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SU-E-J-230: Effect of Metal Hip Prosthesis On the Accuracy of Electromagnetic Localization and Tracking
Purpose: To quantify the effect of metal hip prosthesis on the ability to track and localize electromagnetic transponders. Methods: Three Calypso transponders were implanted into two prostate phantoms. The geometric center of the transponders were identified on computed tomography and set as the isocenter. With the phantom stationary on the treatment table and the tracking array 14-cm above the isocenter, data was acquired by the Calypso system at 10 Hz to establish the uncertainty in measurements. Transponder positional data was acquired with unilateral hip prostheses of different metallic compositions and then with bilateral hips placed at variable separation from the phantom. Results: Regardless of hip prosthesis composition, the average vector displacement in the presence of a unilateral prosthesis was < 0.5 mm. The greatest contribution to overall vector displacement occurred in the lateral dimension. With bilateral hip prosthesis, the average vector displacement was 0.3 mm. The displacement in the lateral dimension was markedly reduced compared with a unilateral hip, suggesting that there was a countervailing effect with bilateral hip prosthesis. The greatest average vector displacement was 0.6 mm and occurred when bilateral hip prostheses were placed within 4 cm of the detector array. Conclusion: Unilateral and bilateral hip prostheses did not have any meaningful effect on the ability to accurately track electromagnetic transponders implanted in a prostate phantom. At clinically realistic distances between the hip and detection array, the average tracking error is negligible.
SU-F-T-374: Dosimetric Effects of Irradiation Through a Bilateral Hip Prosthesis in a MRI Linac
Purpose: To evaluate the interface effects when irradiating through a hip prosthesis in the presence of an orthogonal 1.5 T magnetic field using Monte Carlo simulations. Methods: A 20×20×38 cm virtual phantom with two 5×5×5 cm sections of bilateral titanium hip prosthesis was created in GPU-based Monte Carlo (MC) algorithm (GPUMCD, Elekta AB, Stockholm Sweden). The lateral prosthesis spacing was based on a representative patient CT scan. A treatment SAD of 143.5 cm was chosen, corresponding to the Elekta AB MRI Linac and the beam energy distribution was sampled from a histogram representing the true MRI Linac spectrum. A magnetic field of 1.5 T was applied perpendicular to the plane of irradiation. Dose was calculated, in voxels of side 1 mm, for 2×2, 5×5, and 10×10 cm treatment field sizes with normal beam incidence (gantry at 90° or 270°) and at 5° and 10° from normal, representing the range of incidence through the bilateral prosthesis. Results: With magnetic field ON (B-On) and normal beam incidence the backscatter dose at the interfaces of proximal and distal implants is reduced for all the field sizes compared to the magnetic field OFF (B-Off) case. The absolute reduction in doses at the interface was in the range of 12.93% to 13.16% for the proximal implant and 13.57% to 16.12% for the distal implant. Similarly for the oblique incidences of 5o and 10o the dose in the plane adjacent to the prosthetic implants is lower when the magnetic field is ON. Conclusion: The dosimetric effects of irradiating through a hip prosthesis in the presence of a transverse magnetic field have been determined using MC simulation. The backscatter dose reduction translates into significantly lower hot spots at the prosthetic interfaces, which are otherwise substantially high in the absence of the magnetic field. This project was supported through funding provided by ElektaTM.
