Clinical Implementation and Initial Validation of Respiratory-Gated Stereotactic Body Radiotherapy for Thoracoabdominal Tumors Under Abdominal Compression Using an Anzai Laser-Based Gating Device With Visual Guidance on an Elekta Linear Accelerator.

We have clinically implemented gated stereotactic body radiotherapy under abdominal compression using an Anzai laser-based gating device with visual guidance in combination with an Elekta linear accelerator. To ensure accuracy, we configured the gating window for each patient by correlating the respiratory curve from the laser sensor and the tumor positions from the 4D computed tomography (CT) images reconstructed with the aid of the respiratory curve. This allowed us to define a patient-specific gating window to keep the tumor displacement below 5 mm from the end-expiration, assuming the reproducibility of the tumor trajectories and the laser-based body surface measurements. Results are summarized as follows: 1) A patient-specific gating window internal target volume (ITV) with a prespecified maximum tumor displacement relative to the end-expiration was obtained by acquiring a 4D CT consisting of 20 phase CT sets and a respiratory curve from the Anzai system. 2) Respiratory hysteresis was managed by setting two different thresholds on the respiratory curve based on the predetermined maximum tumor displacement relative to end-expiration. 3) Abdominal compression increased gating window width, thereby presumably leading to faster gated-beam delivery. 4) Gamma index pass rates in sliding-window gated intensity-modulated radiotherapy (IMRT) were superior to those in gated volumetric modulated arc therapy (VMAT). 5) Intrafraction gated cone-beam computed tomography (CBCT) demonstrated that the tumor appeared to remain within the gating window ITV during the stereotactic gated sliding-window IMRT. In conclusion, we have successfully implemented gated stereotactic body radiotherapy at our clinic and achieved a favorable clinical validation result. More cases need to be evaluated to increase the validity.

Abdominal compression as motion management for stereotactic radiotherapy of ventricular tachycardia.

Background and purpose: Stereotactic body radiotherapy (SBRT) has emerged as a promising treatment for patients with ventricular tachycardia (VT) who do not respond to standard treatments. However, the management of respiratory motion during treatment remains a challenge. This study aimed to investigate the effect of abdominal compression (AC) on respiratory induced motion in the heart. Materials and methods: A patient cohort of 18 lung cancer patients was utilized, where two four-dimensional computed tomography (4DCT) scans were performed for each patient, one with and one without AC. The patient setup consisted of an AC plate together with a stereotactic body frame. The left coronary artery, the left anterior descending artery, the lateral wall of the left ventricle, the heart apex, the carina, and the right and left diaphragm were delineated in max expiration and max inspiration phases in both 4DCT scans. The center of mass shift from expiration to inspiration phase was determined to assess the AC's impact on respiratory motion. Results: A significant reduction in motion in the superior-inferior direction was found for all heart structures when AC was used. The median respiratory motion of the heart structures decreased by approximately 1-3 mm with AC in the superior-inferior direction, and approximately 60% of the patients had a motion reduction ≥3 mm in the left ventricle wall. Conclusion: These findings suggest that AC has the potential to improve the motion management of SBRT for VT patients, by reducing the respiratory induced motion in the heart.

Impact of abdominal compression on intra-fractional motion and delivered dose in magnetic resonance image-guided adaptive radiation ablation of adrenal gland metastases.

PURPOSE: The current study investigated the impact of abdominal compression on motion and the delivered dose during non-gated, magnetic resonance image (MRI)-guided radiation ablation of adrenal gland metastases. METHODS: Thirty-one patients with adrenal gland metastases treated to 45-60 Gy in 3-8 fractions on a 1.5 T MRI-linac were included in the study. The patients were breathing freely (n = 14) or with motion restricted by using an abdominal compression belt (n = 17). The time-resolved position of the target in online 2D cine MR images acquired during treatment was assessed and used to estimate the dose delivered to the GTV and abutting luminal organs at risk (OAR). RESULTS: The median (range) 3D root-mean-square target position error was significantly higher in patients treated without a compression belt [2.9 (1.9-5.6) mm] compared to patients using the belt [2.1 (1.2-3.5) mm] (P < 0.01). The median (range) GTV V95% was significantly reduced from planned 98.6 (65.9-100) % to delivered 96.5 (64.5-99.9) % due to motion (P < 0.01). Most prominent dose reductions were found in patients showing either large target drift or respiration motion and were mainly treated without abdominal compression. Motion did not lead to an increased number of constraint violations for luminal OAR. CONCLUSIONS: Acceptable target coverage and dose to OAR was observed in the vast majority of patients despite intra-fractional motion during adaptive MRI-guided radiation ablation. The use of abdominal compression significantly reduced the target position error and prevented the most prominent target coverage degradations and is, therefore, recommended as motion management at MRI-linacs.

