CT-based Simulation Research Articles

Placing the tibial component of an ankle prosthesis: results of a CT-based simulation in healthy adults.

To characterize the 3D geometry of the distal tibia resection area from healthy individuals using CT-based digital implantation for proper preoperative sizing of TAA tibia component placement. Standardized CT images of healthy ankle joints serving as intra-individual references for treatment of contralateral injuries were identified. The tibial cross section dedicated to virtually host the tibial component was digitally prepared, and the size of the virtual contact surface was calculated. Finally, out of five prototypes the one fitting best in terms of size and alignment was identified. CT scans taken from 319 subjects were used for the virtual implantation procedure. Body height and size of the distal tibia contact area correlated (r = 0.49 and 0.42 in females and males, each p < 0.001). Prosthesis sizes 2 and 3 fit well for the vast majority of patients, while the smallest and largest sizes are rarely required. Digital implantation of the tibial component should be considered a valuable tool for preoperative planning as well as for the development of new implant types.

Case Series of First Microinvasive Fully Endoscopic Use of a New Mitral Prosthesis.

The use of bioprostheses is increasing in younger patients, but it is associated with the risk of later valve deterioration, especially in the mitral position. A new bioprosthesis for mitral valve replacement offers possible longer-term durability and improved hemodynamics. Objectives: Here, we report the implantation of the novel Edwards MITRIS RESILIA mitral valve (Edwards Lifesciences Inc., Irvine, CA, USA) through microinvasive fully endoscopic access as an innovative surgical approach based on a series of twelve patients. Methods: Contrast-based ECG gated CT was preoperatively performed in all patients to determine the intravascular calcifications and vascular parameters, as well as to assess noticeable problems during the operation. CT software for cardiac interventions (3Mensio Medical Imaging BV) was used to simulate surgical prostheses digitally inside the native annulus. With this, a digital LVOT and neo LVOT was created, and the difference between the valve prostheses was measured. Implantation of the MITRIS RESILIA valve was performed in 12 patients according to the instructions for use through microinvasive access in a fully endoscopic fashion using 3D visualization. Results: The mean patient age was 56.50 years, and 7/12 (58.33%) were redo procedures. All patients survived the first 30 days after the procedure, the mean aortic cross-clamp time was 40.17 ± 13.72 min. and mean postoperative transvalvular gradient was 4.45 ± 1.74 mmHg. The neo LVOT in the CT-based simulation was measured with an average area of 414.98 ± 88.69 mm2. The average difference between the LVOT and neo LVOT area was 65.35 ± 34.99 mm2. There was no case of paravalvular leakage or obstruction of the left ventricular outflow tract. Conclusions: The novel MITRIS RESILIA valve is a promising new bioprosthesis for mitral valve replacement that offers improved features as compared to other prostheses. The ease of implantation is increased by this prosthesis by the improved pliability of the sewing cuff and the inward folding of the struts, which was confirmed by short operative times in our series.

An Attempt to Reduce Lung Dose-Volume in the Era of Radiotherapy Combined Immunotherapy

In immunotherapy era, the safety of thoracic radiotherapy, especially pneumonia is a concern of clinical and patients. The incidence of pneumonia in KEYNOTE 799 is higher than that in PACIFIC and GEMSTONE301, and the incidence of pneumonia is related to V20 Gy. This study aims to explore how to reduce the lung dose of immunotherapy plus concurrent chemoradiation therapy (cCRT). We prospectively selected 32 patients treat with IMRT for untreated, locally advanced, stage III NSCLC. They all received immunochemotherapy in the first cycle treatment and completed the first CT-based simulation. In the second cycle treatment, all patients received cCRT plus ICIs and each patient received the second radiotherapy location after 10 or 20 fractions of radiotherapy. The initial and second treatment plan based on CT image are Plan1 and Plan2. The volume changes of gross tumor volume (GTV) between primary and secondary CT scans were compared, and the dose-volume parameters such as lung volume (V5 Gy, V20 Gy, V30 Gy) and heart volume (V30 Gy) in Plan2 were compared with those of Plan1. Compared with the first and second CT scan, the mean volume of GTV is decreased by 34%. The dose-volume parameters of total lung and heart were significantly lower than those in Plan1.Among them the V20 Gy, V30 Gy of total lung have statistical difference (Z = -2.068, P = 0.039; Z = -3.008, P = 0.003; respectively) and decreased by 31%, 33%, respectively. Additionally, the V20 resected after the 10-fraction radiotherapy is less than the 20th (V20 Gy = 25.1%, 26.3%; respectively). Meanwhile, for treatment-related pneumonitis, there is only one case (5%) in grade 3 or higher pneumonitis, and most of pneumonitis can be relieved after symptomatic treatment. In the mode of immunotherapy plus cCRT, timely reduction measures in the process of radiotherapy will effectively reduce lung dose-volume (V20 Gy), so as to decrease pulmonary toxicity. Two-cycle induction therapy were followed by radiotherapy may be a potent treatment candidate.

