Respiratory-gated Radiotherapy Research Articles

EP-1242: Respiratory-gated radiotherapy in filter-free photon mode for the treatment of liver carcinomas

EP-1242: Respiratory-gated radiotherapy in filter-free photon mode for the treatment of liver carcinomas

Potential benefits and pitfalls of respiratory‐gated radiotherapy in the treatment of thoracic malignancy

Despite advances in radiotherapy delivery, the prognosis of lung cancer remains poor. Higher doses of radiation have been associated with improved outcomes but may result in higher toxicities. Respiratory gated radiotherapy (RGRT) has the potential to reduce pulmonary toxicity but there are significant limitations and pitfalls to its use. The aim of this article is to (i) describe the RGRT technique currently employed at Nepean and Westmead Hospitals; (ii) discuss the practical issues of implementing such a program; (iii) present the results of our RGRT program and (iv) review the potential uncertainties in using this technique and the methods we have used to overcome these. A retrospective review of all patients who had a 4D-computed tomography (4D-CT) scan was undertaken. Records from treatment planning systems were used to assess the prospective gating program. Between September 2007 and June 2011, 53 patients at Nepean and 26 patients at Westmead Hospital underwent a 4D-CT. Between April and August 2011, 26 patients at Westmead Hospital underwent a prospective 4D-CT scan as treatment verification. Two of the 26 patients (7.7%) were found to have incomplete coverage of the planning target volume. Both patients underwent respiratory re-coaching, alleviating the need for replanning. RGRT may reduce doses to organs at risk with the potential for dose escalation. However its implementation requires significant staff training, treatment time and resources. Treatment verification with image guided radiation therapy are essential for safe delivery.

A Computer-Controlled Dynamic Phantom for Respiratory-Gated Medical Radiotherapy Research

This paper describes the breathing phantom built to test a six-degree-of freedom sensing device designed for use in Respiratory-Gated Radiotherapy (RGRT). It is focussed on the construction of a test bed that was designed to address tumour motion issues while, at the same time, behaving in much the same way as the human tissues when irradiated. The phantom can produce respiratory movement in three dimensions. Shift differences between the motion axes can be introduced. The position error in the worst case scenario is not greater that 0.4 mm. Emphasis is made on the technical limitations of current sensing technologies, especially with regard to acceleration sensitivity. This study demonstrates that the sensitivity of accelerometers used to sense tumour motion should be 0.05 mG or less.

Improvement in the accuracy of respiratory-gated radiation therapy using a respiratory guiding system

The accuracy of respiratory-gated radiation therapy (RGRT) depends on the respiratory regularity because external respiratory signals are used for gating the radiation beam at particular phases. Many studies have applied a respiratory guiding system to improve the respiratory regularity. This study aims to evaluate the effect of an in-house-developed respiratory guiding system to improve the respiratory regularity for RGRT. To verify the effectiveness of this system, we acquired respiratory signals from five volunteers. The improvement in respiratory regularity was analyzed by comparing the standard deviations of the amplitudes and the periods between free and guided breathing. The reduction in residual motion at each phase was analyzed by comparing the standard deviations of sorted data within each corresponding phase bin as obtained from free and guided breathing. The results indicate that the respiratory guiding system improves the respiratory regularity, and that most of the volunteers showed significantly less average residual motion at each phase. The average residual motion measured at phases of 40, 50, and 60%, which showed lower variation than other phases, were, respectively, reduced by 41, 45, and 44% during guided breathing. The results show that the accuracy of RGRT can be improved by using the in-house-developed respiratory guiding system. Furthermore, this system should reduce artifacts caused by respiratory motion in 4D CT imaging.

