Translational Correction Research Articles

Poster ‐ 57: Statistical analysis of setup correction for radical IMRT lung patients on a treatment couchtop with six degrees of freedom

Purpose:To characterize the distributions of setup corrections for radical IMRT lung patients treated on a couchtop with six degrees of freedom (6DOF).Methods:Translational and rotational setup corrections were retrospectively analyzed for patients treated on the HexaPODTM 6DOF couchtop. Conventional and hypo‐fractioned radical IMRT lung treatments were included, for a total of 152 patients and 2,042 fractions. The distribution of setup corrections was analyzed for each DOF. Potential correlations between pairs of corrections were examined and possible causes identified. Intra‐patient variability of setup corrections was characterized.Results:For lateral, longitudinal and vertical setup corrections, the mean ± 1 S.D. (in mm) were: −0.6 ± 3.8, 2.8 ± 5.1, and 1.1 ± 3.9. Each of the three means is statistically significant from the theoretical population mean of zero (p<0.01). For rotations, the means were within 0.1° from zero, with a standard deviation of 1.3°. Moderate correlation (r = −0.45) was observed between longitudinal and pitch corrections, which can be caused by changes in the spinal column position, to which registration is mostly done. The standard deviation for intra‐patient corrections varies among patients: 2 – 10 mm for translations and 0.5 – 3° for rotations. Intra‐patient variability in translations has a positive correlation with that in rotations.Conclusions:In 6DOF setup corrections for lung patients, systematic translational corrections were observed, with moderate correlation between longitudinal and pitch corrections. Careful setups and custom immobilization may help reduce such offsets, correlations, and intra‐patient setup variability.

Interfraction Anatomical Variability Can Lead to Significantly Increased Rectal Dose for Patients Undergoing Stereotactic Body Radiotherapy for Prostate Cancer.

Stereotactic body radiotherapy for prostate cancer is rapidly growing in popularity. Stereotactic body radiotherapy plans mimic those of high-dose rate brachytherapy, with tight margins and inhomogeneous dose distributions. The impact of interfraction anatomical changes on the dose received by organs at risk under these conditions has not been well documented. To estimate anatomical variation during stereotactic body radiotherapy, 10 patients were identified who received a prostate boost using robotic stereotactic body radiotherapy after completing 25 fractions of pelvic radiotherapy with daily megavoltage computed tomography. Rectal and bladder volumes were delineated on each megavoltage computed tomography, and the stereotactic body radiotherapy boost plan was registered to each megavoltage computed tomography image using a point-based rigid registration with 3 fiducial markers placed in the prostate. The volume of rectum and bladder receiving 75% of the prescription dose (V75%) was measured for each megavoltage computed tomography. The rectal V75% from the daily megavoltage computed tomographies was significantly greater than the planned V75% (median increase of 0.93 cm3, P < .001), whereas the bladder V75% on megavoltage computed tomography was not significantly changed (median decrease of -0.12 cm3, P = .57). Although daily prostate rotation was significantly correlated with bladder V75% (Spearman ρ = .21, P = .023), there was no association between rotation and rectal V75% or between prostate deformation and either rectal or bladder V75%. Planning organ-at-risk volume-based replanning techniques using either a 6-mm isotropic expansion of the plan rectal contour or a 1-cm expansion from the planning target volume in the superior and posterior directions demonstrated significantly improved rectal V75% on daily megavoltage computed tomographies compared to the original stereotactic body radiotherapy plan, without compromising plan quality. Thus, despite tight margins and full translational and rotational corrections provided by robotic stereotactic body radiotherapy, we find that interfraction anatomical variations can lead to a substantial increase in delivered rectal doses during prostate stereotactic body radiotherapy. A planning organ-at-risk volume-based approach to treatment planning may help mitigate the impact of daily organ motion and reduce the risk of rectal toxicity.