Cup Overhanging in Anatomic Socket Position or High Hip Center of Rotation in Total Hip Arthroplasty for Crowe III and IV Dysplasia: A CT-Based Simulation.

Cup overhanging in total hip arthroplasty is a predisposing factor to iliopsoas impingement. In dysplastic hips, cup implantation was simulated in an anatomic hip center of rotation (AHCR) and in high hip center (HHCR). We sought to assess: (1) the percentage of prominent cups; (2) quantify the cup protrusion at different sites on frontal, axial and sagittal views. In 40 Crowe III-IV hips, using a 3D CT-based planning software, cup planning in AHCR and HHCR (CR height ≥ 20 mm) was performed for every hip. Cup prominence was assessed on every plane. HHCR cups were less anteverted (p < 0.01), less medialized (p < 0.001) and less caudal (p = 0.01) than AHCR sockets. AHCR cups were more frequently prominent on at least one plane (92.5% vs. 77.5%), with minimal agreement between the two configurations (k = 0.31, p = 0.07). AHCR cups protruded more than HHCR sockets in the sagittal (p = 0.02) and axial planes (p < 0.001). Axially, at the center of the cup, prominence 6−11 mm occurred in nine (22.5%) AHCR and one (2.5%) HHCR socket. In conclusion, while a routine high hip center should not be recommended, cup placement at a center of rotation height < 20 mm is associated with higher rates and magnitudes of anterior cup protrusion in severe dysplasia.

Associations between implant alignment or position and patient-reported outcomes after total hip arthroplasty

BackgroundWe aimed to evaluate the associations between implant alignment/position and patient-reported outcomes following total hip arthroplasty using CT-based simulation software. MethodsWe reviewed hips of 137 patients (27 males, 110 females, mean age: 67.3 years old) who underwent total hip arthroplasty. Radiographic evaluations were based on the software for evaluation of the parameters related to implant alignment/position and femoral/3-dimensional offset using post-operative CT data. Pre-operative and one-year post-operative patient-reported outcomes using Japanese Orthopaedic Association Hip Disease Evaluation Questionnaire scores were evaluated. FindingsThe total and movement scores of normal combined anteversion and stem anteversion angle groups were significantly higher than those of lower and higher groups. The pain and movement scores of decreased femoral offset group were significantly lower than those of restored and increased femoral offset group. There were no significant differences in all scores in cup inclination and anteversion angle, stem coronal alignment, and 3-dimensional femoral offset among groups. Moreover, investigation of the associations between combined anteversion angle/stem anteversion/femoral offset and movement scores revealed that combined anteversion angle and stem anteversion were significantly associated with the movement that needs deep hip flexion and occasionally deep abduction, and high femoral offset was also associated with the movement that needs deep hip flexion. InterpretationSurgeons should consider the stem anteversion, stem sagittal alignment, and combined anteversion, in addition to the femoral offset to achieve patient's post-operative satisfaction, although the surgeon may have a relatively larger choice for the implant positioning, especially on the cup side.

