Because there are indications for an increased risk of cardiovascular diseases after radiotherapy of the left chest wall the dose to the heart should be reduced as far as possible. With respiratory gating technique irradiation can be restricted to only the inspiration plateau phase and so the distance between heart and chest wall will be increased. As a result the dose to the heart, in particular to the anterior wall, can be reduced. We investigated in all patients with left-sided breast cancer dose reduction to the heart when treated only in the inspiration phase compared with not gated treatments and correlated the dose reduction with other parameters as movements of the chest wall or diaphragm, age and body mass index. Between September 04 and April 2007 80 patients with left-sided breast cancer were treated with respiratory gating technique based on a retrospective 4D CT scan. With this technique we irradiate only in inspiration phase with an amplitude range between 80%-50% as lower threshold and 100% as upper threshold. For the investigation of real dose reduction to the heart we performed for all of these patients a normal and a respiratory gated planning CT. Planning was done with the same treatment parameters in both CT. DVH for the entire heart and the anterior wall of the left ventricle wall were calculated. 79/80 of these patients were treated with 2 Gy single doses to a total dose of 50 Gy to the entire left breast/chest wall, 1 pat with 1.8 Gy single doses to 50.4 Gy. 42 pat. had an additional boost of 10 Gy. The PTV was in 64 pat. after breast conserving surgery the left breast, in 16 pat. after mastectomy the left chest wall. In 13 pat. also the loco-regional lymph nodes were treated with 50 Gy. The mean dose to the entire heart was 0.7 Gy (0.1 Gy–1.7 Gy) without and 0.5 Gy (0.1 Gy–1.6 Gy) with respiratory gating (p = 0.005). To median dose to the anterior ventricle wall was 2.3 Gy (0.5 Gy–7.9 Gy) without and 1.3 Gy (0.1 Gy–5.6 Gy) with respiratory gating (p = 0.001). The median maximal dose to the anterior wall was 45.2 Gy (5.5 Gy–52.3 Gy) without and 4.5 Gy (0.9 Gy–50.6 Gy) with respiratory gating (p = 0.001). In 52 pat. the maximum dose reduction to the anterior wall was >20 Gy. In this pat. the mean movement of the diaphragm was 26 mm against 16 mm for pat. with dose reduction 20 Gy) and 5.2 mm (>20 Gy) (p = 0.05). We didn't find a correlation between age or body mass index and dose reduction to the heart. Respiratory gating and irradiation only in the inspiration phase significantly reduce radiation dose to the heart and especially to the anterior wall of the heart. Patients with maximal use of the diaphragm (abdominal breathing) seem to profit more from treating only in inspiration phase.

Purpose: For image‐guided radiotherapy (IGRT) the different vendors of linear accelerators offer new kV imaging tools. These systems include — besides a radiographic and fluoroscopic mode — CT functionality. The aim of this study was to evaluate the future potential of such a cone beam CT option for therapy planning purposes allowing dynamic adaptation for target volume changes. Method and Materials: The Varian On‐Board Imager™ (OBI) Cone Beam CT (CBCT) option consists of a kV‐source and kV‐Imager mounted on robotic arms perpendicular to the MV therapy beam. In a single 360° rotation a volumetric CT data set can be acquired with a 25 or 45 cm field‐of‐view. In order to calibrate the system with regard to HU a special phantom has been designed to include the whole imager area. Removable inserts allow the measurement of central axis doses. A planning study has been carried out to determine the usability of CBCT data and compare these to with diagnostic CT date. Results: Comparisons of data between a diagnostic CT scanner and the 3D‐calibrated Cone Beam CT with regard to image quality and hounsfield units representation for an humanoid phantom (RSD Alderson) indicate good accordance. Central axis doses applied during the acquisition of one volumetric data set are between 1 and 3 cGy depending on the geometry. Results with real patient data show appropriate image quality. Relative dose distributions in CBCT‐based plans show minor differences to plans calculated using a diagnostic CT image dataset (p=0.002) and absolute dosage deviations are within 1% (p=0.001). Conclusion: This work illustrates that a properly calibrated Cone Beam CT option allows off‐line treatment planning. Furthermore the image quality is sufficient for contouring of target outlines. CBCT can serve as control CT in order to adapt the target volume and resize the treatment fields and/or optimize the treatment plan.

Gated treatments using the Varian RPM-gating TM System include in a standard configuration a coaching tool based on voice commands ("breathe-in"/"breathe-out") called audio-coaching. As this configuration does not include feedback information like amplitude and breathing period, there are limitations concerning respiration depth and breathing pattern. The aim of this study was to evaluate the impact of video-coaching as biofeedback to achieve more regular breathing and–as a consequence–quality improvements of the 4D CT scans as well as duty cycle reductions. Varian RPM-gating system is used for acquisition of the CT-Scan (4D-CT) as well as the treatments; for the latter it manages the controlled switching of the radiation beam during a pre-selected specific phase of the respiratory cycle. 40 patients with gated treatments have been analyzed, whereas 20 were only audio-coached and 20 audio-coached with video-feedback. We evaluated periodicity and amplitude changes as well as compliance with regard to the theoretically calculated duty cycle and determined the dependency of the parameters on the coaching type. For the CT acquisitions several changes has been observed, i.e., fluctuations of the inspiration maxima are significantly smaller (p = 0.005) and the breathing curves are smoother. The compliance during the treatment course was significantly increased: almost all video-coached patients reached in average their theoretical duty cycle, whereas 60% of the patients with audio-coaching only had more than 25% longer treatment times due to inappropriate amplitudes. Periodicity is not dependent on the kind of coaching (p = 0.01). Video-coaching is suitable to significantly improve the quality of 4D scans and allows optimizing the treatment time due to better compliance. In the meantime we also implemented this feedback technology combined with deep inspiration breath hold technique thus allowing the patient to control the treatment themselves in a direct way. These results indicate that this approach could suit the individual patient need in a better way.

