Vacuum Cushion Research Articles

Implementing safe and robust Total Marrow Irradiation using Helical Tomotherapy – A practical guide

Total Marrow Irradiation (TMI) with Helical Tomotherapy is a radiotherapy treatment technique that targets bone marrow and sanctuary sites prior to stem cell or bone marrow transplantation (SCT/BMT). TMI is a complex procedure that involves several critical steps that all need to be carefully addressed for a successful implementation, such as dose homogeneity in field junctions, choice of target margins, integrity of treatment and back-up planning. In this work we present our solution for a robust and reproducible workflow throughout the treatment chain and data for twenty-three patients treated to date. Material & MethodsPatients were immobilized in a whole body vacuum cushion and thermoplastic mask. CT-scanning and treatment were performed in two parts with field matching at the upper thigh. Target consisted of marrow containing bone and sanctuary sites. Lungs, kidneys, bowel, heart and liver were defined as organs at risk (OAR). A fast surface scanning system was used to position parts of the body not covered by the imaging system (MVCT) as well as to reduce treatment time. ResultsAll patients completed their treatment and could proceed with SCT/BMT. Doses to OARs were significantly reduced and target dose homogeneity was improved compared to TBI. Robustness tests performed on field matching and patient positioning support that the field junction technique is adequate. Replacing MVCT with optical surface scanning reduced the treatment time by 25 min per fraction. ConclusionThe methodology presented here has shown to provide a safe, robust and reproducible treatment for Total Marrow Irradiation using Tomotherapy.

A Noninvasive Method to Reduce Radiotherapy Positioning Error Caused by Respiration for Patients With Abdominal or Pelvic Cancers.

Purpose:To develop an infrared optical method of reducing surface-based registration error caused by respiration to improve radiotherapy setup accuracy for patients with abdominal or pelvic tumors.Materials and Methods:Fifteen patients with abdominal or pelvic tumors who received radiation therapy were prospectively included in our study. All patients were immobilized with vacuum cushion and underwent cone-beam computed tomography to validate positioning error before treatment. For each patient, after his or her setup based on markers fixed on immobilization device, initial positioning errors in patient left-right, anterior-posterior, and superior-inferior directions were validated by cone-beam computed tomography. Then, our method calculated mismatch between patient and immobilization device based on surface registration by interpolating between expiratory- and inspiratory-phase surface to find the specific phase to best match the surface in planning computed tomography scans. After adjusting the position of treatment couch by the shift proposed by our method, a second cone-beam computed tomography was performed to determine the final positioning error. A comparison between initial and final setup error will be made to validate the effectiveness of our method.Results:Final positioning error confirmed by cone-beam computed tomography is 1.59 (1.82), 1.61 (1.84), and 1.31 (1.38) mm, reducing initial setup error by 24.52%, 51.04%, and 53.63% in patient left-right, anterior-posterior, and superior-inferior directions, respectively. Wilcoxon test showed that our method significantly reduced the 3-dimensional distance of positioning error (P < .001).Conclusion:Our method can significantly improve the setup precision for patients with abdominal or pelvic tumors in a noninvasive way by reducing the surface-based registration error caused by respiration.

Monte-Carlo Based Total-Body Irradiation Using Linac-Based Volumetric Modulated Arc Therapy

