Accuracy and stability of deep inspiration breath hold in gated breast radiotherapy – A comparison of two tracking and guidance systems

Use of a pressure sensor array for multifunctional patient monitoring in radiotherapy: A feasibility study

BACKGROUND

Modern radiotherapeutic techniques, such as intensity-modulated radiation therapy or stereotactic body radiotherapy, require high-dose delivery precision. However, the precise localization of tumors during patient respiration remains a challenge. Therefore, it is essential to investigate effective methods for monitoring respiration to minimize potential complications. Despite several systems currently in clinical use, there are drawbacks, including the complexity of the setup, the discomfort to the patient, and the high cost.

PURPOSE

This study investigated the feasibility of using a novel pressure sensor array (PSA) as a tool to monitor respiration during radiotherapy treatments. The PSA was positioned between the treatment couch and the back of the patient lying on it and was intended to overcome some limitations of current methods. The main objectives included assessing the PSA's capability in monitoring respiratory behavior and to investigate prospective applications that extend beyond respiratory monitoring.

METHODS

A PSA with 31 pressure-sensing elements was used in 12 volunteers. The participants were instructed to breathe naturally while lying on a couch without any audio or visual guidance. The performance of the PSA was compared to that of a camera-based respiratory monitoring system (RPM, Varian, USA), which served as a reference. Several metrics, including pressure distribution, weight sensitivity, and correlations between PSA and RPM signals, were analyzed. The PSA's capacity to provide information on potential applications related to patient stability was also investigated.

RESULTS

The linear relationship between the weight applied to the PSA and its output was demonstrated in this study, confirming its sensitivity to pressure changes. A comparison of PSA and RPM curves revealed a high correlation coefficient of 0.9391 on average, indicating consistent respiratory cycles. The PSA also effectively measured the weight distribution at the volunteer's back in real-time, which allows for monitoring the patient's movements during the radiotherapy.

CONCLUSION

PSA is a promising candidate for effective respiratory monitoring during radiotherapy treatments. Its performance is comparable to the established RPM system, and its additional capabilities suggest its multifaceted utility. This paper shows the potential use of PSA for patient monitoring in radiotherapy and suggests possibilities for further research, including performance comparisons with other existing systems and real-patient applications with respiratory training.

Carbon-fiber alternative to the commercial gating surrogate for the Varian Truebeam™

BACKGROUND

In this study we present the Tracking Accessory 3 (TA3) as an alternative to the commercial gating block (GB) surrogate for the Varian Truebeam™ gating system (TGS). The TGS requires three visible reflectors to track the surrogate, presenting an opportunity for a surrogate to be made with less material and thus smaller dosimetric footprint than the commercial four reflector model.

MATERIALS AND METHODS

Relative dose and depth dose profiles below the TA3 and the GB were measured with radiosensitive film. Accuracy and reproducibility of the detected motion amplitude for three TA3s and one GB were determined using a respiratory phantom with surrogate to determine the camera's tracking volume. Clinical performance was evaluated prospectively in 10 breast cancer patients treated with deep inspiration breath hold monitored with TA3 and compared to previously published results. Non-parametric statistics were applied to test for significance.

RESULTS AND CONCLUSIONS

Surface doses were increased up to 94% and 187% for the TA3 and GB, respectively, compared to no surrogate. The surface area influenced by at least 25% increase in dose was 12 cm2 and 105 cm2 for the TA3 and GB, respectively. The water equivalent thickness of the surrogates was found to be 1 mm for the TA3 and 3 mm for GB. The difference in measured amplitude were <0.2 mm for TA3 compared to the GB. The TA3s and GB were detected at all extremes of the clinically relevant tracking volume of the TGS. Clinical performance showed no significant differences. The TA3 caused less surface dose increase compared to the commercial GB. In the tested range all surrogates measured motion amplitude within 0.2 mm of reference value, which is not a clinically relevant difference. The TA3 showed no significant differences in clinical performance to similarly positioned surrogates.

Technical note: Clinical evaluation of a newly released surface-guided radiation therapy system on DIBH for left breast radiation therapy

BACKGROUND

It has been shown that a significant reduction of mean heart dose and left anterior descending artery (LAD) dose can be achieved through the use of DIBH for left breast radiation therapy. Surface-guided DIBH has been widely adopted during the last decade, and there are mainly three commercially available SGRT systems. The reports of the performance of a newly released SGRT system for DIBH application are currently very limited.

PURPOSE

To evaluate the clinical performance of a newly released SGRT system on DIBH for left breast radiation therapy.

