通过随访磁共振成像和磷-31磁共振波谱评估高剂量辐射对犬大腿肌肉的影响。

Choe B Y, Jee W H, Suh T S, Lee H K, Shinn K S

Department of Biomedical Engineering, Kangnam St. Mary's Hospital, Catholic University Medical College, Seoul, Korea.

Invest Radiol. 1998 May;33(5):300-7. doi: 10.1097/00004424-199805000-00007.

RATIONALE AND OBJECTIVES

The authors investigate alterations of proton T1 and T2 relaxation times and phosphorus metabolites of canine thigh muscle tissue after high dose x-ray irradiation by follow-up magnetic resonance imaging (MRI) and phosphorus-31 (31P) magnetic resonance spectroscopy (MRS).

METHODS

A group of 20 dogs was used for MRI and in vivo 31P MRS. Single doses of 5,000 and 10,000 cGy were delivered to the right thigh muscle of groups of 10 dogs each. All MRI and 31P MRS examinations were performed before irradiation and 1, 7, 14, 28, 42, and 56 days after irradiation. For measurement of T1, repetition time (TR) was measured at 300, 500, 1000, 1500, 2000 msec and echo time (TE) was fixed at 12 msec. Also, for measurement of T2, TE was measured at 20, 40, 60, and 80 msec and TR was fixed at 2000 msec. Image selected in vivo spectroscopy (ISIS) pulse sequence was used to obtain 31P MR spectra. Peak areas for each phosphorus metabolite were measured using a Marquart algorithm.

RESULTS

Magnetic resonance imaging signal began to change at 28 days after a single dose of 10,000 cGy, whereas there was no significant MRI signal change until 56 days after a single dose of 5,000 cGy. Also, extensive MRI signal changes were observed at 42 days after a single dose of 10,000 cGy. Significant correlation was established between T2 and a lapse of time although there was no correlation between T1 and a lapse of time. T2 value increased substantially corresponding to the time period after x-ray irradiation. Although MR spectral change was not observed until 42 days after a single dose of 5,000 cGy, it began at 14 days after a single dose of 10,000 cGy. And, significant MR spectral changes were observed at 28 and 42 days. Inorganic phosphate and phosphodiesters signal intensities increased while phosphocreatine signal intensity decreased. The pH value was 7.22 +/- 0.05 at control, and 6.98 +/- 0.04 at 42 days after a single dose of 10,000 cGy.

CONCLUSIONS

The postirradiation follow-up MRI and 31P MRS studies demonstrated that morphologic and metabolic changes were dependent upon the x-ray dose and a lapse of time.

原理与目的

作者通过后续磁共振成像（MRI）和磷-31（³¹P）磁共振波谱（MRS）研究高剂量X射线照射后犬大腿肌肉组织的质子T1和T2弛豫时间以及磷代谢物的变化。

方法

一组20只狗用于MRI和体内³¹P MRS检查。将单剂量5000和10000 cGy分别给予每组10只狗的右大腿肌肉。所有MRI和³¹P MRS检查均在照射前以及照射后1、7、1十四、28、42和56天进行。为测量T1，重复时间（TR）在300、500、1000、1500、2000毫秒测量，回波时间（TE）固定为12毫秒。同样，为测量T2，TE在20、40、60和80毫秒测量，TR固定为2000毫秒。采用图像选择体内波谱（ISIS）脉冲序列获取³¹P MR波谱。使用Marquart算法测量每种磷代谢物的峰面积。

结果

单剂量10000 cGy照射后28天磁共振成像信号开始变化，而单剂量5000 cGy照射后直到56天MRI信号无明显变化。此外，单剂量10000 cGy照射后42天观察到广泛的MRI信号变化。T2与时间推移之间建立了显著相关性，而T1与时间推移之间无相关性。T2值随着X射线照射后的时间段大幅增加。虽然单剂量5000 cGy照射后直到42天未观察到MR波谱变化，但单剂量10000 cGy照射后14天开始出现变化。并且，在28和42天观察到显著的MR波谱变化。无机磷酸盐和磷酸二酯信号强度增加，而磷酸肌酸信号强度降低。对照组pH值为7.22±0.05，单剂量10000 cGy照射后42天为6.98±0.0⁴。