To assess the accuracy, feasibility, and reliability of a total-body irradiation (TBI) technique with linac-based volumetric modulated arc therapy (VMAT) in patients with acute myeloid leukemia (AML) or acute lymphoblastic leukemia (ALL). From 2015-2017, 26 patients (15 men, 11 women) with AML or ALL underwent allogenic stem-cell transplantation following TBI with linac-based VMAT technique, which consisted of three isocenters and three overlapping arcs for head first CT sets. We added one or two more overlapping arcs, depending on the height of the patient for feet first CT sets. Patient age ranged from 6-63 years with a mean and median age of 20.5 and 17.5 years, respectively. TBI dose was prescribed to 90% of the clinical target volume receiving 12 Gy in six fractions, at two fractions per day. Mean lung and kidney doses were restricted less than 10 Gy, and maximum lens dose less than 6 Gy. Dose rate was variable, and mean dose rate was 250 MU/min. Calculation parameters were grid spacing 0.4 cm, minimum segment width 0.5 cm, maximum 180 control points per arc, fluence-smoothing medium, statistical uncertainty 1.0% per calculation, gantry increment of 30°, and calculate dose deposition to medium. Patients were immobilized in supine position using customized thermoplastic masks for head support and a vacuum cushion for body support on an adjustable combined immobilization board. Laser-based optical surface-guided devices were used for patient positioning and intra-fraction motion detection. Quality assurance (QA) comprised the verification of the radiation plans via dose-volume histograms (DVH) based 3D patient QA system. Average mean lung dose was 9.7 ± 0.2 Gy, mean kidney dose 9.6 ± 0.2 Gy, maximum lens dose 4.5 ± 0.4 Gy, mean planning treatment volume (PTV) dose 12.7 ± 0.1 Gy, and heterogenity index of PTV was 1.16 ± 0.02 in all patients. Overall acute toxicity was low with only grade 1 and 2 morbidity: patchy mucositis in 16 (62%), nausea not requiring antiemetics in 12 (46%), headache in 11 (42%), fatigue in 9 (35%), neck pain in 8 (31%), xerostomia in 7 (27%), loss of appetite in 6 (23%), and faint or dull erythema in 4 (15%) patients. Grade 3 and more acute radiation toxicity was not observed. All patients are stil alive. When comparing plan and DVH-based 3D patient QA results, average differences of 3.4% ± 1.3 in mean kidney doses, 1.0% ± 0.7 in mean lung doses, and 0.9% ± 0.4 in mean target doses were observed. Linac-based VMAT simplifies the process of TBI, and is accurate, feasible, and reliable. Partial cone-beam CT and optical surface-guided system assure patient positioning. Moreover, up to 6-mm longitudinal misalignment does not cause an average more than 3.5% mean lung dose enhancement. DVH-based 3D patient dose verification QA was possible with linac-based VMAT showing small differences between planned and delivered doses.

FV 10 Automated motor unit counting (MSCAN) in amyotrophic lateral sclerosis

Introduction Motor unit number estimations methods have been used to quantify the loss of motor units underlying ALS, a deadly neurodegenerative disease. MUNIX relies on surface interference patterns (SIP) recorded during voluntary isometric contractions. In contrast, the recently developed MSCAN techniques is based on threshold tracking and uses natural threshold oscillations of single axons to identify the number of motor units present. MSCAN allows to estimate the composition of the CMAP from single units and allows to simulate the composition of single motor units. Both studies require approximately 5 min per muscle and an optimal CMAP as starting point. Objective Our goal was to show a loss of motor units and a decrease of CMAP in ALS patients over time with MSCAN under realistic medical care conditions. Using MSCAN records and ALSFRS-R, we wanted to show disease progression. Methods MSCAN measurements were performed in 47 ALS patients in up to three muscles in the less affected side (APB, ADM, TA) by threshold-tracking experienced staff. Follow-up measurements were performed after six months in 21 patients. To minimize movement artifacts, limbs were fixed using vacuum cushions. Disease duration, ALSFRS-R, progression rate, ALSFRS-R subscores, diagnostic certainty and clinical stage were extracted from our local database which is an integral part of patient care and reports patient status continuously. Measurements were correlated with model based parameters of ALS progression. Also we calculated ALSFRS-R at the time of the MSCAN measurement taking into account the duration of the disease and D50, which is the number of months after which ALSFRS is reduced to 50% and therefore reflects disease progression. Results MSCAN values and CMAP amplitudes showed a linear correlation in all muscles in base measurement as well as in follow-up measurement. In the follow-up measurements, a decrease compared with base values could be shown in all three muscles. Concerning motor units, this effect could also be detected in the two hand muscles, but not in TA. The quality and stability of the measurements were greatly improved by fixation of the limbs and using bipolar stimulation. MSCAN values did not correlate with total ALSFRS-R, cervical respectively lumbal ALSFRS-subscores nor disease duration in our cohort. A trend was seen in MSCAN units respectively CMAP and calculated ALSFRS and D50. Conclusion MSCAN measurements in clinical routine are feasible and show a reduction of motor units and CMAP in ALS patients over time. The correlation with functional measures was limited, likely due to the focal nature of the measurement. Further longitudinal studies are required to estimate MSCANs value as a prognostic and disease monitoring marker. Acknowledgment This research is supported by BMBF ( Bundesministerium fur Bildung and Forschung ) in the framework of the E-RARE programme (PYRAMID) and JPND (OnWebDUALS) of the European Union.