Does accelerometer-based portable navigation provide more accurate and precise cup orientation without prosthetic impingement than conventional total hip arthroplasty? A randomized controlled study

This prospective randomized controlled study examined whether accelerometer-based navigation resulted in more accurate or precise cup orientation than a conventional mechanical guide. We used a simulation to evaluate how cup orientation affected potential hip range of motion (RoM) and freedom from prosthetic impingement. Sixty hips were randomly allocated 1:1 to accelerometer-based portable navigation or conventional guidance. Procedures were performed through a standard posterolateral approach and combined anteversion technique. Cup inclination, cup anteversion, and stem anteversion were measured using computed tomography (CT). Using CT-based simulation, we evaluated impingement-free potential RoM and the proportion of hips with potential RoM required for daily activities. Absolute cup inclination and anteversion error averaged 4.3° ± 3.2° and 4.4° ± 2.9° for the navigation cohort and 5.6° ± 3.7° and 5.7° ± 4.2° for the conventional cohort, with no significant differences. Navigation resulted in significantly less variation in anteversion error than the conventional guide (p = .0049). Flexion, internal rotation (IR) at 90° of flexion, extension, and external rotation (ER) averaged 123° ± 12°, 46° ± 13°, 50° ± 10°, and 73° ± 23°, respectively, in the navigation cohort and 127° ± 10°, 52° ± 14°, 45° ± 10°, and 63° ± 12°, respectively, in the conventional cohort (p = .15, .15, .03, and .03, respectively). Flexion > 110°, IR > 30° at 90° of flexion, extension > 30°, and ER > 30° were achieved by 93%, 90%, 100%, and 100% of hips, respectively, in the navigation cohort and 97%, 93%, 97%, and 100% of hips, respectively, in the conventional cohort, with no significant differences. Cup anteversion with the navigation system was more precise, but not more accurate, than with the conventional guide. The navigation cohort exhibited greater potential extension and ER than the conventional cohort, but no significant difference in impingement within the potential RoM required for daily activities. 29036. Date of registration: November 14, 2017.

Abstract 10236: Prospective Assessment of ECG-Image-based Real-Time Individual Virtual-Heart Automatic Localization (RIVAL) for Scar-Related Ventricular Tachycardia (VT)

Background: We developed a novel RIVAL system that consists of a CT-based computational simulation to identify VT circuits and an ECG-based automated approach to localize VT exit sites. Objective: Prospectively assess the ability of the RIVAL system to localize VT circuits and exits. Methods: Patients presenting for VT ablation were enrolled into the study. Pre-procedural cardiac CT was performed and used to conduct heart simulations for predicting VT circuits. The patient’s CT geometry with the predicted VT circuits was registered to the electroanatomic shell created during the procedure and imported into the RIVAL program. During the procedure, exit sites of induced VTs are localized in real-time using the 12-lead ECG onto the patient-specific CT surface. Predicted ablation regions obtained by combining RIVAL-predicted VT circuits with exit sites were analyzed offline to assess localization accuracy to the invasive VT ablation procedure. Results: Four patients with ischemic cardiomyopathy undergoing VT ablation had preprocedural cardiac CT. In P1, two VTs were induced during the procedure. The RIVAL predicted 2 VT circuits and achieved a mean localization error of 7.0mm for VT exit site prediction (Fig1). There was a spatial concordance between the predicted ablation areas and the clinical ablation regions. For P2, three VTs were induced during the VT ablation. A large area of scar was associated with 6 RIVAL-predicted VT circuits. The exit site localization accuracy could not be precisely quantitated because the VTs terminated with ablation at a mid-diastolic site. For P3, no VTs were inducible, however substrate modification (SM) was performed in the anterior-apical LV. The RIVAL predicted only one VT circuit located in the area where SM was performed. No VT was induced for P4 and the RIVAL did not predict any VT circuits. Conclusions: The RIVAL predicts the VT circuit and exit accurately, which may improve the precision of ablation therapies and procedure outcomes.

Fluoroscopic landmarks and trajectories for safe posterior percutaneous transarticular C1-C2 screw insertion: a CT-based simulation study.

