Deep Inspiration Breath Hold Patients Research Articles

WE‐DE‐209‐01: Dosimetric Benefits of DIBH

Breast radiation therapy is associated with some risk of lung toxicity as well as cardiac toxicity for left‐sided cases. Radiation doses to the lung and heart can be reduced by using the deep inspiration breath hold (DIBH) technique, in which the patient is simulated and treated during the deep inspiration phase of the breathing cycle. During DIBH, the heart is usually displaced posteriorly, inferiorly, and to the right, effectively expanding the distance between the heart and the breast/chest wall. As a result, the distance between the medial treatment field border and heart/lung is increased. Also, in a majority of DIBH patients, the air drawn into the thoracic cavity increases the total lung volume.The DIBH was discussed by an AAPM Task Group 10 years ago in the AAPM TG 76 report. However, DIBH is still not the standard of care in many clinics, which may be partially due to challenges associated with its implementation. Therefore, this seccion will focus primarily on how to clinically implement four different DIBH techniques: (1) Active Breathing Control, (2) Spirometric Motion Management, (3) 3D Surface Image‐Guided, and (4) Self‐held Breath Control with Respiratory Monitoring and Feedback Guidance. Learning Objectives: Describe the physical displacement of the heart and the change in lung volume during DIBH and discuss dosimetric consequences of those changes. Provide an overview of the technical aspects. Describe work flow for patient simulation and treatment. Give an overview of commissioning and routine. Provide practical tips for clinical implementation.

WE‐DE‐209‐04: 3D Surface Image‐Guided

Breast radiation therapy is associated with some risk of lung toxicity as well as cardiac toxicity for left‐sided cases. Radiation doses to the lung and heart can be reduced by using the deep inspiration breath hold (DIBH) technique, in which the patient is simulated and treated during the deep inspiration phase of the breathing cycle. During DIBH, the heart is usually displaced posteriorly, inferiorly, and to the right, effectively expanding the distance between the heart and the breast/chest wall. As a result, the distance between the medial treatment field border and heart/lung is increased. Also, in a majority of DIBH patients, the air drawn into the thoracic cavity increases the total lung volume.The DIBH was discussed by an AAPM Task Group 10 years ago in the AAPM TG 76 report. However, DIBH is still not the standard of care in many clinics, which may be partially due to challenges associated with its implementation. Therefore, this seccion will focus primarily on how to clinically implement four different DIBH techniques: (1) Active Breathing Control, (2) Spirometric Motion Management, (3) 3D Surface Image‐Guided, and (4) Self‐held Breath Control with Respiratory Monitoring and Feedback Guidance. Learning Objectives: Describe the physical displacement of the heart and the change in lung volume during DIBH and discuss dosimetric consequences of those changes. Provide an overview of the technical aspects. Describe work flow for patient simulation and treatment. Give an overview of commissioning and routine. Provide practical tips for clinical implementation.

WE‐DE‐209‐03: Spirometric Motion Management System

Breast radiation therapy is associated with some risk of lung toxicity as well as cardiac toxicity for left‐sided cases. Radiation doses to the lung and heart can be reduced by using the deep inspiration breath hold (DIBH) technique, in which the patient is simulated and treated during the deep inspiration phase of the breathing cycle. During DIBH, the heart is usually displaced posteriorly, inferiorly, and to the right, effectively expanding the distance between the heart and the breast/chest wall. As a result, the distance between the medial treatment field border and heart/lung is increased. Also, in a majority of DIBH patients, the air drawn into the thoracic cavity increases the total lung volume.The DIBH was discussed by an AAPM Task Group 10 years ago in the AAPM TG 76 report. However, DIBH is still not the standard of care in many clinics, which may be partially due to challenges associated with its implementation. Therefore, this seccion will focus primarily on how to clinically implement four different DIBH techniques: (1) Active Breathing Control, (2) Spirometric Motion Management, (3) 3D Surface Image‐Guided, and (4) Self‐held Breath Control with Respiratory Monitoring and Feedback Guidance. Learning Objectives: Describe the physical displacement of the heart and the change in lung volume during DIBH and discuss dosimetric consequences of those changes. Provide an overview of the technical aspects. Describe work flow for patient simulation and treatment. Give an overview of commissioning and routine. Provide practical tips for clinical implementation.

