Contrast-enhanced T1-weighted Spin-echo Images Research Articles

Evaluation of tumour necrosis during chemotherapy with diffusion-weighted MR imaging: preliminary results in osteosarcomas

During successful chemotherapy of osteosarcomas tumour size does not diminish significantly because the therapy has limited impact on the mineralized matrix of the tumour. Treatment response is considered successful if, histologically, more than 90% of tumour cells show necrosis. To determine if osteosarcomas change their water diffusion during preoperative chemotherapy in relation to the amount of tumour necrosis. Eight patients (age 11-19 years) with histologically proven limb osteosarcoma underwent T1-weighted, fat-suppressed T2-weighted and contrast-enhanced T1-weighted spin-echo imaging together with diffusion-weighted EPI sequences (b = 700) at 1.5 T before and after five cycles of standard chemotherapy. Tumour volume and apparent diffusion coefficient (ADC) maps were calculated before and after chemotherapy. The degree of tumour necrosis after chemotherapy was assessed using the histological Salzer-Kuntschik classification (grades 1-6). During chemotherapy, the ADC values of osteosarcomas changed significantly. The ADC of untreated tumour was 2.1 +/- 0.4 x 10(-3) mm(2)/s (mean +/- SD) (95% CI 1.6-2.0). The ADC of chemotherapy-treated sarcomas was 2.5 +/- 0.4 x 10(-3) mm(2)/s (95% CI 1.8-2.2). Necrotic areas, which were confirmed by macroscopic examination, showed ADC values up to 2.7 x 10(-3) mm(2)/s. Four patients with little viable tumour tissue within the neoplasm (Salzer-Kuntschik grades 1-2) had an increase in ADC of 0.4 up to 0.7 x 10(-3) mm(2)/s. Four patients with larger areas of viable tumour (Salzer-Kuntschik grade 4) showed a lesser increase in ADC of 0.0 up to 0.3 x 10(-3) mm(2)/s. The differences in ADC values in tumour tissue before and after chemotherapy were highly significant (P = 0.01). During chemotherapy of osteosarcomas, tumour ADC changes are related to the degree of tumour necrosis.

Brain Tumors: Full- and Half-Dose Contrast-enhanced MR Imaging at 3.0 T Compared with 1.5 T—Initial Experience

To prospectively and intraindividually compare the effect of magnetic resonance (MR) imaging at a higher magnetic field strength (3.0 T) on contrast-to-noise ratio (CNR) at different doses of a T1-shortening contrast agent in patients with contrast-enhancing brain lesions, with 1.5-T MR imaging as a reference standard. Institutional review board approval and informed consent were obtained for all patient and volunteer studies. Twelve patients (six women, six men; mean age, 58 years; range, 29-76 years) with 12 enhancing brain lesions (11 patients with primary brain tumors and one with a solitary cerebral metastasis) underwent contrast material-enhanced MR imaging three times, on three separate days: once at 1.5 T with a full dose of 0.10 mmol/kg gadopentetate dimeglumine, once at 3.0 T with a full dose, and once at 3.0 T with half that dose, 0.05 mmol/kg. The same contrast-enhanced T1-weighted spin-echo images (repetition time msec/echo time msec, 500/12; section thickness, 5 mm; matrix, 256 x 205) were obtained at both 3.0 T and 1.5 T after prior optimization of parameters at 3.0 T. The number and conspicuity of enhancing brain lesions were assessed with blinded clinical image reading. Signal-to-noise ratio and CNR were determined with region of interest analysis of enhancing lesions and normal contralateral white matter. For 3.0 T with half the standard dose and with the full dose, CNR of lesions was intraindividually compared with CNR at 1.5 T with the full dose by using the Wilcoxon matched-pairs signed rank test. At 3.0 T and full dose, CNR was 2.8-fold higher than that at 1.5 T and full dose (P < .001). At the same time, higher lesion conspicuity at clinical image reading was observed. With only half the standard dose, MR imaging at 3.0 T still yielded higher CNR (1.3-fold higher) than that with full dose at 1.5 T (P < .01). With the same amount of contrast agent, MR imaging at 3.0 T offered a significantly higher CNR of enhancing cerebral lesions, compared with that at 1.5 T; even with the dose reduced by half, CNR was still higher at 3.0 T.

MR signal intensity characteristics in Legg-Calvé-Perthes disease. Value of fat-suppressed (STIR) images and contrast-enhanced T1-weighted images.

