Voluntary Breath Hold Research Articles

Interfractional Reproducibility of Lung Tumor Location Using Various Methods of Respiratory Motion Mitigation

To determine interfractional reproducibility of the location of lung tumors using respiratory motion mitigation. Free-breathing four-dimensional computed tomography (CT) data sets and CT data sets during breath hold were acquired weekly for 17 patients undergoing treatment for non-small-cell lung cancer. Distances between the center of the gross tumor volume (GTV) and a reproducible bony reference point under conditions of breath hold on end inspiration (EI) and end expiration (EE) and during free breathing on the 0% phase (corresponding to EI) and 50% phase (corresponding to EE) were analyzed for interfractional reproducibility. Systematic uncertainties in tumor location were determined as the difference in distance between the GTV center on the first CT data set and the mean location of GTV centers on the subsequent data sets. Random uncertainties in tumor location were determined as the standard deviation of the distances between the GTV centers and the bony reference points. Margins to account for systematic and random interfractional variations were estimated based on these uncertainties. Mean values of interfractional setup uncertainties were as follows: systematic uncertainties--EI, 0.3 cm; EE, 0.2 cm; 0% phase, 0.3 cm; and 50% phase, 0.3 cm; and random uncertainties--EI, 0.3 cm; EE, 0.3 cm; 0% phase, 0.3 cm; and 50% phase, 0.3 cm. There does not appear to be any correlation between uncertainties and GTV size, but there appears to be a weak positive correlation between uncertainties and the magnitude of GTV excursion. Voluntary breath hold and gating on either EI or EE appear to be equally reliable methods of ensuring the reproducibility of lung tumor position. We recommend setup margins of 0.3 cm if using cone-beam CT or kilovoltage X-ray with fiducials and aligning directly to the tumor and 0.8 cm when aligning to a nearby bony surrogate using cone-beam CT or kilovoltage X-ray.

SU‐FF‐J‐77: Interfractional Reproducibility of Lung Tumor Position Using Breath Hold

Purpose: The purpose of the present work is to quantify the reproducibility of the position of a lung tumor under breath‐hold conditions. Methods and Materials: Weekly computed tomography (CT) data sets under voluntary breath hold at normal end inspiration and end expiration were acquired for 18 patients with diagnosed non‐small cell lung cancer. Gross tumor volumes (GTV) were outlined by a radiation oncologist. The distances between the centers of the GTV and a bony reference landmark were evaluated on a weekly basis, and the standard deviations (SD) of the distances were taken as a metric for assessing tumor position reproducibility. Results: The mean SDs for end inspiration were as follows: lat − 0.27±0.12 cm; AP 0.34±0.21 cm; SI 0.42±0.22 cm; distance 0.32±0.18 cm, whereas for end expiration the mean SDs were as follows: lat 0.23±0.10 cm; AP 0.31±−.19 cm; SI 0.38±0.15 cm; distance 0.25±0.11 cm. Conclusions: Voluntary breath hold appears to be a reliable method of ensuring reproducibility of lung tumor position. Setup margins used in our present practice of 0.5 cm for kV image‐guided patient setups and 0.3 cm for cone‐beam CT‐guided patient setups appear to be appropriate. Reproducibility under end expiration appears to be slightly better than that under end inspiration but the difference may not be significant.Research sponsored in part by Philips Medical Systems.

WE-C-303A-04: Quantifying the Reproducibility of Heart Position with Respect to Bony Anatomy in Daily Set Up and the Corresponding Delivered Heart Dose in Voluntary Deep Inhalation Breath Hold for Left Breast Cancer Patients Via External Beam Radiotherapy

Purpose: Voluntary deep inhalation breath hold (DIBH) technique help reduce the heart toxicity during radiation treatment of the left breast. We present the results of the first study performed to quantify the reproducibility of heart position and the heartdose in daily setup for voluntary DIBH patients. Method and Materials: Ten left breast patients undergoing treatment with voluntary DIBH were studied. Each patient had two CT scans, one with free breathing and one with voluntary DIBH, to evaluate the dose under these two conditions to the Heart, anterior most point of left anterior descending (LAD) coronary artery, and left Lung. At the treatment machine, daily and weekly KV orthogonal images were acquired using onboard imaging for each patient. Mosaiq™ software was used to register the full bony anatomy of thorax (including the spine, ribs, anterior chest wall and heart) with KV images to the planning DRRs. Once the patient is aligned on the treatment machine using bony anatomy registration, the difference between the bony anatomy registration and the heart registration is the daily heart position. These differences were transferred into treatment planning system to obtain the delivered dose.Results: The dosimetric evaluation shows clinically significant reduced dose to heart,lung, and LAD in the DIBH case compared to the free breathing case, as previous studies have shown. The weekly heart position shifts are in the order of few mm. Dosimetric evaluations for these shifts indicate that dose to the heart in the daily treatment with DIBH remains low. Conclusion: The setup and breath hold accuracy and the daily delivered dose to the heart was evaluated for voluntary DIBH breast patients. Results indicate a clear reduction of dose delivered to the heart throughout the treatment when voluntary DIBH technique is employed.