The benefit of deep inspiration breath hold: evaluating cardiac radiation exposure in patients after mastectomy and after breast-conserving surgery.

This study aims to evaluate the reduction of cardiac radiation dose and volume with deep inspiration breath hold (DIBH) technique compared to free breathing (FB) in patients with left-sided breast cancer. The study also aims to evaluate whether the benefits of DIBH vary in patients who had whole breast radiotherapy (RT) after breast-conserving surgery (BCS) and those who had chest wall RT post-mastectomy (M). FB and DIBH plans were generated for 15 consecutive post-BCS patients and 17 post-M patients who underwent RT with DIBH using varian real-time position management (RPM) system. Cardiac shields were used in all post-BCS plans, provided that clinical treatment volume coverage was not compromised, while chest wall coverage took priority in post-M plans. The prescribed dose was 50Gy in 25 fractions for the whole breast or the chest wall. Parameters of interest were cardiac V5, mean LAD dose, maximum LAD dose, and mean heart dose. The impact of DIBH was compared in post-BCS and post-M patients using paired t tests. To gauge clinically meaningful outcome, the proportion of patients with V5<5% and mean cardiac dose <2Gy were compared using McNemar's test. DIBH decreased V5 by an absolute 4.5% (2.3 vs. 6.8%; p<0.0001) in post-M group, and by an absolute 2.4% (1.3 vs. 3.7%; p=0.0028) in post-BCS group. DIBH decreased the mean heart dose by 107.0cGy (127.4 vs. 234.4cGy; p=0.0002) in post-M group, and by 58.9cGy (82.2 vs. 141.1cGy; p=0.0012) in post-BCS group. DIBH decreased mean LAD by 1201.6cGy (670 vs. 1872.5cGy; p=0.0006) in post-M group, and by 799.0cGy (425.3 vs. 1224.3cGy; p=0.0003) in post-BCS group. DIBH also decreased max LAD dose by 1244.3cGy (2776.0 vs. 4020.3cGy; p=0.0014) in post-M group, and by 1856.3cGy (1898.7 vs. 3754.9cGy; p=0.0005) in post-BCS group. In post-BCS group, cardiac V5<5% was achieved in 10/15 (67%) FB patients, and in 15/15 (100%) DIBH patients (p=0.002), and mean heart dose <2Gy was achieved in 12/15 (80%) FB patients and in 15/15 (100%) DIBH patients (p<0.001). This compares with post-M group, in which V5<5% was achieved in 6/17 (35%) FB patients and in 16/17 (94%) DIBH patients (p=0.05), and mean heart dose <2Gy was achieved in 7/17 FB (41%) an 16/17 DIBH patients (94%) (p=0.03). The results of this study suggest that there is considerable reduction in cardiac exposure in most patients with DIBH compared to FB, although less reduction is observed in the post-BCS patients. The use of cardiac shields and collimators/gantry adjustments, more readily applicable for post-BCS cases, may limit the additional benefits of DIBH. In an environment where DIBH availability is limited, the result of this study supports the preferential use of DIBH in post-M patients over post-BCS patients.