Purpose: Because there are indications for an increased risk of cardiovascular diseases after radiotherapy of the left chest wall the dose to the heart should be reduced as far as possible. With respiratory gating technique irradiation can be restricted only to the inspiratory plateau phase. We investigated in all patients with left sided breast cancer dose reduction to the heart when treated only in the inspiration phase compared with not gated treatments. Materials and Methods: Between Sept 2004 and Feb 2006 107 patients with left sided breast cancer were treated with respiratory gating technique based on a retrospective 4D CT scan. We performed for all of these patients a normal and a respiratory gated planning CT. Planning was done with the same treatment parameters in both CT. DVH for the entire heart and the anterior left ventricle wall were calculated. All patients were treated with 2 Gy single dose to a total dose of 50 Gy to the entire left breast/chest wall. 68 patients received an additional boost of 10 Gy. Results: The mean dose to the entire heart was 0.7 Gy without and 0.6 Gy with respiratory gating (p=0.04) whereas the mean maximal dose was 40.2 Gy without and 11.7 Gy with respiratory gating (p=0.0003). The anterior heart wall receives 2.4 Gy without and 1.2 Gy with respiratory gating (p=0.0001) with a mean maximal dose of 39.6 Gy without and 10.1 Gy with respiratory gating (p=0.0004). Conclusion: 4D analysis has shown that the distance between the PTV and the heart is influenced by two separate parameters. Besides the movements of the chest wall the heart is pushed into the irradiated volume also by the diaphragm. Respiratory gating and irradiation only in the inspiratory phase significantly reduces radiation doses to the heart and especially to the anterior heart wall.

Purpose: Gated treatments using the Varian RPM—gating™ System include in a standard configuration a coaching tool based on voice commands (“breathe‐in”/“breathe‐out”) called audio‐coaching. As this configuration does not include feedback information like amplitude and breathing period, there are limitations concerning respiration depth and breathing pattern. The aim of this study was to evaluate the impact of video‐coaching as biofeedback to improve gated treatments of breast cancer.Method and Materials: Varian RPM‐gating system is used for acquisition of the CT‐Scan (4D‐CT) as well as the treatments; for the latter it manages the controlled switching of the radiation beam during a pre‐selected specific phase of the respiratory cycle. 100 patients with gated treatments have been analyzed, whereas 50 were only audio‐coached and 50 audio‐coached with video‐feedback. We evaluated periodicity and amplitude changes as well as compliance with regard to the theoretically calculated duty cycle and determined the dependency of the parameters on the coaching type. Results: For the CT acquisition several changes has been observed, i.e. amplitude fluctuations are significantly smaller (p=0.005) and the breathing curves are smoother. This leads to an increased compliance during the treatment course: almost all video‐coached patients reached in average their theoretical duty cycle, whereas 60% of the patients with audio‐coaching only had more than 25% longer treatment times due to inappropriate amplitudes. Periodicity is not dependent on the kind of coaching (p=0.01). Conclusion: Video‐coaching is suitable to significantly improve the quality of 4D scans and allows optimizing the treatment time due to better compliance. In a next step we are currently implementing this feedback technology combined with deep inspiration breath hold technique thus allowing the patient to control the treatment themselves in a direct way. Preliminary results indicate that this approach could suit the individual patient need in a better way.

Purpose: The aim of this study was to evaluate the impact of the Varian RPM‐gating™ System for gated treatment of breast cancer/thoracic wall cancer as well as Varian On‐Board Imager™ (OBI) Fluoroscopic Pretreatment Setup Verification for gated treatment of lung cancers/upper intestinal tract cancers. Method and Materials: A passive, infrared light reflecting marker is placed on the patient's chest wall over the xiphoid process. The vertical motion of the marker, i.e. the breathing excursion, is tracked by an infrared sensitive video‐camera‐based hardware. The system is used for acquisition of the CT‐Scan (4D‐CT) as well as the treatments; for the latter it manages the controlled switching of the radiation beam during a pre‐selected specific phase of the respiratory cycle. The additional Fluoroscopic Setup Verification allows a fluoroscopy analysis of inner target movement with regard to a chosen therapeutic window of the RPM Gating system just prior to treatment. Results: Varian RPM‐gating technology optimizes the dose delivery to regions with respiration‐induced movements of the target. Safety margins and thereby irradiated critical volumes can be significantly reduced for breast cancer with RPM‐gating as well as lung cancer with the OBI Fluoroscopic Pretreatment Setup Verification. Conclusion: Gating offers the possibility to apply doses with higher accuracy. As typical duty cycles are around 50% ore even 10%, the overall beam‐on time is prolonged by a factor of up to 4. In order to compensate for this effect, a dose rate change from 300 to 600 MU/min when using enhanced dynamic wedges was chosen; in case of electronic compensation a dose rate change is not needed. The additional fluoroscopy mode offers for the very first time the possibility to verify patient positioning with regard to the moving target, which ‐ for most cases — shows a phase shift relative to the RPM marker box movement.