SU‐F‐J‐106: Dose Adaptation with a Virtual 6D Couch for Frameless Brain Radiosurgery Via a Dedicated Gamma‐Ray Device

Purpose:The couch for Gamma Knife Radiosurgery (GKSRS) is limited to translational movements. With frameless designs, patient positional rotations may become an important factor. Therefore, we investigated the effect of rotations for GKSRS and the ability to correct for these rotations with simple couch translations.Methods:Seven previously treated GKSRS patients with different disease types (tumor volumes 0.01–12cc) were selected for this study. The planning MRI images were processed in order to digitally rotate the stereotactic frame (Leksell G‐frame) to ±1, ±2, ±3, ±5, and ±10‐degrees in the transverse plane from the nominal position. These images were imported back into the clinical planning system (LGP 10.2) and dose from the original treatment plan was calculated with these rotational errors. Translation corrections for each shot based on the rotation transform matrix were applied to the plan and coverage and Paddick conformity index (PCI) were evaluated for the uncorrected and corrected plans.Results:The rotational errors resulted in large decreases in plan coverage, with some small tumors being missed completely with rotations of ±3‐degrees or more. The rotated plans resulted in an average (range) decreased coverage of 8% (0–33%), 28% (0–87%), 43% (0–100%), 57% (0–100%), and 72% (5–100%) for ±1, ±2, ±3, ±5, and ±10‐degrees, respectively. For the corrected plans, the average (range) decrease in coverage was only 1% (0–4%), even for the rotations of ±10‐degrees. The PCI differences improved as well, with the rotated plans resulting in decreased PCI of 2% (0–11%), 13% (0–32%), 22% (0–50%), 31% (1–56%), 42% (4–67%) for ±1, ±2, ±3, ±5, and ±10‐degrees, respectively, which improved to 1% for all of the corrected plans with a range from 5% decrease to 13% increase in PCI.Conclusion:The applications of simple 3D couch translations were successful in recovering rotation uncertainties up to ±10‐degrees for frameless GKSRS.

Highly efficient nonrigid motion-corrected 3D whole-heart coronary vessel wall imaging.

PurposeTo develop a respiratory motion correction framework to accelerate free‐breathing three‐dimensional (3D) whole‐heart coronary lumen and coronary vessel wall MRI.MethodsWe developed a 3D flow‐independent approach for vessel wall imaging based on the subtraction of data with and without T2‐preparation prepulses acquired interleaved with image navigators. The proposed method corrects both datasets to the same respiratory position using beat‐to‐beat translation and bin‐to‐bin nonrigid corrections, producing coregistered, motion‐corrected coronary lumen and coronary vessel wall images. The proposed method was studied in 10 healthy subjects and was compared with beat‐to‐beat translational correction (TC) and no motion correction for the left and right coronary arteries. Additionally, the coronary lumen images were compared with a 6‐mm diaphragmatic navigator gated and tracked scan.ResultsNo significant differences (P > 0.01) were found between the proposed method and the gated and tracked scan for coronary lumen, despite an average improvement in scan efficiency to 96% from 59%. Significant differences (P < 0.01) were found in right coronary artery vessel wall thickness, right coronary artery vessel wall sharpness, and vessel wall visual score between the proposed method and TC.ConclusionThe feasibility of a highly efficient motion correction framework for simultaneous whole‐heart coronary lumen and vessel wall has been demonstrated. Magn Reson Med 77:1894–1908, 2017. © 2016 International Society for Magnetic Resonance in Medicine

Nonrigid Motion Correction With 3D Image-Based Navigators for Coronary MR Angiography.