Real-world effectiveness and safety of stereotactic body radiotherapy for liver metastases with different respiratory motion management techniques.

PURPOSE: Stereotactic body radiotherapy (SBRT) has been firmly established as a treatment choice for patients with oligometastases, as it has demonstrated both safety and efficacy by consistently achieving high rates of local control. Moreover, it offers potential survival benefits for carefully selected patients in real-world clinical settings. METHODS: Between January 2008 and May 2020, a total of 149 patients (with 414 liver metastases) received treatment. The Active Breathing Coordinator device was used for 68 patients, while respiratory gating was used for 65 and abdominal compression was used for 16 patients. The most common histological finding was colorectal adenocarcinoma, with 37.6% of patients having three or more metastases, and 18% having two metastases. The prescribed dose ranged from 36 to 60 Gy, delivered in 3-5 fractions. RESULTS: Local control rates at 2 and 3 years were 76.1% and 61.2%, respectively, with no instances of local recurrence after 3 years. Factors negatively impacting local control included colorectal histology, lower prescribed dose, and the occurrence of new liver metastases. The median overall survival from SBRT was 32 months, with the presence of metastases outside the liver and the development of new liver metastases after SBRT affecting survival. The median disease-free survival was 10 months. No substantial differences in both local control and survival were observed between the respiratory motion control techniques employed. Treatment tolerance was excellent, with only one patient experiencing acute grade IV thrombocytopenia and two patients suffering from ≥ grade II chronic toxicity. CONCLUSION: For radical management of single or multiple liver metastases, SBRT is an effective and well-tolerated treatment option. Regardless of the technology employed, experienced physicians can achieve similarly positive outcomes. However, additional studies are required to elucidate prognostic factors that can facilitate improved patient selection.

The impact of abdominal compression devices on colonoscopy outcomes: a systematic review and meta-analysis of randomized controlled trials.

OBJECTIVE: Colonoscopy is the gold standard method for colorectal cancer screening. Looping occurs in 91% of cases undergoing colonoscopy and can cause patient discomfort, prolonged cecal intubation time (CIT), and colon perforation. This meta-analysis investigates the impact of abdominal compression devices (ACD) on colonoscopy outcomes. METHODS: A systematic review and meta-analysis synthesizing randomized controlled trials (RCTs), retrieved by systematically searching: PubMed, EMBASE, WOS, SCOPUS, and Cochrane through February 2nd, 2023. Continuous and dichotomous outcomes were pooled using mean difference (MD) and risk ratio (RR) along with confidence interval (CI) using Revman. Our review protocol was prospectively published on PROSPERO with ID: CRD42023397344. RESULTS: We included eight RCTs with a total of 1,889 patients. ACD was effective to decrease CIT (MD: -2.15 with a 95% CI [-3.49, -0.80], p = .002), postural change (RR: 0.57 with 95% CI [0.49, 0.66], p = .00001), and VAS pain score (MD: -1.49 with 95% CI [-1.81, -1.17], p = .0001). However, there was no difference between ACD and control groups regarding manual compression (RR: 0.65 with 95% CI [0.42, 1.00], p = .05), complete colonoscopy rate (CCR) (RR: 1.01 with 95% CI [0.99, 1.04], p = .31), and cecal intubation length (CIL) (MD: -2.25 with 95% CI [-7.64, 3.14], p = .41). CONCLUSION: ACD during colonoscopy may enhance patient comfort by reducing CIT, pain, and postural changes. Nevertheless, additional RCTs are necessary to validate these results and determine the most suitable approach to utilize ACD for colonoscopy.

Selection of motion management in liver stereotactic body radiotherapy and its impact on treatment time.

Background and purpose: Reduction of respiratory tumour motion is important in liver stereotactic body radiation therapy (SBRT) to reduce side effects and improve tumour control probability. We have assessed the distribution of use of voluntary exhale breath hold (EBH), abdominal compression (AC), free breathing gating (gating) and free breathing (FB), and the impact of these on treatment time. Materials and Methods: We assessed all patients treated in a single institution with liver SBRT between September 2017 and September 2021. Data from pre-simulation motion management assessment using fluoroscopic assessment of liver dome position in repeat breath holds, and motion with and without AC, was reviewed to determine liver dome position consistency in EBH and the impact of AC on motion. Treatment time was assessed for all fractions as time from first image acquisition to last treatment beam off. Results: Of 136 patients treated with 145 courses of liver SBRT, 68 % were treated in EBH, 20 % with AC, 7 % in gating and 5 % in FB. AC resulted in motion reduction < 1 mm in 9/26 patients assessed. Median treatment time was higher using EBH (39 min) or gating (42 min) compared with AC (30 min) or FB (24 min) treatments. Conclusions: Motion management in liver SBRT needs to be assessed per-patient to ensure appropriate techniques are applied. Motion management significantly impacts treatment time therefore patient comfort must also be taken into account when selecting the technique for each patient.

