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Achilles tendinopathy remains one of the most prevalent overuse injuries in elite as well as recreational athletes. Regardless of the fact that the aetiology of tendinopathy has not been fully understood, therapeutic mechanical loading programs have emerged as being the treatment of choice. In this light, mechanical properties of the tendon and their response to changes in loading or unloading have been the subject of many previous investigations. One of these properties often investigated is strain, a measure of relative deformation. By means of a systematic review, an overview was given of research in this field, with a primary objective to list the methods used and secondary aim to synthesize data on strain mapping in the Achilles tendon. Following the guidelines of the PRISMA statement, 47 articles were found appropriate for qualitative assessment. Achilles tendon strain has been investigated across a variety of contexts, including the response to exercise, walking, unloading, ageing, hormonal changes and weight. Only three studies investigated the effect of the presence of tendinopathy on strain. Ultrasound was the most often used imaging modality to measure or estimate strain. Further methodological parameters, e.g. the location of measurement, differed greatly between all different studies. Nearly all studies considered global strain. Some studies investigated the transverse strain response of the Achilles tendon. Recently, however, the role of local - intratendinous - strain distribution has been found to be of critical importance and further studies should focus on imaging modalities to investigate these local changes.

Background and purpose: There is a huge difference in radiosensitivity of lungs between patients. The present study aims to identify and quantify patient-specific radiosensitivity based on a single pre-treatment CT scan. Materials and methods: 130 lung cancer patients were studied: 60 stereotactic ablative 'radiotherapy (SABR) treatments and 70 conventional treatments (20 and 30 patients from external datasets, respectively). A 3 month-follow-up scan (CT3M) was non-rigidly registered to the planning CT scan (CT0). Changes in Hounsfield Units (Delta HU = HU3M - HU0) inside lung subvolumes were analyzed per dose bin of 5 Gy. Delta HU was modeled as a function of local dose using linear and sigmoidal fits. Sigmoidal fit parameters Delta HUmax (saturation level) and D-50 (dose corresponding to 50% of Delta HUmax) were collected for all patients. Results: Sigmoidal fits outperformed linear fits in the SABR groups for the majority of patients. Sigmoidal dose-responses were also observed in both conventional groups but to a lesser extent. Distributions of D-50 and Delta HUmax showed a large variation between patients in all datasets. Higher baseline lung density (p

Background Little attention has been paid to the effect of implant restorations on speech. Purpose The aim of this study was threefold: (1) to find out if speech problems occur after inserting a fixed provisional restoration in the edentulous maxilla; (2) to explore speech adaptation in case articulation problems arise after rehabilitation; and (3) to describe the effect of changing the shape of the restoration on improving speech. Materials and Methods Ten patients with an edentulous maxilla were treated with fixed rehabilitation on implants. Speech evaluation was performed at four occasions: before implant surgery, immediately after restoration, and 3 weeks later before and after managing the speech problem by changing the shape of the restoration if speech problems occurred. Comparative three-dimensional-analysis of casts of the restoration before and after changing the shape of the restoration was carried out. Results The majority of patients (n = 7) experienced speech problems immediately after rehabilitation. Three weeks later, none of the seven patients with deteriorated speech returned to baseline speech. Then, volumetric reduction of the palatal aspects of the (pre)molars was performed, which allowed speech to return to baseline levels in five out of seven patients. In the two remaining patients, the intervention resulted in an improvement of speech without reaching their baseline levels. Three-dimensional-analysis showed that reducing the palatal volume of the premolars was effective in correcting speech. Conclusions Speech problems may frequently occur after fixed rehabilitation of the completely edentulous maxilla. A novel speech management concept, consisting of reducing the palatal volume of the (pre)molars, is introduced, demonstrating to solve speech problems in most cases.

Purpose: To automatically detect intrafraction motion during arc radiotherapy for prostate cancer patients by tracking fiducial markers in two‐dimensional MV images acquired using the treatment beam, in order to adjust radiationdose accordingly. Methods: Four fiducial gold markers are implanted in a patient's prostate. Patients are irradiated using a Varian Linac 2100 C/D with RapidArc upgrade (Varian Medical Systems, Palo Alto, CA). MV images (1024 × 768 pixels, 0.392 × 0.392 mm2 pixel size) acquired during a 360 degree gantry rotation at a one second interval (5 degrees) are preprocessed by subtracting a smoothed version of the image to retain only high image frequencies. Edge detection is then applied, followed by a one pixel wide dilation and erosion to transform the edges into contiguous regions. Next, our method searches the centers of visible markers (i.e. not covered by the MLC), constrained by marker estimates from the planning CT. This is done by finding all contiguous regions and maximizing a marker‐region distance criterion for every visible marker. A two‐dimensional estimate correction over consecutive projections is also implemented to improve marker estimates during gantry rotation. Results: We applied our method on four treatment fractions of the same patient. As such, a total of 191 projections with manually indicated marker ends as ground truth were used as validation. Markers were indicated twice on all images, to include observer errors. Results show a mean detection error of less than 0.5 mm in the projection image (standard deviation 0.6 mm), with an execution time of less than one second per image in matlab. Undetected markers and false positives mostly occurred at moving leaf boundaries, where marker visibility was determined by the observer. Conclusions: Preliminary findings demonstrate that this method can be used to detect intrafraction motion during arc radiotherapy by only using projected MV images. Research sponsored by Varian Medical Systems, Palo Alto, CA.