Clinical value of negative pressure vacuum cushion combined with thermoplastic body membrane in radiotherapy for Wilms tumor in children

Objective To investigate the clinical value of negative pressure vacuum cushion combined with thermoplastic body membrane in radiotherapy for Wilms tumor in children. Methods A total of 42 pediatric patients with Wilms tumor who received radiotherapy after surgery were enrolled in the study and were randomly divided into two groups according to the fixation positions: group A and group B. During radiotherapy, the patients in group A were fixed with negative pressure vacuum cushion, and those in group B were fixed by negative pressure vacuum cushion combined with thermoplastic body membrane. The setup errors, short-term effects, adverse reactions, and prognosis were compared between the two groups. Results Group B showed significantly lower translational errors and rotational errors, as well as significantly higher rates of ≤3 mm and ≤5 mm errors, compared with the group A (P=0.04, 0.04, 0.04, 0.03, 0.00, 0.04, 0.04, 0.00, 0.04). Group B also showed significantly higher complete remission rates and response rates than group A (P=0.02, 0.04). There were no significant differences in the adverse reaction rates (P=0.75) and the overall survival (OS) rates at 2 and 3 years (P=0.68, 0.74) between the two groups. Group A had the MPTV values in left-right (LR) direction (x-axis), superior-inferior (SI) direction (y-axis), and anterior-posterior (AP) direction (z-axis) being 5.74 mm, 5.93 mm, and 5.94 mm, respectively, and group B had the MPTV values at LR, SI, and AP directions being 4.21 mm, 5.71 mm, and 4.61 mm, respectively. Conclusions In the radiotherapy positioning for Wilms tumor in children, fixation limbs with negative pressure vacuum cushion combined with thermoplastic body membrane effectively reduces the setup errors and improves the effect of radiotherapy, so it holds promise for clinical application. Key words: Wilms tumor/radiotherapy; Vacuum negative pressure pad; Thermoplastic body membrane; Treatment effect; Adverse reaction

CBCT analysis of displacement of titanium clips for tumor bed localization after breast-conserving surgery for breast cancer

Objective To analyze the displacement of titanium clips for tumor bed localization after breast-conserving surgery for breast cancer and its influential factors. Methods A retrospective analysis was performed on the cone-beam computed tomography (CT) images of 14 patients with breast cancer who received radiotherapy after breast-conserving surgery from April to October, 2016.The relative position of the chest wall and the errors of the titanium clips in radiotherapy were measured. A Pearson correlation analysis was used to analyze the correlation of the displacement of titanium clips with the relative position of titanium clips, the breast volume, the vertical distance between the titanium clips and the tangential line of the chest wall, and the maximum thickness of the breast. Results The system errors of the chest wall in left-right, superior-inferior, and anterior-posterior directions were 4.42, 3.44, and 5.13 mm, respectively, and the random errors were 3.55, 3.07, and 4.54 mm, respectively. The titanium clips had a large displacement relative to the chest wall, mainly in the left-right direction. The maximum system error was 4.39 mm and the random error was 2.42 mm. The displacement of titanium clips was not significantly correlated with the breast volume and the maximum thickness of the breast (P>0.05). However, the relative position of titanium clips in superior-inferior direction was significantly correlated with the displacement of the lowest, the most lateral, the most anterior, and the most posterior titanium clips (P<0.05). As to the uppermost clips, there was a significant difference in displacement between the clips close to the chest wall and the clips far from the chest wall (P=0.02). Conclusions Due to large setup error and displacement of titanium clips during radiotherapy, simultaneous integrated boost is not suitable for patients with breast cancer who are immobilized by vacuum cushion and received radiotherapy. The unstable immobilization may be the major influential factor for the displacement of titanium clips. Key words: Tomography, X-ray computed, cone beam; Breast neoplasms/surgery; Variation of surgical clips

