Deep inspiration breath-hold technique for lung tumors: the potential value of target immobilization and reduced lung density in dose escalation

Many lung cancer patients who undergo radiation therapy are treated with higher energy photons (15‐18 MV) to obtain deeper penetration and better dose uniformity. However, the longer range of the higher energy recoil electrons in the low‐density medium may cause lateral electronic disequilibrium and degrade the target coverage. To compare the dose homogeneity achieved with lower versus higher energy photon beams, we performed a dosimetric study of 6 and 15 MV three‐dimensional (3D) conformal treatment plans for lung cancer using an accurate, patient‐specific dose‐calculation method based on a Monte Carlo technique. A 6 and 15 MV 3D conformal treatment plan was generated for each of two patients with target volumes exceeding 200 cm3 on an in‐house treatment planning system in routine clinical use. Each plan employed four conformally shaped photon beams. Each dose distribution was recalculated with the Monte Carlo method, utilizing the same beam geometry and patient‐specific computed tomography (CT) images. Treatment plans using the two energies were compared in terms of their isodose distributions and dose‐volume histograms (DVHs). The 15 MV dose distributions and DVHs generated by the clinical treatment planning calculations were as good as, or slightly better than, those generated for 6 MV beams. However, the Monte Carlo dose calculation predicted increased penumbra width with increased photon energy resulting in decreased lateral dose homogeneity for the 15 MV plans. Monte Carlo calculations showed that all target coverage indicators were significantly worse for 15 MV than for 6 MV; particularly the portion of the planning target volume (PTV) receiving at least 95% of the prescription dose false(V95false) dropped dramatically for the 15 MV plan in comparison to the 6 MV Spinal cord and lung doses were clinically equivalent for the two energies. In treatment planning of tumors that abut lung tissue, lower energy (6 MV) photon beams should be preferred over higher energies (15–18 MV) because of the significant loss of lateral dose equilibrium for high‐energy beams in the low‐density medium. Any gains in radial dose uniformity across steep density gradients for higher energy beams must be weighed carefully against the lateral beam degradation due to penumbra widening.PACS number(s): 87.90.+y, 87.52.–g

Section: Introductionmentioning

confidence: 99%

Dosimetric advantage of using 6 MV over 15 MV photons in conformal therapy of lung cancer: Monte Carlo studies in patient geometries

Wang

Yorke

Desobry

et al. 2002

“…The AlignRT (3) or the Catalyst (4) system use full, continuous surface imaging to account for motion, do not require markers, and may be associated to third‐party gating apparatus. Other use similar optoelectronic localization technology, 5 , 6 , 7 or derive from spirometer techniques (8) . Combining the two approaches, the Novalis system (Brainlab AG, Feldkirchen, Germany) uses both X‐ray imaging and external signals to assess tissue motion.…”

Section: Introductionmentioning

confidence: 99%

Technical Note: A respiratory monitoring and processing system based on computer vision: prototype and proof of principle

Leduc

Atallah

Escarmant

et al. 2016

Monitoring and controlling respiratory motion is a challenge for the accuracy and safety of therapeutic irradiation of thoracic tumors. Various commercial systems based on the monitoring of internal or external surrogates have been developed but remain costly. In this article we describe and validate Madibreast, an in‐house‐made respiratory monitoring and processing device based on optical tracking of external markers. We designed an optical apparatus to ensure real‐time submillimetric image resolution at 4 m. Using OpenCv libraries, we optically tracked high‐contrast markers set on patients' breasts. Validation of spatial and time accuracy was performed on a mechanical phantom and on human breast. Madibreast was able to track motion of markers up to a 5 cm/s speed, at a frame rate of 30 fps, with submillimetric accuracy on mechanical phantom and human breasts. Latency was below 100 ms. Concomitant monitoring of three different locations on the breast showed discrepancies in axial motion up to 4 mm for deep‐breathing patterns. This low‐cost, computer‐vision system for real‐time motion monitoring of the irradiation of breast cancer patients showed submillimetric accuracy and acceptable latency. It allowed the authors to highlight differences in surface motion that may be correlated to tumor motion.PACS number(s): 87.55.km

“…Motion management requires both acquisition and correction techniques. Acquisition techniques incorporate the following tools: methods that acquire signals and images using a spirometer combined with artificial manipulation of the patient's respiration; 4 , 8 sensors that are used in real‐time position management (RPM), such as the Anzai, Calypso, and ExacTrac systems; fluoroscopy; and cone‐beam computed tomography (CBCT) 9 , 17 …”

Section: Introductionmentioning

confidence: 99%

“…Acquisition techniques can be classified into three groups: respiration‐based, sensor‐based, and image‐based techniques. Hanley et al (4) reported a PTV margin decrease from 1–2 cm to 0.2–0.5 cm using deep inspiration breath‐holding (DIBH) for lung tumors. The authors demonstrated that the target dose escalation improved because of the decreased response of normal lungs to high doses.…”

Section: Introductionmentioning

confidence: 99%

Evaluation of mechanical accuracy for couch‐based tracking system (CBTS)

Lee

Chang

Shim

et al. 2012

This study evaluated the mechanical accuracy of an in‐house–developed couch‐based tracking system (CBTS) according to respiration data. The overall delay time of the CBTS was calculated, and the accuracy, reproducibility, and loading effect of the CBTS were evaluated according to the sinusoidal waveform and various respiratory motion data of real patients with and without a volunteer weighing 75 kg. The root mean square (rms) error of the accuracy, the reproducibility, and the sagging measurements were calculated for the three axes (X, Y, and Z directions) of the CBTS. The overall delay time of the CBTS was 0.251 sec. The accuracy and reproducibility in the Z direction in real patient data were poor, as indicated by high rms errors. The results of the loading effect were within 1.0 mm in all directions. This novel CBTS has the potential for clinical application for tumor tracking in radiation therapy.PACS number: 87.55.ne