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Purpose This study determined the dosimetric comparison of moderate deep inspiration breath-hold using active breathing control and free-breathing intensity-modulated radiotherapy (IMRT) after breast-conserving surgery for left-sided breast cancer. Patients and methods Thirty-one patients were enrolled. One free breathe and two moderate deep inspiration breath-hold images were obtained. A field-in-field-IMRT free-breathing plan and two field-in-field-IMRT moderate deep inspiration breath-holding plans were compared in the dosimetry to target volume coverage of the glandular breast tissue and organs at risks for each patient. Results The breath-holding time under moderate deep inspiration extended significantly after breathing training ( P < 0.05). There was no significant difference between the free-breathing and moderate deep inspiration breath-holding in the target volume coverage. The volume of the ipsilateral lung in the free-breathing technique were significantly smaller than the moderate deep inspiration breath-holding techniques ( P < 0.05); however, there was no significant difference between the two moderate deep inspiration breath-holding plans. There were no significant differences in target volume coverage between the three plans for the field-in-field-IMRT (all P > 0.05). The dose to ipsilateral lung, coronary artery and heart in the field-in-field-IMRT were significantly lower for the free-breathing plan than for the two moderate deep inspiration breath-holding plans (all P < 0.05); however, there was no significant difference between the two moderate deep inspiration breath-holding plans. Conclusion The whole-breast field-in-field-IMRT under moderate deep inspiration breath-hold with active breathing control after breast-conserving surgery in left-sided breast cancer can reduce the irradiation volume and dose to organs at risks. There are no significant differences between various moderate deep inspiration breath-holding states in the dosimetry of irradiation to the field-in-field-IMRT target volume coverage and organs at risks. [ABSTRACT FROM AUTHOR]

Abstract: Purpose: In radiotherapy for left-sided breast cancer, Active Breathing Control enables a decrease of cardiac and Left Anterior Descending (LAD) coronary artery dose. We compared 3D-Conformal (3D-CRT) to Intensity Modulated Radiotherapy (IMRT) treatment plans based on free-breathing (FB) and breath-hold (BH). We investigated whether IMRT enables an additional decrease of cardiac dose in radiotherapy plans with and without BH. Methods and materials: Twenty patients referred for whole breast irradiation were included. The whole breast, heart and LAD-region were contoured. Four treatment plans were generated: FB_3D-CRT; FB_IMRT; BH_3D-CRT; BH_IMRT. Several doses were obtained from Dose Volume Histograms and compared. Results were compared statistically using the Wilcoxin Signed Rank Test. For heart and LAD-region, a significant dose reduction was found in BH (p <0.01). For both BH and FB, a significant dose reduction was found using IMRT (p <0.01). By using IMRT an average reduction of 5% was noted in the LAD-region for the volume receiving 20Gy. In 5 cases, the LAD-region remained situated in the vicinity of the radiation portals even in BH. Nevertheless, with IMRT the LAD dose was reduced in these cases. Conclusion: IMRT results in a significant additional decrease of dose in the heart and LAD-region in both breath-hold and free-breathing. [Copyright &y& Elsevier]

Purpose: To investigate the feasibility of using lipiodol as a direct surrogate for target localization using cone-beam CT (CBCT) image guidance in radiotherapy (RT) of patients with unresectable liver tumors after transarterial chemoembolization. Methods and Materials: Forty-six patients with an unresectable solitary liver tumor were enrolled for RT using active breathing control (ABC) and CBCT image guidance after transarterial chemoembolization. Each patient had pre- and posttreatment CBCT in the first 10 fractions of treatment. Lipiodol retention was evaluated using daily CBCT scans, and volume of lipiodol retention in the liver was calculated and compared between planning CT and post-RT CT. Influence of lipiodol on dosimetry was evaluated by measuring doses using an ion chamber with and without the presence of lipiodol. Margin analysis was performed on the basis of both inter- and intrafractional target localization errors. Results: Twenty-eight patients successfully completed the study. The shape and size of lipiodol retention did not vary substantially during the course of treatment. The mean Dice similarity coefficient for the lipiodol volume in pretreatment CT and that in posttreatment CT was 0.836 (range, 0.817–0.885). The maximum change (ratio of the lipiodol volume in pretreatment CT to that in posttreatment CT) was 1.045. The mean dose changes with the presence of <10 mL lipiodol were −1.44% and 0.13% for 6 MV and 15 MV, respectively. With ABC and online CBCT image guidance, clinical target volume–planning target volume margins were determined to be 2.5 mm in the mediolateral direction, 2.9 mm in the anteroposterior direction, and 4.0 mm in the craniocaudal direction. Conclusions: Lipiodol could be used as a direct surrogate for CBCT image guidance to improve the localization accuracy for RT of liver tumors. Combination of ABC and CBCT image guidance with lipiodol can potentially reduce the clinical target volume–planning target volume margin. [ABSTRACT FROM AUTHOR]

