Mm For Reconstruction Research Articles

Low-cost Design and Manufacturing of Surgical Guides for Mandibular Reconstruction Using a Fibula.

Background:Surgical cutting guides are used in mandibular reconstruction involving osteotomy of the mandible and fibula. Cutting guides produced using computer-aided design (CAD) and computer-aided manufacturing (CAM) technologies have been reported recently. These guides aim to increase the benefits to patients by improving the accuracy, shortening the operating time, and correcting occlusion. However, the availability of these advanced technologies is limited in some regions of the world. To test whether we could produce low-cost surgical cutting guides, we made surgical guides and investigated their accuracy.Methods:Using free CAD software, we designed surgical cutting guides for the mandible and fibula and used these to perform virtual mandibular segmental osteotomies and fibula transplants in 12 model surgeries. The cutting guides were printed on a 3-dimensional (3D) printer. The model surgeries were performed using 3D mandibular models and cutting guides to check their accuracy. Deviations between the virtually simulated plan and the actual model surgery were investigated.Results:CAD and CAM technologies were used to design and 3D print the cutting guides and models. The guided surgeries were performed. The deviations were about 1.3 mm for mandibular osteotomy, less than 1 mm for fibular osteotomy, and within 2.4 mm for reconstructions of the mandible.Conclusions:Without using expensive software or products, we were able to design surgical cutting guides for the mandible and fibula and used these to perform virtual simulation of mandibular segmental osteotomy and fibular reconstruction. Model surgeries using 3D-printed surgical guides showed that the accuracy of reconstruction was within a 3-mm deviation. In circumstances where commercial CAD/CAM guides are not available, it may be possible to use CAD/CAM surgical guides in the clinic if doctors are willing to volunteer their time for the design and printing.

SU‐E‐I‐56: Scan Angle Reduction for a Limited‐Angle Intrafraction Verification (LIVE) System

Purpose:To develop a novel adaptive reconstruction strategy to further reduce the scanning angle required by the limited‐angle intrafraction verification (LIVE) system for intrafraction verification.Methods:LIVE acquires limited angle MV projections from the exit fluence of the arc treatment beam or during gantry rotation between static beams. Orthogonal limited‐angle kV projections are also acquired simultaneously to provide additional information. LIVE considers the on‐board 4D‐CBCT images as a deformation of the prior 4D‐CT images, and solves the deformation field based on deformation models and data fidelity constraint. LIVE reaches a checkpoint after a limited‐angle scan, and reconstructs 4D‐CBCT for intrafraction verification at the checkpoint. In adaptive reconstruction strategy, a larger scanning angle of 30° is used for the first checkpoint, and smaller scanning angles of 15° are used for subsequent checkpoints. The onboard images reconstructed at the previous adjacent checkpoint are used as the prior images for reconstruction at the current checkpoint. As the algorithm only needs to reconstruct the small deformation occurred between adjacent checkpoints, projections from a smaller scan angle provide enough information for the reconstruction. XCAT was used to simulate tumor motion baseline drift of 2mm along sup‐inf direction at every subsequent checkpoint, which are 15° apart. Adaptive reconstruction strategy was used to reconstruct the images at each checkpoint using orthogonal 15° kV and MV projections.Results:Results showed that LIVE reconstructed the tumor volumes accurately using orthogonal 15° kV‐MV projections. Volume percentage differences (VPDs) were within 5% and center of mass shifts (COMS) were within 1mm for reconstruction at all checkpoints.Conclusion:It's feasible to use an adaptive reconstruction strategy to further reduce the scan angle needed by LIVE to allow faster and more frequent intrafraction verification to minimize the treatment errors in lung cancer treatments.Grant from Varian Medical System

Posterolateral Knee Repair Versus Reconstruction

Objectives:Our goal was to compare clinical, functional and radiographic outcomes of posterolateral knee injuries treated with repair versus reconstruction. In addition, we compared varus stress radiographs of these patients with controls.Methods:A retrospective chart review was performed to identify patients that underwent posterolateral knee reconstruction or repair from January 1, 2000 to March 1, 2012. Patients were asked to return for a clinical exam and varus stress radiographs, as well as fill out IKDC and Lysholm knee scales. Patients that could not return to clinic were assessed via phone interviews. Chart reviews were performed on patients that could not be contacted.Further, we compared varus stress radiographs of 20 control knees, with no history of knee trauma, to both posterolateral knee repair and reconstruction groups.Results:We identified 61 knees in 60 patients who underwent posterolateral knee reconstruction or repair. 26 knees in 25 patients (17 reconstructions and 9 repairs) were evaluated at mean of 41.86 months postoperatively (range: 6-108). Average IKDC scores for reconstruction and repair were 68.23 and 71.30, respectively. Average Lysholm scores for these groups were 83.11 for reconstructions and 83.30 for repairs. There were no statistically significant differences in IKDC or Lysholm scores between the repair and reconstruction groups. Average varus gapping with the knee at zero degrees was 8.21 and 8.84 millimeters (mm) for reconstructions and repairs, respectively. Average varus gapping at 20 degrees knee flexion was 11.25 mm for reconstructions and 10.34 mm for repairs. No statistically significant differences were observed in varus gapping between the two groups. Control knee measurements, 20 knees in 20 different controls, showed average varus gapping of 5.27 mm at zero degrees and 6.55 mm at 20 degrees knee flexion. There was a statistically significant difference in varus gapping when comparing the operatively treated knees to the control group. On review of all 61 knees, there were five failures: three failed reconstructions, two failed repairs. The other complication included one small wound dehiscence in the reconstruction group that resolved without intervention.Conclusion:Unlike previous studies, we did not find statistical differences in our posterolateral knee patients treated with reconstruction versus repair. We did find statistically significant differences in varus gapping, at both 0 and 20 degrees of knee flexion, between control knees and the operatively treated groups. However, this did not correlate to poor clinical outcomes in either group..

TH‐C‐BRB‐03: Reconstructing Images of Prompt Gammas Emitted during Proton Radiotherapy

Purpose: Recent studies have shown that prompt gammas emitted during proton therapy are strongly correlated to the distribution of dose and proton beam range in the patient. This has led to an increasing interest in the measurement of prompt gammas as a means of providing in‐vivo beam range verification. The purpose of this work was to investigate the feasibility of reconstructing images of prompt gamma emission from tissues irradiated during proton radiotherapy. Methods: For this study we developed an iterative image reconstruction program based on the Stochastic Origin Ensembles (SOE) technique that used data calculated using a Monte Carlo (MC) model of prompt gamma measurement by a 3‐stage Compton camera during proton irradiation. We studied the ability of the SOE technique to reconstruct 2D and 3D images that accurately reproduced the prompt gamma distribution in irradiated tissue phantoms as a function of image pixel size, number of measured prompt gammas, and number of iterations performed by the reconstruction program. Results: Using data from our MC model, we were able to reconstruct images of the prompt gamma emission profile in tissue phantoms irradiated with a clinical proton beams (pencil beam, broad beam, and spread out Bragg peak). The beam range in the reconstructed images agreed with the prompt emission range to within 1–2 mm for reconstructions with 1 mm pixel size, 10,000 iterations, and using 1.5 million measured prompt gammas. Conclusions: We conclude that it is possible to reconstruct both 2D and 3D images of prompt gamma ray emission during proton radiotherapy. Although, the reconstruction algorithm used in this study is not optimal and much more development is needed, we believe the image resolution (1–2 mm) achieved in this study shows the feasibility of prompt gamma imaging (PGI) as clinical technique for verifying in‐vivo dose range for proton radiotherapy.This work was supported by award number R21CA137362 from the National Cancer Institute.