METHODS

Twenty-five left breast cancer patients treated with DIBH utilizing Varian's Identify system were included (total 493-fraction treatments). Four aspects of the clinical performance were evaluated: Identify offsets of free breathing post patient setup from tattoos, Identify offsets during DIBH, Identify agreement with radiographic ports during DIBH, and DIBH reference surface re-capture post patient shifts. The systematic and random errors of free breathing Identify offsets post patient setup were calculated for each patient, as well as for offsets during DIBH. Radiographic ports were taken when the patient's DIBH position was within the clinical tolerance of (± 0.3 cm, ± 30 ), and these were then compared with treatment field DRRs. If the ports showed that the patient alignment did not agree with the DRRs within 3 mm, a patient shift was performed. A new reference surface was captured and verification ports were taken.

RESULTS

The all-patient average systematic and random errors of Identify offsets for free breathing were within (0.4 cm, 1.50 ) post tattoo setup. The maximum per-patient systematic and random errors were (1.1 cm, 6.20 ) and (0.9 cm, 20 ), and the maximum amplitude of Identify offsets were (2.59 cm, 90 ). All 493-fraction DIBH treatments were delivered and successfully guided by the Identify SGRT system. The systematic and random errors of Identify offsets for DIBH were within (0.2 cm, 2.30 ). Seven patients needed re-captured surface references due to surface variation or position shifts based on the ports. All patient DIBH verification ports guided by Identify were approved by attending physicians.

CONCLUSION

This evaluation showed that the Identify system performed effectively for surface-guided patient setup and surface-guided DIBH imaging and treatment delivery. The feature of color-coded real-time patient surface matching feedback facilitated the evaluation of the patient alignment accuracy and the adjustment of the patient position to match the reference.

Initial end-to-end testing of the ExacTrac dynamic deep inspiration breath hold workflow using a breath hold breast phantom

ExacTrac Dynamic (ETD) provides a Deep Inspiration Breath Hold (DIBH) workflow for breast patients. Stereoscopic x-ray imaging combined with optical and thermal mapping allows localisation against simulation imaging, alongside surface guided breath hold monitoring. This work aimed to determine appropriate imaging parameters, the optimal Hounsfield Unit (HU) threshold for patient contour generation and workflow evaluation via end-to-end (E2E) positioning using a custom breast DIBH phantom. After localisation via existing Image Guidance (IG), stereoscopic imaging was performed with a range of parameters to determine best agreement. Similarly, residual errors in prepositioning were minimised using a range of HU threshold contours. E2E positioning was completed for clinical workflows allowing residual isocentre position error measurement and existing IG comparison. Parameters of 60 kV and 25mAs were determined appropriate for patient imaging and HU thresholds between -600 HU and -200 HU enabled adequate prepositioning. The average and standard deviation in residual isocentre position error was 1.0 ± 0.9 mm, 0.4 ± 1.0 mm and 0.1 ± 0.5 mm in the lateral, longitudinal and vertical directions, respectively. Errors measured using existing IG were -0.6 ± 1.1 mm, 0.5 ± 0.7 mm and 0.2 ± 0.4 mm in the lateral, longitudinal and vertical directions, and 0.0 ± 1.0o, 0.5 ± 1.7o and -0.8 ± 1.8o for pitch roll and yaw. The use of bone weighted matching increased residual error, while simulated reduction of DIBH volume maintained isocentre positioning accuracy despite anatomical changes. This initial testing indicated suitability for clinical implementation during DIBH breast treatments.

Evaluation of surface image guidance and Deep inspiration Breath Hold technique for breast treatments with Halcyon

PURPOSE

To evaluate the accuracy/agreement of a three-camera Catalyst Surface Guided Radiation Therapy (SGRT) system on a closed-gantry Halcyon for Free-Breathing (FB) and Deep Inspiration Breath Hold (DIBH) breast-only treatments.

METHODS

The SGRT positioning agreement with Halcyon couch and cone-beam computed tomography (CBCT) was evaluated on phantom and by evaluation of 2401 FB and 855 DIBH breast-only treatment sessions. The DIBH agreement was evaluated using a programmable moving support. Dose agreement was evaluated for manual SGRT-assisted beam interruption and Halcyon arc beam interruption.

