Original CT Research Articles

Novel Multimodal Atlas Template for Spatial Normalization of Whole-Brain Images of Newborns

Due to the complications of the brain study in the first two years of life, the investigations conducted in the field of neonatal brain are limited. An efficient means for obtaining information about the neonatal brain is the brain template. In this paper, we represent the results of our research in the field of MR and CT atlas templates. At first, we construct a new MR atlas by utilizing a set of high-resolution T1-weighted MR images captured from a group of newborns with the gestational ages of 39 to 42 weeks at the examination date. Afterwards, we construct an original CT template, which is practically consistent with the MR atlas, by utilizing a set of high-resolution CT images captured from a group of newborns with the identical gestational ages. In spite of multifarious clinical applications, no modern CT template had been proposed to facilitate the normalization of neonatal CT images before we concentrated on providing the neonatal CT atlas. The developed atlases are evaluated qualitatively and quantitatively, for instance through the visual inspection and assessment of the anatomical local deviations. At the presence of both MR and CT modalities, further improvement could be attained in the medical diagnoses by the simultaneous utilization of the presented templates.

A mixed reality approach for stereo-tomographic quantification of lung nodules.

To reduce the radiation dose and the equipment cost associated with lung CT screening, in this paper we propose a mixed reality based nodule measurement method with an active shutter stereo imaging system. Without involving hundreds of projection views and subsequent image reconstruction, we generated two projections of an iteratively placed ellipsoidal volume in the field of view and merging these synthetic projections with two original CT projections. We then demonstrated the feasibility of measuring the position and size of a nodule by observing whether projections of an ellipsoidal volume and the nodule are overlapped from a human observer's visual perception through the active shutter 3D vision glasses. The average errors of measured nodule parameters are less than 1 mm in the simulated experiment with 8 viewers. Hence, it could measure real nodules accurately in the experiments with physically measured projections.

Noninvasive microwave ablation zone radii estimation using x-ray CT image analysis.

The aims of this study were to noninvasively and automatically estimate both the radius of the ablated liver tissue and the radius encircling the treated zone, which also defines where the tissue is definitely untreated during a microwave (MW) thermal ablation procedure. Fourteen ex vivo bovine fresh liver specimens were ablated at 40 W using a 14 G microwave antenna, for durations of 3, 6, 8, and 10 min. The tissues were scanned every 5 s during the ablation using an x-ray CT scanner. In order to estimate the radius of the ablation zone, the acquired images were transformed into a polar presentation by displaying the Hounsfield units (HU) as a function of angle and radius. From this polar presentation, the average HU radial profile was analyzed at each time point and the ablation zone radius was estimated. In addition, textural analysis was applied to the original CT images. The proposed algorithm identified high entropy regions and estimated the treated zone radius per time. The estimated ablated zone radii as a function of treatment durations were compared, by means of correlation coefficient and root mean square error (RMSE) to gross pathology measurements taken immediately post-treatment from similarly ablated tissue. Both the estimated ablation radii and the treated zone radii demonstrated strong correlation with the measured gross pathology values (R(2) ≥ 0.89 and R(2) ≥ 0.86, respectively). The automated ablation radii estimation had an average discrepancy of less than 1 mm (RMSE = 0.65 mm) from the gross pathology measured values, while the treated zone radii showed a slight overestimation of approximately 1.5 mm (RMSE = 1.6 mm). Noninvasive monitoring of MW ablation using x-ray CT and image analysis is feasible. Automatic estimations of the ablation zone radius and the radius encompassing the treated zone that highly correlate with actual ablation measured values can be obtained. This technique can therefore potentially be used to obtain real time monitoring and improve the clinical outcome.

Can CT image deblurring improve finite element predictions at the proximal femur?