SU-F-T-196: Hypo-Fractionation with Intensity Modulated Proton Therapy for Unilateral Metallic Prosthesis Prostate Cancer Patients
Purpose: The purpose of this study is to investigate the dosimetric feasibility of hypo-fractionated intensity modulated proton therapy (IMPT) for unilateral metallic prosthesis prostate cancer patients based on proton collaborative group (PCG)-GU002-10 (NCT01230866) protocol criteria. Methods: A total of five unilateral metallic prosthesis prostate cancer cases were included in this retrospective study. For each case, IMPT plans were generated for treatment to be delivered with 7.6 Gy[RBE] per fraction in 5 fractions per week for a total dose of 38 Gy(RBE). Each plan was generated using two anterior-oblique beams and one lateral beam. Treatment plans were optimized with an objective meeting PCG-GU002-10 (NCT01230866) protocol criteria: (i) planning target volume (PTV): D99.5% > 36.1 Gy[RBE], (ii) rectum: V24 < 35%, V33.6 < 10%, (iii) bladder: V39 < 8 cc, and (iv) femoral head: V23 < 1cc. Results: All five cases satisfied PTV D99.5% (average=36.82 Gy[RBE]; range, 36.36–37.13 Gy[RBE]). PTV D95% ranged from 36.66 Gy[RBE] to 38.65 Gy[RBE] and PTV V100 ranged from 95.47% to 97.95%. For the rectum, V24 was less than 35% (average=14.07 Gy[RBE]; range, 6.22–18.42%, whereas V33.6 Gy[RBE] was less than 10% (average=6.83; range, 3.06 – 9.15%). Rectal mean dose ranged from 4.22 Gy[RBE] to 9.97 Gy[RBE]. For the bladder, V39 was found to be less than 8 cc (average=3.69 cc; range, 0.19–7.68 cc). Bladder mean dose ranged from 4.22 Gy[RBE] to 18.83 Gy[RBE]. For the femoral head, V23 was 0 in all five cases. Conclusion: All five unilateral metallic prosthesis prostate cancer IMPT plans generated with one lateral and two anterior-oblique beams satisfied the dosimetric criteria of PCG-GU002-10 (NCT01230866) protocol.
Comparison of Motion Analysis Systems in Tracking Upper Body Movement of Myoelectric Bypass Prosthesis Users
Current literature lacks a comparative analysis of different motion capture systems for tracking upper limb (UL) movement as individuals perform standard tasks. To better understand the performance of various motion capture systems in quantifying UL movement in the prosthesis user population, this study compares joint angles derived from three systems that vary in cost and motion capture mechanisms: a marker-based system (Vicon), an inertial measurement unit system (Xsens), and a markerless system (Kinect). Ten healthy participants (5F/5M; 29.6 ± 7.1 years) were trained with a TouchBionic i-Limb Ultra myoelectric terminal device mounted on a bypass prosthetic device. Participants were simultaneously recorded with all systems as they performed standardized tasks. Root mean square error and bias values for degrees of freedom in the right elbow, shoulder, neck, and torso were calculated. The IMU system yielded more accurate kinematics for shoulder, neck, and torso angles while the markerless system performed better for the elbow angles. By evaluating the ability of each system to capture kinematic changes of simulated upper limb prosthesis users during a variety of standardized tasks, this study provides insight into the advantages and limitations of using different motion capture technologies for upper limb functional assessment.
Three‐dimensional custom‐made carbon‐fiber prosthesis for sternal reconstruction after sarcoma resection
Radical resection is the preferred therapy for primary malignant sternal tumors. Sternal reconstruction is required to guarantee the best preservation of respiratory mechanics, and adequate mediastinal protection and acceptable cosmetic results after extensive tumor resection. A wide variety of methods and materials have been described for sternal reconstruction. Titanium implants are preferred by many surgeons because of their optimal features. However, the smooth surface of the metal prostheses does not facilitate the inward growth of the tissue, and the high density of metal can block the X‐ray and cause adverse effects on postoperative imaging and radiotherapy. Therefore, in this article we present a case of sternal reconstruction by means of a three dimensional (3D) custom‐made carbon‐fiber prosthesis following extensive resection of a sternal synovial sarcoma. The microporous structure on the surface of the carbon fiber composite material facilitates the inward growth of the tissue. Low density (1.5 g/cm 3 ) of carbon‐fiber implant will not block the X‐ray and eliminates the adverse effects caused by metal material of postoperative imaging and radiotherapy. The 3D custom‐made carbon‐fiber prosthesis matched the thoracic defect perfectly and the chest wall reconstruction was stable for more than 24 months.