RESULTS

Geometrical phantom agreement was < 0.4 mm. Couch and SGRT agreement for an anthropomorphic phantom resulted in 95% limits of agreement in Right-Left/Feet-Head/Posterior-Anterior (RL/FH/PA) directions of respectively ± 0.4/0.8/0.5 mm and ± 1.1/1.1/0.6 mm in the virtual and real isocenter. FB-SGRT-assisted patient positioning compared to CBCT positioning resulted in RL/FH/PA systematic differences of -0.1/0.1/2.0 mm with standard deviations of 2.7/2.8/2.4 mm. This mean systematic difference had three origins: a) couch sag/isocenter difference of ≤ 0.5 mm. b) Average reconstructed FB-CBCT images do not visually represent the average respiratory position. c) CBCT-based positioning focused on the inner thoracic interface, which can introduce a mean positioning difference between SGRT and CBCT. Manual SGRT-assisted beam interruption and arc interruptions resulted in mean gamma passing rates > 97% (0.5%/0.5 mm) and mean absolute differences < 0.3%.

CONCLUSIONS

Accuracy was comparable with breast-only C-arm SGRT techniques, with different tradeoffs. Depending on the patient's morphology, real-time tracking accuracy in the real isocenter can be reduced. This study demonstrates possible discordances between SGRT and CBCT positioning for breast.

Surface guided 3DCRT in deep-inspiration breath-hold for left sided breast cancer radiotherapy: implementation and first clinical experience in Iran

Background

The aim of the study is to evaluate the overall accuracy of the surface-guided radiotherapy (SGRT) workflow through a comprehensive commissioning and quality assurance procedures and assess the potential benefits of deep-inspiration breath-hold (DIBH) radiotherapy as a cardiac and lung dose reduction approach for left-sided breast cancer irradiation.

Materials and methods

Accuracy and reproducibility of the optical surface scanner used for DIBH treatment were evaluated using different phantoms. Patient positioning accuracy and reproducibility of DIBH treatment were evaluated. Twenty patients were studied for treatment plan quality in target dose coverage and healthy organ sparing for the two different treatment techniques.

Results

Reproducibility tests for the surface scanner showed good stability within 1 mm in all directions. The maximum position variation between applied shifts on the couch and the scanner measured offsets is 1 mm in all directions. The clinical study of 200 fractions showed good agreement between the surface scanner and portal imaging with the isocenter position deviation of less than 3 mm in each lateral, longitudinal, and vertical direction. The standard deviation of the DIBH level showed a value of < 2 mm during all evaluated DIBHs. Compared to the free breathing (FB) technique, DIBH showed significant reduction of 48% for heart mean dose, 43% for heart V25, and 20% for ipsilateral lung V20.

Conclusion

Surface-guided radiotherapy can be regarded as an accurate tool for patient positioning and monitoring in breast radiotherapy. DIBH treatment are considered to be effective techniques in heart and ipsilateral lung dose reductions for left breast radiotherapy.

First clinical experience with real-time portal imaging-based breath-hold monitoring in tangential breast radiotherapy

Background and purpose

Real-time treatment monitoring with the electronic portal imaging device (EPID) can conceptually provide a more accurate assessment of the quality of deep inspiration breath-hold (DIBH) and patient movement during tangential breast radiotherapy (RT). A system was developed to measure two geometrical parameters, the lung depth (LD) and the irradiated width (named here skin distance, SD), along three user-selected lines in MV EPID images of breast tangents. The purpose of this study was to test the system during tangential breast RT with DIBH.

Materials and methods

Measurements of LDs and SDs were carried out in real time. DIBH was guided with a commercial system using a marker block. Results from 17 patients were assessed. Mean midline LDs, <mLDs>, per tangent were compared to the planned mLDs; differences between the largest and smallest observed <mLDs> (<mSDs>) per tangent were calculated.

Results

For 56% (162/288) of the tangents tested, <mLDs> were outside the tolerance window. All but one patient had at least one fraction showing this behaviour. The largest difference found between an <mLD> and its planned mLD was −16.9 mm. The accuracy of patient positioning and the quality of marker-block-based DIBH guidance contributed to the differences. Fractions with patient position verification using a single EPID image taken before treatment showed a lower rate (34%), suggesting reassessment of setup procedures.

Conclusions

Real-time treatment monitoring of the internal anatomy during DIBH delivery of tangential breast RT is feasible and useful. The new system requires no additional radiation for the patient.

TROG 14.04: Multicentre Study of Feasibility and Impact on Anxiety of DIBH in Breast Cancer Patients

AIMS

The aim of TROG 14.04 was to assess the feasibility of deep inspiration breath hold (DIBH) and its impact on radiation dose to the heart in patients with left-sided breast cancer undergoing radiotherapy. Secondary end points pertained to patient anxiety and cost of delivering a DIBH programme.

