Evaluation of the use of abdominal compression of the lung in stereotactic radiation therapy.

The goal of this retrospective study was to determine the benefit in using abdominal compression to reduce tumor motion for patients treated with lung stereotactic body radiotherapy. Forty-four lung lesions (n = 44) from 37 patients (N = 37) treated at the University of Toledo's Dana Cancer Center were assessed by determining the overall tumor displacement along with possible surrogates such as change in tidal volume and diaphragm displacement, with and without abdominal compression. Measurements of lung capacity were acquired from the 4DCT at maximum and minimum respiration in order to determine the tidal volume, with and without abdominal compression. Tumor centroid and diaphragm apex motion was then assessed in 3 dimensions from phase 0 to phase 50. This was measured in centimeters using the ruler method on MIM software, both with and without the compression belt. Change in overall tumor movement was 0.61 cm ± 0.09 cm with compression, and 0.60 cm ± 0.09 cm without the compression belt. Delta tumor motion was reduced in 5 cases, increased (made worse) in 6 cases, and did not clinically impact the remaining 33 cases. Average tidal volume with abdominal compression was 379.7 mL or 12.0% ± 0.724% of total lung volume while average tidal volume without abdominal compression was 337.7 mL or 10.5% ± 0.649% of total lung volume. Change in diaphragm position throughout the breathing cycle was 1.21 cm ± 0.10 cm with compression, and 1.28 ± 0.13 cm without the compression belt. These findings indicate that abdominal compression may not be an effective method in the reduction of respiratory motion, and can even negatively impact tumor motion by increasing its displacement. Compression decreased tumor motion in 5 out of the 44 cases studied. The 5 cases that benefitted tended to be lesions close to the diaphragm but these 5 corresponded to less than half of the inferior lesions, suggesting that even inferior lung lesions may not be prime candidates for abdominal compression.

Retrospective dosimetric analysis of brain lesions planned in Pinnacle 9.8 via a HDMLC linac.

The University of Toledo Medical Center's Eleanor N. Dana Cancer Center located in northwest Ohio currently utilizes the Edge Radiosurgery System (Varian Medical Systems Inc., Palo Alto, CA) to deliver stereotactic radiosurgery for the treatment of brain lesions. The purpose of this study is to determine the quality of conformal arc radiotherapy in treating patients with brain lesions at The University of Toledo Medical Center and to provide more data for conformity and gradient indices (due to a lack of current data) to hopefully improve national standards by allowing centers to compare among each other. Treatment plans were assessed using the Pinnacle3 v9.8 Radiation Therapy Planning System (Philips Healthcare, Amsterdam, Netherlands). For patients (n = 41) presenting with small brain lesions (n = 82) and treated with conformal arc radiotherapy via the Edge Radiosurgery System, the RTOG conformity index, Paddick conformity index, conformity gradient index, gradient index, and dose gradient index were determined for each plan. This study additionally provides data to suggest the more accurate method of volume derivation provided by the Pinnacle3 v9.8 software. Using this method, average values for each of the following indices were calculated: RTOG conformity index = 1.36 ± 0.29; Paddick conformity index = 0.72 ± 0.12; conformity gradient index = 214.67 ± 12.35; gradient index = 3.64 ± 1.09; dose gradient index = -0.11 ± 0.16. Thus, The University of Toledo Medical Center provides favorable conformity of dose to intracranial target lesions.