The Effect of Breathing Biofeedback on Breathing Reproducibility and Patient's Dose in Respiration-gated Radiotherapy

135 This work was supported by the Industrial Strategic technology development program (10035527) funded by the Ministry of Knowledge Economy (MKE, Korea). Submitted September, 27, 2012, Accepted September, 2, 2013 Corresponding Author: Rena Lee, Department of Radiation Oncology, School of Medicine, Ewha Womans University, Mok 5-dong, Yangcheon-gu, Seoul 158-710, Korea Tel: 02)2650-2022, Fax: 02)2654-0363 E-mail: heraash@hanmail.net The Effect of Breathing Biofeedback on Breathing Reproducibility and Patient’s Dose in Respiration-gated Radiotherapy

Recent developments in radiotherapy for hepatocellular carcinoma

The role of radiotherapy in practice is mainly palliative. According to the Practice Guidelines for Management of Hepatocellular Carcinoma (2009) developed by the Korean Liver Cancer Study Group and the National Cancer Center, Korea, radiotherapy can be applied for 1) refractoriness to trans-catheter hepatic arterial chemo-embolization, 2) portal vein tumor thrombosis, and 3) palliative therapy to reduce the symptoms caused by hepatocellular carcinoma. Radiotherapy is one of the most rapidly developing fields of medical research. Recent advances in intensity-modulated radiotherapy, image-guided radiotherapy, and respiratory-gated radiotherapy technologies have enabled more accurate and precise radiation delivery for the treatment of hepatocellular carcinoma. Proton therapy is also emerging as a candidate therapy for ablative measures for patients ineligible for other curative local therapies. Due to recent advances in radiotherapy technologies, radiotherapy for hepatocellular carcinoma has been evolving into stereotactic ablative radiotherapy, which delivers an ablative dose of radiation in 1 to 4 sessions. Clinical series have confirmed that it is safe in Child-Pugh A patients and local control is sustained. The possibility for performing phase 3 randomized clinical trials involving the radiotherapy modality has increased with those advances. Not merely palliative, the role of radiotherapy in the treatment of hepatocellular carcinoma will be expanded to potentially curative therapy in patients who are ineligible for other curative local therapies.

Promising Early Results of Stereotactic Body Radiation Therapy for Hepatocellular Carcinoma With Respiratory Gated Radiation Therapy

Promising Early Results of Stereotactic Body Radiation Therapy for Hepatocellular Carcinoma With Respiratory Gated Radiation Therapy

Respiratory Gated Radiation Therapy With Hypofractionated Doses for Lung Tumors: Four Years' Experience of a Single Institution

Respiratory Gated Radiation Therapy With Hypofractionated Doses for Lung Tumors: Four Years' Experience of a Single Institution

Patient-specific Quality Assurance Using a 4-dimensional Programmable Motion Platform in Respiratory Gated Radiation Therapy

Patient-specific Quality Assurance Using a 4-dimensional Programmable Motion Platform in Respiratory Gated Radiation Therapy

Clinical Experience With Respiratory-Gated Stereotactic Body Radiation Therapy (SBRT) for Lung Tumors Using Audio Coaching

Stereotactic Body Radiation Therapy (SBRT) for Stage I Non-small Cell Lung Cancer (NSCLC): Analysis Based on the New TNM Classification and Difference Due to Histology C. Hashizume, Y. Shibamoto, Y. Mori, T. Tsugawa, S. Otsuka, A. Hayashi, and H. Nakazawa; Nagoya Kyoritsu Hospital-Radiosurgery Center, Nagoya, Japan, Department of Radiology and Radiation Oncology, Nagoya City University Graduate School of Medical Sciences, Nagoya, Japan

Reproducibility of image quality for moving objects using respiratory-gated computed tomography: a study using a phantom model

To investigate the reproducibility of computed tomography (CT) imaging quality in respiratory-gated radiation treatment planning is essential in radiotherapy of movable tumors. Seven series of regular and six series of irregular respiratory motions were performed using a thorax dynamic phantom. For the regular respiratory motions, the respiratory cycle was changed from 2.5 to 4 s and the amplitude was changed from 4 to 10 mm. For the irregular respiratory motions, a cycle of 2.5 to 4 or an amplitude of 4 to 10 mm was added to the base data (i.e. 3.5-s cycle, 6-mm amplitude) every three cycles. Images of the object were acquired six times using respiratory-gated data acquisition. The volume of the object was calculated and the reproducibility of the volume was decided based on the variety. The registered image of the object was added and the reproducibility of the shape was decided based on the degree of overlap of objects. The variety in the volumes and shapes differed significantly as the respiratory cycle changed according to regular respiratory motions. In irregular respiratory motion, shape reproducibility was further inferior, and the percentage of overlap among the six images was 35.26% in the 2.5- and 3.5-s cycle mixed group. Amplitude changes did not produce significant differences in the variety of the volumes and shapes. Respiratory cycle changes reduced the reproducibility of the image quality in respiratory-gated CT.