SU-FF-T-565: Implementation of Feedback Guided Voluntary Breath Hold Gating for CBCT Based Stereotactic Body Radiotherapy

Purpose: To implement feedback guided voluntary breathhold for CBCT based stereotactic body radiotherapy.Methods and materials: 8 patients with early stage lungtumors eligible for stereotactic body radiotherapy and with respiratory induced tumor motion of > 1 cm (determined from 4D CT) were selected for feedback guided breath hold implementation. Visual feedback was provided to assist patients in maintaining consistent breath hold levels. Multiple fast spiral CT scans were acquired, both within and between successive breath holds. A single breath hold CT was chosen as the reference. Gross tumor volume (GTV) was delineated to encompass the suspected tumor volume on all breath hold CT acquisitions. Standard margins for treatment planning were 0.8 cm (CTV) and 0.3 cm (PTV). Prior to each treatment delivery, a CBCT was acquired under a series of breathholds. Changes in volume, shape and size from reference were determined using 3D‐3D matching tools. Shifts made based on 3D‐3D matching were then verified through 2D‐2D matching of acquired orthogonal MV breath hold images.Results: Overall median breath hold duration was 20 sec (max 52 sec; min 3 sec). CBCTs required 2 – 3 breathholds and were noted to be of superior quality to those obtained during normal respiration. Intra and inter breath hold reproducibility (RMS) of GTV centroid position at the time of repeat simulation was 1.2, 2.1 and 1.0 mm (AP, SI, LR). Inter fraction breath hold reproducibility of GTV position with respect to bony anatomy was 0.5,1.7 and 0.4 mm (AP, SI, LR ‐ systematic) and 1.3, 1.9 and 1.1 mm (AP, SI, LR ‐ random). Conclusions: Respiratory feedback and image guided breath hold gating can improve the accuracy/precision of stereotactic body radiotherapy, especially for mobile tumors.

Reproducibility of The Abdominal and Chest Wall Position by Voluntary Breath-Hold Technique Using a Laser-Based Monitoring and Visual Feedback System

The voluntary breath-hold (BH) technique is a simple method to control the respiration-related motion of a tumor during irradiation. However, the abdominal and chest wall position may not be accurately reproduced using the BH technique. The purpose of this study was to examine whether visual feedback can reduce the fluctuation in wall motion during BH using a new respiratory monitoring device. We developed a laser-based BH monitoring and visual feedback system. For this study, five healthy volunteers were enrolled. The volunteers, practicing abdominal breathing, performed shallow end-expiration BH (SEBH), shallow end-inspiration BH (SIBH), and deep end-inspiration BH (DIBH) with or without visual feedback. The abdominal and chest wall positions were measured at 80-ms intervals during BHs. The fluctuation in the chest wall position was smaller than that of the abdominal wall position. The reproducibility of the wall position was improved by visual feedback. With a monitoring device, visual feedback reduced the mean deviation of the abdominal wall from 2.1 +/- 1.3 mm to 1.5 +/- 0.5 mm, 2.5 +/- 1.9 mm to 1.1 +/- 0.4 mm, and 6.6 +/- 2.4 mm to 2.6 +/- 1.4 mm in SEBH, SIBH, and DIBH, respectively. Volunteers can perform the BH maneuver in a highly reproducible fashion when informed about the position of the wall, although in the case of DIBH, the deviation in the wall position remained substantial.