Reduction of intrafraction pancreas motion using an abdominal corset compatible with proton therapy and MRI.

Background and purpose: Motion mitigation is of crucial importance in particle therapy (PT) of patients with abdominal tumors to ensure high-precision irradiation. Magnetic resonance imaging (MRI) is an excellent modality for target volume delineation and motion estimation of mobile soft-tissue tumors. Thus, the aims of this study were to develop an MRI- and PT-compatible abdominal compression device, to investigate its effect on pancreas motion reduction, and to evaluate patient tolerability and acceptance. Materials and methods: In a prospective clinical study, 16 patients with abdominal tumors received an individualized polyethylene-based abdominal corset. Pancreas motion was analyzed using time- and phase resolved MRI scans (orthogonal 2D-cine and 4D MRI) with and without compression by the corset. The pancreas was manually segmented in each MRI data set and the population-averaged center-of-mass motion in inferior-superior (IS), anterior-posterior (AP) and left-right (LR) directions was determined. A questionnaire was developed to investigate the level of patient acceptance of the corset, which the patients completed after acquisition of the planning computed tomography (CT) and MRI scans. Results: The corset was found to reduce pancreas motion predominantly in IS direction by on average 47 % - 51 % as found in the 2D-cine and 4D MRI data, respectively, while motion in the AP and LR direction was not significantly reduced. Most patients reported no discomfort when wearing the corset. Conclusion: An MRI- and PT-compatible individualized abdominal corset was presented, which substantially reduced breathing-induced pancreas motion and can be safely applied with no additional discomfort for the patients. The corset has been successfully integrated into our in-house clinical workflow for PT of tumors of the upper abdomen.

Dosimetric impact of intrafraction motion under abdominal compression during MR-guided SBRT for (Peri-) pancreatic tumors.

Objective. Intrafraction motion is a major concern for the safety and effectiveness of high dose stereotactic body radiotherapy (SBRT) in the upper abdomen. In this study, the impact of the intrafraction motion on the delivered dose was assessed in a patient group that underwent MR-guided radiotherapy for upper abdominal malignancies with an abdominal corset.Approach. Fast online 2D cine MRI was used to extract tumor motion during beam-on time. These tumor motion profiles were combined with linac log files to reconstruct the delivered dose in 89 fractions of MR-guided SBRT in twenty patients. Aside the measured tumor motion, motion profiles were also simulated for a wide range of respiratory amplitudes and drifts, and their subsequent dosimetric impact was calculated in every fraction.Main results. The average (SD)D99%of the gross tumor volume (GTV), relative to the plannedD99%, was 0.98 (0.03). The average (SD) relativeD0.5ccof the duodenum, small bowel and stomach was 0.99 (0.03), 1.00 (0.03), and 0.97 (0.05), respectively. No correlation of respiratory amplitude with dosimetric impact was observed. Fractions with larger baseline drifts generally led to a larger uncertainty of dosimetric impact on the GTV and organs at risk (OAR). The simulations yielded that the delivered dose is highly dependent on the direction of on baseline drift. Especially in anatomies where the OARs are closely abutting the GTV, even modestLRorAPdrifts can lead to substantial deviations from the planned dose.Significance. The vast majority of the fractions was only modestly impacted by intrafraction motion, increasing our confidence that MR-guided SBRT with abdominal compression can be safely executed for patients with abdominal tumors, without the use of gating or tracking strategies.

Evaluation of abdominal compression-decompression combined with chest compression CPR performed by a new device: Is the prognosis improved after this combination CPR technique?