A study on the set-up accuracy by using body plate with vacuum cushion and thermoplastic mask technique in comparison with the conventional arm support technique in thoracic tumor radiotherapy

A study on the set-up accuracy by using body plate with vacuum cushion and thermoplastic mask technique in comparison with the conventional arm support technique in thoracic tumor radiotherapy

EP-1620: The immobilizing effect of the vacuum cushion in spinal SBRT and the impact of pain

EP-1620: The immobilizing effect of the vacuum cushion in spinal SBRT and the impact of pain

Clinical benefits of new immobilization system for hypofractionated radiotherapy of intrahepatic hepatocellular carcinoma by helical tomotherapy

ObjectiveA comprehensive clinical evaluation was conducted, assessing the Body Pro-Lok immobilization and positioning system to facilitate hypofractionated radiotherapy of intrahepatic hepatocellular carcinoma (HCC), using helical tomotherapy to improve treatment precision. MethodsClinical applications of the Body Pro-Lok system were investigated (as above) in terms of interfractional and intrafractional setup errors and compressive abdominal breath control. To assess interfractional setup errors, a total of 42 patients who were given 5 to 20 fractions of helical tomotherapy for intrahepatic HCC were analyzed. Overall, 15 patients were immobilized using simple vacuum cushion (group A), and the Body Pro-Lok system was used in 27 patients (group B), performing megavoltage computed tomography (MVCT) scans 196 times and 435 times, respectively. Pretreatment MVCT scans were registered to the planning kilovoltage computed tomography (KVCT) for error determination, and group comparisons were made. To establish intrafractional setup errors, 17 patients with intrahepatic HCC were selected at random for immobilization by Body Pro-Lok system, undergoing MVCT scans after helical tomotherapy every week. A total of 46 MVCT re-scans were analyzed for this purpose. In researching breath control, 12 patients, randomly selected, were immobilized by Body Pro-Lok system and subjected to 2-phase 4-dimensional CT (4DCT) scans, with compressive abdominal control or in freely breathing states, respectively. Respiratory-induced liver motion was then compared. ResultsMean interfractional setup errors were as follows: (1) group A: X, 2.97 ± 2.47mm; Y, 4.85 ± 4.04mm; and Z, 3.77 ± 3.21mm; pitch, 0.66 ± 0.62°; roll, 1.09 ± 1.06°; and yaw, 0.85 ± 0.82°; and (2) group B: X, 2.23 ± 1.79mm; Y, 4.10 ± 3.36mm; and Z, 1.67 ± 1.91mm; pitch, 0.45 ± 0.38°; roll, 0.77 ± 0.63°; and yaw, 0.52 ± 0.49°. Between-group differences were statistically significant in 6 directions (p < 0.05). Mean intrafractional setup errors with use of the Body Pro-Lok system were as follows: X, 0.41 ± 0.46mm; Y, 0.86 ± 0.80mm; Z, 0.33 ± 0.44mm; and roll, 0.12 ± 0.19°. Mean liver-induced respiratory motion determinations were as follows: (1) abdominal compression: X, 2.33 ± 1.22mm; Y, 5.11 ± 2.05mm; Z, 2.13 ± 1.05mm; and 3D vector, 6.22 ± 1.94mm; and (2) free breathing: X, 3.48 ± 1.14mm; Y, 9.83 ± 3.00mm; Z, 3.38 ± 1.59mm; and 3D vector, 11.07 ± 3.16mm. Between-group differences were statistically different in 4 directions (p < 0.05). ConclusionsThe Body Pro-Lok system is capable of improving interfractional and intrafractional setup accuracy and minimizing tumor movement owing to respirations in patients with intrahepatic HCC during hypofractionated helical tomotherapy.