Abdominal Organ Motion During Conformal Radiation

Purpose/Objective: Radiation has recently been established as an integral modality in the adjuvant therapy of R0 resected adenocarcinoma of the stomach/GE junction (GC). There are no published studies assessing motion of the residual stomach, anastomosis and nodal groups or effects of respiration on target motion. Measurement of translation and deformation due to variable filling of hollow organs, as well as breathing motion, is necessary for accurate delivery of conformal radiotherapy and intensity modulated radiation therapy (IMRT). The current arbitrary PTV margin (1cm) could result in excess normal tissue toxicity or insufficient target coverage. The aims of this study are to determine interfraction motion of abdominal organs during adjuvant 3D conformal radiation for GC, quantify displacement due to respiratory motion, and assess the stability of these organs in voluntary breath hold. Materials/Methods: 20 patients receiving adjuvant chemoradiation for GC will undergo CT scans in free breath (FB), normal voluntary breathhold inhale (I) and exhale (E) immobilized with BodyFix, in week 1, 3 and 5 of therapy. A standard light meal is taken by patients not less that an hour prior to the scans. The serial CT scans are imported into Pinnacle v6.2b and registered to the freebreath planning scan (CT0) using automated bone registration. Volumes of interest (VOIs) are contoured on each scan (stomach, pancreas, kidneys, porta hepatis, celiac axis), by the same physician. Points of interest (POIs) are defined as the centre of mass for each VOI, dome of diaphragm and splenic hilum. Motion during treatment is assessed by measuring differences in position of POIs and in volumes of VOIs in FB scans compared to CT0, in right-left (RL), craniocaudal (CC) and posteroanterior (PA) directions. POIs and VOIs are compared in FB, I and E scans, using week 1 scans as baseline, to determine stability of breath hold. Respiratory movement is determined from I/E scans. Results: 47 CTs from 5 patients have been analyzed. Median absolute displacement for all organs was determined for all scans (see table). Greatest magnitude of displacement in freebreath scans was seen in the CC direction for the kidneys, stomach and splenic hilum, where individual translations were as great as 20 to 50 mm. Breathing motion, determined from I and E scans, showed greatest absolute displacement in CC direction for the diaphragm (median 15mm, range 0 to 50mm) and the porta hepatis (median 12mm, range 2 to 28mm). Displacements were similar when comparing FB, I and E scans, except for greater displacement seen in the CC direction on I scans. Median absolute change in volume (%) compared to week 1 scans in FB/I/E was: stomach 37/ 24.7/ 19.05, pancreas 33.2/ 19.8/ 21.4, kidneys 6.2/ 4/ 5.39. Conclusions: Displacement of the abdominal organs can be substantial, with offsets up to 5cm. This may alter the dose to targets and organs at risk and indicates the potential need for individualised and/or adaptive planning. Tabled 1Median displacement over all organs in mm (range of medians)

Breathing adapted radiotherapy for breast cancer: Comparison of free breathing gating with the breath-hold technique

Background and purposeAdjuvant radiotherapy after breast-conserving surgery for breast cancer implies a risk of late cardiac and pulmonary toxicity. This is the first study to evaluate cardiopulmonary dose sparing of breathing adapted radiotherapy (BART) using free breathing gating, and to compare this respiratory technique with voluntary breath-hold. Patients and methods17 patients were CT-scanned during non-coached breathing manoeuvre including free breathing (FB), end-inspiration gating (IG), end-expiration gating (EG), deep inspiration breath-hold (DIBH) and end-expiration breath-hold (EBH). The Varian Real-time Position Management system (RPM™) was used to monitor respiratory movement and to gate the scanner. For each breathing phase, a population based internal margin (IM) was estimated based on average chest wall excursion, and incorporated into an individually optimised three-field mono-isocentric wide tangential photon field treatment plan for each scan. The target included the remaining breast, internal mammary nodes and periclavicular nodes. ResultsThe mean anteroposterior chest wall excursion during FB was 2.5mm. For IG and EG, the mean excursions within gating windows were 1.1 and 0.7mm, respectively, whereas for DIBH and EBH the excursions were 4.1 and 2.6mm, respectively.For patients with left-sided cancer, the median heart volume receiving more than 50% of the prescription dose was reduced from 19.2% for FB to 2.8% for IG and 1.9% for DIBH, and the median left anterior descending (LAD) coronary artery volume was reduced from 88.9% to 22.4% for IG and 3.6% for DIBH. Simultaneously, the median ipsilateral relative lung volume irradiated to >50% of the prescribed target dose for both right- and left-sided cancers was reduced from 45.6% for FB to 29.5% for IG and 27.7% for DIBH. For EBH and EG, both the irradiated heart, LAD and lung volumes increased compared to FB. ConclusionsThis is the first study to demonstrate the dosimetric benefits of free breathing gated breast cancer radiotherapy. IG compared favourably with DIBH, substantially reducing cardiac doses simultaneous with significant pulmonary tissue sparing.

