Dynamic MR measurements of brachytherapy caused microenvironmental changes in cervical cancer

Purpose: The change of tumor volume is not significant enough for representing the alteration caused by the irradiation. Signal intensity in Dynamic Magnetic Resonance (DMR) image visualizes the activity of the tumor and its vascular permeability. In cervical cancer patient, the response to radiotherapy shows individual contrast material enhancement changes in DMR as well as radiotherapy induced DNA damage. The goal was to determine the quantity of intensity in “good responders” and its change in time as a predictor for radio sensitivity.
Material and methods: Our DMR study based on contrast enhancement comparison. Thirteen patients (age 31-77, stage I/b-III/a) with cervical cancer took part in a prospective DMR study. The pharmacokinetics of 0.1 ml/kg Gadopentate-Dimeglumine was studied with one Tesla Shimadzu MR to measure the tumor and the healthy muscles- and uterine tissues. The enhancement was detected in axial view fast field sequence (TR: 180, TE: 10, FLP: 60, with: 5 mm, Pitch: 8 mm) in 30 seconds intervals, 8 times. The region of interest was 4 mm² in the tumor as well as in the healthy endometrial and myometrial tissues. To get proper data to compare we used the postcontrast Signal Intensity Ratio (SIR) method and we figured out a new formula: the Rate of the Signal Intensity Increase (RISI). The calculated RISI and SIR were compared by matching the proper DMR dates before and after radiation therapy. These were compared with operation histology in 10 cases. Changes after 3 × 6 Gy high dose rate intrauterine brachytherapy and consecutive 50 Gy Cobalt external beam irradiation 10 patients were searched.
Results: The Magnevist enhancement in DMR examination reflects the tumor activity. Significant differences were found in the first 60 sec RISI and in the SIR in all cervical cancer. We experienced that the SIR and RISI values differ in every patient and are characteristic. Still there is a tendency that the infiltrated and non-infiltrated territories are in different segment of enhancement scale and the diminishing of the RISI of the tumor and the healthy tissues differ from each other. The most significant change is in the enhancement between the first and second measurements, so that might suggest taking the first SIR and RISI as a basis of the following. The average of SIR in tumor was 100.84%, in the healthy tissues 52.93% and in the control muscles 14.82%, average of RISI in cervical...


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