P36. Dosimetric impact of treatment couch modelling and contention in pulmonary stereotactic treatment

Introduction During a treatment of lung lesion in stereotactic condition, for greater reproducibility, patients are immobilized with a complex and customized contention. The objective of this study is to determine the dosimetric impact of contention used in CGFL with the treatment couch. Materials and methods Pulmonary stereotactic contentions used at CGFL are customizable vacuum cushions (BlueBAG™ BodyFIX). Ten treatment plans was performed without contention and couch. Each uses an arrangement of non modulated beams of 6 MV. Dose distributions of the resulting plans were re-calculated with the obtained Monitor Units, but with including of BlueBAG and treatment couch (“Exact IGRT” of Varian). Hounsfield Units used for internal structure couch are −945 and −300 for external structure. All dose distributions were calculated with Acuros XB V.11 (Varian Medical System). Results New dose calculation with treatment couch and contention indicate a deterioration of around 1.9% of the D 98% . Note that in 9 of the 10 case of the study, this D 98% remains above the prescribe dose. The volume PTV receiving a dose is reduced by 1.6%. The most significant degradation was observed on the D 50% and is 2.5% on average. Conclusions Dosimetric impact of treatment couch modelling and contention in pulmonary stereotactic treatment is moderate. Although a significant deterioration of the dosimetric index was observed, coverage of prescribed dose remains acceptable.

Influence of lower limb movements on setup errors in radiotherapy for rectal cancer using kilovoltage cone-beam CT (KV-CBCT)

Objective To investigate the influence of fixation of both lower limbs with negative pressure vacuum cushion and fixation of both ankles with self-made foam mat on setup errors in radiotherapy for rectal cancer. Methods A total of 12 patients with rectal cancer were enrolled in 2014 and randomly divided into group A (using negative pressure vacuum cushion) and group B (using self-made foam mat). An offline registration analysis was performed for the images of 108 times (A, B group of 54 times) of kilovoltage cone-beam CT (CBCT) before and after treatment. Grey scale translation error registration was used, and the results of registration were analyzed. The setup errors in x-axis (left-right direction), y-axis (cranial-caudal direction), and z-axis (anterior-posterior direction) were compared between the two groups. Results There was no significant difference in the absolute setup error in the y-axis between the two groups (2.13±0.64 mm vs.2.61±1.17 mm, P=0.399), while group A showed significantly lower absolute setup errors in the x-axis and z-axis than group B (x-axis: 1.51±0.28 mm vs. 2.70±1.05 mm, P=0.039; with an error rate of 7.41% vs. 42.59%; z-axis: 1.10±0.29 mm vs. 2.37±0.71 mm, P=0.002; with an error rate of 1.85% vs. 35.19%). Conclusions In the radiotherapy positioning for rectal cancer, fixation of both lower limbs with negative pressure vacuum cushion effectively avoids the translation and rotation of both lower limbs, reduces absolute setup errors, and has higher accuracy than fixation of both ankles with self-made foam mat. Key words: Tomography, X-ray computed, cone beam, kilovolt; Negative pressure vacuum cushion fixation; Self-made foam mat fixation; Set-up error; Rectal neoplasms/radiotherapy

MRI quantification of pancreas motion as a function of patient setup for particle therapy -a preliminary study.