To evaluate the MR signal intensity characteristics in Legg-Calvé-Perthes disease on fat-suppressed (STIR) images and contrast-enhanced T1-weighted spin-echo images, and to develop criteria for the administration of contrast material. Twenty children with Legg-Calvé-Perthes disease underwent conventional radiography and MR imaging of the hip utilizing fat-suppressed (STIR) sequences and T1-weighted spin-echo sequences before and after i.v. contrast administration. The signal intensity characteristics of the femoral head and the proximal femoral metaphysis were assessed retrospectively by two pediatric radiologists. Evaluation of the MR images revealed six different signal patterns within the femoral head: 1) isointense signal on all images; 2) complete signal void on all images; 3) hyperintense signal on STIR images with; or 4) without contrast enhancement on T1-weighted spin-echo images; 5) isointense signal on STIR images with; or 6) without contrast enhancement on T1-weighted images. Within the metaphysis three different signal patterns were differentiated. Combination of fat-suppressed (STIR) sequences and T1-weighted pre- and post-contrast sequences allows an accurate evaluation of Legg-Calvé-Perthes disease. In patients without signal alterations or complete signal loss on fat-suppressed and T1-weighted spin-echo images, administration of i.v. contrast is not necessary. In case of bone marrow edema on fat-supressed images, contrast-enhanced T1-weighted images are required to identify viable osseous fragments.

MR signal intensity characteristics in LEgg-Calve-Perthes disease. Value of fat-suppressed (STIR) images and contrast-enhanced T1-weighted images

Purpose: To evaluate the MR signal intensity characteristics in Legg-Calve-Perthes disease on fat-suppressed (STIR) images and contrast-enhanced T1-weighted spin-echo images, and to develop criteria for the administration of contrast material. Material and Methods: Twenty children with Legg-Calve-Perthes disease underwent conventional radiography and MR imaging of the hip utilizing fat-suppressed (STIR) sequences and T1-weighted spin-echo sequences before and after i.v. contrast administration. The signal intensity characteristics of the femoral head and the proximal femoral metaphysis were assessed retrospectively by two pediatric radiologists. Results: Evaluation of the MR images revealed six different signal patterns within the femoral head: 1) isointense signal on all images; 2) complete signal void on all images; 3) hyperintense signal on STIR images with; or 4) without contrast enhancement on T1-weighted spin-echo images; 5) isointense signal on STIR images with; or 6) without contrast enhancement on T1-weighted images. Within the metaphysis three different signal patterns were differentiated. Conclusion: Combination of fat-suppressed (STIR) sequences and T1-weighted pre- and post-contrast sequences allows an accurate evaluation of Legg-Calve-Perthes disease. In patients without signal alterations or complete signal loss on fat-suppressed and T1-weighted spin-echo images, administration of i.v. contrast is not necessary. In case of bone marrow edema on fat-supressed images, contrast-enhanced T1-weighted images are required to identify viable osseous fragments.

MRI screening for acoustic neuroma without gadolinium: value of 3DFT-CISS sequence.

To evaluate the efficacy of a gradient-echo sequence (3DFT-CISS) in the diagnosis of acoustic neuromas, two independent observers twice reviewed the images of the temporal bones of 83 patients. Contrast-enhanced T1-weighted spin echo images were used as the reference, showing 18 acoustic neuromas, including 5 purely intracanalicular and one intralabyrinthine tumours. High sensitivity (89-94%), specificity (94-97%) and accuracy (94-95%) were found. Intraobserver (kappa 0.93-1) and interobserver (kappa 0.83-0.84) reproducibility were very good. The smallest intracanalicular tumour was overlooked twice by both observers; the intralabyrinthine tumour once by one observer. All tumours were detected with a less stringent decision criterion, at the expense of lower specificity.

Improved contrast of enhancing brain lesions using contrast-enhanced T1-weighted fast spin-echo MR imaging.

The purpose of this study was to evaluate the ability of T1-weighted fast spin-echo MR sequences to provide improved contrast-to-noise ratios for contrast-enhanced lesions during acquisition times shorter than those used for conventional T1-weighted spin-echo MR sequences. We compared contrast-to-noise ratios of 32 enhancing brain lesions in 25 patients on T1-weighted spin-echo (546/10 [TR/TE]; two excitations; acquisition time, 4 min 12 sec) and on fast spin-echo (546/10 [TR/effective TE]; echo-train length, 4; echo spacing, 10 msec; two excitations; acquisition time, 1 min 45 sec) MR images obtained at 1.5 T after i.v. administration of 0.10 mmol/kg gadopentetate dimeglumine. The contrast-enhanced T1-weighted fast spin-echo MR images showed approximately a 12% reduction in the signal-to-noise ratios of the background white matter without an accompanying reduction in the signal-to-noise ratios of the enhancing lesions or CSF when compared with the contrast-enhanced T1-weighted spin-echo MR images. The contrast-enhanced T1-weighted fast spin-echo MR images provided a 23% improvement in the contrast-to-noise ratios of enhancing lesions over the contrast-enhanced T1-weighted spin-echo images (p < .001). Contrast-enhanced T1-weighted fast spin-echo MR imaging showed a statistically significant improvement in contrast-to-noise ratios at much shorter scan times than those used in conventional contrast-enhanced T1-weighted spin-echo MR imaging.