To determine the safe screw trajectory for posterior transarticular fixation of C1-C2 without direct visualisation of C2 lateral masses and by using fluoroscopic landmarks only. Fluoroscopic models of the craniovertebral region in frontal and sagittal planes were reconstructed using 1-mm interval computed tomography scans of the cervical spine in 30 patients. The imitation model of the screw trajectory was then applied with verification of the exact screw localisation using multiplanar reconstruction. Twenty-seven trajectories for 60 oblique C1-C2 reformations were tested. In the frontal plane, all correct trajectories passed through the medial waistline point (WstP) of C3 and through the middle of the lateral mass of C1. In the lateral plane, the posterior spinal process-lateral mass (SpLM) point-middle C1 anterior tuberculum point (ATP), middle SpLM-upper ATP, and lower SpLM-odontoid point (ODP)-had relatively low rates of vertebral artery (VA) injury (2.3%, 4.6%, and 7%, respectively) and other screw malpositions (6.9%, 4.6%, and 4.6%, respectively). In cases of an isthmus height exceeding 8mm, there were no incidences of VA injury. Patients with an isthmus width greater than 7mm had a lower risk of screw malposition. We identified potentially safe trajectories for percutaneous posterior transarticular fixation of C1-C2. Using SpLM, ATP, and ODP landmarks in the lateral plane, and WstP and C1 middle landmarks in the frontal plane, it is possible to achieve an acceptable screw position without direct visualisation of the C2 lateral mass.

CT-based simulation of ultrasound propagation and cavitation in the human body for the assessment of acoustic therapy monitoring in high intensity focused ultrasound

In situ control of therapy parameters based on real time monitoring of ablation targets is a promising strategy to improve the safety and efficacy of extracorporeal high-intensity focused ultrasound (HIFU). In this work, we present an approach to evaluate the accuracy of acoustic monitoring techniques using computational fluid dynamics simulation. In the numerical setup, computed tomography images are used to model anatomical structures that can scatter and dissipate therapy waves in the body of the patient, including fat, bone, tissues, and organs. An in-house, compressible flow solver is used to simulate ultrasound generation from a transducer, nonlinear focusing of the wave toward therapy targets in the body, and backscattering toward the body surface. The simulation also captures excitation of cavitation bubbles in the focal region and their influence on the pressure fields in the body. Sensing and processing of the scattered signals provide for acoustic monitoring. For demonstration, we apply this approach to HIFU-based lithotripsy that uses burst waves with a focal pressure of O(1) MPa and frequency of O(100) kHz. Accuracies of acoustic monitoring are compared for various sensing and signal processing methods in quantifying the effects of anatomical structures and cavitation on ultrasound irradiation into targeted kidney stones. Finally, we discuss the use of these numerical experiments for control and optimization of therapy parameters. [Work supported by NIH P01-DK043881.]

Is lateral acetabular rotation sufficient to correct anterolateral deficiency in periacetabular reorientation osteotomy? A CT-Based simulation study

BackgroundResidual acetabular deficiency after periacetabular reorientation osteotomy can result in suboptimal outcome. The optimal algorithm of acetabular fragment correction to achieve normal anterolateral acetabular coverage is not well characterized. The aim of this study was to determine the prevalence of residual anterolateral deficiency after lateral acetabular rotation and to evaluate the ability of additional sagittal and axial rotation of the acetabulum to normalize the acetabular coverage in periacetabular osteotomy. MethodsWe performed computed tomography-based simulated periacetabular osteotomy on 85 patients (85 hips) with hip dysplasia. The acetabular fragment was rotated laterally to achieve a lateral center-edge angle (CEA) of 30°. For hips with residual anterolateral deficiency, which were identified based on the reference interval of the anterior CEA, the acetabulum was further rotated in the sagittal or axial direction in 5-degree increments from 5° to 20°, and the ability of these two manoeuvres to restore a normal anterior CEA was assessed. ResultsAfter lateral acetabular rotation, 16 hips (19%) had residual anterolateral deficiency, 67 hips (79%) had normal acetabular coverage, and 2 hips (2.4%) had acetabular overcoverage. A preoperative anterior CEA <37° predicted residual deficiency (sensitivity, 94%; specificity, 81%). Additional anterior sagittal rotation was more effective than posterior axial rotation in normalizing the anterior CEA, while minimizing the decrease in posterior CEA. The highest number of hips with normal anterior and posterior CEA was noted at 10° sagittal rotation (81%), which was followed by 15° sagittal rotation (63%). ConclusionsNormal anterolateral coverage was achieved in 79% of patients after rotating the acetabulum laterally. However, lateral rotation of the acetabulum may be insufficient to correct the anterolateral deficiency in patients with an anterior CEA of <37°. In them, additional 10°–15° anterior sagittal rotation may be appropriate to achieve sufficient anterolateral coverage while retaining posterolateral coverage.