Purpose: To evaluate a rapid automated treatment planning process for the selection of patients with left-sided breast cancer for a moderate deep inspiration breath-hold (mDIBH) technique using active breathing control (ABC); and to determine the dose reduction to the left anterior descending coronary artery (LAD) and the heart using mDIBH. Method and Materials: Treatment plans were generated using an automated method for patients undergoing left-sided breast radiotherapy (n = 53) with two-field tangential intensity-modulated radiotherapy. All patients with unfavorable cardiac anatomy, defined as having >10 cm3 of the heart receiving 50% of the prescribed dose (V50) on the free-breathing automated treatment plan, underwent repeat scanning on a protocol using a mDIBH technique and ABC. The doses to the LAD and heart were compared between the free-breathing and mDIBH plans. Results: The automated planning process required approximately 9 min to generate a breast intensity-modulated radiotherapy plan. Using the dose–volume criteria, 20 of the 53 patients were selected for ABC. Significant differences were found between the free-breathing and mDIBH plans for the heart V50 (29.9 vs. 3.7 cm3), mean heart dose (317 vs. 132 cGy), mean LAD dose (2,047 vs. 594 cGy), and maximal dose to 0.2 cm3 of the LAD (4,155 vs. 1,507 cGy, all p <.001). Of the 17 patients who had a breath-hold threshold of ≥0.8 L, 14 achieved a ≥90% reduction in the heart V50 using the mDIBH technique. The 3 patients who had had a breath-hold threshold <0.8 L achieved a lower, but still significant, reduction in the heart V50. Conclusions: A rapid automated treatment planning process can be used to select patients who will benefit most from mDIBH. For selected patients with unfavorable cardiac anatomy, the mDIBH technique using ABC can significantly reduce the dose to the LAD and heart, potentially reducing the cardiac risks. [ABSTRACT FROM AUTHOR]

Abstract: Background and purpose: To investigate the feasibility of using intravenous contrast-enhanced computed tomography (CT) scans in 3-dimensional conformal radiotherapy (3D-CRT), stereotactic body radiation therapy (SBRT) and intensity-modulated radiotherapy (IMRT) treatment planning for lung cancers, respectively. Materials and methods: Twelve patients with bulky lung tumors and 14 patients with small lung tumors were retrospectively analyzed. Each patient took two sets of CT in the same position with active breathing control (ABC) technique before and after intravenous contrast agent (CA) injections. Bulky tumors were planned with 3D-CRT, while SBRT plans were generated for patients with small tumors based on CT scans with intravenous CA. In addition, IMRT plans were generated for patients with bulky tumors to continue on a planning study. All plans were copied and replaced on the scans without intravenous CA. The radiation doses calculated from the two sets of CTs were compared with regard to planning volumes (PTV), the organ at-risk (OAR) and the lungs using Wilcoxon’s signed rank test. Results: In comparisons for 3D-CRT plans, CT scans with intravenous CA reduced the mean dose and the maximum dose of PTV with significant differences (p <0.05) that were within 1.0%. Comparing IMRT and SBRT plans, CT scans with intravenous CA obviously increased the minimum irradiation dose and dose of 95% volume of target received (D95) for targets, respectively (p <0.05). There was no statistical significance for lung parameters between two sets of scans in SBRT plans and IMRT plans. Conclusions: The enhanced CT scans can be used for both target delineation and treatment planning in 3D-CRT. The dose difference caused by intravenous CA is small. But for SBRT and IMRT, the minimum irradiation dose in targets may be estimated to be increased up to 2.71% while the maximum dose may be estimated to be decreased up to 1.36%. However, the difference in dose distribution in most cases were found to be clinical tolerable. [Copyright &y& Elsevier]