Particle therapy (PT) has shown positive therapeutic results in local control of locally advanced pancreatic lesions. PT effectiveness is highly influenced by target localization accuracy both in space, since the pancreas is located in proximity to radiosensitive vital organs, and in time as it is subject to substantial breathing‐related motion. The purpose of this preliminary study was to quantify pancreas range of motion under typical PT treatment conditions. Three common immobilization devices (vacuum cushion, thermoplastic mask, and compressor belt) were evaluated on five male patients in prone and supine positions. Retrospective four‐dimensional magnetic resonance imaging data were reconstructed for each condition and the pancreas was manually segmented on each of six breathing phases. A k‐means algorithm was then applied on the manually segmented map in order to obtain clusters representative of the three pancreas segments: head, body, and tail. Centers of mass (COM) for the pancreas and its segments were computed, as well as their displacements with respect to a reference breathing phase (beginning exhalation). The median three‐dimensional COM displacements were in the range of 3 mm. Latero–lateral and superior–inferior directions had a higher range of motion than the anterior–posterior direction. Motion analysis of the pancreas segments showed slightly lower COM displacements for the head cluster compared to the tail cluster, especially in prone position. Statistically significant differences were found within patients among the investigated setups. Hence a patient‐specific approach, rather than a general strategy, is suggested to define the optimal treatment setup in the frame of a millimeter positioning accuracy.PACS number(s): 87.55.‐x, 87.57.nm, 87.61

Verification of the dose attenuation of a newly developed vacuum cushion for intensity-modulated radiation therapy of prostate cancer.

This study measured the dose attenuation of a newly developed vacuum cushion for intensity-modulated radiation therapy (IMRT) of prostate cancer, and verified the effect of dose-correction accuracy in a radiation treatment planning system (RTPS). The new cushion was filled with polystyrene foams inflated 15-fold (Sφ≒1mm) to reduce contraction caused by air suction and was compared to normal polystyrene foam inflated to 50-fold (Sφ≒2mm). The dose attenuation at several thicknesses of compression bag filled with normal and low-inflation materials was measured using an ionization chamber; and then the calculated RTPS dose was compared to ionization chamber measurements, while the new cushion was virtually included as region of interest in the calculation area. The dose attenuation rate of the normal cushion was 0.010%/mm (R (2)=0.9958), compared to 0.031%/mm (R (2)=0.9960) in the new cushion. Although the dose attenuation rate of the new cushion was three times that of the normal cushion, the high agreement between calculated dose by RTPS and ionization chamber measurements was within approximately 0.005%/mm. Thus, the results of the current study indicate that the new cushion may be effective in clinical use for dose calculation accuracy in RTPS.

Alignment Accuracy and Intrafraction Motion Analysis in Frameless Functional Image Guided Radiosurgery

Alignment Accuracy and Intrafraction Motion Analysis in Frameless Functional Image Guided Radiosurgery

Local interfractional setup reproducibility for 2 individual head and neck supports in head and neck cancer patients

PurposeIn radiation therapy, head and neck (H&N) supports and thermoplastic masks are used to reproduce the setup of patients for H&N treatment. Individualized supports that include the shoulders may improve the immobilization of the upper thorax region. The purpose of this study was to compare the local misalignment of the supraclavicular region using a vacuum cushion H&N support to a more simple in-house modified, clinically standard H&N support. Methods and materialsTwo groups of 15 patients were evaluated: the first group of patients was positioned using a vacuum cushion as an individual head support and the second group with a modified Posifix headrest (MPH). A total of 316 cone beam computed tomography (CBCTs; ~ 10 scans per patient) were evaluated using a multiple region of interest registration protocol. Local setup errors were measured using chamfer matching on the CBCT scan to the planning CT scan for 9 bony structures (cervical vertebrae 1, 3, 5, and 7 [C7], lower jaw, hyoid bone, larynx, skull, and jugular notch). In this study, we compared the local residual misalignments of the bony structures and in particular those of the jugular notch and C7 as surrogates of the shoulders and thorax region. The workload was qualitatively evaluated on the basis of open interviews. ResultsThe significant differences in group mean, systematic error, and random error of the local residual misalignments between the 2 groups for jugular notch and C7 were equal or smaller than 0.5 mm and 0.1 degrees, and for the other 7 bony structures were equal to or smaller than 0.6 mm and 1.2 degrees (larynx). There were no large differences in workload. ConclusionsNo clinically relevant differences were found between a modified Posifix headrest and an individual vacuum cushion for H&N cancer patients in local posture change at the level of the clavicle and upper thorax.

