定量磁共振和同位素成像：脑辐射损伤的早期评估。

Quantitative magnetic resonance and isotopic imaging: early evaluation of radiation injury to the brain.

作者信息

Miot E, Hoffschir D, Pontvert D, Gaboriaud G, Alapetite C, Masse R, Fetissof F, Le Pape A, Akoka S

机构信息

Laboratoire de Biophysique Cellulaire et RMN/INSERM U316, Tours, France.

出版信息

Int J Radiat Oncol Biol Phys. 1995 Apr 30;32(1):121-8. doi: 10.1016/0360-3016(94)00413-F.

DOI:10.1016/0360-3016(94)00413-F

PMID:7721608

Abstract

PURPOSE

Using magnetic resonance (MR) and isotopic imaging to investigate the cerebral alterations after highdose single-fraction irradiation on a pig model. We assessed the nuclear magnetic resonance (NMR) relaxation times as early markers of radiation injury to the healthy brain.

METHODS AND MATERIALS

A total of 17 animals was studied; 15 irradiated and 2 unirradiated controls. Pigs were irradiated with a 12 MeV electron beam at a rate of 2 Gy/min. Ten animals received 40 Gy at the 90% isodose, five animals received 60 Gy, and two animals were unirradiated. The follow-up intervals ranged from 2 days to 6 months. T1-weighted scans, T2-weighted scans, and scintigrams were performed on all animals to study neurological abnormalities, cerebral blood flow, and blood-brain barrier (BBB) integrity. T1 and T2 relaxation times were measured in selected regions of interest (ROIs) within the irradiated and contralateral hemispheres. A ratio T1 after irradiation/T1 before irradiation, and a ratio T2 after irradiation/T2 before irradiation, were calculated, pooled for each dose group, and followed as a function of time after irradiation.

RESULTS

Scintigraphy visualized the brain perfusion defect and BBB disruption in all irradiated brains. The ratio T2 after irradiation/T2 before irradiation was proportional to the effective dose received. The T2 ratio kinetics could be analyzed in three phases:an immediate and transient phase, two long-lasting phases, which preceded compression of the irradiated lateral ventricle, and edema and necrosis at later stages of radiation injury, respectively. The magnetic resonance imaging (MRI) observations correlated well with histological analysis.

CONCLUSION

The results show that quantitative imaging is a sensitive in vivo method for early detection of cerebral radiation injury. The reliability and dose dependence of T2 relaxation time may offer new opportunities to detect and understand brain pathophysiology after high-dose single-fraction irradiation.

摘要

目的

利用磁共振（MR）和同位素成像技术，在猪模型上研究单次大剂量照射后脑的变化。我们评估了核磁共振（NMR）弛豫时间，将其作为健康脑辐射损伤的早期标志物。

方法和材料

共研究了17只动物，其中15只接受照射，2只为未照射的对照。猪以2 Gy/分钟的速率接受12 MeV电子束照射。10只动物在90%等剂量线处接受40 Gy照射，5只动物接受60 Gy照射，2只动物未接受照射。随访时间间隔为2天至6个月。对所有动物进行T1加权扫描、T2加权扫描和闪烁扫描，以研究神经功能异常、脑血流量和血脑屏障（BBB）完整性。在照射侧和对侧半球的选定感兴趣区域（ROI）测量T1和T2弛豫时间。计算照射后T1/照射前T1以及照射后T2/照射前T2的比值，按剂量组汇总，并跟踪其作为照射后时间的函数变化。