A gated deep inspiration breath-hold radiation therapy technique using a linear position transducer

For patients with thoracic and abdominal lesions, respiration-induced internal organ motion and deformations during radiation therapy are limiting factors for the administration of high radiation dose. To increase the dose to the tumor and to reduce margins, tumor movement during treatment must be minimized. Currently, several types of breath-synchronized systems are in use. These systems include respiratory gating, deep inspiration breath-hold, active breathing control, and voluntary breath-hold. We used a linear position transducer (LPT) to monitor changes in a patient's abdominal cross-sectional area. The LPT tracks changes in body circumference during the respiratory cycle using a strap connected to the LPT and wrapped around the patient's torso. The LPT signal is monitored by a computer that provides a real-time plot of the patient's breathing pattern. In our technique, we use a CT study with multiple gated acquisitions. The Philips Medical Systems Q series CT imaging system is capable of operating in conjunction with a contrast injector. This allows a patient performing the deep inspiration breath-hold maneuver to send a signal to trigger the CT scanner acquisitions. The LPT system, when interfaced to a LINAC, allows treatment to be delivered only during deep inspiration breath-hold periods. Treatment stops automatically if the lung volume drops from a preset value. The whole treatment can be accomplished with 1 to 3 breath-holds. This technique has been used successfully to combine automatically gated radiation delivery with the deep inspiration breath-hold technique. This improves the accuracy of treatment for moving tumors, providing better target coverage, sparing more healthy tissue, and saving machine time. PACS numbers: 87.53.2j, 87.57.-s

Respiration‐correlated treatment delivery using feedback‐guided breath hold: A technical study

Respiratory motion causes movement of internal structures in the thorax and abdomen, making accurate delivery of radiation therapy to tumors in those areas a challenge. To reduce the uncertainties caused by this motion, we have developed feedback-guided breath hold (FGBH), a novel delivery technique in which radiation is delivered only during a voluntary breath hold that is sustained for as long as the patient feels comfortable. Here we present the technical aspects of FGBH, which involve (1) fabricating the hardware so the respiratory trace can be displayed to the patient, (2) assembling a delay box to be used as a breath-hold detector, and (3) performing quality control tests to ensure that FGBH can be delivered accurately and safely. A commercial respiratory tracking system that uses an external fiducial to monitor abdominal wall motion generates and displays the breathing trace and specific positions in the breathing cycle where a breath hold needs to occur. Hardware was developed to present this display to the patient in the treatment position. Patients view the presentation either on a liquid crystal display or through a pair of virtual reality goggles. Using the respiratory trace as a visual aid, the patient performs a breath hold so that the position representing the location of a fiducial is held within a specified gating window. A delay box was fabricated to differentiate between gating signals received during free breathing and those received during breath hold, allowing radiation delivery only when the fiducial was within the breath-hold gating window. A quality control analysis of the gating delay box and the integrated system was performed to ensure that all of the hardware and components were ready for clinical use.

559 poster Voluntary self breath hold to minimize the heart dose during left breast radiation therapy: verification of the breath hold stability using electronic portal images in movie mode

559 poster Voluntary self breath hold to minimize the heart dose during left breast radiation therapy: verification of the breath hold stability using electronic portal images in movie mode

Reproducibility of organ position using voluntary breath hold method with spirometer during extracranial stereotactic radiotherapy

Reproducibility of organ position using voluntary breath hold method with spirometer during extracranial stereotactic radiotherapy

Obstructive apnea during sleep is associated with peripheral vasoconstriction.

Obstructive apnea during sleep is associated with a substantial transient blood pressure elevation. The mechanism of this pressor response is unclear. In this study we measured muscle sympathetic nerve activity (MSNA), mean arterial pressure (Psa), and mean limb blood velocity as an index of blood flow (MBV, Doppler) and calculated changes in limb vascular resistance during and after apneas during both wakefulness and sleep in patients with the obstructive sleep apnea syndrome. Immediately postapnea during sleep Psa increased significantly compared with the earlier stages of apnea and this was preceded by a rise of MSNA (n = 5). In contrast to blood pressure, MBV remained unchanged. Because resistance = blood pressure/blood flow, limb vascular resistance increased by 29 +/- 8% from late apnea to postapnea (n = 7, p < 0.002). Voluntary breathhold maneuvers during room air exposure evoked similar responses (n = 10). Supplemental oxygen administered via nonrebreather face mask attenuated the MSNA and vasoconstrictor responses to obstructive (n = 2) and voluntary apneas (n = 10). Our data suggest that obstructive apneas in patients with the obstructive apnea syndrome are accompanied by transient limb vasoconstriction. This vasoconstrictor response appears to be, at least in part, mediated by the sympathetic nervous system and may be linked to hypoxia.

