CT Perfusion Imagmg Of Radiation Encephalopathy Following Radiotherapy For Nasopharyngeal Carcinoma

Objective: To evaluate the microcirculatory hemodynamic changes and the pathological basis of radiation encephalopathy(RE) by using CT perfusion imaging, and infer the possible pathogenic mechanism of RE. Materials and Methods: (1)CT perfusion images were obtained in 20 patients with RE following radiotherapy for nasopharyngeal carcinoma. RE was diagnosed by clinical appearances. CT and MRI.(2)A slip-ring CT scanner (Somaton Plus 4,Siemens) was used. The lesion slice which was over the line between the external auditory canal and supraorbit was chosen for dynamic CT during a bolus intravenous administration of non-ionic contrast. The contrast agent was Ultravist 300(300mgIIml), injection rate 9mIIs,total dose 50m1, injected by a mechanical injector. The scan parameters: continuous data acquisition was performed for 35s starting 5s after the injection. 1 slice/s, reconstruction interval time 0.75s,then a total of 48 images were obtained.(3)The data were evaluated at the workstation with a perfusion CT software (Siemens).The cerebral blood flow (CBF), mean transit time (MTT), time-to-peak(PT) of lesions and normal brain stems or white matter in normal temporal lobes (TL) were calculated by using time-density curves in brain tissue and cerebral arteries or superior sagittal sinuses. CBF(nil.rnin? lOOg?=(Maximum rate of tissue enhancement /peak arterial enhancement)x60. (4)Statistical analysis was performed using SPSS windows 8.0 version software package. Stardard descriptive statistical mean ?SD were obtaind. Two-tailed t test was used to compare normally and nonnormally distributed data respectively. Statistical significant difference, very significant difference and tendency were declared at a level of 0.05, 0.0001 and 0.1 respectively. -4- Results: (l)Twenty-six areas of reduced CBFS CBV and prolonged PT were detected with the aid of functional images in 20 patients with MRI and CT proved. Twenty-three were in the white matter of TL, 3 in brain stem. In the 7 necrotic areas of 23 TL lesions, no blood perfusion was observed. (2)The mean盨D values of CBF MTT~ PT in the 16 non-necrotic lesions(lesion for short) in white matter were 14.63?.27 ml昺in1?bOg jrange7.14 ? 24.85m1.mirU1.100g1), 23.47?.96s (range 18?8s) and 23. 19?.41s (range 18?7s) respectively. The mean盨D values of CBF.. MTTS PT in the 22 mormal ROTs of TL white matter were 29.57?.61 nii.min?100g1 (range 21.36?3.13 ml.min1.100g1), 16.66?.45s (range l5?0s)~ 21.63?.Ols (range 18?4s). CBF was much lower, MTT was much longer in the lesions than in the normal controls, P <0.0001.There were very signifkant differences between the two groups. PT was a little prolonged in the lesions than in the normal controls ,P<0. I .There was a prolonged tendency between the two groups. The mean 盨D values of CBFS MTTS PT in the normal brain stem were 31.66?.76 ml.niin1.100g1(range 21.41?3.50 m1~min 1.1 OOg? ~. 16.56? .88s (range 14?20s) . 1 7?.02s(rangel 6 ?2s) respectively. The mean 盨D value of CBF in the 3 areas of RE in brain stem were 28.45 mI昺in挄100g1~ 19.50 ml.min拁l00g拁 18.0 ml.min?100g1, MTT were 16s~ l7s~ 18.5s,and PT were 23s~ 22.5s~. 21s respectively. (3)The maximum enhancement of the arterial density during passage of the contrast medium was on the average 162.65?.20 Llousfieid uints (mean盨D) (range 100? 224.7HU). (4)The total radiation dose in the dynamic CT scan was 421.lmGy. It was lower than the conventional plain CT sca...