A Novel Method to Set Appropriate Gating Window for Deep Inspiration Breath Hold Patients

Patients receiving radiation therapy for left breast cancer (LBC) are at increased risk of cardiac toxicity. Deep inspiration breath-hold (DIBH) is used to reduce organ-at-risk (OAR) doses. The breath-hold window (BHW), as defined during patient simulation, is set qualitatively without accurate knowledge of potential dose benefits. Furthermore, a patient’s inability to reproducibly perform DIBH during treatment may compromise planned OAR doses. We aim to determine the ideal BHW and evaluate OAR dose consequences for patients unable to maintain DIBH. Twenty LBC patients treated with DIBH at our institution were identified in this IRB approved retrospective study. Using a respiration phase monitor, the window width, and level of breath-hold for each patient was set during CT simulation. Treatment plans with opposed tangents computed on free-breathing (FB) and DIBH CT scans were normalized to deliver >95% dose to >95% PTV. Minimum cardiac to chest wall distance (CCD) measured on the CT slice containing maximum heart in tangent field was recorded for both FB and DIBH. Using this data, we determined the change in OAR Dmean as a function of CCD. To correlate OAR doses with all ten phases of breathing cycle, we generated treatment plans on FB and 4DCT scans from 10 additional patients. These data were used to estimate dosimetric gains for different breath-hold levels: shallow, moderate, and deep inspiration and to set an optimal BHW. Plans were evaluated based on student t-test. Compared to FB plans, DIBH significantly reduced average heart Dmean: 1.8Gy vs 3.0Gy. The corresponding reductions in average Dmean for left ventricle (LV) and left anterior descending artery (LAD) were 2.5Gy vs 4.4Gy, and 8.4Gy vs 19.5Gy, respectively. These dose improvements correlated with an average increase of 16.1mm in CCD as measured on patient CT scans. The calculated rate of change (% dose/mm of CCD) for heart, LV, and LAD Dmean were 2.8%/mm, 2.6%/mm and 3.6%/mm, respectively. This linear correlation between OAR dose and CCD was validated with 4DCT patient data showing similar trend. We analyzed OAR dose change for three levels of breath-hold based on CCD range: shallow (0-5mm), moderate (5-10 mm) and deep (10-15mm). It was found that at these BH levels, 30%, 20%, and 10% of patients respectively had their mean heart dose exceed our institutional threshold (3Gy). In contrast, 50% of FB patients exceeded heart dose threshold. Hence, for our patients, a +/- 5 mm BH window at 15 mm above inspiration level was found to be appropriate. We have developed a novel method to set an optimal breath hold window for DIBH patients which should lead to more reproducible and consistent treatments with greater OAR dose benefit. The method also provides an estimate of dose consequences for patients unable to adequately breath-hold during treatment.

SU‐E‐T‐426: Dose Delivery Accuracy in Breast Field Junction for Free Breath and Deep Inspiration Breath Hold Techniques

Purpose:The purpose of this work was to verify the accuracy of the dose distribution along the field junction in a half beam irradiation technique for breast cancer patients receiving radiation to the breast or chest wall (CW) and the supraclavicular LN region for both free breathing and deep inspiration breath hold (DIBH) technique.Methods:We performed in vivo measurements for nine breast cancer patients receiving radiation to the breast/CW and to the supraclavicular LN region. Six patients were treated to the left breast/CW using DIBH technique and three patients were treated to the right breast/CW in free breath. We used five microMOSFET dosimeters: three located along the field junction, one located 1 cm above the junction and the fifth microMOSFET located 1 cm below the junction. We performed consecutive measurements over several days for each patient and compared the measurements to the TPS calculation (Eclipse, Varian™).Results:The calculated and measured doses along the junction were 0.97±0.08 Gy and 1.02±0.14 Gy, respectively. Above the junction calculated and measured doses were 0.91±0.08 Gy and 0.98±0.09 Gy respectively, and below the junction calculated and measured doses were 1.70±0.15 Gy and 1.61±0.09 Gy, respectively. All differences were not statistically significant. When comparing calculated and measured doses for DIBH patients only, there was still no statistically significant difference between values for all dosimeter locations. Analysis was done using the Mann‐Whitney Rank‐Sum Test.Conclusion:We found excellent correlation between calculated doses from the TPS and measured skin doses at the junction of several half beam fields. Even for the DIBH technique, where there is more potential for variance due to depth of breath, there is no over or underdose along the field junction. This correlation validates the TPS, as well an accurate, reproducible patient setup.