&lt;b&gt;Development of a spinal load evaluation method from &lt;/b&gt;&lt;b&gt;human body mass distribution using DXA &lt;/b&gt;&lt;b&gt;(dual-energy X-ray absorptiometry) &lt;/b&gt;

Many patients have neck and back pain, and their standing posture (spinal alignment) is sometimes considered to be one of the factors that contributes to such pain. Thus, it would be useful to evaluate spinal loads in that posture. A method to evaluate individual spinal loads using link segment models made from body mass distributions using DXA (dual–energy X–ray absorptiometry) was developed. An element was defined as 1.30 × 1.22 cm, and a detailed body mass distribution consisting of 7473 elements was constructed using DXA equipment (QDR4500). The subjects' bodies were divided into cervicofacial (vertex–C7 ⁄ T1), thoracic (C7 ⁄ T1 – T12 ⁄ L1), and lumbar (T12 ⁄ L1 – L4 ⁄ 5) segments. Each mass, M1, M2, and M3, and the center of the masses were calculated. With these parameters and DXA images, each torque, TC7/T1, TT12/L1, and TL4/5, was calculated from the following formulas: TC7/T1 = M1gr1cosθ1, TT12/L1 = M1g (l2cosθ2 + r1cosθ1) + M2gr2cosθ2, and TL4/5 = M1g (l3cosθ3 + l2cosθ2 + r1cosθ1) + M2g (l3cosθ3 + r2cosθ2) + M3gr3cosθ3 (r1, r2, and r3: lengths from the rotation center to each center of mass; l2 and l3: lengths of C7 ⁄ T1 – T12 ⁄ L1 and T12 ⁄ L1 – L4 ⁄ 5; θ1, θ2, and θ3: angles formed between a horizontal line and r1, r2, and r3). In order to reproduce the standing posture on DXA, the standing side was formed by a vacuum cushion for operative position in advance. The parameters from DXA in the lateral view were as follows. In case 1 (38–year–old man, healthy, 164.0 cm and 55.5 kg), they were M1 = 4.50, M2 = 13.24, M3 = 6.92 kg, TC7/T1 = –0.28, TT12/L1 = –3.80, and TL4/5 = –6.42 Nm (facing right, clockwise: positive). In case 2 (76–year–old man, lumbar spondylosis, 156.9 cm and 59.6 kg), they were M1 = 4.83, M2 = 14.27, M3 = 10.34 kg, TC7/T1 = –1.69, TT12/L1 = –16.1, and TL4/5 = –44.3 Nm. In case 3 (71–year–old woman, lumbar spondylosis, scoliosis, 147.2 cm and 49.0 kg), they were M1 = 4.63, M2 = 11.42, M3 = 5.36 kg, TC7/T1 = –2.53, TT12/L1 = –16.0, and TL4/5 = –27.0 Nm. Torques at L4/5 were 6.9 and 4.2 times greater in cases 2 and 3 than in case 1. Total masses calculated from DXA were 54.5, 59.0, and 47.6 kg, and errors between these and actual weights were –1.8, –1.0, and –2.9％, respectively. A method for evaluating spinal loads as torques was developed using DXA. In the future, it will be possible to use this method to evaluate factors such as pain and the effect of rehabilitation. The relationships between torques and various scales (such as pain, depression, ADL, and QOL) need to be examined, taking into account age, sex, muscular strength, etc.

