An effective preoperative three-dimensional radiotherapy target volume for extremity soft tissue sarcoma and the effect of margin width on local control.

Purpose: There is little information on the appropriate three-dimensional (3D) preoperative radiotherapy (XRT) volume for extremity soft-tissue sarcomas (STS). We retrospectively analyzed the pattern of local failure (LF) to help elucidate optimal field design.

Methods And Materials: We analyzed the 56 patients who underwent computed tomography-planned XRT for Stage I to III extremity STS between June 2000 and December 2006.

Four-dimensional imaging and treatment planning of moving targets.

Four-dimensional CT acquisition is commercially available, and provides important information on the shape and trajectory of the tumor and normal tissues. The primary advantage of four-dimensional imaging over light breathing helical scans is the reduction of motion artifacts during scanning that can significantly alter tumor appearance. Segmentation, image registration, visualization are new challenges associated with four-dimensional data sets because of the overwhelming increase in the number of images.

Quantification of respiration-induced abdominal tumor motion and its impact on IMRT dose distributions.

Purpose: The treatment of moving targets with intensity-modulated radiotherapy may introduce errors in dose delivery. The motion of tumors in the abdomen was studied using quantitative fluoroscopic analysis, and the effect on dose delivery to the target was studied.

Methods And Materials: Fluoroscopy sessions for 7 patients with pancreas or liver tumors and fiducial clips were recorded, converted to digital format, and analyzed to quantify the characteristics of tumor motion.

Artifacts in computed tomography scanning of moving objects.

Target volumes in the thorax and abdomen are commonly computed tomography (CT) scanned during light respiration. In this article, we analyze the distortions introduced in helical scanning of moving objects. Objects of known geometry are placed on a moving sled and scanned in a multirow helical CT scanner.

Dependence of fluence errors in dynamic IMRT on leaf-positional errors varying with time and leaf number.

In d-MLC based IMRT, leaves move along a trajectory that lies within a user-defined tolerance (TOL) about the ideal trajectory specified in a d-MLC sequence file. The MLC controller measures leaf positions multiple times per second and corrects them if they deviate from ideal positions by a value greater than TOL. The magnitude of leaf-positional errors resulting from finite mechanical precision depends on the performance of the MLC motors executing leaf motions and is generally larger if leaves are forced to move at higher speeds.

An experimental investigation on intra-fractional organ motion effects in lung IMRT treatments.

Respiration-induced tumour motion can potentially compromise the use of intensity-modulated radiotherapy (IMRT) as a dose escalation tool for lung tumour treatment. We have experimentally investigated the intra-fractional organ motion effects in lung IMRT treatments delivered by multi-leaf collimator (MLC). An in-house made motor-driven platform, which moves sinusoidally with an amplitude of 1 cm and a period of 4 s, was used to mimic tumour motion.