Respiration induced heart motion and indications of gated delivery for left-sided breast irradiation.
ABSTRACT To investigate respiration-induced heart motion for left-sided breast irradiation using a four-dimensional computed tomography (4DCT) technique and to determine novel indications to assess heart motion and identify breast patients who may benefit from a gated treatment.
Images of 4DCT acquired during free breathing for 20 left-sided breast cancer patients, who underwent whole breast irradiation with or without regional nodal irradiation, were analyzed retrospectively. Dose distributions were reconstructed in the phases of 0%, 20%, and 50%. The intrafractional heart displacement was measured in three selected transverse CT slices using D(LAD) (the distance from left ascending aorta to a fixed line [connecting middle point of sternum and the body] drawn on each slice) and maximum heart depth (MHD, the distance of the forefront of the heart to the line). Linear regression analysis was used to correlate these indices with mean heart dose and heart dose volume at different breathing phases.
Respiration-induced heart displacement resulted in observable variations in dose delivered to the heart. During a normal free-breathing cycle, heart-induced motion D(LAD) and MHD changed up to 9 and 11 mm respectively, resulting in up to 38% and 39% increases of mean doses and V(25.2) for the heart. MHD and D(LAD) were positively correlated with mean heart dose and heart dose volume. Respiratory-adapted gated treatment may better spare heart and ipsilateral-lung compared with the conventional non-gated plan in a subset of patients with large D(LAD) or MHD variations.
Proposed indices offer novel assessment of heart displacement based on 4DCT images. MHD and D(LAD) can be used independently or jointly as selection criteria for respiratory gating procedure before treatment planning. Patients with great intrafractional MHD variations or tumor(s) close to the diaphragm may particularly benefit from the gated treatment.
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ABSTRACT: Thousands of women diagnosed with breast cancer each year receive breast-conserving surgery followed by adjuvant radiation therapy. For women with left-sided breast cancer, there is risk of potential cardiotoxicity from the radiation therapy. As data have become available to quantify the risk of cardiotoxicity from radiation, strategies have also developed to reduce the dose of radiation to the heart without compromising radiation dose to the breast. Several broad categories of techniques to reduce cardiac radiation doses include breath hold techniques, prone positioning, intensity-modulated radiation therapy, and accelerated partial breast irradiation, as well as many small techniques to improve traditional three-dimensional conformal radiation therapy. This review summarizes the published scientific literature on the various techniques to decrease cardiac irradiation in women treated to the left breast for breast cancer after breast-conserving surgery.Frontiers in Oncology 11/2014; 4:327.
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ABSTRACT: PurposeThe purpose of this study was to explore the correlation between the respiration-induced target motion and volume variation with the dosimetric variance on breast and organ at risk (OAR) during free breathing.Methods and materialsAfter breast-conserving surgery, seventeen patients underwent respiration-synchronized 4DCT simulation scans during free breathing. Treatment planning was constructed using the end inspiration scan, then copied and applied to the other phases and the dose distribution was calculated separately to evaluate the dose-volume histograms (DVH) parameters for the planning target volume (PTV), ipsilateral lung and heart. RESULTS: During free breathing, the treated breast motion vector was 2.09 +/- 0.74 mm, and the volume variation was 3.05 +/- 0.94%. There was no correlation between the breast volume and target/OAR dosimetric variation (|r| = 0.39 ~ 0.48). In the anteroposterior, superoinferior and vector directions, breast movement correlated well with the mean PTV dose, conformal index, and the lung volume receiving high dose (|r| = 0.651-0.975); in the superoinferior and vector directions, breast displacement only correlated with the heart volume receiving >5 Gy (V5) (r = -0.795, 0.687). The lung volume and the lung volume receiving high dose correlated reasonably well (r = 0.655 ~ 0.882), and a correlation only existed between heart volume and V5 (r = -0.701). CONCLUSION: Target movement correlated well with the target/OAR dosimetric variation in certain directions, indicating that whole breast IMRT assisted by breathing control or respiratory-adapted gated treatment promotes the accuracy of dose delivery during radiotherapy. During free breathing, the effect of breast volume variation can be ignored in whole breast IMRT.Radiation Oncology 05/2013; 8(1):111. · 2.36 Impact Factor
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ABSTRACT: The methane–air detonation experiments are performed to characterize high pressure explosion processes that may occur in sealed areas of underground coal mines. The detonation tube used for these studies is 73 m long, 105 cm internal diameter, and closed at one end. The test gas is 97.5% methane with about 1.5% ethane, and the methane–air test mixtures varied between 4% and 19% methane by volume. Detonations were successfully initiated for mixtures containing between 5.3% and 15.5% methane. The detonations propagated with an average velocity between 1512 and 1863 m/s. Average overpressures recorded behind the first shock pressure peak varied between 1.2 and 1.7 MPa. The measured detonation velocities and pressures are close to their corresponding theoretical Chapman-Jouguet (CJ) detonation velocity (DCJ) and detonation pressure (PCJ). Outside of these detonability limits, failed detonations produced decaying detached shocks and flames propagating with velocities of approximately 1/2 DCJ. Cell patterns on smokefoils during detonations were very irregular and showed secondary cell structures inside primary cells. The measured width of primary cells varied between 20 cm near the stoichiometry and 105 cm (tube diameter) near the limits. The largest detonation cell (105 cm wide and 170 cm long) was recorded for the mixture containing 15.3% methane.Journal of Loss Prevention in the Process Industries 03/2013; · 1.35 Impact Factor