比較電腦斷層掃描儀低對比偵測度於目視法與CNR判分法差異分析

Comparison of Discriminant Analysis between Visual Inspection and Contrast-Noise Ratio of Low Contrast Detectability Test in Computed Tomography Quality Assurance

黃姍姒(Shan-Su Huang) ； 杜俊元(Chun-Yuan Tu) ； 江蓮(Lien Chiang) ； 楊邦宏(Bang-Hung Yang) ； 張建法(Chien-Fa Chang)

《臺灣醫事放射期刊》 9卷1期 (2021/07) Pp. 1-6

https://doi.org/10.6717/JTMRT.202107_9(1).0001

摘要

近年來醫學發展迅速，對於醫學影像需求也越來越大，而在電腦斷層檢查日益普及的情況下，為了提升輻射醫療影像品質以及合理抑制減少病患可能接受之輻射劑量，根據行政院原子能委員會游離輻射防護法及輻射醫療曝露品質保證標準，確保輻射醫療儀器各方面均維持一定品質外，亦保障民眾之輻射醫療品質。在電腦斷層年度品質保證作業中，低對比偵測度是其中一項校驗項目，在現行法規中，低對比偵測度的判定方式為使用目視法，然而目視法在執行校驗時，容易受到人為主觀因素而有所差異，因此美國放射線學院（American College of Radiology, ACR）在2012年電腦斷層掃描儀品質保證手冊中，在低對比偵測度的部分，加入了對比雜訊比（Contrast to noise ratio, CNR）判分法為評估標準之一。本研究目的為比較電腦斷層掃描儀品質保證作業之低對比偵測度於目視法與CNR判分法差異分析。收集全國新裝機的38台電腦斷層掃描儀（包括34台診斷用電腦斷層掃描儀、4台電腦斷層模擬定位掃描儀），實地訪視進行假體掃描，並同時使用目視法與CNR判分法測定低對比偵測度。在進行低對比偵測度的38台電腦斷層掃描儀中，使用目視法的通過率皆是100%，而CNR判分法的通過率成人腹部與成人頭部則分別為89.47%與91.67%。使用CNR判分法進行低對比偵測度，相比使用目視法來說，可以較為客觀的評估低對比偵測度，避免因操作人員主觀因素、螢幕品質、燈光亮度等外在因素造成的誤差，是未來的趨勢。

關鍵字

電腦斷層掃描 ； 醫療曝露品質保證作業 ； 低對比偵測度 ； 對比雜訊比

並列摘要

As medical technology advances rapidly in recent years, the demand for medical imaging has increased dramatically. In the light of the widespread use of computed tomography (CT) examinations, the quality enhancements of medical image and dose delivery accuracy to a patient in compliance with the Atomic Energy Council's (AEC) Ionizing Radiation Protection Act and standards for Medical Exposure Quality Assurance to ensure the medical devices to achieve optimal quality in all aspects and also protect the public health. Low contrast detectability (LCD) is one of the tests on annual quality control performance of CT Scanners. In the current regulations, the LCD test uses the visual inspection which the result may differentiate affected by personal factors. Hence, according to CT Quality Control Manual 2012 issued by American College of Radiology (ACR), ACR suggests to add the contrast to noise ratio (CNR) test as one of criteria in CT quality control performance. The aim of this study is to compare and analyze the discriminant analysis between visual inspection of LCD and CNR in CT quality assurance. We have collected nationwide 38 newly installed CT scanners (34 CT scanners and 4 CT simulators) and arranged onsite visits to scan the phantoms by using LCD and CNR tests at the same time. We used 38 CT scanners to perform the LCD test. The pass rates of visual inspection was 100%, and CNR test in the abdomen and head in adult were 89.47% and 91.67%. Comparing with the visual inspection of LCD and CNR, the use of CNR measurements would be more objective in personal factors, quality of screening, light and extrinsic factors would be more objective in evaluation, and is a future trend.

並列關鍵字

computed tomography ； medical exposure quality assurance ； low contrast detectability ； contrast to noise ratio