Abstract: Introduction: One method to overcome the problem of lung tumour movement in patients treated with radiotherapy is to restrict tumour motion with an active breathing control (ABC) device. This study evaluated the feasibility of using ABC in patients receiving radical radiotherapy for non-small cell lung cancer. Methods: Eighteen patients, median (range) age of 66 (44–82) years, consented to the study. A training session was conducted to establish the patient’s breath hold level and breath hold time. Three planning scans were acquired using the ABC device. Reproducibility of breath hold was assessed by comparing lung volumes measured from the planning scans and the volume recorded by ABC. Patients were treated with a 3-field coplanar beam arrangement and treatment time (patient on and off the bed) and number of breath holds recorded. The tolerability of the device was assessed by weekly questionnaire. Quality assurance was performed on the two ABC devices used. Results: 17/18 patients completed 32 fractions of radiotherapy using ABC. All patients tolerated a maximum breath hold time >15s. The mean (SD) patient training time was 13.8 (4.8)min and no patient found the ABC very uncomfortable. Six to thirteen breath holds of 10–14 s were required per session. The mean treatment time was 15.8min (5.8min). The breath hold volumes were reproducible during treatment and also between the two ABC devices. Conclusion: The use of ABC in patients receiving radical radiotherapy for NSCLC is feasible. It was not possible to predict a patient’s ability to hold breath. A minimum tolerated breath hold time of 15 s is recommended prior to commencing treatment. [Copyright &y& Elsevier]

Purpose: The present treatment planning study compared whole breast radiotherapy (WBRT) to accelerated partial breast irradiation (APBI) for different external beam techniques and geometries (e.g., free breathing [FB] and deep inspiration breath hold [DIBH]). Methods and Materials: After approval by our institutional review board, a treatment planning study was performed of 10 patients with left-sided Stage 0-I breast cancer enrolled in a Phase I-II study of APBI using intensity-modulated radiotherapy (IMRT). After lumpectomy, patients underwent planning computed tomography scans during FB and using an active breathing control device at DIBH. For the FB geometry, standard WBRT and three-dimensional conformal radiotherapy (3D-CRT) APBI plans were created. For the DIBH geometry with active breathing control, WBRT, 3D-CRT, and IMRT APBI plans were created. Results: All APBI techniques had excellent planning target volume coverage. The maximal planning target volume dose was reduced from 116% of the prescription dose to 108% with the IMRT(DIBH) APBI plan. The maximal heart dose was >30 Gy for the WBRT techniques, 8.2 Gy for 3D-CRT(FB), and <5.0 Gy for 3D-CRT(DIBH) and IMRT(DIBH) techniques. The mean left anterior descending artery dose was significantly reduced from 11.4 Gy with WBRT(FB) to 4.2 with WBRT(DIBH) and <2.0 Gy with all APBI techniques. Conclusion: Although planning target volume coverage was acceptable with all techniques, the plans using the DIBH geometry resulted in a marked reduction in the normal tissue dose compared with WBRT planned in the absence of cardiac blocking. Additional study is needed to determine whether these techniques result in clinical benefits. [Copyright &y& Elsevier]

Abstract: Introduction: The prognosis from non-small cell lung cancer remains poor, even in those patients suitable for radical radiotherapy. The ability of radiotherapy to achieve local control is hampered by the sensitivity of normal structures to irradiation at the high tumour doses needed. This study aimed to look at the potential gain in tumour control probability from dose escalation facilitated by moderate deep inspiration breath-hold. Method: The data from 28 patients, recruited into two separate studies were used. These patients underwent planning with and without the use of moderate deep inspiration breath-hold with an active breathing control (ABC) device. Whilst maintaining the mean lung dose (MLD) at the level of the conventional plan, the ABC plan dose was theoretically escalated to a maximum of 84Gy, constrained by usual normal tissue tolerances. Calculations were performed using data for both lungs and for the ipsilateral lung only. Resulting local progression-free survival at 30months was calculated using a standard logistic model. Results: The prescription dose could be escalated from 64Gy to a mean of 73.7±6.5Gy without margin reduction, which represents a statistically significant increase in tumour control probability from 0.15±0.01 to 0.29±0.11 (p <0.0001). The results were not statistically different whether both lungs or just the ipsilateral lung was used for calculations. Conclusion: A near-doubling of tumour control probability is possible with modest dose escalation, which can be achieved with no extra increase in lung dose if deep inspiration breath-hold techniques are used. [Copyright &y& Elsevier]

