Khoo V S, Joon D L
Royal Marsden Hospital, Institute of Cancer Research, Fulham Road, London SW3 6JJ, UK.
Br J Radiol. 2006 Sep;79 Spec No 1:S2-15. doi: 10.1259/bjr/41321492.
MRI is being increasingly used in oncology for staging, assessing tumour response and also for treatment planning in radiotherapy. Both conformal and intensity-modulated radiotherapy requires improved means of defining target volumes for treatment planning in order to achieve its intended benefits. MRI can add to the radiotherapy treatment planning (RTP) process by providing excellent and improved characterization of soft tissues compared with CT. Together with its multiplanar capability and increased imaging functionality, these advantages for target volume delineation outweigh its drawbacks of lacking electron density information and potential image distortion. Efficient MR distortion assessment and correction algorithms together with image co-registration and fusion programs can overcome these limitations and permit its use for RTP. MRI developments using new contrast media, such as ultrasmall superparamagnetic iron oxide particles for abnormal lymph node identification, techniques such as dynamic contrast enhanced MRI and diffusion MRI to better characterize tissue and tumour regions as well as ultrafast volumetric or cine MR sequences to define temporal patterns of target and organ at risk deformity and variations in spatial location have all increased the scope and utility of MRI for RTP. Information from these MR developments may permit treatment individualization, strategies of dose escalation and image-guided radiotherapy. These developments will be reviewed to assess their current and potential use for RTP and precision high dose radiotherapy.
磁共振成像（MRI）在肿瘤学中越来越多地用于分期、评估肿瘤反应以及放疗的治疗计划制定。适形放疗和调强放疗都需要改进确定治疗计划靶区体积的方法，以实现预期的治疗效果。与计算机断层扫描（CT）相比，MRI能够提供出色且更完善的软组织特征，从而有助于放疗治疗计划（RTP）流程。凭借其多平面成像能力和增强的成像功能，这些在靶区体积勾画方面的优势超过了其缺乏电子密度信息和潜在图像失真的缺点。高效的MR失真评估和校正算法以及图像配准和融合程序可以克服这些限制，并允许其用于RTP。使用新型造影剂的MRI技术发展，如用于识别异常淋巴结的超小超顺磁性氧化铁颗粒、动态对比增强MRI和扩散MRI等技术以更好地表征组织和肿瘤区域，以及超快容积或电影MR序列来定义靶区和危及器官的畸形及空间位置变化的时间模式，所有这些都增加了MRI在RTP中的应用范围和效用。这些MR技术发展所提供的信息可能允许实现个体化治疗、剂量递增策略和图像引导放疗。本文将对这些进展进行综述，以评估它们目前以及在RTP和精确高剂量放疗中的潜在应用。