MATERIALS AND METHODS

The study comprised two groups - left-sided breast cancer patients engaging DIBH and right-sided breast cancer patients using free breathing through radiotherapy. The primary end point was the feasibility of DIBH, defined as left-sided breast cancer patients' ability to breath hold for 15 s, decrease in heart dose in DIBH compared with the free breathing treatment plan and reproducibility of radiotherapy delivery using mid-lung distance (MLD) assessed on electronic portal imaging as the surrogate. The time required for treatment delivery, patient-reported outcomes and resource requirement were compared between the groups.

RESULTS

Between February and November 2018, 32 left-sided and 30 right-sided breast cancer patients from six radiotherapy centres were enrolled. Two left-sided breast cancer patients did not undergo DIBH (one treated in free breathing as per investigator choice, one withdrawn). The mean heart dose was reduced from 2.8 Gy (free breathing) to 1.5 Gy (DIBH). Set-up reproducibility in the first week of treatment assessed by MLD was 1.88 ± 1.04 mm (average ± 1 standard deviation) for DIBH and 1.59 ± 0.93 mm for free breathing patients. Using a reproducibility cut-off for MLD of 2 mm (1 standard deviation) as per study protocol, DIBH was feasible for 67% of DIBH patients. Radiotherapy delivery using DIBH took about 2 min longer than for free breathing. Anxiety was not significantly different in DIBH patients and decreased over the course of treatment in both groups.

CONCLUSION

Although DIBH was shown to require about 2 min longer per treatment slot, it has the potential to reduce heart dose in left-sided breast cancer patients by nearly a half, provided careful assessment of breath hold reproducibility is carried out.

AAPM task group report 302: Surface guided radiotherapy

The clinical use of surface imaging has increased dramatically with demonstrated utility for initial patient positioning, real-time motion monitoring, and beam gating in a variety of anatomical sites. The Therapy Physics Subcommittee and the Imaging for Treatment Verification Working Group of the American Association of Physicists in Medicine commissioned Task Group 302 to review the current clinical uses of surface imaging and emerging clinical applications. The specific charge of this task group was to provide technical guidelines for clinical indications of use for general positioning, breast deep-inspiration breath-hold (DIBH) treatment, and frameless stereotactic radiosurgery (SRS). Additionally, the task group was charged with providing commissioning and on-going quality assurance (QA) requirements for surface guided radiation therapy (SGRT) as part of a comprehensive QA program including risk assessment. Workflow considerations for other anatomic sites and for computed tomography (CT) simulation, including motion management are also discussed. Finally, developing clinical applications such as stereotactic body radiotherapy (SBRT) or proton radiotherapy are presented. The recommendations made in this report, which are summarized at the end of the report, are applicable to all video-based SGRT systems available at the time of writing. Review current use of non-ionizing surface imaging functionality and commercially available systems. Summarize commissioning and on-going quality assurance (QA) requirements of surface image-guided systems, including implementation of risk or hazard assessment of surface guided radiotherapy as a part of a total quality management program (e.g., TG-100). Provide clinically relevant technical guidelines that include recommendations for the use of SGRT for general patient positioning, breast DIBH, and frameless brain SRS, including potential pitfalls to avoid when implementing this technology. Discuss emerging clinical applications of SGRT and associated QA implications based on evaluation of technology and risk assessment. This article is protected by copyright. All rights reserved.

Evaluation of image-guided and surface-guided radiotherapy for breast cancer patients treated in deep inspiration breath-hold: A single institution experience

INTRODUCTION

Nowadays, deep inspiratory breath-hold is a common technique to reduce heart dose in left-sided breast radiotherapy. This study evaluates the evolution of the breath-hold technique in our institute, from portal imaging during dose delivery to continuous monitoring with surface-guided radiotherapy (SGRT).

MATERIALS AND METHODS

Setup data and portal imaging results were analyzed for 98 patients treated before 2014, and SGRT data for 228 patients treated between 2018 and 2020. For the pre-SGRT group, systematic and random setup errors were calculated for different correction protocols. Residual errors and reproducibility of breath-holds were evaluated for both groups. The benefit of using SGRT for initial positioning was evaluated for another cohort of 47 patients.