Computed tomography-based virtual simulation versus ultrasound-based clinical setup in electron breast boost radiotherapy: Methodology for CT-based electron virtual simulation

PurposeTo compare clinical setup using ultrasound (U/S)-delineated target versus computed tomography (CT) virtual simulation using CT-outlined target in breast electron boost. To describe a methodology for electron virtual simulation and collision testing with the treatment planning system (TPS). MethodsThe two techniques were compared in a prospective study on 12 patients, who were treated using a clinical setup. Target definition was performed by both U/S and CT imaging. The U/S-based target was made visible on CT images by placing a radio-opaque wire on U/S skin markings. The dose distribution of the clinical setup was reproduced in the TPS using the actual electron patient treatment parameters. A CT-based TPS virtual simulation/dose optimization was compared to the clinical setup technique. ResultsMean beam aperture was larger by 16.3 cm2 (p = 0.011) for U/S compared to CT-outlined target. Target mean depth difference (CT minus U/S) was 0.03 cm (p = 0.875). Target coverage at depth was adequate in all cases with CT-based simulation while under/overcovering the target at depth by more than 5 mm in 2 out of 12 cases with clinical setup. Mean target V90% was 98.5% (CT-based simulation) and 84.4% (clinical setup). Ipsilateral lung/breast were better spared with CT-based simulation. To date, the methodology for CT virtual simulation was applied on 152 patients and collision was avoided in all cases. ConclusionsCT-based simulation and target delineation allows for improved definition of the en-face electron field with less amount of normal tissue irradiated while including the entire target with an adequate margin and optimal electron energy.

MS08.01 Adjuvant Radiotherapy for Resected Thymic Carcinoma

Thymic carcinoma is a rare malignancy with peak incidence in the 4th-6th decade. In contrast to thymoma, it is commonly associated with higher rates of both lymph node and distant metastatic spread and also with shorter disease free survival. For localized or locally advanced disease, surgical resection, with the intention of complete disease extirpation, remains the standard of care. Due to its rarity however, definitive clinical trial data regarding optimal and appropriate addition of adjuvant therapy is lacking. Thus, decision making for post-operative patients is guided by data from large institutional, national or international retrospective series or databases (evidence level IV or V). Recommendations for adjuvant therapy for thymic carcinoma are influenced principally by stage and adequacy of resection (R0 vs R1 vs R2). Thymic carcinoma is classically staged us the Masaoka-Koga (MK) system but, based on recommendation to the AJCC by the IASLC Staging Prognostic Factors Committee and the International Thymic Malignancy Interest Group (ITMIG), using a database of more than 10 000 patients (Detterbeck et al 2014), a TNM-based system has now been incorporated into the 8th Edition of the AJCC/UICC TNM Classification of Malignant Tumours. However, since much of the published data regarding thymic malignancies is based on the Masaoka-Koga system, at present this remains commonly used for clinical decision-making but, as data continues to accumulate, will likely be superseded by the TNM system over time. Post-operative radiotherapy is routinely recommended for patients with MK stage III (TNM Stage I – T1bN0, Stage II, IIIA/B) thymic carcinoma following R0 resection. Similarly, adjuvant radiation is recommended following R1 resection, regardless of stage, with adjuvant chemoradiation recommended following R2 resection. Adjuvant radiotherapy is not recommended for MK I or IIA (TNM Stage 1 T1aN0 with no extension to mediastinal fat) disease. Controversy exists regarding the utility of adjuvant radiotherapy in the management of MK IIB (TNM Stage I – T1aN0 with extension to mediastinal fat) disease but can be considered for this group of patients. The optimal adjuvant radiotherapy dose remains undefined for thymic carcinoma patients but typical doses reported in the literature for patients in the above recommended groups range from 45-50 Gy in 1.8-2 Gy per fraction daily. Following R1 resection, 50-54 Gy in 1.8-2 Gy per fraction is typically recommended. Following R2 resection, 60-70 Gy (with or without concurrent chemotherapy) is considered standard. Nodal involvement is much more frequent in patients with thymic carcinoma compared with thymoma. Resected, unexpectedly N+ patients are typically recommended to receive adjuvant RT to 45-60 Gy if complete resection was obtained or 60-70 Gy (with or without concurrent chemotherapy) if residual nodal disease is suspected/documented. Under the TNM staging system, N1 nodes are defined as those in the anterior mediastinal compartment (IASLC levels 1, 3a, 6 and/or supradiaphragmatic/inferior phrenics/pericardial) and N2 nodes are defined as deep intrathoracic or cervical nodes (IASLC levels 2, 4, 5, 7, 10 and/or internal mammary nodes). Whether inclusion of N1 or N2 nodal compartments in adjuvant RT target volumes is of benefit for N0 or completely resected N1 or N2 patients remains unknown but may be prudent to consider during radiotherapy planning based on clinical factors. Radiotherapy should conform to modern standards with CT-based simulation with photon-based 3D conformal or beam-modulated treatment delivery, motion management and image guidance to reduce margins and dose to organs at risk. The utility of adjuvant proton-based RT for patients with resected thymic malignancy remains the focus of ongoing study but may offer some dosimetric advantages with respect to OAR dose (e.g. lung or heart). Selected