Intérêts dosimétriques et cliniques de la radiothérapie asservie à la respiration des cancers du poumon et du sein : résultats du Stic 2003

PurposeTo compare respiratory-gated conformal radiotherapy versus conventional conformal radiotherapy for the irradiation of non-small cells lung cancer and breast cancer. Patients and methodsThe STIC 2003 project was a comparative, non-randomized, multicenter and prospective study that included in 20 French centers between April 2004 and June 2008, 634 evaluable patients, 401 non-small cells lung cancer and 233 breast cancers. ResultsThe final results confirmed the feasibility and good reproducibility of the various respiratory-gated conformal radiotherapy systems regardless of tumour location. The results of this study demonstrated a marked reduction of dosimetric parameters predictive of pulmonary, cardiac and esophageal toxicity, especially for non-small cells lung cancer, as a result of the various respiratory gating techniques. These dosimetric benefits were mainly observed with deep inspiration breath-hold techniques (ABC and SDX), which markedly increased the total lung volume compared to the inspiration-synchronized system based on tidal volume (RPM). For non-small cells lung cancer, these theoretical dosimetric benefits were correlated with a significant reduction in clinically acute and late toxicities, especially the pulmonary. For breast cancer, although less clear due to the lower total dose, there was a decrease in the dose delivered to the heart, potentially reducing the risk of cardiac toxicity in the long-term, especially during the irradiation of the left breast, and a reduction in dose to the contra lateral breast. ConclusionRespiratory-gated radiotherapy appears to be essential to reduce the risk of acute and late toxicities, especially for lungs and heart, during irradiation of non-small cells lung cancer and breast cancers.

Accuracy and Consistency of Respiratory Gating in Abdominal Cancer Patients

To evaluate respiratory gating accuracy and intrafractional consistency for abdominal cancer patients treated with respiratory gated treatment on a regular linear accelerator system. Twelve abdominal patients implanted with fiducials were treated with amplitude-based respiratory-gated radiation therapy. On the basis of daily orthogonal fluoroscopy, the operator readjusted the couch position and gating window such that the fiducial was within a setup margin (fiducial-planning target volume [f-PTV]) when RPM indicated "beam-ON." Fifty-five pre- and post-treatment fluoroscopic movie pairs with synchronized respiratory gating signal were recorded. Fiducial motion traces were extracted from the fluoroscopic movies using a template matching algorithm and correlated with f-PTV by registering the digitally reconstructed radiographs with the fluoroscopic movies. Treatment was determined to be "accurate" if 50% of the fiducial area stayed within f-PTV while beam-ON. For movie pairs that lost gating accuracy, a MATLAB program was used to assess whether the gating window was optimized, the external-internal correlation (EIC) changed, or the patient moved between movies. A series of safety margins from 0.5 mm to 3 mm was added to f-PTV for reassessing gating accuracy. A decrease in gating accuracy was observed in 44% of movie pairs from daily fluoroscopic movies of 12 abdominal patients. Three main causes for inaccurate gating were identified as change of global EIC over time (∼43%), suboptimal gating setup (∼37%), and imperfect EIC within movie (∼13%). Inconsistent respiratory gating accuracy may occur within 1 treatment session even with a daily adjusted gating window. To improve or maintain gating accuracy during treatment, we suggest using at least a 2.5-mm safety margin to account for gating and setup uncertainties.

SU-E-J-168: 4D-PET for Target Volume Delineation in Respiratory-Gated Radiation Therapy.