OC-0396: Evaluation of the positioning accuracy of head and neck patients with/without an additional vacuum cushion

OC-0396: Evaluation of the positioning accuracy of head and neck patients with/without an additional vacuum cushion

A novel setup approach for helical tomotherapy in head and neck cancer: A case report

Head and neck cancers that are associated with high-risk factors have a poor prognosis. In such patients, post-operative radiochemotherapy is mandatory. The present study describes the case of a 71-year-old high-risk head and neck cancer patient who was not able to tolerate the supine position for the radiotherapy setup. A lateral immobilization with a head mask and a vacuum cushion was performed. The patient underwent daily computed tomography (CT)-guided radiation therapy [image-guided radiation therapy (IGRT)]. At nine months post-radiotherapy, the patient had no xerostomia and no swallowing dysfunction. However, the patient suffered a local recurrence and succumbed due to bleeding of the tumor a number of weeks after the recurrence. A recalculation of the actual delivered dose, taking the daily delivered dose into account, was performed. The recurrence occurred within the high-dose region. In selected cases of patients with head and neck cancers who are unable to tolerate the supine position, lateral positioning and high precision treatment is possible using daily IGRT.

Image-guided radiation therapy for carcinoma of gallbladder: implication on margin for set-up errors

AbstractPurposeA retrospective study was undertaken to analyse set-up variations in patients being treated with post-operative radiation therapy for carcinoma of gall bladder by image-guided radiotherapy (IGRT) using cone-beam computed tomography (CBCT) scans and paired kilovoltage beam portals (kVps).Materials and methodsThree consecutive patients receiving post-operative radiation therapy for carcinoma of gall bladder were studied. A total of 32 imaging studies were performed. The immobilisation system was an all-in-one system along with a thermoplastic mask, with knees either resting on the knee rest or in a vacuum cushion. The CBCT scans and kVps were reviewed in an off-line mode. The surrogate markers used for matching during co-registration were 12th rib, coeliac trunk, vertebral bodies and canal. Individual readings were used to calculate mean shifts (m); the mean of these means (M) was calculated to arrive at the systematic error in each direction and its standard deviation (Σ) was calculated. The margins for set-up error (SM) were then calculated.ResultsThere were a total of 32 readings of which 21 were CBCTs and 11 were kVps. The mean shifts in each direction for each patient were 0·06, 0·25 and 0·15 cm in vertical, longitudinal and lateral directions, respectively. The resultant planning target volume margins calculated were 0·24, 0·9 and 0·47 cm in vertical, longitudinal and lateral directions.ConclusionsIGRT for upper abdominal malignancies using CBCT and kVps is a useful method to keep the margins for set-up error low. The use of surrogates for matching should be relevant to the target volume. Good immobilisation system helps in keeping the margins low.

Dosimetric comparison of patient setup strategies in stereotactic body radiation therapy for lung cancer

In this work, the authors retrospectively compared the accumulated dose over the treatment course for stereotactic body radiation therapy (SBRT) of lung cancer for three patient setup strategies. Ten patients who underwent lung SBRT were selected for this study. At each fraction, patients were immobilized using a vacuum cushion and were CT scanned. Treatment plans were performed on the simulation CT. The planning target volume (PTV) was created by adding a 5-mm uniform margin to the internal target volume derived from the 4DCT. All plans were normalized such that 99% of the PTV received 60 Gy. The plan parameters were copied onto the daily CT images for dose recalculation under three setup scenarios: skin marker, bony structure, and soft tissue based alignments. The accumulated dose was calculated by summing the dose at each fraction along the trajectory of a voxel over the treatment course through deformable image registration of each CT with the planning CT. The accumulated doses were analyzed for the comparison of setup accuracy. The tumor volume receiving 60 Gy was 91.7 ± 17.9%, 74.1 ± 39.1%, and 99.6 ± 1.3% for setup using skin marks, bony structures, and soft tissue, respectively. The isodose line covering 100% of the GTV was 55.5 ± 7.1, 42.1 ± 16.0, and 64.3 ± 7.1 Gy, respectively. The corresponding average biologically effective dose of the tumor was 237.3 ± 29.4, 207.4 ± 61.2, and 258.3 ± 17.7 Gy, respectively. The differences in lung biologically effective dose, mean dose, and V20 between the setup scenarios were insignificant. The authors' results suggest that skin marks and bony structure are insufficient for aligning patients in lung SBRT. Soft tissue based alignment is needed to match the prescribed dose delivered to the tumors.