Morphometric geometrical analysis to determine the centre of the acetabular component placement in Crowe type IV hips undergoing total hip arthroplasty.

We analyzed the acetabular morphology of Crowe type IV hips using CT data to identify a landmark for the ideal placement of the centre of the acetabular component, as assessed by morphometric geometrical analysis, and its reliability. A total of 52 Crowe IV hips (42 patients; seven male, 35 female; mean age 68.5 years (32 to 82)) and 50 normal hips (50 patients; eight male, 42 female; mean age 60.7 years (34 to 86)) undergoing total hip arthroplasty were retrospectively identified. In this CT-based simulation study, the acetabular component was positioned at the true acetabulum with a radiological inclination of 40° and anteversion of 20°. Acetabular shape and the position of the centre of the acetabular component were analyzed by morphometric geometrical analysis using the generalized Procrustes analysis. The acetabular shapes of Crowe IV hips were distinctively triangular; the ideal position of the centre of the acetabular component was superior on the posterior bony wall. The first and second relative warps explained 34.2% and 18.4% of the variance, respectively, compared with that of 28.6% and 18.0% in normal hips. We defined the landmark as one-third the distance from top on the posterior bony wall in Crowe IV hips. The average distance from the centre of the acetabular component was 5.6 mm. Crowe IV hips are distinctively triangular; the point one-third from the top on the posterior bony wall was a useful landmark for placing the acetabular component.

Inversely and adaptively planned interstitial brachytherapy: A single implant approach

ObjectiveTo evaluate the efficacy, feasibility and safety of image-based, inversely and adaptively planned high-dose rate interstitial brachytherapy (HDR-ISBT) to treat advanced primary or recurrent gynecologic malignancy in a single implant, three-consecutive-day regimen. MethodsClinical demographics and outcome data were abstracted from all patients with primary and recurrent gynecologic malignancies who received HDR-ISBT boost from 2014 to 2017. Treatment consisted of a single implant (~7 Gy × 4 fractions) of interstitial needles using the Syed-Neblett template over a three-day hospital admission. CT-based (3D) simulation with inverse and adaptive planning was utilized for each fraction. MR prior to and MR immediately after external beam therapy were fused for HDR-ISBT target delineation. ResultsForty women with an overall median follow-up of 18 months (range: 6–54 months) received an HDR-ISBT boost. Of the 30 primary cases (83% cervix, 10% vaginal, 7% uterine), 44% had organ invasion (bladder, rectal or both) on MRI. Median coverage and dose are reported (V100: 98%, HR-CTV EQD2: 85.1 Gy, D90: 92 Gy). A significant association existed between rectal doses exceeding GEC-ESTRO recommendations (D2cc < 75 Gy) and the development of grade 3 gastrointestinal toxicity with a relative risk of 1.4 [1.1–1.8] (p = .046). Actuarial two-year overall survival (OS), local control (LC) and progression-free survival (PFS) were 81%, 81% and 64%, respectively. ConclusionsA four fraction, inversely and adaptively planned, single-implant approach of image-based HDR-ISBT provides excellent coverage, minimal toxicity and effective local control in patients with advanced and recurrent disease.