To develop a retrospective nonrigid motion-correction method based on 3D image-based navigators (iNAVs) for free-breathing whole-heart coronary magnetic resonance angiography (MRA). The proposed method detects global rigid-body motion and localized nonrigid motion from 3D iNAVs and compensates them with an autofocusing algorithm. To model the global motion, 3D rotation and translation are estimated from the 3D iNAVs. Two sets of localized nonrigid motions are obtained from deformation fields between 3D iNAVs and reconstructed binned images, respectively. A bank of motion-corrected images is generated and the final image is assembled pixel-by-pixel by selecting the best focused pixel from this bank. In vivo studies with six healthy volunteers were conducted to compare the performance of the proposed method with 3D translational motion correction and no correction. In vivo studies showed that compared to no correction, 3D translational motion correction and the proposed method increased the vessel sharpness by 13% ± 13% and 19% ± 16%, respectively. Out of 90 vessel segments, 75 segments showed improvement with the proposed method compared to 3D translational correction. We have developed a nonrigid motion-correction method based on 3D iNAVs and an autofocusing algorithm that improves the vessel sharpness of free-breathing whole-heart coronary MRA. Magn Reson Med 77:1884-1893, 2017. © 2016 International Society for Magnetic Resonance in Medicine.

Preliminary Evaluation of a Novel Thermoplastic Mask System with Intra-fraction Motion Monitoring for Future Use with Image-Guided Gamma Knife.

Objectives A non-invasive immobilization system consisting of a thermoplastic mask with image-guidance using cone-beam CT (CBCT) and infrared (IR) tracking has been developed to ensure minimal inter- and intra-fractional movement during Gamma Knife radiosurgery. Prior to clinical use for patients on a Gamma Knife, this study clinically evaluates the accuracy and stability of this novel immobilization system with image-guidance in patients treated with standard fractionated radiation therapy on a linear accelerator.Materials & methodsThis prospective cohort study evaluated adult patients planned for fractionated brain radiotherapy. Patients were immobilized with a thermoplastic mask (with the nose cut out) and customized head cushion. A reflective marker was placed on the patient’s nose tip and tracked with a stereoscopic IR camera throughout treatment. For each fraction, a pre-treatment, verification (after any translational correction for inter-fraction set-up variation), and post-treatment CBCT was acquired to evaluate inter- and intra-fraction movement of the target and nose. Intra-fraction motion of the nose tip measured on CBCT and IR tracking were compared.Results Corresponding data from 123 CBCT and IR datasets from six patients are summarized. The mean ± standard deviation (SD) intra-fraction motion of the nose tip was 0.41±0.36 mm based on pre- and post-treatment CBCT data compared with 0.56±0.51 mm using IR tracking. The maximum intra-fraction motion of the nose tip was 1.7 mm using CBCT and 3.2 mm using IR tracking. The mean ± SD intra-fraction motion of the target was 0.34±0.25 mm, and the maximum intra-fraction motion was 1.5 mm.Conclusions: This initial clinical evaluation of the thermoplastic mask immobilization system using both IR tracking and CBCT demonstrate that mean intra-fraction motion of the nose and target is small. The presence of isolated measures of larger intra-fraction motion supports the need for image-guidance and intra-fraction motion management when using this mask-based immobilization system for radiosurgery.

Joint approach of translational and rotational phase error corrections for high‐resolution inverse synthetic aperture radar imaging using minimum‐entropy

In high-resolution inverse synthetic aperture radar (ISAR) imaging, the rotational motion of the targets tends to introduce the time-variant Doppler modulation in the echo, which acts as the range-variant phase errors in the phase history. Moreover, the performance of translational phase error correction may be dramatically degraded without properly considering the range-variant phase errors. In this study, a joint approach of translational and rotational phase error corrections is introduced into high-resolution ISAR imaging. In the procedure, the joint phase error correction is modelled as that of range-invariant and range-variant phase errors using a metric of minimum entropy. Then, the minimum-entropy optimisation is solved by employing a coordinate descend method based on quasi-Newton solver. In comparison of the conventional methods, the proposed approach in this study promises a better performance of phase error correction with a higher efficiency. Finally, experiments based on simulated and measured data are performed to confirm the effectiveness of the proposed algorithm.