Estimation of strain in tendons for tendinopathy assessment is a hot topic within the sports medicine community. It is believed that, if accurately estimated, existing treatment and rehabilitation protocols can be improved and presymptomatic abnormalities can be detected earlier. State-of-the-art studies present inaccurate and highly variable strain estimates, leaving this problem without solution. Out-of-plane motion, present when acquiring two-dimensional (2D) ultrasound (US) images, is a known problem and may be responsible for such errors. This work investigates the benefit of high-frequency, three-dimensional (3D) US imaging to reduce errors in tendon strain estimation. Volumetric US images were acquired in silico, in vitro, and ex vivo using an innovative acquisition approach that combines the acquisition of 2D high-frequency US images with a mechanical guided system. An affine image registration method was used to estimate global strain. 3D strain estimates were then compared with ground-truth values and with 2D strain estimates. The obtained results for in silico data showed a mean absolute error (MAE) of 0.07%, 0.05%, and 0.27% for 3D estimates along axial, lateral direction, and elevation direction and a respective MAE of 0.21% and 0.29% for 2D strain estimates. Although 3D could outperform 2D, this does not occur in in vitro and ex vivo settings, likely due to 3D acquisition artifacts. Comparison against the state-of-the-art methods showed competitive results. The proposed work shows that 3D strain estimates are more accurate than 2D estimates but acquisition of appropriate 3D US images remains a challenge.

In head and neck cancer, diffusion weighted MRI (DWI) can predict response early during treatment. Treatment-induced changes and DWI-specific artifacts hinder an accurate registration between apparent diffusion coefficient (ADC) maps. The aim of the study was to develop a registration tool which calculates and visualizes regional changes in ADC.Twenty patients with stage IV HNC treated with primary radiotherapy received an MRI including DWI before and early during treatment. Markers were manually placed at anatomical landmarks on the different modalities at both time points. A registration method, consisting of a fully automatic rigid and nonrigid registration and two semi-automatic thin-plate spline (TPS) warps was developed and applied to the image sets. After each registration step the mean registration errors were calculated and ΔADC was compared between good and poor responders.Adding the TPS warps significantly reduced the registration error (in mm, 6.3 ± 6.2 vs 3.2 ± 3.3 mm, p0.001). After the marker based registration the median ΔADC in poor responders was significantly lower than in good responders (7% vs. 21%; p0.001).This registration method allowed for a significant reduction of the mean registration error. Furthermore the voxel-wise calculation of the ΔADC early during radiotherapy allowed for a visualization of the regional differences of ΔADC within the tumor.

To determine the accuracy of the latest cone beam computed tomography (CBCT) machines in comparison to multi-slice computer tomography (MSCT) and micro computed tomography (micro-CT) for objectively assessing trabecular and cortical bone quality prior to implant placement.Eight edentulous human mandibular bone samples were scanned with seven CBCT scanners (3D Accuitomo 170, i-CAT Next Generation, ProMax 3D Max, Scanora 3D, Cranex 3D, Newtom GiANO and Carestream 9300) and one MSCT system (Somatom Definition Flash) using the clinical exposure protocol with the highest resolution. Micro-CT (SkyScan 1174) images served as a gold standard. A volume of interest (VOI) comprising trabecular and cortical bone only was delineated on the micro-CT. After spatial alignment of all scan types, micro-CT VOIs were overlaid on the CBCT and MSCT images. Segmentation was applied and morphometric parameters were calculated for each scanner. CBCT and MSCT morphometric parameters were compared with micro-CT using mixed-effect models. Intraclass correlation analysis was used to grade the accuracy of each scanner in assessing trabecular and cortical quality in comparison with the gold standard. Bone structure patterns of each scanner were compared with micro-CT in 2D and 3D to facilitate the interpretation of the morphometric analysis.Morphometric analysis showed an overestimation of the cortical and trabecular bone quantity during CBCT and MSCT evaluation compared to the gold standard micro-CT. The trabecular thickness (Tb.Th) was found to be significantly (P 0.05) different and the smallest overestimation was found for the ProMax 3D Max (180 µm), followed by the 3D Accuitomo 170 (200 µm), Carestream 9300 (220 µm), Newtom GiANO (240 µm), Cranex 3D (280 µm), Scanora 3D (300 µm), high resolution MSCT (310 µm), i-CAT Next Generation (430 µm) and standard resolution MSCT (510 µm). The underestimation of the cortical thickness (Ct.Th) in ProMax 3D Max (-10 µm), the overestimation in Newtom GiANO (10 µm) and the high resolution MSCT (10 µm) were neglible. However, a significant overestimation (P 0.05) was found for 3D Accuitomo 170 (110 µm), Scanora 3D (140 µm), standard resolution MSCT (150 µm), Carestream 9300 (190 µm), Cranex 3D (190 µm) and i-CAT Next Generation (230 µm). Comparison of the 2D network and 3D surface distance confirmed the overestimation in bone quantity, but only demonstrated a deviant trabecular network for the i-CAT Next Generation and the standard resolution MSCT. Intraclass correlation coefficients (ICCs) showed a significant (P 0.05) high intra-observer reliability (ICC 0.70) in morphometric evaluation between micro-CT and commercially available CBCT scanners (3D Accuitomo 170, Newtom GiANO and ProMax 3D Max). The ICC for Tb.Th and Ct.Th were 0.72 and 0.98 (3D Accuitomo 170), 0.71 and 0.96 (Newtom GiANO), and 0.87 and 0.92 (ProMax 3D Max), respectively.High resolution CBCT offers a clinical alternative to MSCT to objectively determine the bone quality prior to implant placement. However, not all tested CBCT machines have sufficient resolution to accurately depict the trabecular network or cortical bone. Conflict-of-interest statement: There is no conflict of interest to declare.Fellowship support came from Research Foundation Flanders (FWO) from the Belgian government, and Coordination for the Improvement of Higher Education Personnel (CAPES) program and Science without borders from the Brazilian government.

