Increases in the number of brain metastases detected at frame-fixed, thin-slice MRI for gamma knife surgery planning

Abstract

For gamma knife planning, 2.4-mm-slice MRIs are taken under rigid frame fixation, so tiny tumors become visible. This study evaluated differences in the numbers of brain metastases between conventional contrast-enhanced MRI (6 ± 1 mm slice thickness) taken before patient referral and contrast-enhanced MRI for gamma knife planning. The numbers of metastases on the 2 images were counted by at least 2 oncologists. For gamma knife planning, spoiled gradient-recalled echo images were obtained after 0.1 mmol/kg gadolinium administration using a 1.5-T system. Images from 1045 patients with an interval between the 2 MRI studies of 6 weeks or less were analyzed. Increases in the number of metastases were found in 33.7% of the 1045 patients, whereas the number was identical in 62.3%. In 4.0%, the number decreased, indicating overdiagnosis at conventional MRI. These proportions did not differ significantly by the interval before gamma knife. An increase from single to multiple metastases was found in 16.0%. Meningeal dissemination was newly diagnosed in 2.3%. On planning images, the proportions of patients with 1, 2, 3, and 4 or more lesions were 37.6%, 19.3%, 9.3%, and 33.8%, respectively. In cases of colorectal cancer and hepatoma, the proportions of patients with a single metastasis (32 of 61 [52%] and 5 of 6 [83%], respectively) were higher than that of patients with other malignancies. In about one-third of the patients, an increased number of metastases were found on the thin-slice images. This should be kept in mind when deciding the treatment strategy for brain metastases.

Time-delayed contrast-enhanced MRI improves detection of brain metastases and apparent treatment volumes

“…16 To optimize lesion conspicuity, gadobenate dimeglumine was selected for this study because it has been shown to have a higher contrast-to-noise ratio compared with other gadolinium-based agents. 24 Patients were examined using thin-section imaging (0.9-1.0-mm slice thickness, which increases the sensitivity of lesion detection 6,17 ), and isotropic imaging data are needed for SRS treatment planning for reliable morphological contouring.…”

Renal carcinoma with brain metastases. Prognostic factors and treatment outcomes

“…По данным литературы, локальный контроль оча-гов после радиохирургического лечения МГМ РП до-стигается в интервале 83-96 % [16,25]. Медиана ОВ больных с МГМ РП, сообщенная другими центрами, варьирует от 6 до 13 мес [8,10,11,15,18,19,21,26].…”

Time window for postoperative reactive enhancement after resection of brain tumors: less than 72 hours

“…Additionally, other technical advantages such as new head coils with better signal-to-noise performance and also the parameters of the T1-weighted sequence might influence detectability of the benign enhancement. 3,19,25,38,39 However, confounding findings from early reactive enhancement may be limited if the imaging criteria of this enhancing pattern are considered. In our study, the types of enhancement shown on the first postoperative reactive MR scan could easily be attributed to reactive enhancement or residual gross tumor by comparing preand postsurgical scans, the latter revealing identical parts of the presurgical enhancing tumor.…”