The aim of this study was to determine if a CT image deblurring algorithm can improve CT-based FE modelling accuracy at the proximal femur.Experimental data (CT scans of fourteen proximal fresh-frozen cadaveric femurs, non-destructive surface strain measurements in stance and sideways fall loading configurations on all femurs, and failure loads obtained in stance for seven specimens, in sideways fall for the other seven) were taken from a recent study (Schileo et al., 2014). An estimate of the 3D Point Spread Function for each CT scan was used within a deconvolution solver to perform the deblurring. The most proximal regions of three specimens were scanned using an HRpQCT scanner and compared to the original and deblurred CT images to quantify errors in bone contour estimates and determine correlation of intensity values within the bone contours. Subject-specific FE models of the proximal femur were generated. The accuracy of deblurred FE predictions against experimental measurements was compared to the published (non-deblurred) FE results.When compared to HRpQCT, CT deblurring led to lower mean surface distances (0.31 vs. 0.49mm) and higher CT intensity correlations with respect to the original CT. All indicators of strain prediction accuracy were significantly improved in deblurred FE models, more markedly at the femoral neck (peak error reduced by 38%). Failure load prediction, based on a simple elastic limit model, was also improved in deblurred FE models, although differently for stance and sideways fall loading conditions. In stance, correlation was unchanged, but specimen-wise errors were reduced (mean error 10% vs. 15%). In sideways fall, correlation notably increased (R2=0.95 vs. 0.81), despite a general overestimation of failure load.In summary, the proposed CT deblurring technique yielded moderate but significant improvements in FE predictions, and may thus be considered a first step toward the improvement of CT-based FE models of the human femur.

Sudden Onset Headache in a Post-Partum Young Female

We present the case of a 33 year old female presenting with acute neurological signs including right sided neglect and confusion four days postpartum. The original non-contrast CT brain demonstrated an acute left temporal intraparenchymal hemorrhage. A cerebral catheter angiogram was performed and demonstrated the typical appearances of RCVS (Reversible cerebral vasoconstriction syndrome).

Fecal microbiota transplantation via fluoroscopy-guided nasojejunal catheter placement: indications, technique, and the role of radiology.

Clostridium difficile is a well-established cause of nosocomial gastrointestinal disease. Although antibiotics remain an effective first-line treatment for C. difficile colitis (CDC), relapse and recurrence are common. FMT has emerged as one of the safest and most effective known therapies available for recurrent or refractory CDC, which is likely due to restoration of the protective microbiotic barrier of the gastrointestinal tract. FMT varies greatly across institutions by route of delivery, dose, and protocol. We present our experience with FMT via fluoroscopic-guided nasojejunal catheter placement. The discussion will include indications and contraindications, protocol, and procedural technique, and include a case presentation incorporating original CT and fluoroscopic images. Specifically, we will address the advantages and disadvantages of image-guided FMT via the upper GI tract with respect to nasogastric-, colonoscopic-, and enema-based delivery. The efficacy of FMT for the treatment of C. difficile has been widely demonstrated in several prospective and case studies. We feel that nasojejunal FMT is an underutilized radiologic procedure which can benefit selected patients, particularly given the advantages in risk profile, cost, convenience, and lack of routine sedation.

TU‐AB‐BRA‐03: Atlas‐Based Algorithms with Local Registration‐Goodness Weighting for MRI‐Driven Electron Density Mapping

Purpose:To develop image‐analysis algorithms to synthesize CT with accurate electron densities for MR‐only radiotherapy of head & neck (H&N) and pelvis anatomies.Methods:CT and 3T‐MRI (Philips, mDixon sequence) scans were randomly selected from a pool of H&N (n=11) and pelvis (n=12) anatomies to form an atlas. All MRIs were pre‐processed to eliminate scanner and patient‐induced intensity inhomogeneities and standardize their intensity histograms. CT and MRI for each patient were then co‐registered to construct CT‐MRI atlases. For more accurate CT‐MR fusion, bone intensities in CT were suppressed to improve the similarity between CT and MRI. For a new patient, all CT‐MRI atlases are deformed onto the new patients’ MRI initially. A newly‐developed generalized registration error (GRE) metric was then calculated as a measure of local registration accuracy. The synthetic CT value at each point is a 1/GRE‐weighted average of CTs from all CT‐MR atlases. For evaluation, the mean absolute error (MAE) between the original and synthetic CT (generated in a leave‐one‐out scheme) was computed. The planning dose from the original and synthetic CT was also compared.Results:For H&N patients, MAE was 67±9, 114±22, and 116±9 HU over the entire‐CT, air and bone regions, respectively. For pelvis anatomy, MAE was 47±5 and 146±14 for the entire and bone regions. In comparison with MIRADA medical, an FDA‐approved registration tool, we found that our proposed registration strategy reduces MAE by ∼30% and ∼50% over the entire and bone regions, respectively. GRE‐weighted strategy further lowers MAE by ∼15% to ∼40%. Our primary dose calculation also showed highly consistent results between the original and synthetic CT.Conclusion:We've developed a novel image‐analysis technique to synthesize CT for H&N and pelvis anatomies. Our proposed image fusion strategy and GRE metric help generate more accurate synthetic CT using locally more similar atlases (Support: Philips Healthcare).The research is supported by Philips HealthCare