Abstract: Background and purpose: To investigate the feasibility and effectiveness of utilizing active breathing coordinator (ABC) in 3DCRT for HCC. Materials and methods: A dosimetric comparison between the free-breathing (FB) plan and ABC plan in HCC 3DCRT was performed. Set-up errors and reproducibility of diaphragm position using ABC were measured, and patients’ acceptance was also recorded. Results: From April 2005 to February 2007, 28 HCC were irradiated with ABC and they tolerated ABC well. The mean dose to normal liver was reduced from 16.9Gy in FB plan to 14.3Gy in ABC plan. PTV for ABC and FB plans were 529cm3 and 781cm3, respectively, and V 23 were reduced from 45% to 30%. The predicted incidences of radiation-induced liver disease by Lyman model were 1% and 2.5%, respectively, in favor of ABC plan. The systematic and random errors for the ABC and FB plans were 1.2mm vs. 4.7mm, 1.6mm vs. 3.5mm, and 1.8mm vs. 2.7mm, respectively, in cranio-caudal, anterior-posterior, and left-right directions. The average intrafraction reproducibility of diaphragm position in cranio-caudal direction was 1.6mm, and the interfraction, 6.7mm. Conclusions: The utilization of ABC in HCC 3DCRT is feasible, and can reduce liver irradiation. [Copyright &y& Elsevier]

Abstract: Background: The effectiveness of ABC has been traditionally measured as the reduction in internal margin (IM) within the planning target volume (PTV). Not to overestimate the benefit of ABC, the effect of patient movement during treatment also needs to be taken into account. We determined the IM and set-up error with ABC and the effect on physical lung parameters compared to standard margins used with free breathing. We also assessed interfraction oesophageal movement to determine a planning organ at risk volume (PRV). Materials and methods: Two sequential studies were performed using ABC in NSCLC patients suitable for radical radiotherapy (RT). Twelve out of 14 patients in Study 1 had tumours visible fluoroscopically and had intrafraction tumour movement assessed with and without ABC. Sixteen patients were recruited to Study 2 and had interfraction tumour movement measured using ABC in a moderate deep inspiration breath-hold, of these 7 patients also had interfraction oesophageal movement recorded. Interfraction movement was assessed by CT scan prior to and in the middle and final week of RT. Displacement of the tumour centre of mass and oesophageal borders relative to the first scan provided a measure of movement. Set-up error was measured in 9 patients treated with an in-house lung board adapted for the ABC device. Combining movement and set-up errors determined PTV and PRV margins with ABC. The effect of ABC on mean lung dose (MLD), lung V 20 and V 13 was calculated. Results: ABC in a moderate deep inspiration breath-hold was tolerated in 25 out of 30 patients (83%) in Study 1 and 2. The random contribution of periodic tumour motion was reduced by 90% in the y direction with ABC compared to free-breathing. The magnitude of motion reduction was less in the x and z direction. Combining the systematic and random set-up error in quadrature with the systematic and random intrafraction and interfraction tumour variations with ABC results in a PTV margin of 8.3mm in the x direction, 12.0mm in the y direction and 9.8mm in the z direction. There was a relative mean reduction in MLD, lung V 20 and V 13 of 25%, 21% and 18% with the ABC PTV compared to a free-breathing PTV. Oesophageal movement combined with set-up error resulted in an isotropic PRV of 4.7mm. Conclusions: The reduction in PTV size with ABC resulted in an 18–25% relative reduction in physical lung parameters. PTV margin reduction has the potential to spare normal lung and allow dose-escalation if coupled with image-guided RT. The oesophageal PRV needs to be considered when irradiating central disease and is of increasing importance with altered RT fractionation and concomitant chemoradiation schedules. Further reductions in PTV and PRV may be possible if patient set-up error was minimised, confirming that attention to patient immobilisation is as important as attempts to control tumour motion. [Copyright &y& Elsevier]

Purpose: The short-term displacement and reproducibility of the breast or chest wall, and the internal mammary (IM), infraclavicular (ICV), and supraclavicular (SCV) nodal regions have been assessed as a function of breath-hold state using an active breathing control (ABC) device for patients receiving loco-regional breast radiation therapy.Methods and Materials: Ten patients underwent computed tomographic scanning using an ABC device at breath-hold states of end-exhale and 20%, 40%, 60%, and 80% of vital capacity (VC). Patients underwent scanning before treatment and at one third and two thirds of the way through treatment. A regional registration was performed for each target using a rigid-body transformation with mutual information as a metric.Results: Between exhale and 40% of VC, the mean displacement was 0.27/0.34, 0.24/0.31, 0.22/0.19, and 0.13/0.19 cm anterior/superior for the breast or chest wall, and IM, ICV, and SCV nodes, respectively. At 80% of VC, the mean displacement from exhale was 0.84/.88, 0.76/.79, 0.70/0.79, and 0.54/0.56 cm anterior/superior for the breast or chest wall, and IM, ICV, and SCV nodes, respectively. The short-term reproducibility (standard deviation) was <0.3 and Conclusions: The short-term reproducibility of target position is