Breathing-synchronized radiotherapy program at the University of California Davis Cancer Center.

In this paper we present a complete description of the breathing synchronized radiotherapy (BSRT) system, which has been jointly developed between the University of California Davis Cancer Center and Varian Associates. BSRT is a description of an emerging radiation oncology procedure, where simulation, CT scan, treatment planning, and radiation treatment are synchronized with voluntary breath-hold, forced breath-hold, or breathing gating. The BSRT system consists of a breathing monitoring system (BMOS) and a linear accelerator gating hardware and software package. Two methods, a video camera-based method and the use of wraparound inductive plethysmography (RespiTrace), generate the BMOS signals. The BMOS signals and the synchronized fluoroscopic images are simultaneously recorded in the simulation room and are later analyzed to define the ideal treatment point (ITP) where organ motion is stationary. The BMOS signals at ITP can be used to gate a CT scanner or a linear accelerator to maintain the same organ configuration as in the simulation. The BSRT system allows breath-hold or gating. This dual role allows the system to be applicable for a variety of patients, i.e., the breath-hold method for those patients who can maintain and reproduce the ITP, and the forced breath-hold or gating method for those who are not ideal for voluntary breath-hold.

Voluntary breath holding in the obese.

Alveolar gas tensions and arterial O2 saturation (Sao2) during a voluntary breath hold at functional residual capacity (FRC) were examined in 13 healthy seated subjects. An excellent correlation (r = 0.80) was found between the fall of alveolar O2 tensions (delta PETo2) and body weight, expressed as the ratio of weight to height (wt/ht, kg/cm). An even greater correlation (r = 0.89) was found between delta PETo2 and the ratio of breath-hold time X O2 consumption/FRC. Alveolar Po2 decreased to 70 mmHg in the obese group after just 15 s of apnea, whereas this degree of hypoxia did not occur in the nonobese until the breath hold was sustained for 30 s. This variable rate of fall of alveolar Po2 during a breath hold can be ascribed to the changes of O2 consumption (Vo2) and FRC associated with changing body weight. In the obese, Vo2/FRC was twice as large as in the nonobese, thus accounting for the differences of breath-hold time needed to obtain the same alveolar Po2. Sao2 measured at the end of the breath hold was the same as that value predicted from the reduction of PETo2. This suggests that the fall of alveolar Po2 can entirely account for the observed fall of O2 saturation and that venous admixture had not increased during the 15-s apnea. In patients with sleep apnea, the ratio of Vo2/(initial lung volume) may also be an important determinant of the severity of hypoxemia observed.

Dive and breath hold metabolism of the brown water snake, Natrix taxispilota

1. 1. Average heart rates of restrained snakes were significantly higher and took longer to reach minimal levels during dives than measurements for voluntary divers. 2. 2. Heart rate differences between voluntary dives and breath holds were significant only after an apnea. 3. 3. Oxygen consumption was not significantly different during a voluntary dive or breath hold, but was significantly higher during forced or scare dives. 4. 4. Anaerobic mechanisms, which have been reported during dives in N. Taxispilota, appear less important during breath holds. 5. 5. Results from the present study suggest that while minimal metabolic and cardiac measurements were acceptably close to other published values, true standard rates may not have been achieved.

Mechanical and chemical control of breath holding.

The relationship between the maximum duration of a voluntary breath hold (BHT) and the alveolar Pco2 at the start and finish of the period of apnoea has been investigated in six subjects over a wide range of CO2 tensions, for breath holds made at VC, 60 per cent VC, and FRC. Alveolar Po2 was maintained above the level at which hypoxia is a significant factor in stimulating pulmonary ventilation. The results suggest that the relationship between BHT and Pco2 at breaking point may be approximated by two straight line segments: for short breath holds (with a high initial Pco2), BHT and breaking point Pco2 are linearly related; for long breath holds (with a low initial Pco2) final Pco2 is independent of the duration of the breath hold. These results suggest that the mechanical component of the drive to resume breathing saturates during long breath holds, the level of saturation depending on the lung volume at which the breath is held.