INTRODUCTION: This study was designed to compare the outcomes of standard cardiopulmonary resuscitation (STD-CPR) and combined chest compression and abdominal compression-decompression cardiopulmonary resuscitation (CO-CPR) with a new device following out-of-hospital cardiac arrest (OHCA). Moreover, we investigated whether patient prognosis improved with this combination treatment. METHODS: This trial was a single-centre, prospective, randomized trial, and a blinded assessment of the outcomes was performed. A total of 297 consecutive patients with OHCA were initially screened, and 278 were randomized to the STD-CPR group (n = 135) or the CO-CPR group (n = 143). We compared the proportions of patients who achieved a return of spontaneous circulation (ROSC), survived to hospital admission and survived to hospital discharge. In addition, we also performed the Kaplan-Meier analysis with a log-rank test at the end of the follow-up period to compare the survival curves of the two groups. RESULTS: The differences were not statistically significant in the proportion of patients who achieved ROSC [31/135 (23.0%) versus 35/143 (24.5%)] and survived to hospital admission [28/135 (20.7%) versus 33/143 (23.1%)] between the CO-CPR group and STD-CPR group. However, there was a significant difference in the proportion of patients who survived to hospital discharge [16/135 (11.9%) versus 7/143 (4.9%)] between the two groups. Nine patients (6.7%) in the CO-CPR group and 2 patients (1.4%) in the STD group showed good neurological outcomes according to the cerebral performance category (CPC) scale score, and the difference was statistically significant (P = 0.003). The Kaplan-Meier curves showed that the patients in the CO-CPR group achieved better survival benefits than those in the STD-CPR group at the end of the follow-up period (log-rank P = 0.007). CONCLUSION: CO-CPR was more beneficial than STD-CPR in terms of survival benefits in patients who have suffered out-of-hospital cardiac arrest. Trial registration Chinese Clinical Trial Registry, registered number: ChiCTR2100049581 . Registered 30 July 2021- Retrospectively registered. http://www.medresman.org.cn/uc/index.aspx .

An integrated ultrasound imaging and abdominal compression device for respiratory motion management in radiation therapy.

BACKGROUND: Radiotherapy to tumors in the abdomen is challenging because of the significant organ movement and tissue deformation caused by respiration. PURPOSE: A motion management strategy that integrated ultrasound (US) imaging with abdominal compression was developed and evaluated, where US was used to real-time monitor organ motion after abdominal compression. METHODS: A device that combined a US imaging system and an abdominal compression plate (ACP) was developed. Twenty-one healthy volunteers were involved to evaluate the motion management efficacy. Each volunteer was immobilized on a flat bench by the device. Abdominal US data were successively collected with and without ACP compression, and experiments were repeated three times to verify the imaging reproducibility. A template matching algorithm based on normalized cross-correlation was implemented to track the targets (vessels in the liver, pancreas, and stomach) automatically. The matching algorithm was validated by comparing with the manual references. Automatic tracking was judged as failed if the center-of-mass difference from manual tracking was beyond a failure threshold. Based on the locations obtained through the template matching algorithm, the motion correlation between liver and pancreas/stomach was investigated using the Pearson correlation test. Paired Student's t-test was used to analyze the difference between the results without and with ACP compression. RESULTS: The liver motion amplitude over all 21 volunteers was significantly (p < 0.001) reduced from 14.9 ± 5.5/3.4 ± 1.8 mm in superior-inferior (SI)/anterior-posterior (AP) direction before ACP compression to 7.3 ± 1.5/1.6 ± 0.7 mm after ACP compression. The mean liver motion standard deviation before compression was on average 2.8/1.4 mm in SI/AP direction and was significantly (p < 0.001) reduced to 0.9/0.4 mm after compression. The failure rates of automatic tracking for liver, pancreas, and stomach were reduced for failure thresholds of 1-5 mm after applying ACP. The Pearson correlation coefficients between liver and pancreas/stomach were 0.98/0.97 without ACP and 0.96/0.94 with ACP in the SI direction and were 0.68/0.68 and 0.43/0.42 in the AP direction. The motion prediction errors for pancreas/stomach with ACP have significantly (p < 0.001) reduced to 0.45 ± 0.36/0.52 ± 0.43 mm from 0.69 ± 0.56/0.71 ± 0.66 mm without ACP in the SI direction, and to 0.38 ± 0.33/0.39 ± 0.27 mm from 0.44 ± 0.35/0.61 ± 0.59 mm in the AP direction. CONCLUSIONS: The proposed strategy that combines real-time US imaging and abdominal compression has the potential to reduce the abdominal organ motion while improving both target tracking reliability and motion reproducibility. Furthermore, the observed correlation between liver and pancreas/stomach motion indicates the possibility of indirect pancreas/stomach tracking using liver markers as tracking surrogates. The strategy is expected to provide an alternative for respiratory motion management in the radiation treatment of abdominal tumors.

Examining the use of abdominal compression in stereotactic body radiotherapy for liver metastases - a single center's experience of 10 years.