Purpose: To reduce cardiotoxicity from breast radiotherapy (RT), innovative techniques are under investigation. Information about cardiac motion with respiration and positional reproducibility under active breathing control (ABC) is necessary to evaluate these techniques.Methods and Materials: Patients requiring loco-regional RT for breast cancer were scanned by computed tomography using an ABC device at various breath-hold states, before and during treatment. Ten patients were studied. For each patient, 12 datasets were analyzed. Mutual information-based regional rigid alignment was used to determine the magnitude and reproducibility of cardiac motion as a function of breathing state. For each scan session, motion was quantified by evaluating the displacement of a point along the left anterior descending artery (LAD) with respect to its position at end expiration. Long-term positional reproducibility was also assessed.Results: Displacement of the LAD was greatest in the inferior direction, moderate in the anterior direction, and lowest in the left-right direction. At shallow breathing states, the average displacement of LAD position was up to 6 mm in the inferior direction. The maximum displacement in any patient was 2.8 cm in the inferior direction, between expiration and deep-inspiration breath hold. At end expiration, the long-term reproducibility (SD) of the LAD position was 3 mm in the A-P, 6 mm in the S-I, and 4 mm in the L-R directions. At deep-inspiration breath hold, long-term reproducibility was 3 mm in the A-P, 7 mm in the S-I, and 3 mm in the L-R directions.Conclusions: These data demonstrate the extent of LAD displacement that occurs with shallow breathing and with deep-inspiration breath hold. This information may guide optimization studies considering the effects of respiratory motion and reproducibility of cardiac position on cardiac dose, both with and without ABC. [ABSTRACT FROM AUTHOR]

Purpose: The challenge in early Hodgkin's disease (HD) in children is to maintain good survival rates while sparing organs at risk. This study assesses the feasibility of active breathing control (ABC) in children, and compares normal tissue irradiation with and without ABC. Methods and Materials: Between May 2003 and June 2004, seven children with HD with mediastinal involvement, median age 15, were treated by chemotherapy and involved-field radiation therapy. A free-breathing computed tomography simulation scan and one additional scan during deep inspiration using ABC were performed. A comparison between planning treatment with clinical target volume including supraclavicular regions, mediastinum, and hila was performed, both in free breathing and using ABC. Results: For a prescription of 36 Gy, pulmonary dose-volume histograms revealed a mean reduction in lung volume irradiated at more than 20 Gy (V20) and 30 Gy (V30) of 25% and 26%, respectively, using ABC (p = 0.016). The mean volume of heart irradiated at 30 Gy or more decreased from 15% to 12% (nonsignificant). The mean dose delivered to breasts in girls was small in both situations (less than 2 Gy) and stable with or without ABC. Considering axillary irradiation, the mean dose delivered to breasts remained low (<9 Gy), without significant difference using ABC or not. The mean radiation dose delivered to thyroid was stable using ABC or not. Conclusions: Using ABC is feasible in childhood. The use of ABC decreases normal lung tissue irradiation. Concerning heart irradiation, a minimal gain is also shown. No significant change has been demonstrated concerning breast and thyroid irradiation. [ABSTRACT FROM AUTHOR]