Strain rate imaging (SRI) is a new echocardiographic modality that enables accurate measurement of regional myocardial function. We investigated the role of SRI and troponin I (TnI) in the detection of subclinical radiation therapy (RT)-induced cardiotoxicity in breast cancer patients.This study prospectively included 75 women (51 left-sided and 24 right-sided) receiving adjuvant RT to the breast/chest wall and regional lymph nodes. Sequential echocardiographs with SRI were obtained before RT, immediately after RT, and 8 and 14 months after RT. TnI levels were measured on the first and last day of RT.Mean heart and left ventricle (LV) doses were both 9 ± 4 Gy for the left-sided patients and 4 ± 4 Gy and 1 ± 0.4 Gy, respectively, for the right-sided patients. A decrease in strain was observed at all post-RT time points for left-sided patients (-17.5% ± 1.9% immediately after RT, -16.6% ± 1.4% at 8 months, and -17.7% ± 1.9% at 14 months vs -19.4% ± 2.4% before RT, P.01) but not for right-sided patients. When we considered left-sided patients only, the highest mean dose was given to the anterior left ventricular (LV) wall (25 ± 14 Gy) and the lowest to the inferior LV wall (3 ± 3 Gy). Strain of the anterior wall was reduced after RT (-16.6% ± 2.3% immediately after RT, -16% ± 2.6% at 8 months, and -16.8% ± 3% at 14 months vs -19% ± 3.5% before RT, P.05), whereas strain of the inferior wall showed no significant change. No changes were observed with conventional echocardiography. Furthermore, mean TnI levels for the left-sided patients were significantly elevated after RT compared with before RT, whereas TnI levels of the right-sided patients remained unaffected.In contrast to conventional echocardiography, SRI detected a regional, subclinical decline in cardiac function up to 14 months after breast RT. It remains to be determined whether these changes are related to clinical outcome. In the meantime, we encourage the use of radiation techniques that minimize the exposure of the anterior LV wall in left-sided patients.

Purpose: To prospectively evaluate multiparametric magnetic resonance imaging (MRI) for accurate localization of intraprostatic tumor nodules, with whole-mount histopathology as the gold standard. Materials and Methods: Seventy-five patients with biopsy-proven, intermediate, and high-risk prostate cancer underwent preoperative T2-weighted (T2w), dynamic contrast-enhanced (DCE) and diffusion-weighted (DW) MRI at 1.5T. Localization of suspicious lesions was recorded for each of 24 standardized regions of interest on the different MR images and correlated with the pathologic findings. Generalized estimating equations (GEE) were used to estimate the sensitivity, specificity, accuracy, positive, and negative predictive value for every MRI modality, as well as to evaluate the influence of Gleason score and pT-stage. Tumor volume measurements on histopathological specimens were correlated with those on the different MR modalities (Pearson correlation). Results: DW MRI had the highest sensitivity for tumor localization (31.1% vs. 27.4% vs. 44.5% for T2w, DCE, and DW MRI, respectively; P < 0.005), with more aggressive or more advanced tumors being more easily detected with this imaging modality. Significantly higher sensitivity values were obtained for the combination of T2w, DCE, and DW MRI (58.8%) as compared to each modality alone or any combination of two modalities (P < 0.0001). Tumor volume can most accurately be assessed by means of DW MRI (r = 0.75; P < 0.0001). Conclusion: Combining T2w, DCE, and DW imaging significantly improves prostate cancer localization. J. Magn. Reson. Imaging 2013;37:1392–1401. © 2012 Wiley Periodicals, Inc.