Introduction: Stereotactic body radiotherapy (SBRT) with abdominal compression (AC) stands out due to the high tolerance and ease of application in the treatment of liver metastases. The present study aimed to report the safety and efficacy of the AC technique with 10-year follow-up outcomes. Materials and methods: A retrospective review was made of patients in the database who had liver metastases, who did not undergo surgery or any other ablative approach for metastases, and who underwent SBRT with AC. In-field local control (ifLC) and toxicity were evaluated as primary endpoints. Results: The study examined 79 patients who underwent SBRT with AC between 2012 and 2021. Colorectal adenocarcinoma was the most common type of primary tumor (n = 32, 40.5%). The median follow-up was 14 (4-73) months. After treatment, one-year ifLC was 46.4%, six-month ifLC was 76%, one-year out-field local control (ofLC) was 13.6%, and six-month ofLC was 25%. According to the Common Terminology Criteria for Adverse Events Version 5.0, only 8 patients had low-grade acute gastrointestinal toxicity, and no patients had late toxicity. Conclusions: SBRT with AC is a well-tolerated and effective treatment modality for patients with liver metastases.

Radiotherapy respiratory motion management in hepatobiliary and pancreatic malignancies: a systematic review of patient factors influencing effectiveness of motion reduction with abdominal compression.

BACKGROUND: The effectiveness of abdominal compression for motion management in hepatobiliary-pancreatic (HPB) radiotherapy has not been systematically evaluated. METHODS & MATERIALS: A systematic review was carried out using PubMed/Medline, Cochrane Library, Web of Science, and CINAHL databases up to 1 July 2021. No date restrictions were applied. Additional searches were carried out using the University of Manchester digital library, Google Scholar and of retrieved papers' reference lists. Studies conducted evaluating respiratory motion utilising imaging with and without abdominal compression in the same patients available in English were included. Studies conducted in healthy volunteers or majority non-HPB sites, not providing descriptive motion statistics or patient characteristics before and after compression in the same patients or published without peer-review were excluded. A narrative synthesis was employed by tabulating retrieved studies and organising chronologically by abdominal compression device type to help identify patterns in the evidence. RESULTS: The inclusion criteria were met by 6 studies with a total of 152 patients. Designs were a mix of retrospective and prospective quantitative designs with chronological, non-randomised recruitment. Abdominal compression reduced craniocaudal respiratory motion in the majority of patients, although in four studies there were increases seen in at least one direction. The influence of patient comorbidities on effectiveness of compression, and/or comfort with compression was not evaluated in any study. CONCLUSION: Abdominal compression may not be appropriate for all patients, and benefit should be weighed with potential increase in motion or discomfort in patients with small initial motion (<5 mm). Patient factors including male sex, and high body mass index (BMI) were found to impact the effectiveness of compression, however with limited evidence. High-quality studies are warranted to fully assess the clinical impact of abdominal compression on treatment outcomes and toxicity prospective in comparison to other motion management strategies.

Development of a novel airbag system of abdominal compression for reducing respiratory motion: preliminary results in healthy volunteers.

This study used cine-magnetic resonance imaging (cine-MRI) to evaluate the safety and efficacy of a novel airbag system combined with a shell-type body fixation system in reducing respiratory motion in normal volunteers. The airbag system consists of a six-sided polygon inflatable airbag, a same shape plate, a stiff air supply tube, an air-supply pump and a digital pressure load cell monitor. Piezoelectric sensors were installed in the plate to detect compression pressure load changes; pressure load data were transferred to the digital pressure load cell monitor through Bluetooth. Five volunteers underwent cine-MRI with and without airbag compression to detect differences in the respiratory motion of the organs. The volunteers' physiologic signs were stable during the experiment. The maximum inspiration pressure load was 4.48 ± 0.86 kgf (range, 4.00-6.00 kgf), while the minimum expiration pressure load was 3.69 ± 0.95 kgf (range, 2.8-5.3 kgf). Under airbag compression, the right diaphragm movement was reduced from 19.50 ± 6.43 mm to 9.60 ± 3.61 mm (P < 0.05) in the coronal plane and 23.12 ± 6.30 mm to 11.00 ± 3.69 mm (P < 0.05) in the sagittal plane. The left diaphragm, pancreas and liver in the coronal plane and the right kidney and liver in the sagittal plane also showed significant movement reduction. This novel airbag abdominal compression system was found to be safe during the experiment and successful in the reduction of internal organ respiratory motion and promises to be a convenient and efficient tool for clinical radiotherapy.