Purpose: Extensive radiotherapy volumes for tumors of the chest are partly caused by interfractional organ motion. We evaluated the feasibility of respiratory observation tools using the active breathing control (ABC) system and the effect on breathing cycle regularity and reproducibility. Methods and Materials: Thirty-six patients with unresectable tumors of the chest were selected for evaluation of the ABC system. Computed tomography scans were performed at various respiratory phases starting at the same couch position without patient movement. Threshold levels were set at minimum and maximum volume during normal breathing cycles and at a volume defined as shallow breathing, reflecting the subjective maximal tolerable reduction of breath volume. To evaluate the extent of organ movement, 13 landmarks were considering using commercial software for image coregistration. In 4 patients, second examinations were performed during therapy. Results: Investigating the differences in a normal breathing cycle versus shallow breathing, a statistically significant reduction of respiratory motion in the upper, middle, and lower regions of the chest could be detected, representing potential movement reduction achieved through reduced breath volume. Evaluating interfraction reproducibility, the mean displacement ranged between 0.24 mm (chest wall/tracheal bifurcation) to 3.5 mm (diaphragm) for expiration and shallow breathing and 0.24 mm (chest wall) to 5.25 mm (diaphragm) for normal inspiration. Conclusions: By modifying regularity of the respiratory cycle through reduction of breath volume, a significant and reproducible reduction of chest and diaphragm motion is possible, enabling reduction of treatment planning margins. [ABSTRACT FROM AUTHOR]

Purpose: To evaluate the short-term and long-term reproducibility of lung tumor position for scans acquired using an active breathing control (ABC) device. Methods and Materials: Ten patients with lung cancer were scanned over three sessions during the course of treatment. For each session, two scans were acquired at deep inhale, and one scan each at half of deep inhale and at exhale. Long-term reproducibility was evaluated by comparing the same breathing state scans from two sessions, with setup variation removed by skeletal alignment. Tumor alignment was based on intensity matching of a small volume around the tumor. For short-term reproducibility, the two inhale volumes from the same session were compared. Results: For the short-term reproducibility, the mean and the standard deviation (SD) of the displacement of the center of tumor were 0.0 (1.5) mm in anteroposterior (AP), 0.3 (1.4) mm in superior/inferior (SI), and 0.2 (0.7) mm in right/left (RL) directions. For long-term reproducibility, the mean (SD) were −1.3 (3.1) mm AP, −0.5 (3.8) mm SI, and 0.3 (1.6) mm RL for inhale and −0.2 (2.8) mm AP, 0.2 (2.1) mm SI, and −0.7 (1.1) mm RL for exhale. Conclusion: The ABC device demonstrates very good short-term and long-term reproducibility. Increased long-term variability in position, primarily in the SI and AP directions, indicates the role of tumor-directed localization in combination with breath-held immobilization. [Copyright &y& Elsevier]

Purpose: A six-fraction, high-precision radiotherapy protocol for unresectable liver cancer has been developed in which active breathing control (ABC) is used to immobilize the liver and daily megavoltage (MV) imaging and repositioning is used to decrease geometric uncertainties. We report the accuracy of setup in the first 20 patients consecutively treated using this approach. Methods and Materials: After setup using conventional skin marks and lasers, orthogonal MV images were acquired with the liver immobilized using ABC. The images were aligned to reference digitally reconstructed radiographs using the diaphragm for craniocaudal (CC) alignment and the vertebral bodies for anterior-posterior (AP) and mediolateral (ML) alignment. Adjustments were made for positioning errors >3 mm. Verification imaging was repeated after repositioning to assess for residual positioning error. Offline image matching was conducted to determine the setup accuracy using this approach compared with the initial setup error before repositioning. Real-time beam's-eye-view MV movies containing an air-diaphragm interface were also evaluated. Results: A total of 405 images were evaluated from 20 patients. Repositioning occurred in 109 of 120 fractions because of offsets >3 mm. Three to eight beam angles, with up to four segments per field, were used for each isocenter. Breath holds of up to 27 s were used for imaging and treatment. The average time from the initial verification image to the last treatment beam was 21 min. Image guidance and repositioning reduced the population random setup errors (sigma) from 6.5 mm (CC), 4.2 mm (ML), and 4.7 mm (AP) to 2.5 mm (CC), 2.8 mm (ML), and 2.9 mm (AP). The average individual random setup errors (sigma) were reduced from 4.5 mm (CC), 3.2 mm (AP), and 2.5 mm (ML) to 2.2 mm (CC), 2.0 mm (AP), and 2.0 mm (ML). The standard deviation of the distribution of systematic deviations (Sigma) was also reduced from 5.1 mm (CC), 3.4 mm (ML), and 3.1 mm (AP) to 1.4 mm (CC), 2.0 mm (ML), and 1.9 mm (AP) with image guidance and repositioning. The average absolute systematic errors were reduced from 4.1 mm (CC), 2.4 mm (AP), and 3.1 (ML) to 1.1 mm (CC), 1.3 mm (AP), and 1.6 mm (ML). Analysis of 52 real-time beam's-eye-view MV movies revealed an average absolute CC offset in diaphragm position of 1.9 mm. Conclusion: Image guidance with orthogonal MV imaging and ABC for stereotactic body radiotherapy for liver cancer is feasible, improving setup accuracy compared with ABC without daily imaging and repositioning. [ABSTRACT FROM AUTHOR]