RESULTS

Online correction reduced the population mean error from 3.9 mm (no corrections) to 1.4 mm. Despite online setup correction, deviations greater than 3 mm were observed in about 10% and 20% of the treatment beams in ventral-dorsal and cranial-caudal directions, respectively. However, these percentages were much smaller than with offline protocols or no corrections. Mean absolute differences between breath-holds within a fraction were smaller in the SGRT-group (1.69 mm) than in the pre-SGRT-group (2.10 mm), and further improved with addition of visual feedback (1.30 mm). SGRT for positioning did not improve setup accuracy, but slightly reduced the time for imaging and setup correction, allowing completion within 3.5 min for 95% of fractions.

CONCLUSION

For accurate radiotherapy breast treatments using deep inspiration breath-hold, daily imaging and correction is required. SGRT provides accurate information on patient positioning during treatment and improves patient compliance with visual feedback.

Assessment of visual feedback system for reproducibility of voluntary deep inspiration breath hold in left-sided breast radiotherapy

INTRODUCTION

Deep inspiration breath-hold (DIBH) for left-sided breast cancer radiotherapy reduces the dose exposure of the heart and left anterior descending coronary artery. DIBH requires the patient to maintain an adequate breath-hold position during their daily radiotherapy fraction. This study aimed to assess the reproducibility of the breath-hold position by implementing DIBH with visual feedback (VF) system.

METHODS

Forty-three patients who underwent left-sided radiotherapy with DIBH were reviewed. Data from 35 patients who underwent DIBH with VF (VF-DIBH) were compared with data from 8 patients who underwent DIBH with audio coaching (AC-DIBH). Reproducibility during radiotherapy was evaluated using the portal images obtained. Images were acquired daily during the tangential field treatment with DIBH. The distances between the field edge and chest wall at the central beam axis were manually measured on the portal image and digital reconstruction radiograph (DRR). The displacements of the chest wall during radiotherapy were assessed by subtracting the measurement made on the portal image from the DRR measurement. The overall average distances for the VF-DIBH and AC-DIBH cohorts were compared to assess reproducibility. The statistical analysis was performed using Mann-Whitney U tests (p < 0.05).

RESULTS

The mean chest wall displacement (±2 SD) was 0.59 ± 3.64 mm for VF-DIBH and 2.09 ± 4.96 mm for AC-DIBH, respectively. This value differed significantly between the VF-DIBH and AC-DIBH cohorts (p < 0.001).

CONCLUSION

In DIBH radiotherapy, the implementation of VF was confirmed to improve breath-hold position reproducibility, and the utility of VF for DIBH was demonstrated.

Reducing Cardiac Radiation Dose From Breast Cancer Radiation Therapy With Breath Hold Training and Cognitive Behavioral Therapy

The delivery of radiation therapy shares many of the challenges encountered in imaging procedures. As in imaging, such as MRI, organ motion must be reduced to a minimum, often for lengthy time periods, to effectively target the tumor during imaging-guided therapy while reducing radiation dose to nearby normal tissues. For patients, radiation therapy is frequently a stress- and anxiety-provoking medical procedure, evoking fear from negative perceptions about irradiation, confinement from immobilization devices, claustrophobia, unease with equipment, physical discomfort, and overall cancer fear. Such stress can be a profound challenge for cancer patients' emotional coping and tolerance to treatment, and particularly interferes with advanced radiation therapy procedures where active, complex and repetitive high-level cooperation is often required from the patient.In breast cancer, the most common cancer in women worldwide, radiation therapy is an indispensable component of treatment to improve tumor control and outcome in both breast-conserving therapy for early-stage disease and in advanced-stage patients. High technological complexity and high patient cooperation is required to mitigate the known cardiac toxicity and mortality from breast cancer radiation by reducing the unintended radiation dose to the heart from left breast or left chest wall irradiation. To address this, radiation treatment in daily deep inspiration breath hold (DIBH), to create greater distance between the treatment target and the heart, is increasingly practiced. While holding the promise to decrease cardiac toxicity, DIBH procedures often augment patients' baseline stress and anxiety reaction toward radiation treatment. Patients are often overwhelmed by the physical and mental demands of daily DIBH, including the nonintuitive timed and sustained coordination of abdominal thoracic muscles for prolonged breath holding.While technologies, such as DIBH, have advanced to millimeter-precision in treatment delivery and motion tracking, the "human factor" of patients' ability to cooperate and perform has been addressed much less. Both are needed to optimally deliver advanced radiation therapy with minimized normal tissue effects, while alleviating physical and cognitive distress during this challenging phase of breast cancer therapy.This article discusses physical training and psychotherapeutic integrative health approaches, applied to radiation oncology, to leverage and augment the gains enabled by advanced technology-based high-precision radiation treatment in breast cancer. Such combinations of advanced technologies with training and cognitive integrative health interventions hold the promise to provide simple feasible and low-cost means to improve patient experience, emotional outcomes and quality of life, while optimizing patient performance for advanced imaging-guided treatment procedures - paving the way to improve cardiac outcomes in breast cancer survivors.