Introduction Intrafractional motion consists of two components: (1) the movement between the on-line repositioning procedure and the treatment start and (2) the movement during the treatment delivery. The goal of this study is to estimate this intrafractional movement of the prostate during prostate cancer radiotherapy. Material and methods Twenty-seven patients with prostate cancer and implanted fiducials underwent a marker match procedure before a five-field IMRT treatment. For all fields, in-treatment images were obtained and then processed to enable automatic marker detection. Combining the subsequent projection images, five positions of each marker were determined using the shortest path approach. The residual set-up error (RSE) after kV–MV based prostate localization, the prostate position as a function of time during a radiotherapy session and the required margins to account for intrafractional motion were determined. Results The mean RSE and standard deviation in the antero–posterior, cranio–caudal and left–right direction were 2.3 ± 1.5 mm, 0.2 ± 1.1 mm and −0.1 ± 1.1 mm, respectively. Almost all motions occurred in the posterior direction before the first treatment beam as the percentage of excursions >5 mm was reduced significantly when the RSE was not accounted for. The required margins for intrafractional motion increased with prolongation of the treatment. Application of a repositioning protocol after every beam could decrease the 1 cm margin from CTV to PTV by 2 mm. Conclusions The RSE is the main contributor to intrafractional motion. This RSE after on-line prostate localization and patient repositioning in the posterior direction emphasizes the need to speed up the marker match procedure. Also, a prostate IMRT treatment should be administered as fast as possible, to ensure that the pre-treatment repositioning efforts are not erased by intrafractional prostate motion. This warrants an optimized workflow with the use of faster treatment techniques.

Purpose: A robust and accurate method that allows the automatic detection of fiducial markers in MV and kV projection image pairs is proposed. The method allows to automatically correct for inter or intrafraction motion. Methods: Intratreatment MV projection images are acquired during each of five treatment beams of prostate cancer patients with four implanted fiducial markers. The projection images are first preprocessed using a series of marker enhancing filters. 2D candidate marker locations are generated for each of the filtered projection images and 3D candidate marker locations are reconstructed by pairing candidates in subsequent projection images. The correct marker positions are retrieved in 3D by the minimization of a cost function that combines 2D image intensity and 3D geometric or shape information for the entire marker configuration simultaneously. This optimization problem is solved using dynamic programming such that the globally optimal configuration for all markers is always found. Translational interfraction and intrafraction prostate motion and the required patient repositioning is assessed from the position of the centroid of the detected markers in different MV image pairs. The method was validated on a phantom using CT as ground-truth and on clinical data sets of 16 patients using manual marker annotations as ground-truth. Results: The entire setup was confirmed to be accurate to around 1 mm by the phantom measurements. The reproducibility of the manual marker selection was less than 3.5 pixels in the MV images. In patient images, markers were correctly identified in at least 99% of the cases for anterior projection images and 96% of the cases for oblique projection images. The average marker detection accuracy was 1.4 ± 1.8 pixels in the projection images. The centroid of all four reconstructed marker positions in 3D was positioned within 2 mm of the ground-truth position in 99.73% of all cases. Detecting four markers in a pair of MV images takes a little less than a second where most time is spent on the image preprocessing. Conclusions: The authors have developed a method to automatically detect multiple markers in a pair of projection images that is robust, accurate, and sufficiently fast for clinical use. It can be used for kV, MV, or mixed image pairs and can cope with limited motion between the projection images.

Purpose: To investigate the feasibility of integrating multiple imaging modalities for image-guided radiotherapy in rectal cancer. Patients and Methods: Magnetic resonance imaging (MRI) and fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) were performed before, during, and after preoperative chemoradiotherapy (CRT) in patients with resectable rectal cancer. The FDG-PET signals were segmented with an adaptive threshold-based and a gradient-based method. Magnetic resonance tumor volumes (TVs) were manually delineated. A nonrigid registration algorithm was applied to register the images, and mismatch analyses were carried out between MR and FDG-PET TVs and between TVs over time. Tumor volumes delineated on the images after CRT were compared with the pathologic TV. Results: Forty-five FDG-PET/CT and 45 MR images were analyzed from 15 patients. The mean MRI and FDG-PET TVs showed a tendency to shrink during and after CRT. In general, MRI showed larger TVs than FDG-PET. There was an approximately 50% mismatch between the FDG-PET TV and the MRI TV at baseline and during CRT. Sixty-one percent of the FDG-PET TV and 76% of the MRI TV obtained after 10 fractions of CRT remained inside the corresponding baseline TV. On MRI, residual tumor was still suspected in all 6 patients with a pathologic complete response, whereas FDG-PET showed a metabolic complete response in 3 of them. The FDG-PET TVs delineated with the gradient-based method matched closest with pathologic findings. Conclusions: Integration of MRI and FDG-PET into radiotherapy seems feasible. Gradient-based segmentation is recommended for FDG-PET. Spatial variance between MRI and FDG-PET TVs should be taken into account for target definition. (C) 2009 Elsevier Inc.