To find an optimized workflow for the use of respiratory-gated PET (4D-PET) in target volume delineation of tumors subject to respiratory-gated radiation therapy. 15 patients with lung (11) and pancreas (4) tumors who had FDG-PET-CT for target delineation prior to EBRT were studied. Patients were selected among the group that showed respiratory-induced tumor motion 〉5mm. 4D-PET was performed by means of a Philips Gemini BigBore scanner, using the Varian RPM gating system. An identical system was available at the linac for treatment. The breathing cycle was equally divided in 4 phases, according to a previous study. Since planning was made on a single CT-phase, no ITV was explicitly built from the set of phases. The BTV was identified with SUV=2.2 threshold and the PTV was obtained expanding the BTV by 8mm(S-I), 5mm(A-P) and 3mm(L-R) to account for residual motion and setup errors. The most advantageous CT-phase for treatment planning was then identified by simulating plans on each phase and analyzing the resulting DVHs of OARs (lung, trachea, oesophagus, spinal cord, left ventricle). The observed maximum range of motion was 5.5mm(L-R), 12.3mm(A-P) and 19.2mm(S-I). The standard deviation of the BTV volume in the 4 phases ranged from 6% to 13.7%. V20 (lung) ranged 7.1%-15.2% in inspiration and 7.8%-18.6% in expiration. The mean dose to the oesophagus ranged 0.1-2.2Gy in inspiration and 1.4-2.0Gy in expiration. In general, the dose to OARs was smaller when planning on a single phase than on the overall, respiratory-uncontrolled volume (p-value〈0.05). The BTV volume was almost constant between phases, confirming that the motion might be described by 4 phases. There was no obvious choice of the optimal phase for treatment planning, suggesting patient-by-patient studies. However, planning and delivery on one phase consistently allowed dose sparing to be obtained compared to non-gated techniques.

SU-E-J-166: Development of Real-Time Motion Verification System for Respiratory-Gated Radiotherapy.

To develop an on-line quality assurance tool for RPM (real-time position management system, Varian Medical Systems, Palo Alto, CA) phase-based gated radiotherapy. A real-time motion verification system (RMVS) was developed to verify the positional reproducibility of patient breathing between CT simulation and treatment. Phase-resolved anterior body midlines were extracted from the 4D-CT simulation data to constitute 4D reference lines. During the treatment, multiple infrared reflective markers attached on patient's body midline were tracked by a custom stereo camera system. The RPM-generated phase value was delivered to RMVS via in-house network communication software. The real-time positions of tracked markers were simultaneously compared with the 4D reference line dynamically selected according to the phase value. The technical feasibility of the system was evaluated by simulating a motion phantom under several scenarios such as ideal case (with identical motion parameters between simulation and treatment; cycle = 3.1 s, baseline = 0.0 mm, amplitude = 31.0 mm), cycle change, baseline shift, and amplitude change. The developed system (i.e., RMVS) was fully compatible with RPM. In the phantom experiments, RMVS detected 5.2 ± 1.3, 4.7 ± 1.2, and 9.8 ± 1.2 mm mean absolute errors (MAE) for -5.0, 5.0, and 10.0 mm baseline shifts, respectively. However, revealing about 1.0 mm MAE for both ideal and cycle change scenarios, RMVS turned out to have a systematic error. With 22.0, 26.0, 35.0, and 41.5 mm amplitudes, RMVS detected 2.3 ± 1.3, 1.5 ± 1.1, 2.3 ± 1.4, and 4.9 ± 2.5 mm MAE, respectively. The developed system demonstrated a competence for phase-matching error detection between real-time patient's motion and 4D-CT-based reference. Thus, it could be used as an on-line quality assurance tool for RPM phase-based radiotherapy. This work was supported in part by the SNU Brain Fusion Program Research Grant No. 400-20100049 (2010-2011) and the National Research Foundation of Korea (NRF) grant (800-20110212) funded by the Korea government (MEST).

Adaptive external gating based on the updating method of internal/external correlation and gating window before each beam delivery

The purpose of this study is to evaluate the performance of an adaptive gating method, which is designed to accommodate the beam-to-beam and day-to-day variation of the internal/external correlation, as well as the real tumor position during respiratory-gated fractionated radiotherapy. We define a two-step procedure: (1) before each treatment, target positions are detected and synchronized with an external surrogate for establishing the internal/external correlation model and determining the position of the gating window, and then (2) during the delivery of the treatment beam, the gating is triggered by an external signal based on the updated internal/external correlation and window position. This correlation is described by a linear-quadratic model including a time shift between the internal and external signals. To simulate the proposed method, data of tumor motion in the superior–inferior direction synchronized with an external surrogate during hypo-fractionated radiotherapy from five lung patients are analyzed retrospectively. Duty cycle (DC), target coverage (TC) and the average distance (AD) between the internal target position and the edge of the gating window for all false positives are calculated as evaluative criteria. Under a 5 mm gating window, the average TC is 88.9%, with a DC around 45% and a mean AD of 0.7 mm. A daily update is also simulated for comparison, and it is found that beam-to-beam updating is superior. In conclusion, the combined updating of internal/external correlation and the gating window for each beam can improve the accuracy and reliability of respiratory-gated radiotherapy.

