Vesselov Leonid M, Whittington William, Lilge Lothar
Walsh Medical Devices, Inc., 1200 South Service Road, West Unit 3, Oakville, Ontario, Canada, L6L 5T7.
Lasers Surg Med. 2004;34(4):348-51. doi: 10.1002/lsm.20031.
Dosimetry for intracavity and interstitial light delivery requires next to the knowledge of tissue optical properties and models describing light propagation in tissue also exact knowledge of the spatial light source emission characteristics. However, the emission characteristics of cylindrical diffusers are often ill defined by the manufacturer, and not regularly determined by the end user, thus limiting the attainable dosimetry accuracy.
STUDY DESIGN/MATERIALS AND METHODS: Commercial cylindrical diffusers, with active diffusive lengths of 1-2 cm and outer diameters of </=1 mm, were evaluated regarding their photometric emission characteristics. In addition to traditional tests of homogeneity such as light intensity emitted along the diffuser length and around its circumference (polar angle), azimuth emission was also measured.
It was demonstrated that the light emission distribution is specific to the diffuser manufacturer, and while good polar isotropy is often attained, azimuth isotropy can vary by more than a factor of 5. In hollow organs the latter can result in over treatment of tissue distal to the actual placement of the cylindrical diffusers.
To enable light dosimetry and treatment planning for applications such as photodynamic therapy or interstitial laser hyperthermia or photocoagulation, standardization of emission properties reporting for optical fiber diffusers is required.
腔内和组织间光传输的剂量测定除了需要了解组织光学特性以及描述光在组织中传播的模型外，还需要准确掌握空间光源发射特性。然而，圆柱形扩散器的发射特性制造商通常定义不明确，终端用户也不常进行测定，从而限制了剂量测定的准确性。
研究设计/材料与方法：对有效扩散长度为1 - 2厘米、外径≤1毫米的商用圆柱形扩散器的光度发射特性进行了评估。除了进行传统的均匀性测试，如沿扩散器长度和圆周（极角）发射的光强度测试外，还测量了方位角发射。
结果表明，光发射分布因扩散器制造商而异，虽然通常能实现良好的极向各向同性，但方位角各向同性可能相差5倍以上。在中空器官中，后者可能导致圆柱形扩散器实际放置位置远端的组织过度治疗。
为了实现光动力疗法、组织间激光热疗或光凝等应用的光剂量测定和治疗规划，需要对光纤扩散器的发射特性报告进行标准化。