Effectiveness of a Patient-Specific Immobilization and Positioning System to Limit Interfractional Translation and Rotation Setup Errors in Radiotherapy of Prostate Cancers

Objective: To evaluate the effectiveness of a patient-specific immobilization and positioning device in prostate radiotherapy. Methods: Eighty patients were immobilized and positioned by a patient-specific device. Prostate translations and rotations were estimated from daily cone beam computed tomography scans using a contour-based approach assisted by auto-registration and quantified by the group mean GM, systematic Σ and random σ' errors. Dosimetric impacts of residual prostate rotations where the translation errors were corrected were evaluated by robustness plan analysis. Results: Using the patient-specific immobilization alone without online image-guidance, the GM, Σ and σ' of the prostate translations were 0.8, 1.7, and 1.5 mm (left-right; LR), 0.8, 2.1, and 1.9 mm (superior-inferior; SI), and 0.5, 1.7 and 1.5 mm (anterior-posterior; AP), while for the prostate rotations they were 0.0°, 0.6°, and 0.7° (pitch), 0.2°, 0.5°, and 0.6° (roll), and 0.2°, 0.5°, and 0.6° (yaw). The resulting van Herk’s margin was 5.8 (LR), 7.3 (SI) and 5.8 (AP) mm. With adaptive online image-guidance based on estimates from the first 5 fractions, Σ were reduced by 0.7 - 1.2 mm for the prostate translations, resulting in a margin reduction by 2 - 3.5 mm. Changes of Σ and σ' in the prostate rotations were insignificant regardless of translation corrections. Dosimetric impacts of residual rotation errors were negligible if a 2 mm margin was applied. Conclusions: Our patient-specific immobilization system can effectively limit the prostate translations and rotations, which is important without 6D treatment couches or using ultrasound image-guidance without rotational corrections.

Stereotactic Radiosurgery for the Treatment of Primary and Secondary Ocular Malignancies

isocenter radiosurgery for either single or multiple targets utilizing a flattening filter free LINAC operating at up to 2400 MU/min. The most common treatment geometry was two non-coplanar arcs requiring one room entry. Patients were immobilized in an Aquaplast mask. Imaging workflow included KV-KV 6DOF alignment, CBCT 6DOF alignment, and then a repeat CBCT 6DOF alignment prior to treatment. The magnitudes of the residual translation vector and corrections around each rotation axis were calculated between the KV and first CBCT (CT1) and then between the first and second CBCT (CT2). Results: As shown in the table below, CT1 alignment showed significant residual error after KV only alignment. CT2 alignment demonstrated stability of the patient over a mean imaging interval of 3.19 min between the two CBCT scans including one CBCT acquisition, registration, physician review and movement of the couch. The mean time after the second CBCT until beam-off was 6.44 minutes. Conclusion: The automated KV algorithm did not perform accurately enough to omit CBCT alignment for radiosurgery. CBCT alignment demonstrated stability even though patients were immobilized with only an Aquaplast mask. This data suggests that frameless radiosurgery with 6DOF alignment is feasible without invasive immobilization if treatment time is short. Stable rotational corrections to less than 0.5 degrees are feasible and facilitate single isocenter treatments of multiple targets. Author Disclosure: J. Fiveash: Research Grant; Varian Medical Systems. Consultant; Varian Medical Systems. C.D. Willey: None. M. Bredel: None. R. Popple: Research Grant; Varian Medical Systems. S.A. Spencer: None. K. Dempsey: None. J. Markert: None. K. Riley: None. M.C. Dobelbower: Research Grant; Varian Medical Systems.

Dosimetric effects of roll rotational setup errors on lung stereotactic ablative radiotherapy using volumetric modulated arc therapy.

To evaluate the dosimetric effects of roll-rotational setup errors of stereotactic ablative radiotherapy (SABR) for lung cancer using volumetric modulated arc therapy (VMAT). A total of 23 lung SABR cases were evaluated retrospectively. Each of the planning CT images was intentionally rotated by ±1°, ±2° and ±3°. After that, to simulate the translational couch correction, rotated CT images were moved along the x, y and z axis to match the centroid of the target volume in the rotated CT images with that in the original CT images. The differences in D95% and V100% of the target volume, D0.35cc of spinal cord, D0.35cc and D5cc of oesophagus and V20Gy of lung between the original and the rotated CT images were calculated. The average differences in D95% and V100% of target volume, D0.35cc of spinal cord, D0.35cc and D5cc of oesophagus and V20Gy of lung were -0.3% ± 0.4% and -0.7% ± 2.4%, 1.6 ± 27.9 cGy, -1.6 ± 37.6 cGy, 15.9 ± 25.3 cGy and 0.0% ± 0.1%, respectively. The dosimetric changes in organs at risk (OARs) near the target volume were sometimes considerable due to roll-rotational setup errors, despite the translational correction, and those were patient specific. In the case of coplanar VMAT for lung SABR, dosimetric changes to the target volume due to roll-rotational setup errors could be compensated by translational correction, whereas those to the OARs could not in some cases. Roll-rotational setup errors would increase the dose to OARs despite the translational correction.