Effect of abdominal compression on target movement and extension of the external boundary of peripheral lung tumours treated with stereotactic radiotherapy based on four-dimensional computed tomography.

BACKGROUND: This study aimed to investigate the effect of abdominal compression on tumour motion and target volume and to determine suitable planning target volume (PTV) margins for patients treated with lung stereotactic body radiotherapy (SBRT) based on four-dimensional computed tomography (4DCT). METHODS: Twenty-three patients diagnosed to have a peripheral pulmonary tumour were selected and divided into an all lesions group (group A), an upper middle lobe lesions group (group B), and a lower lobe lesions group (group C). Two 4DCT scans were performed in each patient, one with and one without abdominal compression. Cone beam computed tomography (CBCT) was performed before starting treatment. The gross target volumes (GTVs) were delineated and internal gross target volumes (IGTVs) were defined. IGTVs were generated using two methods: (1) the maximum intensity projections (MIPs) based on the 4DCT were reconstructed to form a single volume and defined as the IGTVMIP and (2) GTVs from all 10 phases were combined to form a single volume and defined as the IGTV10. A 5-mm, 4-mm, and 3-mm margin was added in all directions on the IGTVMIP and the volume was constructed as PTVMIP5mm, PTVMIP4mm, and PTVMIP3mm. RESULTS: There was no significant difference in the amplitude of tumour motion in the left-right, anterior-posterior, or superior-inferior direction according to whether or not abdominal compression was applied (group A, p = 0.43, 0.27, and 0.29, respectively; group B, p = 0.46, 0.15, and 0.45; group C, p = 0.79, 0.86, and 0.37; Wilcoxon test). However, the median IGTVMIP without abdominal compression was 33.67% higher than that with compression (p = 0.00), and the median IGTV10 without compression was 16.08% higher than that with compression (p = 0.00). The median proportion of the degree of inclusion of the IGTVCBCT in PTVMIP5mm, PTVMIP4mm, and PTVMIP3mm ≥ 95% was 100%, 100%, and 83.33%, respectively. CONCLUSIONS: Abdominal compression was useful for reducing the size of the IGTVMIP and IGTV10 and for decreasing the PTV margins based on 4DCT. In IGTVMIP with abdominal compression, adding a 4-mm margin to account for respiration is feasible in SBRT based on 4DCT.

Transmission study of the Abdominal Compression plate (BodyFIX Diaphragm Control) for abdominal and stereotactic body radiotherapy.

PURPOSE: Abdominal Compression is one of the methods available to minimize breathing motion during stereotactic body radiotherapy (SBRT), particularly for abdominal malignancies. It might be necessary to treat some tumors with radiation entering through the compression device. One clinically available compression plate device (Elekta BodyFIX Diaphragm Control) was evaluated to understand its impact on dosimetry during clinical treatments. METHODS: The BodyFIX compression device was CT scanned following departmental stereo scanning protocols. Treatment planning system (TPS) calculations were used to determine attenuation ratios through each section of the compression device: the outer frame, compression plate, and higher density couch fixation points and compression screw. TPS calculated skin doses where the compression plate will come in contact with the skin were recorded. All attenuation ratio fields were measured on an Elekta Versa HD linear accelerator. Where differences in attenuation were observed, TPS density overrides were found to bring calculated doses into agreement with measurement. RESULTS: The compression plate and frame showed low dose attenuation (3%-4%). Only minor density overrides for the frame were required due to artefacts from the limited CT field-of-view. The high-density materials in the couch fixation points resulted in higher attenuation (14%-20%). Similarly, the compression screw recorded very high attenuation (44%-65%), depending on the length of screw used. Skin doses assessed from the TPS calculations showed dose build-up under the compression plate that would result in skin receiving the maximum dose. CONCLUSION: Compression devices can cause significant dose attenuation. Density overrides for TPS calculations are recommended for correcting attenuation in some sections of the device. High-density structures like the fixation screw and frame fixation points create high levels of dosimetric uncertainty, and beam entry through those areas has been disallowed.

MRI evaluation of normal tissue deformation and breathing motion under an abdominal compression device.

