The sagital T2* W MERGE sequence is a sequence in Magnetic Resonance Imaging (MRI) examination of the knee joint in the radiology department of Panti Rapih Hospital Yogyakarta. The value of Flip Angle (FA) on the T2 * W MERGE sequence will affect to anatomical information. The right FA can produce good image contrast of fluid and tissue. This study aims to find out the relationship between FA variations toward anatomical information and to determine the the optimum FA. Ten patients with Anterior Cruciate Ligament (ACL) Tear were scaned by 1.5 Tesla MRI using Sagittal T2 * W MERGE with five flip angle variations: 150, 200, 250, 300, and 350. The anatomical informations were assesed by two qualified radiologists in ACL Tear, Posterior Cruciate Ligament (PCL), Quadriceps Tendon, Joint Effusion, and Hoffa Fat Pad. Data were analyzed by Cross Tabulation, Spearman Rank test and Freadman test. Result showed that there was a significant correlation (p-value < 0,05) between flip angle value to anatomical information (correlation value was -0.55), increasing the FA will reduce the clarity of the anatomical image. Based on Freadman test results, the highest mean rank of image information was 3.89 obtained by FA 200.
Cervical spine radiographic examination with 450 oblique projection can be performed using anteroposterior (AP) oblique or posteroanterior (PA) oblique. There are radiosensitive organs that are exposed to radiation during the examination. This study aims to determine the radiation dose (Entrance Surface Dose) received by thyroid, eye, and breast on radiographic examination in AP oblique and PA oblique projections. Radiographic phantom with equivalent structure to human body was positioned in AP oblique and PA oblique. A modificated protractor was used to maintain the positioning precision. The optimum exposure factors (confirmed by Exposure Index) were used. Radiation dose on the thyroid, the eye, and the breast were measured 9 times using Termoluminisence Dosemeter for each positioning techniques. Data were analyzed by independent t-test. The average radiation dose received by the thyroid, the breast, and the eye between AP oblique and PA oblique projections were (0.915 and 0.174), (0.059 and 0.025), and (0.234 and 0.079), respectively. There were significant differences in the radiation dose received by the thyroid (p value <0.05), the breast (p value <0.05), and the eye (p value <0.05). The radiation dose were lower (81% on thyroid), (58% on breast), (66% on eye) by using PA oblique projection.
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