High-Resolution Inverse Synthetic Aperture Radar Imaging and Scaling With Sparse Aperture

In high-resolution radar imaging, the rotational motion of targets generally produces migration through resolution cells (MTRC) in inverse synthetic aperture radar (ISAR) images. Usually, it is a challenge to realize accurate MTRC correction on sparse aperture (SA) data, which tends to degrade the performance of translational motion compensation and SA-imaging. In this paper, we present a novel algorithm for high-resolution ISAR imaging and scaling from SA data, which effectively incorporates the translational motion phase error and MTRC corrections. In this algorithm, the ISAR image formation is converted into a sparsity-driven optimization via maximum a posterior (MAP) estimation, where the statistics of an ISAR image is modeled as complex Laplace distribution to provide a sparse prior. The translational motion phase error compensation and cross-range MTRC correction are modeled as joint range-invariant and range-variant phase error corrections in the range-compressed phase history domain. Our proposed imaging approach is performed by a two-step process: 1) the range-invariant and range-variant phase error estimations using a metric of minimum entropy are employed and solved by using a coordinate descent method to realize a coarse phase error correction. Meanwhile, the rotational motion can be obtained from the estimation of range-variant phase errors, which is used for ISAR scaling in the cross-range dimension; 2) under a two-dimensional (2-D) Fourier-based dictionary by involving the slant-range MTRC, joint MTRC-corrected ISAR imaging and accurate phase adjustment are realized by solving the sparsity-driven optimization with SA data, where the residual phase errors are treated as model error and removed to achieve a fine correction. Finally, some experiments based on simulated and measured data are performed to confirm the effectiveness of the proposed algorithm.

SU‐E‐J‐05: Use of a 6D Couch for Real‐Time Full Translational and Rotational Head Motion Correction During Stereotactic Radiosurgery: A Feasibility Study

Purpose:This work presents a methodology for correcting full translational and rotational head motion deviations during frameless image‐guided stereotactic radiosurgery (SRS) procedures with a robotic 6D couch. The main objective is to design control algorithms which optimize the correction motion of a 6D couch when sub‐millimeter/sub‐degree accuracy requirements are necessary in SRS.Methods:The system includes 6D position tracking and a 6D couch with three serially connected platforms. The bottom platform controls yaw compensation (around the z axis), the middle one generates full 3D translational motion, and the top platform controls both pitch (around X) and roll (around Y) motion with two linear actuators. Based on the 6D position of the head and the couch at each moment, the desired 6D couch position for correction is calculated, with the required 6 actuator outputs computed by an inverse algorithm accordingly. To minimize their responsive motion, the actuators take action only after the head position deviates beyond certain predetermined thresholds, and for each action the head is returned to the center of desired 6D treatment position.Results:With computer simulation, head motion of an SRS patient was modeled and the simulated couch was used to compensate for this motion in real‐time. For a 15‐minute test with a 0.3 mm and 0.15 degree target position tolerance, the corrected 6D head position was within tolerance over 99.5% of the time. The actuators moved approximately 80 times during the simulation, and the total actuator motion for translational correction was around 205 mm.Conclusion:We investigated a control approach for full translational and rotational head motion correction with a 6D couch. The simulations demonstrated that with moderate correction motion of a 6D couch, the control performance meets real‐time submillimeter and sub‐degree accuracy requirement of frameless SRS.The research is funded by the American Cancer Society (ACS) grant. The grant name is: Frameless SRS Based on Robotic Head Motion Cancellation. The grant number is: RSG‐13‐313‐01‐CCE