: PurposeThe active breathing control (ABC) device allows for temporary immobilization of respiratory motion by implementing a breath hold at a predefined relative lung volume and air flow direction. The purpose of this study was to quantitatively evaluate the ability of the ABC device to immobilize peripheral lung tumors at a reproducible position, increase total lung volume, and thereby reduce lung mass within the planning target volume (PTV).: Methods and materialsTen patients with peripheral non–small-cell lung cancer tumors undergoing radiotherapy had CT scans of their thorax with and without ABC inspiration breath hold during the first 5 days of treatment. Total lung volumes were determined from the CT data sets. Each peripheral lung tumor was contoured by one physician on all CT scans to generate gross tumor volumes (GTVs). The lung density and mass contained within a 1.5-cm PTV margin around each peripheral tumor was calculated using CT numbers. Using the center of the GTV from the Day 1 ABC scan as the reference, the displacement of subsequent GTV centers on Days 2 to 5 for each patient with ABC applied was calculated in three dimensions.: ResultsWith the use of ABC inspiration breath hold, total lung volumes increased by an average of 42%. This resulted in an average decrease in lung mass of 18% within a standard 1.5-cm PTV margin around the GTV. The average (± standard deviation) displacement of GTV centers with ABC breath hold applied was 0.3 mm (± 1.8 mm), 1.2 mm (± 2.3 mm), and 1.1 mm (± 3.5 mm) in the lateral direction, anterior-posterior direction, and superior-inferior direction, respectively.: ConclusionsResults from this study indicate that there remains some inter–breath hold variability in peripheral lung tumor position with the use of ABC inspiration breath hold, which prevents significant PTV margin reduction. However, lung volumes can significantly increase, thereby decreasing the mass of lung within a standard PTV. [Copyright &y& Elsevier]

: PurposeActive breathing control (ABC) was validated using patients with non–small-cell lung cancer (NSCLC) to be treated with continuous hyperfractionated accelerated radiotherapy weekend-less (CHARTWEL). Effects of breath hold (BH) on accuracy and normal tissue doses were evaluated.: Methods and materialsEleven patients were studied. Immediately after a free breathing (FB) planning scan, two ABC scans (ABC 1 and 2) were performed to assess intrafraction variation. A third ABC scan (ABC 3) was performed some weeks later to assess interfraction variation. Assisted BH was set at 75% of vital capacity and reproducibility assessed using computed tomography (CT) lung volumes. Planning target volumes (PTVs), doses to lung and spinal cord for FB and ABC 1 scans were compared.: ResultsResults were available for 10 patients. Disease and elective nodal regions were easier to define on ABC scans making PTVs smaller. ABC lung volumes showed no significant variation over several weeks, percentage volume of whole lung receiving ≥20 Gy (V20) was reduced in all (median 6.4%, p = 0.005), and spinal cord dose in 80% (median 1.03 Gy, p = 0.02), of the plans.: ConclusionsABC allowed reproducible BH, and enabled better delineation of tumor and normal structures, as well as reduction in PTV, V20, and spinal cord dose. [Copyright &y& Elsevier]

