Raylman R R, Wahl R L
Department of Internal Medicine, University of Michigan Medical Center, Ann Arbor 48109-0552, USA.
Med Phys. 1995 Aug;22(8):1285-92. doi: 10.1118/1.597513.
Utilization of radiopharmaceuticals that directly target radioactivity to tumors for treatment has a great deal of promise. Ideally, lethal doses of radiation could be delivered precisely to areas of disease, while, for the most part, sparing normal tissues. This potential, however, has not yet been fully realized. Current limitations of this approach are low tumor uptake of radiopharmaceuticals and dose-limiting radiotoxicity. In an effort to offset low uptake, radionuclides that emit high average-energy electrons have been proposed. Unfortunately, use of these radionuclides increases myelosuppression on a per decay basis. In order to allow for the utilization of high doses of this class of high-energy beta emitters, we propose the application of a strong static homogeneous magnetic field to constrain the beta particles. Monte Carlo computer simulations indicate that application of a 10 T magnetic field can decrease the total radiation dose from bone-avid tracers to marrow located in shafts of human long bones by 14%. More significantly, however, the penetration depth of high-energy electrons from the bone surface into the marrow can be reduced by up to 74.6%. Preservation of marrow in areas distal to the bone has previously been shown to facilitate relatively rapid recovery from pancytopenia produced by radiation damage to trabecular marrow (without marrow transplantation). Magnetically enhanced protection of bone marrow, therefore, may allow administered doses of high-energy beta-emitting radionuclides to be increased. By raising the limits on injected quantities of such highly ionizing radionuclides, amounts of the radiation dose absorbed by both soft and calcified tissue tumors will be increased, compared to conventional treatments.(ABSTRACT TRUNCATED AT 250 WORDS)
利用直接将放射性靶向肿瘤进行治疗的放射性药物具有很大的前景。理想情况下，致死剂量的辐射能够精确地传递到病灶区域，而在很大程度上 sparing 正常组织。然而，这种潜力尚未得到充分实现。这种方法目前的局限性在于放射性药物在肿瘤中的摄取率低以及剂量限制性放射毒性。为了弥补低摄取率，有人提出使用发射高平均能量电子的放射性核素。不幸的是，使用这些放射性核素会在每次衰变时增加骨髓抑制。为了能够使用高剂量的此类高能β发射体，我们建议应用强静态均匀磁场来约束β粒子。蒙特卡罗计算机模拟表明，施加10 T的磁场可使骨亲和性示踪剂对位于人类长骨干中的骨髓的总辐射剂量降低14%。然而，更显著的是，从骨表面进入骨髓的高能电子的穿透深度可降低多达74.6%。先前已表明，保留骨远端区域的骨髓有助于从辐射对小梁骨髓造成损伤（无需骨髓移植）所导致的全血细胞减少中相对快速地恢复。因此，磁场增强对骨髓的保护可能会使高能β发射放射性核素的给药剂量增加。通过提高对这类高电离放射性核素注射量的限制，与传统治疗相比，软组织和钙化组织肿瘤吸收的辐射剂量将会增加。（摘要截短至250字） 注：原文中“sparing”此处存疑，可能有误，正常应该是“spare”（使免遭、使幸免等意思） 。