Stability and reproducibility of 6013 deep inspiration breath-holds in left-sided breast cancer

Purpose

Patients with left-sided breast cancer frequently receive deep inspiration breath-hold (DIBH) radiotherapy to reduce the risk of cardiac side effects. The aim of the present study was to analyze intra-breath-hold stability and inter-fraction breath-hold reproducibility in clinical practice.

Material and methods

Overall, we analyzed 103 patients receiving left-sided breast cancer radiotherapy using a surface-guided DIBH technique. During each treatment session the vertical motion of the patient was continuously measured by a surface guided radiation therapy (SGRT) system and automated gating control (beam on/off) was performed using an audio-visual patient feedback system. Dose delivery was automatically triggered when the tracking point was within a predefined gating window. Intra-breath-hold stability and inter-fraction reproducibility across all fractions of the entire treatment course were analyzed per patient.

Results

In the present series, 6013 breath-holds during beam-on time were analyzed. The mean amplitude of the gating window from the baseline breathing curve (maximum expiration during free breathing) was 15.8 mm (95%-confidence interval: [8.5–30.6] mm) and had a width of 3.5 mm (95%-CI: [2–4.3] mm). As a measure of intra-breath-hold stability, the median standard deviation of the breath-hold level during DIBH was 0.3 mm (95%-CI: [0.1–0.9] mm). Similarly, the median absolute intra-breath-hold linear amplitude deviation was 0.4 mm (95%-CI: [0.01–2.1] mm). Reproducibility testing showed good inter-fractional reliability, as the maximum difference in the breathing amplitudes in all patients and all fractions were 1.3 mm on average (95%-CI: [0.5–2.6] mm).

Conclusion

The clinical integration of an optical surface scanner enables a stable and reliable DIBH treatment delivery during SGRT for left-sided breast cancer in clinical routine.

Predictors of cardiac and lung dose sparing in DIBH for left breast treatment

This retrospective study of left breast radiation therapy (RT) investigates the correlation between anatomical parameters and dose to heart or/and left lung in deep inspiration breath-hold (DIBH) compared to free-breathing (FB) technique. Anatomical parameters of sixty-seven patients, treated with a step-and-shoot technique to 50 Gy or 50.4 Gy were included. They consisted of the cardiac contact distances in axial (CCD_ax) and parasagittal (CCD_ps) planes, and the lateral heart-to-chest distance (HCD). Correlation analysis was performed to identify predictors for heart and lung dose sparing. Paired t-test and linear regression were used for data analysis with significance level of p = 0.05. All dose metrics for heart and lung were significantly reduced with DIBH, however 21% of patients analyzed had less than 1.0 Gy mean heart dose reduction. Both FB-CCD_psdistance and FB-HCD correlated with FB mean heart dose and mean DIBH heart dose reduction. The strongest correlation was observed for the ratio of FB-CCD_psand FB-HCD with heart dose sparing. A FB-CCD_ps and FB-HCD model was developed to predict DIBH induced mean heart dose reduction, with 1.04 Gy per unit of FB-CCD_ps/FB-HCD. Variation between predicted and actual mean heart dose reduction ranged from -0.6 Gy to 0.6 Gy. In this study, FB-CCD_ps and FB-HCD distance served as predictors for heart dose reduction with DIBH equally, with FB-CCD_ps/FB-HCD as a stronger predictor. These parameters and the prediction model could be further investigated for use as a tool to better select patients who will benefit from DIBH.

Real-time control of respiratory motion: Beyond radiation therapy

Motion management in radiation oncology is an important aspect of modern treatment planning and delivery. Special attention has been paid to control respiratory motion in recent years. However, other medical procedures related to both diagnosis and treatment are likely to benefit from the explicit control of breathing motion. Quantitative imaging - including increasingly important tools in radiology and nuclear medicine - is among the fields where a rapid development of motion control is most likely, due to the need for quantification accuracy. Emerging treatment modalities like focussed-ultrasound tumor ablation are also likely to benefit from a significant evolution of motion control in the near future. In the present article an overview of available respiratory motion systems along with ongoing research in this area is provided. Furthermore, an attempt is made to envision some of the most expected developments in this field in the near future.