purpose of multileaf collimator in radiotherapy

Als „volumes of interest“ (VOI) wurden das Planungszielvolumen (PTV Prostataregion inkl. Mittels eines dreidimensionalen Bestrahlungsplanungssystems (Helax TMS 6.1B) wurden die Bestrahlungstechniken für einen 18-MV-Linearbeschleuniger (Primus 1, Siemens) berechnet. Zehn Patienten wurden in die Analyse einbezogen. Especially for irradiation to escalated dose levels, this modification may reduce the dose to the rectum and thus the rectal side effects in comparison to the conventional MLC fields.Įine Modifikation der Bestrahlungstechnik beim Prostatakarzinom wird vorgestellt, die den mehrstufigen Dosisverlauf am Feldrand ausgleicht, wie er bei Verwendung eines Multileaf-Kollimators (MLC) entsteht. The presented technical modification is an effective method to blur the staggered dose distribution that results, when the MLC is conventionally stepped to adapt to the dorsal, irregular PTV border in irradiation of prostate. Median dose to V rectum was 82.6% for technique A and 77.3% for technique B (p 0.05). Results:ĭose to PTV did not differ between technique A and B. Film dosimetry was used to show the dose pattern at the field edge produced by the two techniques. The dose was prescribed for the reference point according to ICRU 50. Dose-volume histograms of PTV, V rectum and V bladder were analyzed. For technique B the collimator angle of the lateral fields was optimized to compensate the cascade field shape. For technique A the MLC was adapted to the PTV using a 0° collimator angle for the lateral fields. Two four-field techniques (0°, 90°, 180°, 270°) were planned using “beam’s eye view” for setting the leaf position of the MLC. The volumes of interest (VOI) were the planning target volume (PTV the region of the prostate including the seminal vesicles), the volume of rectum (V rectum) and urinary bladder (V bladder).

By a three-dimensional planning system (TMS, Helax 6.1B) the irradiation was planned for an 18-MV linear accelerator (Primus 1, Siemens). Ten patients with prostate cancer receiving postoperative, adjuvant irradiation were studied prospectively. A technical modification for radiotherapy of prostate cancer is presented to smooth the scalloped dose pattern that occurs at treatment field edge, when a multileaf collimator (MLC) has been used.

Purpose of multileaf collimator in radiotherapy