Background and purpose: Currently, most available patient alignment tools based on implanted markers use manual marker matching and rigid registration transformations to measure the needed translational shifts. To quantify the particular effect of prostate gland shrinkage, implanted gold markers were tracked during a course of radiotherapy including an isotropic scaling factor to model prostate shrinkage. Materials and methods: Eight patients with prostate cancer had gold markers implanted transrectally and seven were treated with (neo) adjuvant androgen deprivation therapy. After patient alignment to skin tattoos, orthogonal electronic portal images (EPIs) were taken. A semi-automated 2D/3D marker-based registration was performed to calculate the necessary couch shifts. The registration consists of a rigid transformation combined with an isotropic scaling to model prostate shrinkage. Results: The inclusion of an isotropic shrinkage model in the registration algorithm cancelled the corresponding increase in registration error. The mean scaling factor was 0.89 ± 0.09. For all but two patients, a decrease of the isotropic scaling factor during treatment was observed. However, there was almost no difference in the translation offset between the manual matching of the EPIs to the digitally reconstructed radiographs and the semi-automated 2D/3D registration. A decrease in the intermarker distance was found correlating with prostate shrinkage rather than with random marker migration. Conclusions: Inclusion of shrinkage in the registration process reduces registration errors during a course of radiotherapy. Nevertheless, this did not lead to a clinically significant change in the proposed table translations when compared to translations obtained with manual marker matching without a scaling correction.

Speckle tracking echocardiography (STE) is now widely used for measuring strain, deformations, and motion in cardiology. STE involves three successive steps: acquisition of individual frames, speckle detection, and image registration using speckles as landmarks. This work proposes to avoid explicit detection and registration by representing dynamic ultrasound images as sparse collections of moving Gaussian elements in the continuous joint space-time space. Individual speckles or local clusters of speckles are approximated by a single multivariate Gaussian kernel with associated linear trajectory over a short time span. A hierarchical tree-structured model is fitted to sampled input data such that predicted image estimates can be retrieved by regression after reconstruction, allowing a (bias-variance) trade-off between model complexity and image resolution. The inverse image reconstruction problem is solved with an online Bayesian statistical estimation algorithm. Experiments on clinical data could estimate subtle sub-pixel accurate motion that is difficult to capture with frame-to-frame elastic image registration techniques. Schretter C., Sun J., Bundervoet S., Dooms A., Schelkens P., de Brito Carvalho C., Slagmolen P., D'hooge J., ''Continuous ultrasound speckle tracking with gaussian mixtures'', Proceedings 37th annual international conference of the IEEE Engineering in Medicine and Biology Society (EMBS) - EMBC 2015, 4 pp., August 25-29, 2015, Milan, Italy. ispartof: pages:129-132 ispartof: Proceedings EMBC 2015 vol:2015 pages:129-132 ispartof: Annual international conference of the IEEE Engineering in Medicine and Biology Society (EMBS) - EMBC 2015 location:Milan, Italy date:25 Aug - 29 Aug 2015 status: published

Little attention has been paid to the effect of implant restorations on speech.The aim of this study was threefold: (1) to find out if speech problems occur after inserting a fixed provisional restoration in the edentulous maxilla; (2) to explore speech adaptation in case articulation problems arise after rehabilitation; and (3) to describe the effect of changing the shape of the restoration on improving speech.Ten patients with an edentulous maxilla were treated with fixed rehabilitation on implants. Speech evaluation was performed at four occasions: before implant surgery, immediately after restoration, and 3 weeks later before and after managing the speech problem by changing the shape of the restoration if speech problems occurred. Comparative three-dimensional-analysis of casts of the restoration before and after changing the shape of the restoration was carried out.The majority of patients (n = 7) experienced speech problems immediately after rehabilitation. Three weeks later, none of the seven patients with deteriorated speech returned to baseline speech. Then, volumetric reduction of the palatal aspects of the (pre)molars was performed, which allowed speech to return to baseline levels in five out of seven patients. In the two remaining patients, the intervention resulted in an improvement of speech without reaching their baseline levels. Three-dimensional-analysis showed that reducing the palatal volume of the premolars was effective in correcting speech.Speech problems may frequently occur after fixed rehabilitation of the completely edentulous maxilla. A novel speech management concept, consisting of reducing the palatal volume of the (pre)molars, is introduced, demonstrating to solve speech problems in most cases.