SU-F-T-197: Investigating Optimal Oblique-Beam Arrangement for Bilateral Metallic Prosthesis Prostate Cancer in Pencil Beam Scanning Proton Therapy
Purpose: The main purpose of this study is to investigate the optimum oblique-beam arrangement for bilateral metallic prosthesis prostate cancer treatment in pencil beam scanning (PBS) proton therapy. Methods: A computed tomography dataset of bilateral metallic prosthesis prostate cancer case was selected for this retrospective study. A total of four beams (rightanterior- oblique [RAO], left-anterior-oblique [LAO], left-posterior-oblique [LPO], and right-posterior-oblique [RPO]) were selected for treatment planning. PBS plans were generated using multi-field-optimization technique for a total dose of 79.2 Gy[RBE] to be delivered in 44 fractions. Specifically, five different PBS plans were generated based on 2.5% ± 2 mm range uncertainty using five different beam arrangements (i)LAO+RAO+LPO+RPO, (ii)LAO+RAO, (iii)LPO+RPO, (iv)RAO+LPO, and (v)LAO+RPO. Each PBS plan was optimized by applying identical dose-volume constraints to the PTV, rectum, and bladder. Treatment plans were then compared based on the dose-volume histograms results. Results: The PTV coverage was found to be greater than 99% in all five plans. The homogeneity index (HI) was found to be almost identical (range, 0.03–0.04). The PTV mean dose was found to be comparable (range, 81.0–81.1 Gy[RBE]). For the rectum, the lowest mean dose (8.0 Gy[RBE]) and highest mean dose (31.1 Gy[RBE]) were found in RAO+LAO plan and LPO+RPO plan, respectively. LAO+RAO plan produced the most favorable dosimetric results of the rectum in the medium-dose region (V50) and high-dose region (V70). For the bladder, the lowest (5.0 Gy[RBE]) and highest mean dose (10.3 Gy[RBE]) were found in LPO+RPO plan and RAO+LAO plan, respectively. Other dosimetric results (V50 and V70) of the bladder were slightly better in LPO+RPO plan than in other plans. Conclusion: Dosimetric findings from this study suggest that two anterior-oblique proton beams arrangement (LAO+RAO) is a more favorable option with the possibility of reducing rectal dose significantly while maintaining comparable target coverage and acceptable bladder dose.
SU-G-IeP2-03: Comparison of Dose Calculation On MAR (metal Artifact Reduction) and Non-MAR Datasets for Pelvic Patients with Hip Prosthesis and Head and Neck Patients with Dental Filling
Purpose: Metal artifact reduction (MAR) software in computed tomography (CT) was previously evaluated with phantoms demonstrating the algorithm is capable of reducing metal artifacts without affecting the overall image quality. The goal of this study is to determine the dosimetric impact when calculating with CT datasets reconstructed with and without MAR software. Methods: Twelve head and neck cancer patients with dental fillings and four pelvic cancer patients with hip prosthesis were scanned with a GE Optima RT 580 CT scanner. Images were reconstructed with and without the MAR software. 6MV IMRT and VMAT plans were calculated with AAA on the MAR dataset until all constraints met our clinic’s guidelines. Contours from the MAR dataset were copied to the non-MAR dataset. Next, dose calculation on the non-MAR dataset was performed using the same field arrangements and fluence as the MAR plan. Conformality index, D99% and V100% to PTV were compared between MAR and non-MAR plans. Results: Differences between MAR and non-MAR plans were evaluated. For head and neck plans, the largest variations in conformality index, D99% and V100% were −3.8%, −0.9% and −2.1% respectively whereas for pelvic plans, the biggest discrepancies were −32.7%, −0.4% and -33.5% respectively. The dosimetric impact from hip prosthesis is greater because it produces more artifacts compared to dental fillings. Coverage to PTV can increase or decrease depending on the artifacts since dark streaks reduce the HU whereas bright streaks increase the HU. In the majority of the cases, PTV dose in the non-MAR plans is higher than MAR plans. Conclusion: With the presence of metals, MAR algorithm can allow more accurate delineation of targets and OARs. Dose difference between MAR and non-MAR plans depends on the proximity of the organ to the high density material, the streaking artifacts and the beam arrangements of the plan.
