MAGNETIC-RESONANCE-IMAGING IN THE TREATMENT PLANNING OF RADIATION-THERAPY IN CARCINOMA OF THE CERVIX TREATED WITH THE 4-FIELD PELVIC TECHNIQUE

Purpose: To evaluate magnetic resonance imaging (MRI) in the planning of radiation therapy for patients with carcinoma of the cervix treated with a four-field technique. Methods and Materials: Between May 1994 and February 1995, 18 patients with carcinoma of the cervix were enter ed in the study (1 T1 N-; 2 T2a N-; 1 T2b NO; 10 T2b N-; 2 T2b N+; 2 T 3b N+). Node status was assessed by a laparoscopic pelvic lymphadenect omy. During the first step, all the patients were simulated with an is ocentric four-field pelvic technique. In one group (11 patients) simul ation was done based on clinical examination, computed tomography (CT) , and standard guidelines. In the second group (seven patients) simula tion was based on clinical examination, CT, and with the help of diagn ostic MRI, which was available at that time. During the second step, M RI in treatment position with skin markings of the isocenter of the ra diation fields was then performed in every patient. During the third s tep, in each patient, the simulated radiation fields were correlated w ith the MRI defined target volume by superimposing them on midsagittal and midcoronal MR images. The adequacy of the margins was arbitrarly defined as 1 cm around the MRI defined target volume (tumor of the cer vix and its extension, and uterus). Results: In the first group (11 pa tients), MRI in treatment position led to a change in 7 patients: six inadequate margins in the lateral fields and one in the anterior and l ateral field. In almost all the cases, the adjustments were of an incr ease of 10 mm, equally matched between the anterior and posterior bord ers of the lateral fields. In the second group (seven patients), MRI i n treatment position has led to a change in lateral fields in five pat ients. The mean adjustment was 10 mm: four increases (two anterior bor der, one posterior border, one anterior and posterior border), and one decrease of the posterior border. In the two groups, modifications of the anterior border of the lateral fields have allowed adequate margi ns around the uterine fundus and modifications of the posterior border have allowed adequate coverage of the cervical tumor.Conclusion: When treating carcinoma of the cervix with a four-field radiation techniqu e, standard portals do not exist. The design of lateral fields has to be based on individual morbid anatomy, which is given accurately by di agnostic MRI. Magnetic resonance imaging in treatment position assesse s the design of simulated lateral fields. (C) 1997 Elsevier Science In c.