Intensity modulated radiotherapy (IMRT) and volumetric modulated arc therapy have become standard treatments but are more sensitive to anatomical variations than 3D conformal techniques. To correct for inter- and intrafraction anatomical variations, fast and easy to implement methods are needed. Here, the authors propose a full dosimetric IMRT correction that finds a compromise in-between basic repositioning (the current clinical practice) and full replanning. It simplifies replanning by avoiding a recontouring step and a full dose calculation. It surpasses repositioning by updating the preoptimized fluence and monitor units (MU) using a limited number of fiducial points and a pretreatment (CB)CT. To adapt the fluence the fiducial points were projected in the beam's eye view (BEV). To adapt the MUs, point dose calculation towards the same fiducial points were performed. The proposed method is intrinsically fast and robust, and simple to understand for operators, because of the use of only four fiducial points and the beam data based point dose calculations.To perform our dosimetric adaptation, two fluence corrections in the BEV are combined with two MU correction steps along the beam's path. (1) A transformation of the fluence map such that it is realigned with the current target geometry. (2) A correction for an unintended scaling of the penumbra margin when the treatment beams scale to the current target size. (3) A correction for the target depth relative to the body contour and (4) a correction for the target distance to the source. The impact of the correction strategy and its individual components was evaluated by simulations on a virtual prostate phantom. This heterogeneous reference phantom was systematically subjected to population based prostate transformations to simulate interfraction variations. Additionally, a patient example illustrated the clinical practice. The correction strategy was evaluated using both dosimetric (CTV mean dose, conformity index) and clinical (tumor control probability, and normal tissue complication probability) measures.Based on the current experiments, the intended target dose and tumor control probability could be assured by the proposed method (TCP ≥ TCP(intended)). Additionally, the conformity index error was more than halved compared to the current clinical practice (ΔCI(95%) from 40% to 16%) resulting in improved organ at risk protection. All the individual correction steps had an added value to the full correction.A limited number of fiducial points (no organ contours required) and an in-room (CB)CT are sufficient to perform a full dosimetric correction for IMRT plans. In the presence of interfraction variation, the corrected plans show superior dose distributions compared to our current clinical practice.

Background Spirometric parameters are the mainstay for diagnosis of COPD, but cannot distinguish airway obstruction from emphysema. We aimed to develop a computer model that quantifies airway collapse on forced expiratory flow–volume loops. We then explored and validated the relationship of airway collapse with computed tomography (CT) diagnosed emphysema in two large independent cohorts. Methods A computer model was developed in 513 Caucasian individuals with ≥15 pack-years who performed spirometry, diffusion capacity and CT scans to quantify emphysema presence. The model computed the two best fitting regression lines on the expiratory phase of the flow-volume loop and calculated the angle between them. The collapse was expressed as an Angle of collapse (AC) which was then correlated with the presence of emphysema. Findings were validated in an independent group of 340 individuals. Results AC in emphysema subjects (N = 251) was significantly lower (131° ± 14°) compared to AC in subjects without emphysema (N = 223), (152° ± 10°) (p 2 = 0.505, p CO, %predicted and FEV1, %predicted to the total model (total R2 = 0.626, p Conclusions Airway collapse on forced expiration quantified by a computer model correlates with emphysema. An AC below 131° can be considered as a specific cut-off for predicting the presence of emphysema in heavy smokers.

A 24-year-old female patient presented with complaint of palatal swelling and a sinus tract facial to tooth #22. She reported an injury to the tooth 15 years earlier and no recollection of treatment, although there was evidence of an endodontic access into the crown. Radiographically the root appeared to have stopped developing, and it was associated with a large periapical lesion. After 3 unsuccessful attempts at apexification using calcium hydroxide (CH), further examination including use of cone-beam computed tomography (CBCT) was carried out. The latter allowed for better evaluating the situation and for better planning a more comprehensive treatment plan to include surgical removal of the apical lesion. The large radiolucent area extended from tooth #21 to #23. Using a dedicated software tool developed to be used in conjunction with CBCT, volumetric assessment of the lesion was carried out for healing follow up. The root end was filled from the apical direction with newly developed accelerated silicate cement 4–5 mm into the apical part of the canal. Subsequently, the rest of the canal was filled with the same type of cement. At the 1-year postsurgical follow up, the tooth remained asymptomatic, and using the CBCT volumetric program, bony healing could be demonstrated.

Introduction The routine use of high-resolution images derived from 3-dimensional cone-beam computed tomography (CBCT) datasets enables the linear measurement of lesions in the maxillary and mandibular bones on 3 planes of space. Measurements on different planes would make it possible to obtain real volumetric assessments. In this study, we tested, in vitro, the accuracy and reliability of new dedicated software developed for volumetric lesion assessment in clinical endodontics. Methods Twenty-seven bone defects were created around the apices of 8 teeth in 1 young bovine mandible to simulate periapical lesions of different sizes and shapes. The volume of each defect was determined by taking an impression of the defect using a silicone material. The samples were scanned using an Accuitomo 170 CBCT (J. Morita Mfg Co, Kyoto, Japan), and the data were uploaded into a newly developed dedicated software tool. Two endodontists acted as independent and calibrated observers. They analyzed each bone defect for volume. The difference between the direct volumetric measurements and the measurements obtained with the CBCT images was statistically assessed using a lack-of-fit test. A correlation study was undertaken using the Pearson product-moment correlation coefficient. Intra- and interobserver agreement was also evaluated. Results The results showed a good fit and strong correlation between both volume measurements (ρ > 0.9) with excellent inter- and intraobserver agreement. Conclusions Using this software, CBCT proved to be a reliable method in vitro for the estimation of endodontic lesion volumes in bovine jaws. Therefore, it may constitute a new, validated technique for the accurate evaluation and follow-up of apical periodontitis.

