The use of active breathing control (ABC) to reduce margin for breathing motion

A three‐dimensional (3D) optical flow program that includes a multi‐resolution feature has been developed and applied to 3D anatomic structure and gross tumor volume (GTV) contour mapping for four‐dimensional computed tomography (4D CT) data. The present study includes contour mapping for actual CT data sets from 3 patients and also for a thoracic phantom in which the displacement for each voxel was known. Of the CT data sets for the actual patients, one set was used to map lung and GTV contours over all respiration phases, and the other two were studied using only the end inspiration and end expiration phases, in which the displacements between phases were the largest. Including the residual motion in the 4D CT data and motion from table shaking, the optical flow calculation agrees with the known displacement to within 1 mm. Excluding errors not introduced by the optical flow algorithm, agreement for a displacement magnitude of 24 mm can be within 0.1 mm. The mapped contours in 4D CT images of lungs, liver, esophagus, GTV, and other structures for actual patients were acceptable to clinicians. The 3D optical flow program is a good tool for contour mapping of anatomic structure and tumor volume across 4D CT scans.PACS numbers: 87.55.D‐, 87.59.bd

Section: Introductionmentioning

confidence: 99%

Use of three‐dimensional (3D) optical flow method in mapping 3D anatomic structure and tumor contours across four‐dimensional computed tomography data

Zhang

Huang

Guerrero

et al. 2008

“…Researchers have developed alternative techniques that account for respiratory motion to reduce the target volume. These techniques include tumor tracking and gated beam delivery 1, 2, 3, 4, 5, 6, 7, 8…”

Section: Introductionmentioning

confidence: 99%

Does gated beam delivery impact delivery accuracy on an Elekta linac?

Jermoumi¹,

Xie²,

Cao³

et al. 2017

In this study, we evaluated the performance of an Elekta linac in the delivery of gated radiotherapy. Delivery accuracy was examined with an emphasis on the impact of using short gating windows (low monitor unit beam‐on segments) or long beam hold times. The performance was assessed using a 20cm by 20cm open field with the radiation delivered using a range of beam‐on and beam‐off time periods. Gated delivery measurements were also performed for two SBRT plans delivered using volumetric modulated arc therapy (VMAT). Tests included both free‐breathing based gating (covering a variety of gating windows) and simulated breath‐hold based gating. An IBA MatriXX 2D ion chamber array was used for data collection, and the gating accuracy at low MU was evaluated using gamma passing rates. For the 20 cm by 20 cm open field, the measurements generally showed close agreement between the gated and non‐gated beam deliveries. Discrepancies, however, began to appear with a 5‐to‐1 ratio of the beam‐off to beam‐on times. The discrepancies observed for these tight gating windows can be attributed to the small number of monitor units delivered during each beam‐on segment. Dose distribution analysis from the delivery of the two SBRT plans showed gamma passing rates (± 1%, 2%/1 mm) in the range of 95% to 100% for gating windows of 25%, 38%, 50%, 63%, 75%, and 83%. Using a simulated sinusoidal breathing signal with a 4 second period, the gamma passing rate of free‐breathing gating and breath‐hold gating deliveries were measured in the range of 95.7% to 100%. In conclusion, the results demonstrate that Elekta linacs can accurately deliver respiratory gated treatments for both free‐breathing and breath‐hold patients. Some caution should be exercised with the use of very tight gating windows.

“…Korreman et al (24) had shown that voluntary DIBH reduces cardiac doses simultaneous with significant pulmonary tissue sparing, in comparison to the end‐inspiration gating technique. In breast cancer, many investigators 25 , 31 have tried to minimize the variation of the breast motion and reduce the heart and lung volume in the irradiation field 25 , 29 , 30 through deep inspiration by various breath‐holding techniques, such as active breathing control (ABC) 26 , 28 , 31 and DIBH. The treatment usually needs to be broken down into a couple of sections while employing these techniques because the beam delivery time is too long to be given in one breath‐holding.…”

Section: Introductionmentioning

confidence: 99%

The feasibility study of using multiple partial volumetric‐modulated arcs therapy in early stage left‐sided breast cancer patients

Tsai

Lin

Lee

et al. 2012

The purpose of this study was to assess the feasibility of using a multiple partial volumetric‐modulated arcs therapy (MP‐VMAT) technique on the left breast irradiation and to evaluate the dosimetry and treatment efficiency. Ten patients with left‐sided breast cancer who had been treated by whole breast irradiation were selected for the treatment plan evaluation by using six partial volumetric modulated arcs. Each arc consisted of a 50° gantry rotation. The planning target volumes and the normal organs, including the right breast, the bilateral lungs, left ventricle, heart, and unspecified tissue, were contoured on the CT images. Dose‐volume histograms were generated and the delivery time for each arc was recorded. The PTV received greater than 95% of the V95 for all cases, and the maximum dose was within ±1% of 110% of the prescription dose. The mean homogeneity index (HI) was 10.61±0.99, and mean conformity index (CI) was 1.21±0.03. The mean dose, V5, V10, V25, and V30 of the heart were 7.61±1.38 Gy, 59.73% ±15.87%, 24.39% ±6.82%, 2.52% ±1.11%, and 1.57% ±0.71%, respectively. The volume of the left ventricle receiving 25 Gy was 5.15% ±2.23%. The total lung mean dose was 5.57±0.36 Gy, with V5 of 25.39% ±3.88% and V20 of 5.66% ±0.89%. The right breast received a mean dose of 2.13±0.22 Gy, with V5 of 1.83% ±1.22% and V10 of 0.04% ±0.12%. The mean dose of unspecified tissue was 5.34±0.37 Gy and V5 was 22.23% ±1.57%. The volume of the unspecified tissue receiving 50 Gy was 0.50% ±0.14%. The mean delivery time for each arc was 13.9 seconds. The average MU among ten patients was 511 MU (range 443 to 594 MUs). The MP‐VMAT technique for the left‐sided breast cancer patients achieved adequate target dose coverage while maintaining low doses to organs‐at‐risk, and therefore reduced the potential for induction of second malignancy and side effects. The highly efficient treatment delivery would be beneficial for improving patient throughput, providing patient comfort, and achieving precise treatment with the breathing control system.PACS number: 87.55.‐x, 87.55.D‐, 87.55.dk