PURPOSE: Abdominal compression can minimize breathing motion in stereotactic radiotherapy, though it may impact the positioning of dose-limiting normal tissues. This study quantified the reproducibility of abdominal normal tissues and respiratory motion with the use of an abdominal compression device using MR imaging. METHODS: Twenty healthy volunteers had repeat MR over 3 days under an abdominal compression plate device. Normal tissues were delineated on daily axial T2-weighted MR and compared on days 2 and 3 relative to day 1, after adjusting for baseline shifts relative to bony anatomy. Inter-fraction organ deformation was computed using deformable registration of axial T2 images. Deformation > 5 mm was assumed to be clinically relevant. Inter-fraction respiratory amplitude changes and intra-fraction baseline drifts during imaging were quantified on daily orthogonal cine-MR (70 s each), and changes > 3 mm were assumed to be relevant. RESULTS: On axial MR, the mean inter-fraction normal tissue deformation was > 5 mm for all organs (range 5.1-13.4 mm). Inter-fraction compression device misplacements > 5 mm and changes in stomach volume > 50% occurred at a rate of 93% and 38%, respectively, in one or more directions and were associated with larger adjacent organ deformation, in particular for the duodenum. On cine-MR, inter-fraction amplitude changes > 3 mm on day 2 and 3 relative to day 1 occurred at a rate of < 12.5% (mean superior-inferior change was 1.6 mm). Intra-fraction baseline drifts > 3 mm during any cine-MR acquisition occurred at a rate of 23% (mean superior-inferior changes was 2.4 mm). CONCLUSIONS: Respiratory motion under abdominal compression is reproducible in most subjects within 3 mm. However, inter-fraction deformations greater than 5 mm in normal tissues were common and larger than inter- and intra-fraction respiratory changes. Deformations were driven mostly by variable stomach contents and device positioning. The magnitude of this motion may impact normal tissue dosimetry during stereotactic radiotherapy.

Four-dimensional computed tomography scan analysis of liver tumor motion treated with abdominal compression during stereotactic treatment / 中华放射肿瘤学杂志

Objective:To explore the motion and influencing factors of implanted gold markers in guiding liver stereotactic body radiation therapy (SBRT) using abdominal compression.Methods:Twenty patients with oligometastatic colorectal cancer or primary hepatocellular carcinoma from January 2016 to December 2019 were included. All patients were treated with SBRT under abdominal compression, with 1-3 gold markers were implanted within 2 cm from the lesion before positioning. Four-dimensional computed tomography (4DCT) scan was used for treatment planning. The respiratory cycle was divided into 0-90% respiratory phase images based on the respiratory signal, which were reconstructed by the system (Pinnacle 3 version 9.1; Philips Medical System, Madison, WI, USA), and cone beam CT validation images before radiation exposure were obtained. The liver volume was divided into 3 parts: within 2 cm from the main hepatic portal vein, 2-5 cm from the main hepatic portal vein, and>5 cm from the main hepatic portal vein. The motion of different tumor locations was evaluated. Results:The average intrafractional motion amplitude was (2.63±2.81) mm in the cranial-caudal (CC) direction, (1.35±1.23) mm in the anterior-posterior (AP) direction, and (0.76±0.88) mm in the left-right (LR) direction, respectively. The average interfractional motion amplitude was (3.45±3.06) mm, (2.64±2.60) mm, and (2.23±2.07) mm, respectively. Both the intra-or inter-fractional motion amplitudes in the CC direction were the highest, followed by those in the AP and LR direction (all P<0.001). The motion varied at different tumor locations. The longer distance from the main hepatic portal vein, the larger the intrafractional motion (all P<0.05). To cover the 95% population-based confidence interval, the internal target volume (ITV) was suggested to include the expansion of 3.9 mm, 5.2 mm and 7.9 mm in the LR, AP and CC direction. The expansion of 4.3 mm, 4.4 mm and 6.1 mm was delivered within 2 cm from the main hepatic portal vein, and 3.5 mm, 7.3 mm and 9.7 mm>5 cm from the main hepatic portal vein, respectively. The expansion varied significantly depending on the tumor location, whereas the motion in the CC direction was the largest regardless of the tumor location. The longer distance of the tumor from the main portal vein, the larger expansion in the CC direction. The expansion of tumor > 5 cm from the main portal vein in the AP direction was larger than that of inner parts. Conclusion:Liver tumors at different locations require individual external expansion of ITV.

Splanchnic Venous Compression Enhances the Effects of ß-Blockade in the Treatment of Postural Tachycardia Syndrome.