Ultrasound image has already been proved to be a useful tool for non-invasive strain quantifications in soft tissue. While clinical applications only include cardiac imaging, the development of techniques suitable for musculoskeletal system is an active area of research. On this study, a technique for speckle tracking on ultrasound images using non-rigid image registration is presented. This approach is based on a single 2D+t registration procedure, in which the temporal changes on the B-mode speckle patterns are locally assessed. This allows estimating strain from ultrasound image sequences of tissues under deformation while imposing temporal smoothness in the deformation field, originating smooth strain curves. METHODS: The tracking algorithm was systematically tested on synthetic images and gelatin phantoms, under sinusoidal deformations with amplitudes between 0.5% and 4.0%, at frequencies between 0.25Hz and 2.0Hz. Preliminary tests were also performed on Achilles tendons isolated from human cadavers. RESULTS: The strain was estimated with deviations of -0.011%±0.053% on the synthetic images and agreements of ±0.28% on the phantoms. Some tests with real tendons show good tracking results. However, significant variability between the trials still exists. CONCLUSIONS: The proposed image registration methodology constitutes a robust tool for motion and deformation tracking in both simulated and real phantom data. Strain estimation in both cases reveals that the proposed method is accurate and provides good precision. Although the ex-vivo results are still preliminary, the potential of the proposed algorithm is promising. This suggests that further improvements, together with systematic testing, can lead to in-vivo and clinical applications. Almeida N.C.M., Slagmolen P., Barbosa D., Scheys L., Geukens L., Fukagawa S., Peers K., Bellemans J., Suetens P., D'hooge J., ''Tendon strain imaging using non-rigid image registration: a validation study'', Ultrasonic imaging, tomography, and therapy conference, part of SPIE medical imaging, February 5-6, 2012, San Diego, California, USA. ispartof: pages:832010- ispartof: SPIE Medical Imaging 2012 vol:8320 pages:832010- ispartof: SPIE Medical Imaging - Ultrasonic imaging, tomography, and therapy location:San Diego, California, USA date:5 Feb - 6 Feb 2012 status: published

Purpose: To develop and validate an accurate predictive model and a nomogram for pathologic complete response (pCR) after chemoradiotherapy (CRT) for rectal cancer based on clinical and sequential PET-CT data. Accurate prediction could enable more individualised surgical approaches, including less extensive resection or even a wait-and-see policy. Methods and materials: Population based databases from 953 patients were collected from four different institutes and divided into three groups: clinical factors (training: 677 patients, validation: 85 patients), pre-CRT PET-CT (training: 114 patients, validation: 37 patients) and post-CRT PET-CT (training: 107 patients, validation: 55 patients). A pCR was defined as ypT0N0 reported by pathology after surgery. The data were analysed using a linear multivariate classification model (support vector machine), and the model's performance was evaluated using the area under the curve (AUC) of the receiver operating characteristic (ROC) curve. Results: The occurrence rate of pCR in the datasets was between 15% and 31%. The model based on clinical variables (AUC(train) = 0.61 +/- 0.03, AUC(validation) = 0.69 +/- 0.08) resulted in the following predictors: cT- and cN-stage and tumour length. Addition of pre-CRT PET data did not result in a significantly higher performance (AUC(train) = 0.68 +/- 0.08, AUC(validation) = 0.68 +/- 0.10) and revealed maximal radioactive isotope uptake (SUV(max)) and tumour location as extra predictors. The best model achieved was based on the addition of post-CRT PET-data (AUC(train) = 0.83 +/- 0.05, AUC(validation) = 0.86 +/- 0.05) and included the following predictors: tumour length, post-CRT SUV(max) and relative change of SUV(max). This model performed significantly better than the clinical model (p(train)

ispartof: pages:840-843 ispartof: World Congress on Medical Physics and Biomedical Engineering, September 7 - 12, 2009, Munich, Germany vol:25 issue:1 pages:840-843 ispartof: World Congress on Medical Physics and Biomedical Engineering location:Muich, Germany date:7 Sep - 12 Sep 2009 status: published

The goal of radiotherapy is to deliver maximal dose to the tumor and minimal dose to the surrounding tissue. This requires accurate target definition. In sites were the tumor is difficult to see on the CT images, such as for rectal cancer, PET-CT imaging can be used to better define the target. If the information from multiple PETCT images with different tracers needs to be combined, a nonrigid registration is indispensable to compensate for rectal tissue deformations. Such registration is complicated by the presence of different volumes of bowel gas in the images to be registered. In this paper, we evaluate the performance of different nonrigid registration approaches by looking at the overlap of manually delineated rectum contours after registration. Using a B-spline transformation model, the results for two similarity measures, sum of squared differences and mutual information, either calculated over the entire image or on a region of interest are compared. Finally, we also assess the effect of the registration direction. We show that the combination of MI with a region of interest is best able to cope with residual rectal contrast and differences in bowel filling. We also show that for optimal performance the registration direction should be chosen depending on the difference in bowel filling in the images to be registered.

