cases this was not demonstrated by MRI. In all cases, however, MRI showed well-defined tumoral margins. CONCLUSION: MRI clearly depicts fat and other components related to the involutional changes occurring in cases of intraosseous lipoma. The information these images provide is useful for the diagnosis and histologic classification of intraosseous lipoma.

Contrast-Enhanced Magnetic Resonance Angiography: Dose the Test Dose Bolus Represent the Main Dose Bolus Accurately?

OBJECTIVE: To determine whether the time-intensity curves acquired by test and main dose contrast injections for MR angiography are similar. MATERIALS AND METHODS: In 11 patients, repeated contrast-enhanced 2D-turbo-FLASH scans with 1-sec interval were obtained. Both test and main dose time-intensity curves were acquired from the abdominal aorta, and the parameters of time-intensity curves for the test and main boluses were compared. The parame-ters used were arterial and venous enhancement times, arterial peak enhance-ment time, arteriovenous circulation time, enhancement duration and enhance-ment expansion ratio. RESULTS: Between the main and test boluses, arterial and venous enhance-ment times and arteriovenous circulation time showed statistically significant correlation (p < 0.01), with correlation coefficients of 0.95, 0.92 and 0.98 respectively. Although the enhancement duration was definitely greater than infusion time, reasonable measurement of the end enhancement point in the main bolus was impossible. CONCLUSION: Only arterial and venous enhancement times and arteriovenous circulation time of the main bolus could be predicted from the test-bolus results. The use of these reliable parameters would lead to improvements in the scan timing method for MR angiography.

Contrast-Enhanced Magnetic Resonance Angiography: Dose the Test Dose Bolus Represent the Main Dose Bolus Accurately?

OBJECTIVE: To determine whether the time-intensity curves acquired by test and main dose contrast injections for MR angiography are similar. MATERIALS AND METHODS: In 11 patients, repeated contrast-enhanced 2D-turbo-FLASH scans with 1-sec interval were obtained. Both test and main dose time-intensity curves were acquired from the abdominal aorta, and the parameters of time-intensity curves for the test and main boluses were compared. The parame-ters used were arterial and venous enhancement times, arterial peak enhance-ment time, arteriovenous circulation time, enhancement duration and enhance-ment expansion ratio. RESULTS: Between the main and test boluses, arterial and venous enhance-ment times and arteriovenous circulation time showed statistically significant correlation (p < 0.01), with correlation coefficients of 0.95, 0.92 and 0.98 respectively. Although the enhancement duration was definitely greater than infusion time, reasonable measurement of the end enhancement point in the main bolus was impossible. CONCLUSION: Only arterial and venous enhancement times and arteriovenous circulation time of the main bolus could be predicted from the test-bolus results. The use of these reliable parameters would lead to improvements in the scan timing method for MR angiography.

The Optimization of Scan Timing for Contrast-Enhanced Magnetic Resonance Angiography

OBJECTIVE: To determine the optimal scan timing for contrast-enhanced magnetic resonance angiography and to evaluate a new timing method based on the arteriovenous circulation time. MATERIALS AND METHODS: Eighty-nine contrast-enhanced magnetic resonance angiographic examinations were performed mainly in the extremities. A 1.5T scanner with a 3-D turbo-FLASH sequence was used, and during each study, two consecutive arterial phases and one venous phase were acquired. Scan delay time was calculated from the time-intensity curve by the traditional (n = 48) and/or the new (n = 41) method. This latter was based on arteriovenous circulation time rather than peak arterial enhancement time, as used in the traditional method. The numbers of first-phase images showing a properly enhanced arterial phase were compared between the two methods. RESULTS: Mean scan delay time was 5.4 sec longer with the new method than with the traditional. Properly enhanced first-phase images were found in 65% of cases (31/48) using the traditional timing method, and 95% (39/41) using the new method. When cases in which there was mismatch between the target vessel and the time-intensity curve acquisition site are excluded, erroneous acquisition occurred in seven cases with the traditional method, but in none with the new method. CONCLUSION: The calculation of scan delay time on the basis of arteriovenous circulation time provides better timing for arterial phase acquisition than the traditional method.

A Suggestion of New Integrated Prognostic Factor for Aortic Aneurysm: Ta n gential Stress Index

PURPOSE: To construct a useful index for use as a prognostic factor in cases of aortic aneurysm. MATERIALS AND METHODS: Using CT or EBT, we studied nine ruptured aortic aneurysms, 40 unruptured aneurysms, and 42 normalaortas, measuring aortic diameter and wall thickness. Systolic, mean or diastolic blood pressure was used as apressure parameter. Tangential stress(TS) and the tangential stress index ( TSI) were calculated by modified Laplace's law. RESULTS: Average diastolic TS's (TSI's) were 1938 (4.13), 905 (1.84) and 554 (0.94) in rupturedaneurysm, unruptured aneurysm and normal groups, respectively (p<0.01). ROC curves of diastolic TS and TSI wereseen in a "useful study" zone. With a threshold of 1230 (2.90) for TS (TSI), the sensitivity and thespecificity for differentiation of ruptured and unruptured aneurysms were 100% (100%) and 75% (88%), and thepositive and the negative predictive values were 47% (64%) and 100% (100%), respectively (p<0.01). Amongsystolic, mean and diastolic TS 's and TS I 's, the diastolic TSI showed the highest specificity at its maximalsensitivity. CONCLUSION: Diastolic TSI is a more accurate prognostic factor for aortic aneurysm.