Introduction: In the task, we compared MR devices with a strength of 0.3T and 1.5T when imaging the knee. Based on known studies, we decided to compare both devices in objective and subjective measures. Purpose: We wanted to find out whether using a device with a lower magnetic field density (0.3T), we can obtain equally good signal-to-noise ratios and contrast-noise ratios as would be obtained with an MR device with a higher magnetic field density (1.5T). We asked ourselves whether the presumed anatomical structures can be displayed with the same quality on both devices and if the quality of medical images is comparable between the two devices according to the assessment of radiology specialists. Work methods: In the first part of the task, we performed SNR (signal to noise ratio) and CNR (contrast to noise ratio) on selected structures of the knee. For imaging, we selected 25 healthy volunteers, who were imaged on both devices, thus obtaining 50 series of images. In the second part of the assignment, we prepared series of images for evaluation by three doctors specializing in radiology. We chose the structures of anterior and posterior cruciate ligaments, both menisci, articular cartilage and the image as a whole for evaluation. Results: In the results of the objective measure of image quality, we obtained different SNR and CNR values in the area of the medial meniscus. We recorded statistically significant differences in SNR (p<0.001) and CNR (p<0.001) measurements. In the area of the distal part of the femur, we recorded comparable values of SNR (p=0.677) and CNR (p=0.861) between the two devices, without statistically significant differences. The last selected structure was the articular cartilage, where we recorded statistically significant differences in SNR (p<0.001) and CNR (p<0.001) measurements, and higher average values on the 0.3T device. In the results of the subjective measure of image quality, we recorded higher scores and statistically significant differences in all set display criteria for the 1.5T device versus the 0.3T. On the 0.3T device, despite the lower ratings, we recorded good to excellent rating values on average. The agreement between the evaluators was moderate in the criterion of showing menisci, articular cartilage and the image as a whole. A worse match was recorded in the criterion of the display of cruciate ligaments. Discussion and conclusion: In the assignment, we found that we can achieve objectively comparable results between the two devices with the help of a longer signal acquisition time of the 0.3T device, but according to the assessment of radiologists, the visual display on the device with a lower magnetic field density is worse.
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