SU‐E‐J‐45: The Correlation Between CBCT Flat Panel Misalignment and 3D Image Guidance Accuracy

PurposeTo simulate the impact of CBCT flat panel misalignment on the image quality, the calculated correction vectors in 3D image guided proton therapy and to determine if these calibration errors can be caught in our QA process.MethodsThe X‐ray source and detector geometrical calibration (flexmap) file of the CBCT system in the AdaPTinsight software (IBA proton therapy) was edited to induce known changes in the rotational and translational calibrations of the imaging panel. Translations of up to ±10 mm in the x, y and z directions (see supplemental) and rotational errors of up to ±3° were induced. The calibration files were then used to reconstruct the CBCT image of a pancreatic patient and CatPhan phantom. Correction vectors were calculated for the patient using the software's auto match system and compared to baseline values. The CatPhan CBCT images were used for quantitative evaluation of image quality for each type of induced error.ResultsTranslations of 1 to 3 mm in the × and y calibration resulted in corresponding correction vector errors of equal magnitude. Similar 10mm shifts were seen in the y‐direction; however, in the x‐direction, the image quality was too degraded for a match. These translational errors can be identified through differences in isocenter from orthogonal kV images taken during routine QA. Errors in the z‐direction had no effect on the correction vector and image quality.Rotations of the imaging panel calibration resulted in corresponding correction vector rotations of the patient images. These rotations also resulted in degraded image quality which can be identified through quantitative image quality metrics.ConclusionMisalignment of CBCT geometry can lead to incorrect translational and rotational patient correction vectors. These errors can be identified through QA of the imaging isocenter as compared to orthogonal images combined with monitoring of CBCT image quality.

SU-E-J-64: Feasibility Study of Surgical Clips for Fiducial Tracking in CyberKnife System

Purpose: To investigate the ability of CyberKnife to track surgical clips used as fiducial markers. Methods: The Octavius 1000SRS detector and solid water (RW3) slab phantom were used with motion platform to evaluate the study. The RW3 slab phantom was set up to measure the dose distribution from coronal plane. It consists of 9 plates and the thickness of each plate is 10mm. Among them, one plate was attached with 3 surgical clips, which are orthogonally positioned on outer region of array. The length of attached clip was represented as 1cm on planning CT. The clip plate was placed on the 1000SRS detector and 3 slabs were stacked up on the plate to build the measuring depth. Below the detector, 5 slabs were set. The two-axis motion platform was programmed with 1D sinusoidal movement (20mm peak-to-peak, 3s period) toward superior/inferior and left/right directions to simulate target motion. During delivery, two clips were extracted by two X-ray imagers, which led to translational error correction only. Synchrony was also used for dynamic tracking. After the irradiation, the measured dose distribution of coronal plane was compared with the planar dose distribution calculated by the CyberKnife treatment planning system (Multiplan) for cross verification. The results were assessed by comparing the absolute Gamma (γ) index. Results: The dose distributions measured by the 1000SRS detector were in good agreements with those calculated by Multiplan. In the dosimetric comparison using γ-function criteria based on the distance-to-agreement of 3mm and the local dose difference of 3%, the passing rate with γ- parameter ≤1 was 91% in coronal plane. Conclusion: The surgical clips can be considered as new fiducials for robotic radiosurgery delivery by considering the target margin with less than 5mm.

Robotic real-time translational and rotational head motion correction during frameless stereotactic radiosurgery.