SU-F-P-54: Guidelines to Check Image Registration QA of a Clinical Deformation Registration Software: A Single Institution Preliminary Study

Purpose: The objective of this study is to verify and analyze the accuracy of a clinical deformable image registration (DIR) software. Methods: To test clinical DIR software qualitatively and quantitatively, we focused on lung radiotherapy and analyzed a single (Lung) patient CT scan. Artificial anatomical changes were applied to account for daily variations during the course of treatment including the planning target volume (PTV) and organs at risk (OAR). The primary CT (pCT) and the structure set (pST) was deformed with commercial tool (ImSimQA-Oncology Systems Limited) and after artificial deformation (dCT and dST) sent to another commercial tool (VelocityAI-Varian Medical Systems). In Velocity, the deformed CT and structures (dCT and dST) were inversely deformed back to original primary CT (dbpCT and dbpST). We compared the dbpST and pST structure sets using similarity metrics. Furthermore, a binary deformation field vector (BDF) was created and sent to ImSimQA software for comparison with known “ground truth” deformation vector fields (DVF). Results: An image similarity comparison was made by using “ground truth” DVF and “deformed output” BDF with an output of normalized “cross correlation (CC)” and “mutual information (MI)” in ImSimQA software. Results for the lung case were MI=0.66 and CC=0.99. The artificial structure deformation in both pST and dbpST was analyzed using DICE coefficient, mean distance to conformity (MDC) and deformation field error volume histogram (DFEVH) by comparing them before and after inverse deformation. We have noticed inadequate structure match for CTV, ITV and PTV due to close proximity of heart and overall affected by lung expansion. Conclusion: We have seen similarity between pCT and dbpCT but not so well between pST and dbpST, because of inadequate structure deformation in clinical DIR system. This system based quality assurance test will prepare us for adopting the guidelines of upcoming AAPM task group 132 protocol.

TH-AB-207A-12: CT Lung Cancer Screening and the Effects of Further Dose Reduction On CAD Performance

Purpose: CT lung screening is already performed at low doses. In this study, we investigated the effects of further dose reduction on a lung-nodule CAD detection algorithm. Methods: The original raw CT data and images from 348 patients were obtained from our local database of National Lung Screening Trial (NLST) cases. 61 patients (17.5%) had at least one nodule reported on the NLST reader forms. All scans were acquired with fixed mAs (25 for standard-sized patients, 40 for large patients) on a 64-slice scanner (Sensation 64, Siemens Healthcare). All images were reconstructed with 1-mm slice thickness, B50 kernel. Based on a previously-published technique, we added noise to the raw data to simulate reduced-dose versions of each case at 50% and 25% of the original NLST dose (i.e. approximately 1.0 and 0.5 mGy CTDIvol). For each case at each dose level, a CAD detection algorithm was run and nodules greater than 4 mm in diameter were reported. These CAD results were compared to “truth”, defined as the approximate nodule centroids from the NLST forms. Sensitivities and false-positive rates (FPR) were calculated for each dose level, with a sub-analysis by nodule LungRADS category. Results: For larger category 4 nodules, median sensitivities were 100% at all three dose levels, and mean sensitivity decreased with dose. For the more challenging category 2 and 3 nodules, the dose dependence was less obvious. Overall, mean subject-level sensitivity varied from 38.5% at 100% dose to 40.4% at 50% dose, a difference of only 1.9%. However, median FPR quadrupled from 1 per case at 100% dose to 4 per case at 25% dose. Conclusions: Dose reduction affected nodule detectability differently depending on the LungRADS category, and FPR was very sensitive at sub-screening levels. Care should be taken to adapt CAD for the very challenging noise characteristics of screening. Funding support: NIH U01 CA181156; Disclosures (McNitt-Gray): Institutional research agreement, Siemens Healthcare; Past recipient, research grant support, Siemens Healthcare; Consultant, Toshiba America Medical Systems; Consultant, Samsung Electronics.