Hepatic adenoma: MR findings in 51 pathologically proved lesions.

To describe the magnetic resonance (MR) imaging features of hepatic adenoma and correlate these findings with histopathologic findings. MR findings of 51 pathologically proved hepatic adenomas in 29 consecutive patients were retrospectively analyzed. T1- and T2-weighted spin-echo (SE) images were obtained in all patients, and contrast material-enhanced MR images were obtained in 16 patients. At pathologic analysis, a peripheral rim, observed in 16 (31%) hepatic adenomas, corresponded to pseudocapsule, and tumor heterogeneity, observed in 26 (51%) lesions, corresponded to hemorrhagic necrosis and peliosis. Hyperintensity on T1-weighted SE images was observed in 30 (59%) adenomas; 10 (67%) of 15 hepatic adenomas were hyperintense on contrast-enhanced gradient-echo images, and 13 (45%) of 29 were hyperintense on delayed contrast-enhanced T1-weighted SE images. Presence of a peripheral rim, heterogeneity, and hyperintensity are common features of hepatic adenoma.

Treatment of hepatocellular carcinoma with percutaneous ethanol injection: evaluation with contrast-enhanced MR imaging.

The aim of this study was to investigate the usefulness of unenhanced and enhanced MR imaging in evaluating the response of hepatocellular carcinoma to percutaneous injection of ethanol. Thirty-one patients with 40 hepatocellular carcinomas less than 5 cm in diameter were examined with MR imaging before and after percutaneous injection of ethanol. Unenhanced T1- and T2-weighted and contrast-enhanced T1-weighted spin-echo images were obtained. CT and percutaneous biopsy were performed 1 month after the final injection of ethanol and repeated at 6-month intervals to establish the outcome of treatment: complete tumor necrosis was shown in 36 lesions and incomplete tumor necrosis was seen in four lesions. Of the 36 proved necrotic lesions, 31 showed homogeneously low signal intensity on T2-weighted MR images obtained after treatment, owing to coagulative necrosis of the tumor. In the remaining five necrotic lesions, hypointense and hyperintense areas coexisted; the hyperintense areas were caused by liquefactive necrotic material in two cases and by chronic inflammatory tissue along the boundary of the necrotic area in three cases. None of the 36 necrotic lesions showed contrast enhancement on T1-weighted images obtained after IV injection of gadopentetate dimeglumine. In the four lesions with incomplete necrosis, the viable portion of the tumor was identified as a hyperintense area on T2-weighted images and as an enhancing area on contrast-enhanced T1-weighted images. No correlation was found between lesion features on unenhanced T1-weighted images and outcome of therapy. Contrast-enhanced T1-weighted MR images allow a reliable evaluation of the effectiveness of treatment and are more accurate than unenhanced MR studies. Contrast-enhanced MR imaging may be considered a valuable alternative to contrast-enhanced CT in the follow-up of hepatocellular carcinomas treated with percutaneous injection of ethanol.

MR appearance of multiple myeloma of the spine before and after treatment.

The aim of this study was to describe the changes in the MR appearance of painful lesions of the spine before and after treatment in 18 patients with multiple myeloma and to correlate these changes with the clinical response to treatment. Eighteen patients with multiple myeloma and tumor nodules in the spine had MR imaging of the same site in the spine before and after treatment. Unenhanced T1- and T2-weighted spin-echo images, dynamic ultrafast low-angle shot (turbo-FLASH) images before and after IV bolus injection of paramagnetic contrast material, and contrast-enhanced T1-weighted spin-echo images were obtained. Characteristic signal and contrast enhancement before and after treatment were compared and were correlated with clinical data and the results of immunochemical and pathologic tests. Changes in signal intensity and enhancement of the lesions occurred after treatment in 14 of 18 patients. The characteristics of the lesions after treatment had three patterns: (1) rim enhancement or no enhancement of the lesions, (2) early enhancing lesions associated with other nonenhancing lesions or lesions with rim enhancement, and (3) no change from the enhancement pattern seen before treatment. In 13 of 18 patients, these patterns correlated well with the response to treatment. A discrepancy was observed in five patients. The MR appearance of spinal myeloma is different before and after treatment. MR images, particularly contrast-enhanced images, may be helpful in monitoring the response to treatment of focal bone lesions of myeloma.