To develop a control system to correct both translational and rotational head motion deviations in real-time during frameless stereotactic radiosurgery (SRS). A novel feedback control with a feed-forward algorithm was utilized to correct for the coupling of translation and rotation present in serial kinematic robotic systems. Input parameters for the algorithm include the real-time 6DOF target position, the frame pitch pivot point to target distance constant, and the translational and angular Linac beam off (gating) tolerance constants for patient safety. Testing of the algorithm was done using a 4D (XY Z + pitch) robotic stage, an infrared head position sensing unit and a control computer. The measured head position signal was processed and a resulting command was sent to the interface of a four-axis motor controller, through which four stepper motors were driven to perform motion compensation. The control of the translation of a brain target was decoupled with the control of the rotation. For a phantom study, the corrected position was within a translational displacement of 0.35 mm and a pitch displacement of 0.15° 100% of the time. For a volunteer study, the corrected position was within displacements of 0.4 mm and 0.2° over 98.5% of the time, while it was 10.7% without correction. The authors report a control design approach for both translational and rotational head motion correction. The experiments demonstrated that control performance of the 4D robotic stage meets the submillimeter and subdegree accuracy required by SRS.

Modification in Surgical Technique for Posterior Vertebral Column Resection

Introduction Surgical treatment of severe and rigid spinal deformities is usually difficult and challenging to perform. The goal of surgical treatment is to obtain a satisfactory balance both in sagittal and coronal planes. In rigid deformities, the osteotomies are usually insufficient; vertebral column resection is the only option of treatment. To reduce the operation time and complications, a single stage, posterior vertebral column resection (PVCR) is defined by Suk et al. It enables rotational and translational correction of spinal column and provides an opportunity for manipulation of anterior and posterior column simultaneously. In the original PVCR, posterior elements of resection side were removed first and then the anterior part removed and correction was performed. The authors decided to make a modification in PVCR as performing the posterior total laminectomy, facetectomy, and pediclectomy after vertebral body resection. This method has two major advantages; minimization of the blood loss from epidural veins after laminectomy and protection of the neural elements from direct injury during vertebral body resection. Patients and Methods A total of 11 patients between the age of 3 and 63 years, diagnosed with severe spinal deformity with limited flexibility, who underwent modified PVCR were reviewed. The average follow-up was 2 years (range, 5 months–3 years). There were six female and five male patients with a mean age of 18 years. Severe congenital scoliosis was found in seven patients, congenital kyphosis in two patients, neurofibromatosis in one patient, and posttraumatic kyphosis in one patient. The surgery consisted of temporary fixation of vertebral column, resection of vertebral body first then resection of posterior elements, followed by deformity correction and fusion. Results The mean estimated blood loss was 1,072 mL (range, 350–2,000 mL). Overall, 39.45% (range, 33–50%) of total blood loss occurred after vertebral body resection, 60.91% (range, 50–67%) occurred after posterior elements removal. The ratio of estimated blood loss to estimated body blood volume was 26% (range, 19–52%). The deformity correction was 60% in the coronal plane. No neurological complications were encountered. Conclusion The PVCR is a complicated, technically demanding procedure with possible risks for major complications. All correction attempts must be performed under direct inspection, palpation of tension in the spinal cord by a highly experienced surgeon. Spinal cord neuromonitoring is a must to prevent neurological injuries. The authors modified the original technique defined by Suk and performed by various surgeons. The authors believe that making vertebral body resection before laminectomy would decrease the blood loss and protect the spinal cord. The validity of this new modified technique should be demonstrated in a prospective, randomized, controlled study with a larger patient population allowing comparison of age-matched subgroups.

Grain boundary character distribution derived from three-dimensional microstructure reconstruction

Manual serial sectioning which includes consecutive steps of sample preparation and Electron Back Scattering Diffraction (EBSD) measurement was employed to extract the twodimensional (2D) sections of a pure nickel sample and to reconstruct the three-dimensional (3D) microstructure. A general alignment algorithm based on the minimization of misorientation between two adjacent sections has been developed to accurately align the sections. By employing this alignment algorithm, any in-plane (translational) and rotational misalignment as well as the planparallelity can be corrected. Surface triangulation technique was used to reconstruct the grain boundary surfaces. The Grain Boundary Character Distribution (GBCD) was derived from reconstructed grain boundaries. The results show that a smoother grain boundary plane can be obtained after precise translational and rotational alignment and correction of planparallelity.The relative grain boundary energy was computed as a function of the five grain boundary parameters based on equilibrium at triple lines. The results show that the grain boundary planes carrying a Σ3 type misorientation are dominantly parallel to the {111} crystal plane, which indicates the presence of coherent twin boundaries. It was observed that coherent Σ3 type boundaries exhibit the minimum relative grain boundary energy, which is approximately 57% smaller than the average of all Σ3 boundaries, including also incoherent twin boundaries.