TU‐AB‐BRA‐02: An Efficient Atlas‐Based Synthetic CT Generation Method

Purpose:A major obstacle for MR‐only radiotherapy is the need to generate an accurate synthetic CT (sCT) from MR image(s) of a patient for the purposes of dose calculation and DRR generation. We propose here an accurate and efficient atlas‐based sCT generation method, which has a computation speed largely independent of the number of atlases used.Methods:Atlas‐based sCT generation requires a set of atlases with co‐registered CT and MR images. Unlike existing methods that align each atlas to the new patient independently, we first create an average atlas and pre‐align every atlas to the average atlas space. When a new patient arrives, we compute only one deformable image registration to align the patient MR image to the average atlas, which indirectly aligns the patient to all pre‐aligned atlases. A patch‐based non‐local weighted fusion is performed in the average atlas space to generate the sCT for the patient, which is then warped back to the original patient space. We further adapt a PatchMatch algorithm that can quickly find top matches between patches of the patient image and all atlas images, which makes the patch fusion step also independent of the number of atlases used.Results:Nineteen brain tumour patients with both CT and T1‐weighted MR images are used as testing data and a leave‐one‐out validation is performed. Each sCT generated is compared against the original CT image of the same patient on a voxel‐by‐voxel basis. The proposed method produces a mean absolute error (MAE) of 98.6±26.9 HU overall. The accuracy is comparable with a conventional implementation scheme, but the computation time is reduced from over an hour to four minutes.Conclusion:An average atlas space patch fusion approach can produce highly accurate sCT estimations very efficiently. Further validation on dose computation accuracy and using a larger patient cohort is warranted. The author is a full time employee of Elekta, Inc.

Visual Analysis of Defects in Glass Fiber Reinforced Polymers for 4DCT Interrupted In situ Tests

AbstractMaterial engineers use interrupted in situ tensile testing to investigate the damage mechanisms in composite materials. For each subsequent scan, the load is incrementally increased until the specimen is completely fractured. During the interrupted in situ testing of glass fiber reinforced polymers (GFRPs) defects of four types are expected to appear: matrix fracture, fiber/matrix debonding, fiber pull‐out, and fiber fracture. There is a growing demand for the detection and analysis of these defects among the material engineers. In this paper, we present a novel workflow for the detection, classification, and visual analysis of defects in GFRPs using interrupted in situ tensile tests in combination with X‐ray Computed Tomography. The workflow is based on the automatic extraction of defects and fibers. We introduce the automatic Defect Classifier assigning the most suitable type to each defect based on its geometrical features. We present a visual analysis system that integrates four visualization methods: 1) the Defect Viewer highlights defects with visually encoded type in the context of the original CT image, 2) the Defect Density Maps provide an overview of the defect distributions according to type in 2D and 3D, 3) the Final Fracture Surface estimates the material fracture's location and displays it as a 3D surface, 4) the 3D Magic Lens enables interactive exploration by combining detailed visualizations in the region of interest with overview visualizations as context. In collaboration with material engineers, we evaluate our solution and demonstrate its practical applicability.

Anatomic structure-based deformable image registration of brachytherapy implants in the treatment of locally advanced cervix cancer

PurposeTo examine the impact of anatomic structure-based image sets in deformable image registration (DIR) for cervical cancer patients. Methods and MaterialsCT examinations of 7 patients previously treated for locally advanced cervical cancer with external beam radiation therapy and from three to five fractions of high-dose-rate brachytherapy (HDR-BT) were used. Structure-based image sets were created from “free” structures already made for planning purposes, with each structure of interest assigned a unique, homogeneous Hounsfield number. Subsequent HDR fractions were registered to the pretreatment external beam radiation therapy and/or the first HDR fraction using commercially available software by rigid alignment (RIG) followed by DIR. Comparison methods included quantification of external contour displacement between source and target images and calculation of mean voxel displacement values. Registration results for structure-based image sets were then compared and contrasted to intensity-based registrations of the original grayscale images. ResultsUtilization of anatomic structure-based image sets resulted in better initial rigid matching (A-RIG) with more importance on applicator positioning and soft tissue structures. Subsequent DIR of anatomic structure-based images allowed for intermodality registrations, whereas all intermodality registrations using original CT images failed to produce anatomically feasible results. ConclusionsWe have investigated the use of structure-based CT image sets for image registrations and have produced anatomically favorable registrations with excellent matching of external contours as compared to registrations of original grayscale images. Commercial software registrations using treatment-planning structures required no manual tweaking on a per-patient basis, suggesting results are reproducible and broadly applicable.

