| Radiotherapy as an effective means for tumor treatment is increasingly widespread. In fact, many kinds of tumors can be cured. However, local recurrence is still problems. The reason is the lack of timeliness and more accuracy evaluation method. At present, we depend on the conventional images (ultrasound, X-ray, CT, MRI, etc.) to evaluate the response of the treatment. But such images only provide the changes of volume. These are very blind and too late. MR functional imaging break through the constraint of the conventional images and show up ascendancy in qualitation, the judgement of malignant degree and curative effect of tumors from biology, physiology and biochemistry. DWI is one of the MR functional imaging and show physiological and pathological changes through measuring the microscopic molecular movement of water in the tissues. This technique can provide more information for guiding the continued treatment plans and lasting life time. At present, most of the researches in evaluating the response of the tumor treatment using DWI and ADC value is animal study. In human studies, the researches in evaluating the response of the tumor treatment using DWI and ADC is major of brain and rectal tumors. Many scholars has studied in evaluation of curative effect after interventional therapy in hepatocellular carcinoma (HCC)through DWI. But the research in evaluating the response of hepatocellular carcinoma after radiotherapy using DWI and ADC is rare.Objective: In this experiment, we discuss the changes and significance of mean apparent diffusion coefficient(ADC) value in tumor tissue and provid valuable evidences for judgement effect of radiotherapy in the early stage.Methods: 17 patients ( 16 male patients and 1 female patient, aged 28 to 70 years, mean 55 years) with HCC were acceptedγ-knife treatment. Diagnoses of HCC were pathologically confirmed in eleven of the 17 patients. The remaining cases were diagnosed clinically using blood sample data and follow-up imaging examinations. Two of them have tumor embolus in portal vein. Before and after treatment conventional MRI and DWI were performed in 17 patients who were diagnosed HCC, respectively. To choose five(region of interests, ROIs) in ADC map randomly and measure the ADC values of tumor tissue. ROIs get out of zone of necrosis, blood vessel, bile vessel in order to avoid error of measurement. The ADC values of liver and spleen were obtained in the same method. T2WI image were loaded in Argus browser and compute tumor volume through the software. To contrast the changes of ADC value and tumor volume after radiotherapy using Paired-Sample T Test. If P<0.05, the difference was significant. Results:1 When b value is 50, 400 and 1000, tumors were showed Hypso-signal on DWI. DWI image is a sensitive method of displaying tumor.2 Mean tumor volume before radiotherapy is 198.95±147.73 cm3, mean tumor volume after radiotherapy is 197.86±147.20cm3, the changes of mean tumor volume is not statistically significant (P=0.061>0.05) .3 Comparison of mean ADC values of different tissues before and after treatment.3.1 Mean ADC value of tumor tissue before treatment was found to be (0.86±0.13)×10- 3 mm2/s and mean ADC value of tumor tissue after treatment was found to be (1.14±0.20)×10- 3 mm2/s. The change of mean ADC value has statistically significant (P=0.000<0.05). The ADC value increased after radiotherapy.3.2 Mean ADC value of liver before treatment was found to be (0. 88±0.07)×10- 3 mm2/s and mean ADC value of liver after treatment was found to be (0.92±0.08)×10- 3 mm2/s. The change of mean ADC value has not statistically significant (P= 0.093>0.05).3.3 Mean ADC value of spleen before treatment was found to be (0.84±0.08)×10- 3 mm2/s and mean ADC value of spleen after treatment was found to be (0.85±0.07)×10- 3 mm2/s. The change of mean ADC value has not statistically significant (P=0.506>0.05).Conclusion:Mean ADC value of tumor tissue after treatment is higher than before treatment. The changes of ADC value is earlier than tumor volume. Mean ADC value can reflect pathological changes in tumor tissue after radiotherapy. Mean ADC value is quantitative standardization of early stage treatment in hepatocellular carcinoma. DWI is helpful to evaluate curative effect and prognosis of radiotherapy.
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