Using static MLC fields to replace partial transmission cerrobend blocks in treatment planning of rectal carcinoma...

A treatment planning technique has been developed for using static multileaf collimators to replace partial transmission blocks for treating rectal or cervix carcinoma. The static MLC fields were used to replace the partial transmission block of the anterior-posterior pelvis field for the so-called "thunderbird" technique. Treatment plans were developed and evaluated on a commercial three-dimensional treatment planning system (FOCUS, Computerized, Medical Systems, St. Louis, MO). The result of the treatment plan comparison indicates that the static MLC fields are capable of achieving the same target, inguinal and pelvic dose distribution as the partial transmission cerrobend blocked fields. The MLC fields are easy to modify particularly for the match line adjustments. In conclusion, it is efficient and effective to use static MLC fields to replace partial transmission blocks in the "thunderbird" technique for treating rectal or cervix carcinoma.