SU‐C‐207B‐05: Tissue Segmentation of Computed Tomography Images Using a Random Forest Algorithm: A Feasibility Study

Purpose:Develop an automated Random Forest algorithm for tissue segmentation of CT examinations.Methods:Seven materials were classified for segmentation: background, lung/internal gas, fat, muscle, solid organ parenchyma, blood/contrast, and bone using Matlab and the Trainable Weka Segmentation (TWS) plugin of FIJI. The following classifier feature filters of TWS were investigated: minimum, maximum, mean, and variance each evaluated over a pixel radius of 2n, (n = 0–4). Also noise reduction and edge preserving filters, Gaussian, bilateral, Kuwahara, and anisotropic diffusion, were evaluated. The algorithm used 200 trees with 2 features per node. A training data set was established using an anonymized patient's (male, 20 yr, 72 kg) chest‐abdomen‐pelvis CT examination. To establish segmentation ground truth, the training data were manually segmented using Eclipse planning software, and an intra‐observer reproducibility test was conducted. Six additional patient data sets were segmented based on classifier data generated from the training data. Accuracy of segmentation was determined by calculating the Dice similarity coefficient (DSC) between manual and auto segmented images.Results:The optimized autosegmentation algorithm resulted in 16 features calculated using maximum, mean, variance, and Gaussian blur filters with kernel radii of 1, 2, and 4 pixels, in addition to the original CT number, and Kuwahara filter (linear kernel of 19 pixels). Ground truth had a DSC of 0.94 (range: 0.90–0.99) for adult and 0.92 (range: 0.85–0.99) for pediatric data sets across all seven segmentation classes. The automated algorithm produced segmentation with an average DSC of 0.85 ± 0.04 (range: 0.81–1.00) for the adult patients, and 0.86 ± 0.03 (range: 0.80–0.99) for the pediatric patients.Conclusion:The TWS Random Forest auto‐segmentation algorithm was optimized for CT environment, and able to segment seven material classes over a range of body habitus and CT protocol parameters with an average DSC of 0.86 ± 0.04 (range: 0.80–0.99).

SU‐F‐P‐31: Dosimetric Effects of Roll and Pitch Corrections Using Robotic Table

Purpose:To quantify the dosimetric effect of roll and pitch corrections being performed by two types of robotic tables available at our institution: BrainLabTM 5DOF robotic table installed at VERO (BrainLab&MHI) dedicated SBRT linear accelerator and 6DOF robotic couch by IBA Proton Therapy with QFixTM couch top.Methods:Planning study used a thorax phantom (CIRSTM), scanned at 4DCT protocol; targets (IGTV, PTV) were determined according to the institutional lung site‐specific standards. 12 CT sets were generated with Pitch and Roll angles ranging from −4 to +4 degrees each. 2 table tops were placed onto the scans according to the modality‐specific patient treatment workflows. The pitched/rolled CT sets were fused to the original CT scan and the verification treatment plans were generated (12 photon SBRT plans and 12 proton conventional fractionation lung plans). Then the CT sets were fused again to simulate the effect of patient roll/pitch corrections by the robotic table. DVH sets were evaluated for all cases.Results:The effect of not correcting the phantom position for roll/pitch in photon SBRT cases was reducing the target coverage by 2% as maximum; correcting the positional errors by robotic table varied the target coverage within 0.7%. in case of proton treatment, not correcting the phantom position led to the coverage loss up to 4%, applying the corrections using robotic table reduced the coverage variation to less than 2% for PTV and within 1% for IGTV.Conclusion:correcting the patient position by using robotic tables is highly preferable, despite the small dosimetric changes introduced by the devices.

SU‐F‐T‐37: Dosimetric Evaluation of Planned Versus Decay Corrected Treatment Plans for the Treatment of Tandem‐Based Cervical HDR Brachytherapy

