Lien W, Geise R A
Radiology Department, University of Minnesota, Minneapolis 55455, USA.
Health Phys. 1997 Sep;73(3):483-7. doi: 10.1097/00004032-199709000-00006.
When making direct measurements of skin entrance dose for patients undergoing interventional x-ray procedures the dosimeter may be placed near or in direct contact with the skin. The response of such dosimeters to heating during x-ray exposure must be known for accurate dosimetry. Two photographic films and MgB4O7 TLDs used for patient dose monitoring were exposed under different temperature conditions. Film dose response curves were obtained at room temperature and body temperature (22 degrees C and 38 degrees C). The TLD response at room and body temperature was also checked at 14 Gy. Dose response curves of FGP film show at most a 22+/-2% increase in predicted dose at 37 degrees C in the range of 0.3 to 2.8 Gy. LOC4 film showed less than a 2% difference in response between 22 and 37 degrees C over a range of 1 to 11 Gy. The TLDs showed less than a 2% difference at a dose of 14 Gy. Uncertainty in skin dose estimation is less than 2% using LOC4 film and MgB4O7 TLD arrays. Uncertainty in temperature during exposure of Kodak fine grain positive film may lead to errors in dose estimates of +/-11%. Arrays of TLDs and copy film are more suitable for measurements of high doses and are less sensitive to temperature changes during exposure than the fine grain film.
在对接受介入性X射线检查的患者进行皮肤入口剂量的直接测量时，剂量计可放置在皮肤附近或与皮肤直接接触。为了进行准确的剂量测定，必须了解此类剂量计在X射线照射期间对加热的响应。用于患者剂量监测的两张摄影胶片和MgB4O7热释光剂量计（TLD）在不同温度条件下进行了照射。在室温及体温（22摄氏度和38摄氏度）下获得了胶片剂量响应曲线。还在14 Gy剂量下检查了室温及体温时TLD的响应。FGP胶片的剂量响应曲线显示，在0.3至2.8 Gy范围内，37摄氏度时预测剂量最多增加22±2%。LOC4胶片在1至11 Gy范围内，22摄氏度与37摄氏度之间的响应差异小于2%。在14 Gy剂量下，TLD的差异小于2%。使用LOC4胶片和MgB4O7 TLD阵列时，皮肤剂量估计的不确定性小于2%。柯达细颗粒正片胶片曝光期间温度的不确定性可能导致剂量估计出现±11%的误差。TLD阵列和拷贝胶片更适合高剂量测量，并且在曝光期间比细颗粒胶片对温度变化更不敏感。
