Accuracy and Interrater Reliability of CISS Versus Contrast-Enhanced T1-Weighted VIBE for the Presence of Optic Canal Invasion in Tuberculum Sellae Meningiomas.

BACKGROUND: The magnetic resonance imaging sequence used to assess optic canal invasion by tuberculum sella meningiomas (TSMs) has not been standardized. Both constructive interference in steady state (CISS) and contrast-enhanced T1-weighted volume-interpolated breath-hold examination (VIBE) sequences are frequently used. The aim of the present study was to compare the accuracy and interrater reliability of these sequences in predicting optic canal invasion by TSMs. METHODS: In the present retrospective study of 27 patients (54 optic canals) who had undergone endoscopic transtuberculum transplanum resection of TSMs, images from preoperative CISS and contrast-enhanced T1-weighted VIBE sequences were assessed by 5 neuroradiologists who were unaware of the operative findings. The readers evaluated the optic canal in 4 quadrants at 2 locations (the posterior tip of the anterior clinoid process and the optic strut). A quadrant was considered positive for tumor invasion if invasion was present at either of these 2 locations. The reference standard was intraoperative observation of gross optic canal invasion. RESULTS: The interrater agreement was good for the presence or absence of tumor involvement in a particular quadrant (CISS, 0.635; VIBE, 0.643; 95% confidence interval for the difference, -0.086 to 0.010). The mean sensitivity and specificity for optic nerve invasion were 0.643 and 0.438 with CISS and 0.643 and 0.454 with VIBE, respectively. No significant differences were seen between the sequences in terms of reader accuracy when the intraoperative findings were used as the reference standard. CONCLUSION: CISS and VIBE sequences both have good accuracy in predicting for optic canal tumor invasion by TMEs.

Optimal definition of biological tumor volume using positron emission tomography in an animal model.

BACKGROUND: The goal of the study is to investigate (18)F-fluorodeoxyglucose positron emission tomography ((18)F-FDG-PET)'s ability to delineate the viable portion of a tumor in an animal model using cross-sectional histology as the validation standard. METHODS: Syngeneic mammary tumors were grown in female Lewis rats. Macroscopic histological images of the transverse tumor sections were paired with their corresponding FDG micro-PET slices of the same cranial-caudal location to form 51 pairs of co-registered images. A binary classification system based on four FDG-PET tumor contouring methods was applied to each pair of images: threshold based on (1) percentage of maximum tumor voxel counts (Cmax), (2) percentage of tumor peak voxel counts (Cpeak), (3) multiples of liver mean voxel counts (Cliver) derived from PERCIST, and (4) an edge-detection-based automated contouring system. The sensitivity, which represented the percentage of viable tumor areas correctly delineated by the gross tumor area (GTA) generated from a particular tumor contouring method, and the ratio (expressed in percentage) of the overestimated areas of a gross tumor area (GTAOE)/whole tumor areas on the macroscopic histology (WTAH), which represented how much a particular GTA extended into the normal structures surrounding the primary tumor target, were calculated. RESULTS: The receiver operating characteristic curves of all pairs of FDG-PET images have a mean area under the curve value of 0.934 (CI of 0.911-0.954), for representing how well each contouring method accurately delineated the viable tumor area. FDG-PET single value threshold tumor contouring based on 30 and 35 % of tumor Cmax or Cpeak and 6 × Cliver + 2 × SD achieved a sensitivity greater than 90 % with a GTAOE/WTAH ratio less than 10 %. Contouring based on 50 % of Cmax or Cpeak had a much lower sensitivity of 67.2-75.6 % with a GTAOE/WTAH ratio of 1.1-1.7 %. Automated edge detection was not reliable in this system. CONCLUSIONS: Single-value-threshold tumor contouring using (18)F-FDG-PET is able to accurately delineate the viable portion of a tumor. 30 and 35 % of Cmax, 30 and 35 % of Cpeak, and 6 × Cliver + 2 × SD are three appropriate threshold values to delineate viable tumor volume in our animal model. The commonly used threshold value of 50 % of Cmax or Cpeak failed to detect one third of the viable tumor volume in our model.