Purpose:This study evaluated dosimetric parameters for actual treatment plans versus decay corrected treatment plans for cervical HDR brachytherapy.Methods:125 plans of 25 patients, who received 5 fractions of HDR brachytherapy, were evaluated in this study. Dose was prescribed to point A (ICRU‐38) and High risk clinical tumor volume (HR‐CTV) and organs at risk (OAR) were, retrospectively, delineated on original CT images by treating physician. First HDR plan was considered as reference plan and decay correction was applied to calculate treatment time for subsequent fractions, and was applied, retrospectively, to determine point A, HR‐CTV D90, and rectum and bladder doses.Results:The differences between mean point A reference doses and the point A doses of the plans computed using decay times were found to be 1.05%±0.74% (−2.26% to 3.26%) for second fraction; −0.25%±0.84% (−3.03% to 3.29%) for third fraction; 0.04%±0.70% (−2.68% to 2.56%) for fourth fraction and 0.30%±0.81% (−3.93% to 2.67%) for fifth fraction. Overall mean point A dose difference, for all fractions, was 0.29%±0.38% (within ± 5%). Mean rectum and bladder dose differences were calculated to be −3.46%±0.12% and −2.47%±0.09%, for points, respectively, and −1.72%±0.09% and −0.96%±0.06%, for D2cc, respectively. HR‐CTV D90 mean dose difference was found to be −1.67% ± 0.11%. There was no statistically significant difference between the reference planned point A doses and that calculated using decay time to the subsequent fractions (p<0.05).Conclusion:This study reveals that a decay corrected treatment will provide comparable dosimetric results and can be utilized for subsequent fractions of cervical HDR brachytherapy instead of actual treatment planning. This approach will increase efficiency, decrease workload, reduce patient observation time between applicator insertion and treatment delivery. This would be particularly useful for institutions with limited resources or large patient populations with limited access to care.

Dosimetric impact of 4DCT artifact in carbon-ion scanning beam treatment: Worst case analysis in lung and liver treatments

IntroductionWe evaluated the impact of 4DCT artifacts on carbon-ion pencil beam scanning dose distributions in lung and liver treatment. Methods & materials4DCT was performed in 20 liver and lung patients using area-detector CT (original 4DCT). 4DCT acquisition by multi-detector row CT was simulated using original 4DCT by selecting other phases randomly (plus/minus 20% phases). Since tumor position can move over the respiratory range in original 4DCT, mid-exhalation was set as reference phase. Total prescribed dose of 60Gy (RBE) was delivered to the clinical target volume (CTV). Reference dose distribution was calculated with the original CT, and actual dose distributions were calculated with treatment planning parameters optimized using the simulated CT (simulated dose). Dose distribution was calculated by substituting these parameters into the original CT. ResultsFor liver cases, CTV-D95 and CTV-Dmin values for the reference dose were 97.6±0.5% and 89.8±0.6% of prescribed dose, respectively. Values for the simulated dose were significantly degraded, to 88.6±14.0% and 46.3±26.7%, respectively. Dose assessment results for lung cases were 84.8±12.8% and 58.0±24.5% for the simulated dose, showing significant degradation over the reference dose of 95.1±1.5% and 87.0±2.2%, respectively. Conclusions4DCT image quality should be closely checked to minimize degradation of dose conformation due to 4DCT artifacts. Medical staff should pay particular attention to checking the quality of 4DCT images as a function of respiratory phase, because it is difficult to recognize 4DCT artifact on a single phase in some cases

Clinical Use of a Novel Balloon Based Esophageal Brachytherapy Applicator

Purpose: High dose rate endoesophageal brachytherapy is an option in the management of primary and recurrent esophageal cancer in inoperable patients. In a review of a series of patients treated at our institution (Folkert et al Brachytherapy 2013) we found HDR brachytherapy was safe and well tolerated, but was associated with a high rate of local recurrence. To overcome the limitation of surface dose, and enable a dose escalation study we designed a novel balloon based applicator (Cohen and Goodman, Brachytherapy 2015). Here, we report on the initial clinical use of this applicator. Materials and Methods: The esophageal (E) applicator (Ancer Medical, Nashua, NH), a five-balloon self centering applicator with one treatment catheter, was used. Under general anesthesia and with fluoroscopic guidance, the applicator was inserted into the esophagus over a guidewire into the treatment position, and centered by inflating the five balloons. Visualization of the applicator was achieved using the integrated X-ray markers, and 10% CT contrast in the balloons. A CT scan was obtained for planning, the target and surrounding healthy esophagus were contoured, the source channel was traced, and a treatment plan optimization was performed to deliver 15 Gy in 3 fractions (BrachyVision, Varian Medical systems, Charlottesville VA). After review and approval of the plan, the applicator positioning was verified, and the initial treatment was delivered using a GammaMed-Plus HDR afterloader. Anesthesia was reversed at the completion of treatment. For the subsequent two weekly treatments, the original CT plan was used, and the applicator was inserted under fluoroscopic guidance. Positioning of the applicator can be verified by matching the treatment length to fluoroscopically placed surface markers, and by measuring the insertion distance from the incisors using integrated insertion markers. In this case, applicator positioning was verified with respect to a pre-implanted fiducial marker. After confirmation of applicator positioning, the treatments were delivered. Results: The applicator geometry enabled good coverage of the target volume (V100 5 95%, D90 5 108%, and V150 5 44%) while keeping the surface dose within tolerance limits (D0.3cc ! 11Gy) and sparing uninvolved esophageal tissue (D0.3cc 5 92%, D1cc 5 75%, and D2cc 5 58%). Good applicator re-positioning was achieved for all treatments. The applicator shown in the figure below (panels A, B) incorporates X-ray markers to aid with positioning. CT based planning was performed (panels C-F). Because of the non uniform spacing between the source axis and tissue surface, optimization results in non uniform dwell-times (panel E). Fluoroscopic image of the applicator placement is also shown (panel G). Conclusions: This is the first report on using the E applicator in patients. The improved treatment geometry achieved with this applicator provides encouraging feedback for continuation with dose escalation in these patients.