Application of endoscopy-guided titanium clip placement in precision radiotherapy for early esophageal cancer

Objective To evaluate the application of the placement of titanium clips in the upper and lower tumor margins in precision radiotherapy for early esophageal cancer. Methods: Seventeen patients with early esophageal cancer underwent endoscopy-guided implantation of titanium clips to mark the upper and lower tumor margins. CT-based simulation was performed to delineate the gross tumor volume (GTV). The application value of this technology in precision radiotherapy was evaluated. Results: For all patients (including 13 cases with initial treatment and 4 patients requiring radiotherapy after endoscopic resection), the esophageal tumors were not explicitly displayed on CT and barium meal images and the GTV range could not be accurately determined. The esophageal tumors were marked by successful placement of at least one titanium clip in the upper and lower tumor margins. Subsequently, the esophageal tumors were successfully displayed on CT simulation and the target area was accurately delineated. No grade 3-4 adverse events, such as bleeding and perforation occurred. Conclusion Endoscopy-guided titanium clip placement is convenient and feasible for early esophageal cancer, which is of clinical significance for determining the target area of radiotherapy. Key words: Esophageal neoplasm/radiotherapy; Endoscopy; Titanium clip

Acoustic-based proton range verification in heterogeneous tissue: simulation studies

Acoustic-based proton range verification (protoacoustics) is a potential in vivo technique for determining the Bragg peak position. Previous measurements and simulations have been restricted to homogeneous water tanks. Here, a CT-based simulation method is proposed and applied to a liver and prostate case to model the effects of tissue heterogeneity on the protoacoustic amplitude and time-of-flight range verification accuracy. For the liver case, posterior irradiation with a single proton pencil beam was simulated for detectors placed on the skin. In the prostate case, a transrectal probe measured the protoacoustic pressure generated by irradiation with five separate anterior proton beams. After calculating the proton beam dose deposition, each CT voxel’s material properties were mapped based on Hounsfield Unit values, and thermoacoustically-generated acoustic wave propagation was simulated with the k-Wave MATLAB toolbox. By comparing the simulation results for the original liver CT to homogenized variants, the effects of heterogeneity were assessed. For the liver case, 1.4 cGy of dose at the Bragg peak generated 50 mPa of pressure (13 cm distal), a 2× lower amplitude than simulated in a homogeneous water tank. Protoacoustic triangulation of the Bragg peak based on multiple detector measurements resulted in 0.4 mm accuracy for a δ-function proton pulse irradiation of the liver. For the prostate case, higher amplitudes are simulated (92–1004 mPa) for closer detectors (<8 cm). For four of the prostate beams, the protoacoustic range triangulation was accurate to ⩽1.6 mm (δ-function proton pulse). Based on the results, application of protoacoustic range verification to heterogeneous tissue will result in decreased signal amplitudes relative to homogeneous water tank measurements, but accurate range verification is still expected to be possible.

Three-dimensional customized bolus for intensity-modulated radiotherapy in a patient with Kimura's disease involving the auricle

In radiotherapy, a commercial bolus often does not provide a suitable fit over irregular surfaces. To address this issue, we fabricated a customized bolus using 3D printing technology. The aim of our study was to evaluate the application of this 3D-printed bolus in a clinical setting. The patient was a 45-year-old man with recurrent Kimura's disease involving the auricle, receiving radiotherapy in our oncology department. A customized bolus, 5mm in thickness, was fabricated based on reconstruction of computed tomography (CT) images. The bolus was printed on a Dimension 1200 series SST 3D printer. Repeat CT-based simulation indicated an acceptable fit of the 3D-printed bolus to the target region, with a maximum air gap of less than 5mm at the tragus. Most of the surface area of the target region was covered by the 95% isodose line. The plan with the 3D-printed bolus improved target coverage compared to that without a bolus. And the plan with the 3D-printed bolus yielded comparable results to those with the paraffin wax bolus. In conclusion, a customized bolus using a 3D printer was successfully applied to an irregular surface.