Synthesis of cobalt alloy through smelting method and its characterization as prosthesis bone implant
Cobalt-based alloys are widely used as total hip and knee replacements because of their excellent properties, such as corrosion resistance, fatigue strength and biocompatibility. In this work, cobalt alloys with variation of Cr (28.5; 30; 31.5; 33, and 34.5% wt) have been synthesized by smelting method began with the process of compaction, followed by smelting process using Tri Arc Melting Furnace at 200A. Continued by homogenization process at recrystallization temperature (1250° C) for 3 hours to allow the atoms diffuses and transform into γ phase. The next process is rolling process which is accompanied by heating at 1200° C for ± 15 minutes and followed by quenching. This process is repeated until the obtained thickness of ± 1 mm. The evaluated material properties included microstructure, surface morphology, and hardness value. It was shown that microstructure of cobalt alloys with variation of Cr is dominant by γ phase, thus making the entire cobalt alloys have high hardness. It was also shown from the surface morphology of entire cobalt alloys sample indicated the whole process of synthesis that had good solubility were at flat surface area. Hardness value test showed all of cobalt alloys sample had high hardness, just variation of 33% Cr be in the range of ASTMF75, it were 345,24 VHN which is potential to be applied as an implant prosthesis.
The Dynamic Socket: A Better Prosthesis
The issues that amputees experience with current prosthetic devices are discussed and how Sandia National Laboratory is working to make them both functional and comfortable to wear.
CT imaging of inflatable penile prosthesis complications: a pictorial essay
Purpose: Inflatable penile prostheses (IPPs) are widely used in the United States, for patients with erectile dysfunction refractory to other treatments. Complications subsequent to IPP insertion include infection, hematoma, fluid leak, component (cylinder/pump/reservoir) complications, and retained previous IPP components. Radiologists are often called upon to identify and characterize these complications utilizing CT prior to intervention. Our paper aims to provide a guide to familiarize radiologists with normal IPP component imaging and review the CT findings of commonly encountered complications. Methods: In this study, we retrospectively reviewed CT reports with descriptions of IPPs from 108 patients. We collected CT images of normal IPP components as well as reevaluated the CT findings of 33 patients with an IPP complication and correlated with immediately subsequent operative report. Results: The CT appearance of appropriately positioned normal IPP components in asymptomatic patients and each complication were described and compared to previous literature. Conclusions: CT is a very useful modality to assess an IPP-related complication. It is inexpensive, fast, and immediately available in emergent situations, e.g., infection, hematoma, and component erosion. Additionally, CT is very sensitive and makes it easier to diagnose a system leak. It can identify most cylinder complications and pump malposition and can be extremely helpful to the surgeon in preoperative planning if revision is needed. After this review, the radiologist should be able to identify normal IPP components and their complications.
Metal Artifact Reduction for Orthopedic Prosthesis in Lower Extremity CT Venography: Evaluation of Image Quality and Vessel Conspicuity
Purpose: This study evaluates the image quality of lower extremity CT venography reconstructed with orthopedic metal artifact reduction (O-MAR) in patients with unilateral or bilateral metallic prostheses in the hip or knee. Methods: This retrospective study was approved by our institutional review board, and informed consent was waived. Twenty-nine patients of lower extremity CT with 51 metallic hip or knee prostheses were reconstructed to both standard CT images and O-MAR images. The subjective image quality and vessel conspicuity for both images were evaluated by two readers using five-point scales (0–4). Vessel conspicuity scores of 3 or 4 were considered diagnostically acceptable. Image noise was measured in the air and subcutaneous fat. Results: O-MAR images showed significantly higher scores of subjective image quality (p < .001) and vessel conspicuity (p = .002) than standard CT images. Diagnostic acceptance of vessel conspicuity was not significantly different between O-MAR images and standard CT images (p = 1.000). O-MAR images showed significantly less image noise than conventional CT images (p < .001 for both air and subcutaneous fat). Conclusion: O-MAR may be an effective solution for the metal artifacts in lower extremity CT venography; however, the distance between prostheses and vessels affects the diagnostic acceptance in patients with metallic hip or knee prostheses. Level of Evidence: Level 4, Case Series.