Inter-rater Variability Interferes with Reproducibility of Splenic Injury Grades Reported to the American College of Surgeons Committee on Trauma

The objective of this study was to determine reproducibility of our splenic injury grading data, previously reported to the American College of Surgeons Committee on Trauma for our most recent site visit. The institutional registry of a Level I trauma center was queried to identify adult patients presenting with blunt splenic injury between January 1, 2013 and December 31, 2013. Original CT scans were scanned into the picture archiving and communication system and subsequently reviewed by four trauma surgeons and two radiologists for clinical impressions of splenic injury grade. Grades assigned by the clinician and the grade recorded in the registry were compared for inter-rater reliability using the intraclass correlation coefficient, as a means of assessing variance of ordinal data. The intraclass correlation coefficient in our model was 0.77, which indicates that 77 per cent of the observed variance was due to true variance and 23 per cent of the variance was due to error. Variability in grading may, in some cases, underestimate injury severity and compromise the clinician's expectation of clinical outcome, both in real-time, as well as during retrospective review processes such as those used during the trauma center reverification process.

3D-2D Deformable Image Registration Using Feature-Based Nonuniform Meshes.

By using prior information of planning CT images and feature-based nonuniform meshes, this paper demonstrates that volumetric images can be efficiently registered with a very small portion of 2D projection images of a Cone-Beam Computed Tomography (CBCT) scan. After a density field is computed based on the extracted feature edges from planning CT images, nonuniform tetrahedral meshes will be automatically generated to better characterize the image features according to the density field; that is, finer meshes are generated for features. The displacement vector fields (DVFs) are specified at the mesh vertices to drive the deformation of original CT images. Digitally reconstructed radiographs (DRRs) of the deformed anatomy are generated and compared with corresponding 2D projections. DVFs are optimized to minimize the objective function including differences between DRRs and projections and the regularity. To further accelerate the above 3D-2D registration, a procedure to obtain good initial deformations by deforming the volume surface to match 2D body boundary on projections has been developed. This complete method is evaluated quantitatively by using several digital phantoms and data from head and neck cancer patients. The feature-based nonuniform meshing method leads to better results than either uniform orthogonal grid or uniform tetrahedral meshes.

Application of 3D-printing kidney and stones for PCNL planning and teaching: a preliminary research

Objective To explore the possibility of three-dimensional (3D) kidney replications for clinical and teaching of percutaneous nephrolithotomy (PCNL). Methods The CT urography (CTU) DICOM format data from 5 patients with kidney calculi were selected from March 1st to June 1st, 2015.Thresholding technique, region growing technique, edit mask technique and multiple slice edit technique were used in sequence by Mimics software.And five 3D replications were printed by Object 500 3D printer. The sizes of the replications were measured and the replications were punctured. Results The 3D replications of the kidneys were successfully designed and printed.The average difference of the long axes between 3D replications and patients' kidneys was 0.283cm, the average difference of the diameters was 0.212cm, and the average difference of the diameter of the stones was 0.244cm. The sizes of the 3D replications were basically consistent with those of patients' kidneys.The simulative puncturing was successful. Conclusions After comparing the 3D replications with their original 2D CT images, the anatomical details are found basically the same.The 3D replications could provide 3D visual observations of organ anatomy for surgeons. Key words: Kidney calculi; Nephrostomy, percutaneous; 3D-printing; Surgical simulation; Teaching and training