Contribution of Respiratory Gating Techniques for Optimization of Breast Cancer Radiotherapy

A comparative, nonrandomized, multicenter, and prospective analysis were performed between April 2004 and June 2008 in 20 French centers in order to compare clinical aspects of respiratory-gated conformal radiotherapy (RGRT) during breast cancer irradiation versus conventional conformal radiotherapy. The final results based on 233 evaluable patients at 48 months confirm the feasibility and good reproducibility of the RGRT systems. The main results demonstrated a marked reduction of dosimetric parameters predictive of lungs and cardiac toxicities in the RGRT group; especially the dose delivered to the heart during irradiation of the left breast; mostly observed with deep inspiration breath-hold techniques.

Functional Image-Guided Radiotherapy Planning in Respiratory-Gated Intensity-Modulated Radiotherapy for Lung Cancer Patients With Chronic Obstructive Pulmonary Disease

To investigate the incorporation of functional lung image-derived low attenuation area (LAA) based on four-dimensional computed tomography (4D-CT) into respiratory-gated intensity-modulated radiotherapy (IMRT) or volumetric modulated arc therapy (VMAT) in treatment planning for lung cancer patients with chronic obstructive pulmonary disease (COPD). Eight lung cancer patients with COPD were the subjects of this study. LAA was generated from 4D-CT data sets according to CT values of less than than -860 Hounsfield units (HU) as a threshold. The functional lung image was defined as the area where LAA was excluded from the image of the total lung. Two respiratory-gated radiotherapy plans (70 Gy/35 fractions) were designed and compared in each patient as follows: Plan A was an anatomical IMRT or VMAT plan based on the total lung; Plan F was a functional IMRT or VMAT plan based on the functional lung. Dosimetric parameters (percentage of total lung volume irradiated with ≥20 Gy [V20], and mean dose of total lung [MLD]) of the two plans were compared. V20 was lower in Plan F than in Plan A (mean 1.5%, p = 0.025 in IMRT, mean 1.6%, p = 0.044 in VMAT) achieved by a reduction in MLD (mean 0.23 Gy, p = 0.083 in IMRT, mean 0.5 Gy, p = 0.042 in VMAT). No differences were noted in target volume coverage and organ-at-risk doses. Functional IGRT planning based on LAA in respiratory-guided IMRT or VMAT appears to be effective in preserving a functional lung in lung cancer patients with COPD.

4次元照射と呼吸同期照射

4次元照射と呼吸同期照射

Respiratory Gating Techniques for Optimization of Lung Cancer Radiotherapy

The primary objective of the STIC 2003 project was to compare the clinical and economic aspects of respiratory-gated conformal radiotherapy (RGRT), an innovative technique proposed to limit the impact of respiratory movements during irradiation, versus conventional conformal radiotherapy, the reference radiation therapy for lung cancer. A comparative, nonrandomized, multicenter, and prospective cost toxicity analysis was performed in the context of this project between April 2004 and June 2008 in 20 French centers. Only the results of the clinical study are presented here, as the results of the economic assessment have been published previously. The final results based on 401 evaluable patients confirm the feasibility and good reproducibility of the various RGRT systems. The results of this study demonstrated a marked reduction of dosimetric parameters predictive of pulmonary, cardiac and esophageal toxicity as a result of the various respiratory gating techniques. These dosimetric benefits were mainly observed with deep inspiration breath-hold (DIBH) techniques (ABC and SDX systems), which markedly increased the total lung volume compared with the inspiration-synchronized system based on tidal volume (Real-time Position Management). These theoretical dosimetric benefits were correlated clinically with a significant reduction of pulmonary acute toxicity, and the pulmonary, cardiac, and esophageal late toxicities, especially with DIBH techniques. Pulmonary function parameters, although more heterogeneous, especially DLCO, showed a tendency to reduction of pulmonary toxicity in the RGRT group. RGRT seems to be essential to reduce toxicities, especially the pulmonary, cardiac, and esophageal late toxicities with the DIBH methods.