The inhibition of RANKL expression in fibroblasts attenuate CoCr particles induced aseptic prosthesis loosening via the MyD88-independent TLR signaling pathway
Periprosthetic osteolysis and aseptic loosening are mainly caused by wear particles (Ps) that are generated from friction interfaces. However, the mechanisms underlying the development of aseptic loosening remain unclear. Therefore, we aimed toclarify how the myeloid differentiation factor 88 (MyD88)-independent Toll-like receptor (TLR) signaling pathway mediates cobalt and chromium (CoCr)-Ps-induced osteolysis. We quantified the expression levels of TLRs, MyD88, RANKL, and inflammatory factors in patients experiencing aseptic loosening after primary total hip arthroplasty (THA) with metal-on-metal (MoM) bearings and hip osteoarthritis (hOA). We observed the in vitro and in vivo levels of RANKL, TLRs, and MyD88 in fibroblasts challenged with CoCr Ps by applying shMyD88 interference lentivirus vectors to block the MyD88-independent TLR pathway. The levels of TLRs, MyD88, RANKL, and inflammatory factors in the revision THA (rTHA) with MoM group were higher than those in the hOA group. Our data collectively revealed that inhibiting MyD88 expression could reduce osteoclastogenesis in vitro and CoCr-Ps-induced osteolysis in vivo. Our findings suggested that osteoclastogenesis is promoted by the CoCr-Ps-induced expression of RANKL in fibroblasts and that MyD88 is a potential target in the treatment of wear Ps-induced osteolysis.
Compensatory strategies of body-powered prosthesis users reveal primary reliance on trunk motion and relation to skill level
Not Available
Computational reverse shoulder prosthesis model: Experimental data and verification
Not Available
Design of a Vestibular Prosthesis for Sensation of Gravitoinertial Acceleration 1
Abstract not provided
Finite Element Analysis of Constrained Total Condylar Knee Prosthesis Final Report CRADA No. TSB-1152-95
There were two purpose to the CRADA 1. To modify the LLNL High Fidelity Knee Model to accept the geometry of the Exactech Total Knee; and 2. To perform parametric studies of the possible design options in appropriate ranges of motion so that an optimum design could be selected for production.
Sensory integration for neuroprostheses: from functional benefits to neural correlates
In the field of sensory neuroprostheses, one ultimate goal is for individuals to perceive artificial somatosensory information and use the prosthesis with high complexity that resembles an intact system. To this end, research has shown that stimulation elicited somatosensory information improves prosthesis perception and task performance. While studies strive to achieve sensory integration, a crucial phenomenon that entails naturalistic interaction with the environment, this topic has not been commensurately reviewed. Therefore, here we present a perspective for understanding sensory integration in neuroprostheses. First, we review the engineering aspects and functional outcomes in sensory neuroprosthesis studies. In this context, we summarize studies that have suggested sensory integration. We focus on how they have used stimulation-elicited percepts to maximize and improve the reliability of somatosensory information. Next, we review studies that have suggested multisensory integration. These works have demonstrated that congruent and simultaneous multisensory inputs provided cognitive benefits such that an individual experiences a greater sense of authority over prosthesis movements (i.e., agency) and perceives the prosthesis as part of their own (i.e., ownership). Thereafter, we present the theoretical and neuroscience framework of sensory integration. We investigate how behavioral models and neural recordings have been applied in the context of sensory integration. Sensory integration models developed from intact-limb individuals have led the way to sensory neuroprosthesis studies to demonstrate multisensory integration. Neural recordings have been used to show how multisensory inputs are processed across cortical areas. Lastly, we discuss some ongoing research and challenges in achieving and understanding sensory integration in sensory neuroprostheses. Here, resolving these challenges would help to develop future strategies to improve the sensory feedback of a neuroprosthetic system.