利用人員劑量佩章評估施作電腦斷層攝影之病患協助者所接受的輻射劑量

Assessment of the radiation dose received from caregiver in computed tomography

廖俊維(Chun-Wei Liao)

指導教授 ： 高一峰

高雄醫學大學/健康科學院/醫學影像暨放射科學系碩士在職專班/碩士(2017年)

摘要

背景 電腦斷層攝影的發展隨著科技的進步，提供快速、精準的醫學診療，供醫師診斷病患疾病，在國、內外儼然成為研判病患疾病的一大利器。在臺灣各大醫療院所中相當普及，也幫助許多病患能即時得知病症和進一步接受該有的手術醫療。 但在某些躁動不已或因故手臂無法上舉之病患，常造成影像假影，導致醫師難以診斷，故需電腦斷層攝影之醫療曝露協助者，且必須於施作電腦斷層攝影期間，在掃描室內穿著鉛衣協助，幫忙固定病患或言語勸說，使病患可以順利執行檢查，以求影像清晰，以利診斷。 目的 雖然醫療曝露協助者，已穿著鉛衣保護，但所接受的散射劑量是多少，卻不得而知。本研究使用電腦斷層攝影儀，掃描常用的6個部位，利用雙枚和單枚人員劑量佩章方式，量測讀值後，計算協助者所接受的散射劑量。 材料方法 利用TOSHIBA 64列電腦斷層攝影掃描儀、CIRS假體、5 mmPbeq鉛衣、人員劑量佩章。模擬協助者穿著鉛衣，緊靠電腦斷層攝影掃描儀，模擬掃描6組程序，分別為頭部、胸部、腹部含骨盤spiral 掃描；頭部0度、10度、 20度進行sequence掃描。且每個掃描程序皆包含正、側位兩張定位像及掃描該設定部位，連續執行10次後，收取及更換人員劑量佩章，重覆3次，得到左、右兩側，鉛衣內、外，共12枚人員佩章，計算鉛衣內、外劑量平均值，再行帶入蒐集的7個公式，計算協助者，所接受的醫療曝露劑量值。 因考量本實驗僅吊掛鉛衣，鉛衣內人員劑量佩章後方為空氣，為模擬鉛衣內側後方為人體，以10 cm的固態水假體，進行計算回散射值，所得校正因子結果為深部U(10)為1.043±0.02、淺部U(0.07)為1.051±0.07，再進行劑量值校正。 結果 各掃描部位醫療曝露協助者，所接到的散射輻射劑量，以 NCRP兩枚佩章公式計算，頭部spiral 掃描方式為2.52±1.36 μSv最低，腹部含骨盆spiral為10.38 ± 3.71 μSv最高。 討論 以NCRP雙枚佩章公式計算，散射輻射劑量，皆低於國內一張胸部X光劑量20 μSv。以NCRP單枚掛於鉛衣外公式計算，執行sequence 或spiral 應將轉換因子修正為，鉛衣外深部等效劑量分別除以20及29，會更接近NCRP 之兩枚人員劑量佩章計算公式的數據結果。 結論 以歐洲委員會輻射防護單位規範，在醫療曝露協助者為成人但不大於60歲者，不大於3 mSv而言，協助者穿著鉛衣，數據結果顯示，皆未高於此劑量，故電腦斷層攝影協助者，穿著鉛衣，近距離提供病患協助，輻射安全無虞。

關鍵字

電腦斷層攝影 ； 醫療輻射協助者 ； 輻射劑量輻射防護

並列摘要

Background
The development of computed tomography (CT) provides fast and accurately medical images for diagnosis. Furthermore, CT scan is a major option for clinical diagnosis all over the world. In Taiwan, CT scan commonly use in most of medical institutions. It helps patients to discover diseases early and have appropriate therapy.
However, some situations may affect image quality such as agitated patient or patients who cannot raise arms up above the head. The lower quality images, the harder diagnosis from clinical doctors. Therefore, the caregiver is needed in CT scanning room during CT examination. The caregivers who wear lead apron help to suppress or persuade the patient complete CT examination.
Purpose
Although caregivers wear lead aprons during CT examination, the scatter dose they exposed is unknown. In this study, we use double and single badge methods with six common CT scanning protocols to measure scatter dose is received by caregiver standing beside both sides of CT gantry.
Materials and methods
We use TOSHIBA 64-slices CT scanner, CIRS phantom, lead apron, and the badges. We simulate caregivers who wear 5 mmPbeq lead aprons and two badges stand beside CT scanner. The six common scanning protocols we used are head, chest, abdomen plus pelvis in spiral scanning mode and others three head protocol, we make CT gantry in 0, 10, 20 degree in
sequence scanning. Each protocol contains two topograms, AP and lateral, and scanning of setting site. We execute 10-time scan continuously. After we collect and replace TLD badges at left, right, inside and outside of lead aprons and repeated 3 times, total 12 badges, we will get the average radiation dose inside and outside the lead apron. We use 7 formulas to calculate the CT radiation dose of caregivers.
Because of the apron in this study is in hanging mode, there is only air inside the aprons. Therefore, we use 10 cm solid water phantom as simulating that space is human body to calculate the backscattering dose. The correction factor was U(10) 1.043 ± 0.02 for deep and 1.051 ± 0.07 for shallow U (0.07).
Results
If we use suggestions in NCRP, double badges formula, the scattered radiation dose received by CT caregiver is at least 2.52 ± 1.36 μSv in the spiral head scan, and at most 10.38 ± 3.71 μSv in abdomen with pelvis.
Discussion
Effective dose with double badges formula in NCRP, the radiation dose is lower than chest X-ray 20 μSv. The correction factor of effective dose with single badge formula in NCRP used in outside apron must be divided by 20 and 29 in sequence and spiral respectively. Therefore, it will be closer to the calculation data in NCRP double badges formula.
Conclusion
In the Radiation Protection Unit of European Commission suggests caregivers who are adults and below 60 years old cannot receive more than 3mSv radiation dose. All CT caregivers simulating phantoms with lead aprons do not receive more than 3mSv radiation dose. As a result,
caregivers wear lead aprons during CT examination is safe.

並列關鍵字

CT ； caregiver in medical ； radiation dose ； radiation protection

參考文獻

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