Background Splanchnic venous pooling induced by upright posture triggers a compensatory increase in heart rate (HR), a response that is exaggerated in patients with postural tachycardia syndrome. To assess whether abdominal compression attenuates orthostatic tachycardia and improves symptoms, 18 postural tachycardia syndrome patients (32±2 years) were randomized to receive either abdominal compression (40 mm Hg applied with an inflatable binder ≈2 minutes before standing) or propranolol (20 mg) in a placebo-controlled, crossover study. Methods and Results Systolic blood pressure, HR, and symptoms were assessed while seated and standing, before and 2 hours postdrug. As expected, propranolol decreased standing HR compared with placebo (81±2 versus 98±4 beats per minute; P<0.001) and was associated with lower standing systolic blood pressure (93±2 versus 100±2 mm Hg for placebo; P=0.002). Compression had no effect on standing HR (96±4 beats per minute) but increased standing systolic blood pressure compared with placebo and propranolol (106±2 mm Hg; P<0.01). Neither propranolol nor compression improved symptoms compared with placebo. In 16 patients we compared the combination of abdominal compression and propranolol with propranolol alone. The combination had no additional effect on standing HR (81±2 beats per minute for both interventions) but prevented the decrease in standing systolic blood pressure produced by propranolol (98±2 versus 93±2 mm Hg for propranolol; P=0.029), and significantly improved total symptom burden (-6±2 versus -1±2 for propranolol; P=0.041). Conclusions Splanchnic venous compression alone did not improve HR or symptoms but prevented the blood pressure decrease produced by propranolol. The combination was more effective in improving symptoms than either alone. Splanchnic venous compression can be a useful adjuvant therapy to propranolol in postural tachycardia syndrome. Registration URL: https://www.clini​caltr​ials.gov; Unique identifier: NCT00262470.

Helical IMRT-Based Stereotactic Body Radiation Therapy Using an Abdominal Compression Technique and Modified Fractionation Regimen for Small Hepatocellular Carcinoma.

PURPOSE: To assess the efficacy and safety of stereotactic body radiation therapy using an abdominal compression technique and modified fractionation regimen (5-10 fractions) in patients with small-sized hepatocellular carcinoma. METHODS: A total of 101 patients with small-sized hepatocellular carcinoma treated with stereotactic body radiation therapy using an abdominal compression technique and modified fractionation regimen were registered between June 2011 and June 2019 in our hospital. A total dose of 48 to 60 Gy was applied over 5 to 14 consecutive days. Liver motion was controlled by abdominal compression, and a helical intensity-modified radiation therapy-based stereotactic body radiation therapy administrated in tomotherapy platform. RESULTS: The median follow-up period was 23.2 months (range: 4.1-99.2 months). Complete response and partial response were observed in 63 (62.4%) patients and in 24 (23.8%) patients, respectively. At the time of our analysis, the 1-, 3-, and 5-year local control rates after stereotactic body radiation therapy were 96.1%, 89.0%, and 89.0%, respectively. However, logistic regression analysis revealed no correlation between the biologically effective dose and 3-year local control rates. The 1-, 3-, and 5-year overall survival rates were 96.9%, 69.0%, and 64.3%, respectively. For patients who were treatment-naive, the 1-, 3-, and 5-year overall survival were 96.3%, 82.0%, and 82.0%, respectively. No patients experienced classic radiation-induced liver disease or nonclassic radiation-induced liver disease after stereotactic body radiation therapy completion. CONCLUSIONS: When using an abdominal compression technique and modified fractionation regimen (5-10 fractions) based on helical intensity-modified radiation therapy, stereotactic body radiation therapy led to a lower toxicity and comparative rate of local control and overall survival for patients who with small-sized hepatocellular carcinoma.

Effects of Encircled Abdominal Compression Device in Colonoscopy: A Meta-Analysis.

: Background and Aim: The efficacy of encircling abdominal compression devices in colonoscopies is inconsistent. We performed a meta-analysis of randomized controlled trials (RCTs) in which encircling abdominal compression devices were compared with control in colonoscopies. METHODS: We systematically searched RCTs published in the Cochrane Library, PubMed, and the Igaku-Chuo-Zasshi database. The data from the eligible RCTs were combined using the random-effects model. The weighted mean differences (WMDs), pooled odds ratios (ORs), and 95% confidence intervals (CIs) were calculated. RESULTS: Five RCTs were included in this meta-analysis. Compared to the control group, encircling abdominal compression devices significantly reduced the caecal intubation time (WMD: -1.31, 95% CI: -2.40 to -0.23, p = 0.02). Compared to the control group, encircling abdominal compression devices significantly decreased the frequency of postural change (OR 0.30, 95% CI: 0.22 to 0.41, p < 0.00001). Compared to the control group, the use of encircling abdominal compression devices significantly reduced the need for abdominal compression (OR: 0.35, 95% CI: 0.17 to 0.70, p = 0.003). CONCLUSIONS: Encircling abdominal compression devices in colonoscopies was found to reduce the caecal intubation time and the frequency of abdominal compression.