Purpose : To optimize acquisition parameters for three-dimensional fast spin-echo (FSE) imaging of the knee using subjective and objective metrics of image quality. Materials and methods : This prospective, HIPAA-compliant, institutional review board-approved study was performed with informed consent of the subjects. The knees of 8 healthy male and female volunteers were imaged in a 3 T MRI scanner using an 8-channel knee coil. A total of 146 intermediate-weighted isotropic resolution 3D FSE (3D-FSE-Cube) images with varied acquisition parameter settings were acquired with an additional 3D-FSE-Cube scan acquired as a reference for subjective image quality assessment. Images were randomized and graded for overall quality, parallel imaging artifact severity and blurring with respect to the reference. Cartilage, muscle and fluid signal-to-noise ratios (SNR) and fluid-cartilage contrast-to-noise ratios (CNR) were quantified by acquiring scans with and without RF excitation and custom-reconstructing the k-space data to produce signal and noise-only images. Mixed effects regression modeling was used to determine statistically significant effects of the different parameters on image quality. Results : All quality metrics were significantly affected by varying receiver bandwidth, repetition time and echo train length (p < .05). Lowering bandwidth improved image quality for all metrics except blurring. Reader agreement was slight to fair for subjective metrics, but overall trends in quality ratings were apparent. Conclusion : We used a systematic approach to optimize parameters for 3D-FSE-Cube for knee imaging. Image quality was found to be overall improved using a receiver bandwidth of ±31.25 kHz, and blurring increased with lower bandwidth and longer echo trains.

Purpose

The purpose of the study is to assess the reader agreement and accuracy of eight ultrasound imaging features for classifying hepatic steatosis in adults with known or suspected hepatic steatosis.

Methods

This was an IRB-approved, HIPAA-compliant prospective study of adult patients with known or suspected hepatic steatosis. All patients signed written informed consent. Ultrasound images (Siemens S3000, 6C1HD, and 4C1 transducers) were acquired by experienced sonographers following a standard protocol. Eight readers independently graded eight features and their overall impression of hepatic steatosis on ordinal scales using an electronic case report form. Duplicated images from the 6C1HD transducer were read twice to assess intra-reader agreement. Intra-reader, inter-transducer, and inter-reader agreement were assessed using intraclass correlation coefficients (ICC). Features with the highest intra-reader agreement were selected as predictors for dichotomized histological steatosis using Classification and Regression Tree (CART) analysis, and the accuracy of the decision rule was compared to the accuracy of the radiologists' overall impression.

Results

45 patients (18 males, 27 females; mean age 56 ± 12 years) scanned from September 2015 to July 2016 were included. Mean intra-reader ICCs ranged from 0.430 to 0.777, inter-transducer ICCs ranged from 0.228 to 0.640, and inter-reader ICCs ranged from 0.014 to 0.561. The CART decision rule selected only large hepatic vein blurring and achieved similar accuracy to the overall impression (74% to 75% and 68% to 72%, respectively).

Conclusions

Large hepatic vein blurring, liver-kidney contrast, and overall impression provided the highest reader agreement. Large hepatic vein blurring may provide the highest classification accuracy for dichotomized grading of hepatic steatosis.