Purpose: To evaluate the heart and lung sparing effects of moderate deep inspiration breath hold (mDIBH) achieved using an active breathing control (ABC) device, compared with free breathing (FB) during treatment with deep tangents fields (DT) for locoregional (LR) irradiation of breast cancer patients, including the internal mammary (IM) nodes (IMNs). To compare the DT-mDIBH technique to other standard techniques and to evaluate the dosimetric effect of intensity-modulated radiation therapy (IMRT).Methods and Materials: Fifteen patients (9 left-sided and 6 right-sided lesions) with Stages 0–III breast cancer underwent standard FB and ABC computed tomographic (CT) scans in the treatment position. A dosimetric planning study was performed. In FB, the 9 left-sided patients were planned with a 5-field technique where electron fields covering the IM region were matched to shallow tangents using wedges (South West Oncology Group [SWOG] protocol S9927 technique A). This method was compared with a 3-field DT technique covering the breast and the IMNs (SWOG S9927 technique B). Compensation with IMRT was then compared with wedges for each technique. For the 15 total patients, dosimetric planning using DT with IMRT was then reoptimized on the mDIBH CT data set for comparison. Dose-volume histograms for the clinical target volume (CTV) (including the IMNs), planning target volume (PTV), ipsilateral and contralateral breast, and organs at risk (OAR) were analyzed. In addition, normal tissue complication probabilities (NTCP) for lung and heart, mean lung doses, and the number of monitor units (MUs) for a 1.8 Gy fraction were compared.Results: For the 9 left-sided patients, the mean percentage of heart receiving more than 30 Gy (heart V30) was lower with the 5-field wedged technique than with the DT wedged technique (6.8% and 19.1%, respectively, p < 0.004). For the DT technique, the replacement of wedges with IMRT slightly diminished the mean heart V30 to 16.3% (p < 0.51). The introduction of mDIBH to the DT-IMRT technique reduced the heart V30 by 81% to a mean of 3.1% (p < 0.0004). Compared with 5-field IMRT, DT-IMRT with mDIBH reduced the heart V30 for 6 of the 9 patients, entirely avoiding heart irradiation in 2 of these 6 patients. For DT-IMRT, mDIBH reduced the mean lung dose and NTCP to levels obtained with the 5-field IMRT technique. For the 15 patients planned with DT-IMRT in FB, the use of mDIBH reduced the mean percentage of both lungs receiving more than 20 Gy from 20.4% to 15.2% (p < 0.00007). With DT-IMRT, more than 5% of the contralateral breast received more than 10 Gy for 6 of the 9 left-sided patients in FB, 3 of those 9 patients in mDIBH, and only 1 of those 9 patients planned with 5 fields. The mean % of the PTV receiving more than 55 Gy (110% of the prescribed dose) was 36.4% for 5-field wedges, 33.4% for 5-field IMRT, 28.7% for DT-wedges, 12.5% for DT-IMRT, and 18.4% for DT-IMRT mDIBH. The CTV remained covered by the 95% isodose in all the DT plans but one (99.1% of the volume covered). DT-wedges required more MUs than DT-IMRT (mean of 645 and 416, respectively, p < 0.00004).Conclusion: mDIBH significantly reduces heart and lung doses when DT are used for LR breast irradiation including the IMNs. Compared with shallow tangents matched with electrons, DT with mDIBH reduces the heart dose (in most patients) and results in comparable lung toxicity parameters, but may increase the dose to the contralateral breast. IMRT improves dose homogeneity, slightly reduces the dose to the heart, and diminishes the number of MUs required. [Copyright &y& Elsevier]

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Purpose: To estimate errors in soft tissue–based image guidance due to relative changes between primary tumor (PT) and affected lymph node (LN) position and volume, and to compare the results with bony anatomy–based displacements of PTs and LNs during radiotherapy of lung cancer. Methods and Materials: Weekly repeated breath-hold computed tomography scans were acquired in 17 lung cancer patients undergoing radiotherapy. PTs and affected LNs were manually contoured on all scans after rigid registration. Interfraction and intrafraction displacements in the centers of mass of PTs and LNs relative to bone, as well as LNs relative to PTs (LN–PT), were calculated. Results: The mean volume after 5 weeks was 65% for PTs and 63% for LNs. Systematic and random interfraction displacements were 2.6 to 4.6 mm and 2.7 to 2.9 mm, respectively, for PTs; 2.4 to 3.8 mm and 1.4 to 2.7 mm, respectively, for LNs; and 2.3 to 3.9 mm and 1.9 to 2.8 mm, respectively, for LN–PT. Systematic and random intrafraction displacements were less than 1 mm except in the superoinferior direction. Interfraction LN–PT displacements greater than 3 mm were observed in 67% of fractions and require a safety margin of 12 mm in the lateral direction, 11 mm in the anteroposterior direction, and 9 mm in the superoinferior direction. LN–PT displacements displayed significant time trends (p < 0.0001) and depended on the presence of pathoanatomic conditions of the ipsilateral lung, such as atelectasis. Conclusion: Interfraction LN–PT displacements were mostly systematic and comparable to bony anatomy–based displacements of PTs or LNs alone. Time trends, large volume changes, and the influence of pathoanatomic conditions underline the importance of soft tissue–based image guidance and the potential of plan adaptation. [ABSTRACT FROM AUTHOR]