Three-dimensional conformal radiotherapy by delineations on CT-based simulation in different respiratory phases for the treatment of senile patients with non-small cell lung cancer

AimThis study aimed to evaluate the application of three-dimensional conformal radiotherapy (3D-CRT) for elderly patients with non-small cell lung cancer (NSCLC) based on computed tomography (CT) simulations in different respiratory phases.MethodsA total of 64 patients aged >70 years old with NSCLC were treated by 3D-CRT using CT images in different respiratory phases. The gross tumor volumes (GTVs) at the end of inspiration and end of expiration were combined to obtain the total GTV, which was close to the motional range of tumors during respiration, and no additional expansion of the clinical target volume (CTAV) to planning target volume (PTV) (CTAV:PTV) was included during the recording of respiratory movements. Patients were also planned according to the classic 3D-CRT approach. Efficacy, prognostic factors, and side effects were evaluated.ResultsCompared with the classic approach, the average PTV was 18.9% lower (median: 17.3%), and the average lung volume receiving a prescribed dose for a tumor was 22.4% lower (median: 20.9%). The 1-, 2-, and 3-year survival rates were 70.6%, 54.9%, and 29.4%, respectively, with an overall tumor response rate of 79.7%. The Karnofsky performance status and N stage were independent prognostic factors, whereas age was not.ConclusionWithout affecting therapeutic effects, CT simulations in different respiratory phases were well-tolerated in elderly patients with NSCLC, could effectively reduce PTV, and could improve the quality of life.

TH-CD-BRA-01: The Benefit of Adjunct CT Imaging in Clip-Based Treatment of Ocular Melanoma with Protons

Purpose: To evaluate if addition of CT imaging to the treatment-planning process of ocular-melanoma proton therapy will improve the accuracy of target localization. Methods: For a total of 30 patients a treatment plan is made according to the standard protocol: 1) the ophthalmologist sutures 3–5 small clips on the eye surface; 2) during simulation, a set of orthogonal images is taken identifying the clip positions; 3) the treatment-planning software (EyePlan) fits a geometric eye model to the imaged clips; 4) in the model the tumor is delineated based on the clip positions and registered fundus photographs; 5) dose from the treatment beam is calculated using 2.5 mm margins. In this study an additional high-resolution CT scan is taken of each treated eye. The geometric eye model is registered to the CT based on the clip positions. Agreement of the anatomy (lens, sclera, optic nerve) is evaluated. The translation required to go from the clip-based to anatomy-based registration is determined as measure of the accuracy of clip position in the radiograph-based model. A second treatment plan is made based on the CT clip positions. Target coverage and dose to critical structure is compared between the radiograph-based and CT-based plan. Dose deviations are evaluated for correlation with visual acuity, clip location, and tumor size. Results: For 19 patients the shift in clip position between radiograph-only and CT-based simulation is ≤1 mm; for 28 patients ≤2 mm. For the remaining two patients it is 3.6 and 5.0 mm. For most patients (18) the effect on the tumor coverage is minimal: reduction in V99% of ≤ 2.5 %. For 3 patients V99% reduces by >7.5%. Conclusion: The addition of CT imaging to standard planning protocols improves target coverage in 10% of patients.

Optimal anterior femoral offset for functional range of motion in total hip arthroplasty--a computer simulation study.

Compared to medial femoral offset (MFO), the role of anterior femoral offset (AFO) on range of motion (ROM) in total hip arthroplasty (THA) has not been fully examined. We therefore defined AFO as the anterior distance from the centre of the femoral head to the proximal femoral axis in the sagittal plane and determined the optimal AFO required for ROM needed for activities of daily living using a computer-simulated THA model. Various AFOs were obtained by changing stem anteversion (stem-AV) and stem tilt in the sagittal plane (stem-tilt) using a CT-based simulation software. The required ROM was defined as: flexion ≥ 110°, internal rotation at 90° flexion (IR) ≥ 30°, external rotation (ER) ≥ 30°, and extension ≥ 30°, and we determined AFO and MFO to satisfy required ROM. AFO was positively correlated with stem-AV and anterior stem-tilt. MFO was negatively correlated with stem-AV and not influenced by stem-tilt. Flexion and IR increased with both increased AFO and MFO, whereas extension and ER decreased with increased AFO. A smoothing spline curve showed the optimal AFO and MFO for required ROM to be from 15 mm to 25 mm on average and more than 32.1 mm, respectively. This is the first study to show that AFO directly influenced ROM in THA. Optimal AFO as well as MFO should be reconstructed to achieve sufficient ROM.