Cervical osteotomies for neurological deformities.

To report our experience and technique for performing cervical osteotomies under the setting of cervical deformity and myelopathy. Patients who underwent cervical osteotomies for CD with myelopathy were identified in a 10 year period from 2000 to 2010. Demographics, surgery type, osteotomy type, operative details, and radiographs were collected for pre-operative and ultimate post-operative time points. Cervical lordosis (CL) and basion plumb line were collected to assess angular and translational corrections. In the study period, a total of 35 patients underwent a cervical osteotomy for fixed cervical deformity with a diagnosis of cervical myelopathy or myeloradiculopathy with an average follow-up of 3.4 years (range 1.0-6.3). The cohort was separated into two groups based on the type of surgical approach taken to correct their deformity. Anterior osteotomy with or without posterior instrumentation were performed in 31 patients (Group 1). Pedicle subtraction osteotomies were performed in 4 patients (Group 2). For Group 1, the mean angular correction achieved in this was 27.7° (range 9.0-66.0°) and the mean translational correction was 1.8 cm (range 0.1-2.4 cm). In group 2, the mean angular correction was 48.8° (range 38.4-68.3°) and the mean translational correction was 2.8 cm per PSO (range 0.1-5.6 cm). Similar improvements in pre- and post-operative Neck Disability Index scores were achieved with either osteotomy technique. We present our series of patients with cervical myelopathy and/or radiculopathy and concurrent cervical deformity who were treated with cervical osteotomies. The re-alignment of the spine was a key step in preventing the progression of myelopathy and protecting the spinal cord from the continued injury.

Anterior cervical osteotomy for fixed cervical deformities.

Description of surgical technique with case series. To describe the surgical management of fixed cervical deformities using an anterior osteotomy of the cervical spine. Although posteriorly based osteotomies of the cervical spine have been described in the past, there are no reports of the surgical technique for performing an anterior osteotomy of the cervical spine for fixed cervical deformities. Description of a single surgeon's technique for performing an anterior cervical osteotomy and his experience in performing this technique from 2000 to 2010 in a consecutive series of patients. Demographics, operative details, and clinical/radiographical outcomes were collected. The cohort was separated into 2 groups. Group 1 had anterior osteotomy only with or without posterior instrumentation whereas group 2 had anterior osteotomy and Smith-Petersen osteotomies with posterior instrumentation. A total of 38 patients (group 1 = 17, group 2 = 21) underwent an anterior osteotomy in the study period with an average follow-up of 3.4 years (range, 1.0-6.3 yr). All but 7 cases were revision cases. Group 1 had shorter length of surgery and less estimated blood loss than group 2 (length of surgery 220 vs. 313 min, P < 0.01; estimated blood loss 189 vs. 294 mL, P = 0.02).The mean angular correction achieved in group 1 was less than that of group 2, although not statistically significant (23° vs. 33°, P = 0.15). There was less mean translational correction achieved in group 1 compared with group 2 (1.3 vs. 3.7 cm, P = 0.03). Both groups had improvements in the neck disability index with surgery and were similar between groups (20 vs. 19.7, P = 0.78). There were no neurological complications or intraoperative neuromonitoring changes in either group. The use of an anterior osteotomy in the cervical spine is safe and effective for the correction of fixed deformities of the cervical spine. When necessary, Smith-Petersen osteotomies can add to the angular and translational correction to achieve a satisfying outcome for patients. 4.

Patient translational motion correction for reduction of artifacts in a fan-beam CT scanner

Patient translational motion correction for reduction of artifacts in a fan-beam CT scanner