This paper presents a comparison study between 10 automatic and six interactive methods for liver segmentation from contrast-enhanced CT images. It is based on results from the "MICCAI 2007 Grand Challenge" workshop, where 16 teams evaluated their algorithms on a common database. A collection of 20 clinical images with reference segmentations was provided to train and tune algorithms in advance. Participants were also allowed to use additional proprietary training data for that purpose. All teams then had to apply their methods to 10 test datasets and submit the obtained results. Employed algorithms include statistical shape models, atlas registration, level-sets, graph-cuts and rule-based systems. All results were compared to reference segmentations five error measures that highlight different aspects of segmentation accuracy. All measures were combined according to a specific scoring system relating the obtained values to human expert variability. In general, interactive methods reached higher average scores than automatic approaches and featured a better consistency of segmentation quality. However, the best automatic methods (mainly based on statistical shape models with some additional free deformation) could compete well on the majority of test images. The study provides an insight in performance of different segmentation approaches under real-world conditions and highlights achievements and limitations of current image analysis techniques.

Purpose. The purpose of this study is to investigate the use of PET/CT with fluorodeoxyglucose (FDG), fluorothymidine (FLT) and fluoromisonidazole (FMISO) for radiotherapy (RT) target definition and evolution in rectal cancer. Materials and methods. PET/CT was performed before and during preoperative chemoradiotherapy (CRT) in 15 patients with resectable rectal cancer. PET signals were delineated and CT images on the different time points were non-rigidly registered. Mismatch analyses were carried out to quantify the overlap between FDG and FLT or FMISO tumour volumes (TV) and between PET TVs over time. Results. Ninety sequential PET/CT images were analyzed. The mean FDG, FLT and FMISO-PET TVs showed a tendency to shrink during preoperative CRT. On each time point, the mean FDG-PET TV was significantly larger than the FMISO-PET TV but not significantly larger than the mean FLT-PET TV. There was a mean 65% mismatch between the FMISO and FDG TVs obtained before and during CRT. FLT TVs corresponded better with the FDG TVs (25% mismatch before and 56% during CRT). During CRT, on average 61% of the mean FDG TV (7 cc) overlapped with the baseline mean TV (15.5 cc) (n=15). For FLT, the TV overlap was 49% (n=5) and for FMISO only 20% of the TV during CRT remained inside the contour at baseline (n=10). Conclusion. FDG, FLT and FMISO-PET reflect different functional characteristics that change during CRT in rectal cancer. FLT and FDG show good spatial correspondence, while FMISO seems less reliable due to the non-specific FMISO uptake in normoxic tissue and tracer diffusion through the bowel wall. FDG and FLT-PET/CT imaging seem most appropriate to integrate in preoperative RT for rectal cancer.

External beam radiotherapy treats cancer lesions with ionizing radiation. Successful treatment requires a correct definition of the target volume. This is achieved using pre-treatment MR and CT images. However, due to changes in patient position, tumor size and organ location, adaptation of the treatment plan over the different treatment sessions might be wanted. This can be achieved with extra MR and CT images obtained during treatment. Bringing all images into a common reference frame, the initial segmentations can be propagated over time and the integrated dose can be correctly calculated. In this article, we show in two patients with rectum cancer and one with neck cancer that a significant change in tumor position and shape occurs. Our results show that nonrigid registration can correctly detect these shape and position changes in MR images. Validation was performed using manual delineations. For delineations of the mandible, parotid and submandibular gland in the head-and-neck patient, the maximal centroid error decreases from 6 mm to 2 mm, while the minimal Dice similarity criterium (DSC) overlap measure increases from 0.70 to 0.84. In the rectal cancer patients, the maximal centroid error drops from 15 mm to 5 mm, while the minimal DSC rises from 0.22 to 0.57. Similar experiments were performed on CT images. The validation here was infeasible due to significant inaccuracies in the manual delineations.

Purpose: Intensity modulated radiotherapy (IMRT) and volumetric modulated arc therapy have become standard treatments but are more sensitive to anatomical variations than 3D conformal techniques. To correct for inter- and intrafraction anatomical variations, fast and easy to implement methods are needed. Here, the authors propose a full dosimetric IMRT correction that finds a compromise in-between basic repositioning (the current clinical practice) and full replanning. It simplifies replanning by avoiding a recontouring step and a full dose calculation. It surpasses repositioning by updating the preoptimized fluence and monitor units (MU) using a limited number of fiducial points and a pretreatment (CB)CT. To adapt the fluence the fiducial points were projected in the beam's eye view (BEV). To adapt the MUs, point dose calculation towards the same fiducial points were performed. The proposed method is intrinsically fast and robust, and simple to understand for operators, because of the use of only four fiducial points and the beam data based point dose calculations. Methods: To perform our dosimetric adaptation, two fluence corrections in the BEV are combined with two MU correction steps along the beam's path. (1) A transformation of the fluence map such that it is realigned with the current target geometry.more » (2) A correction for an unintended scaling of the penumbra margin when the treatment beams scale to the current target size. (3) A correction for the target depth relative to the body contour and (4) a correction for the target distance to the source. The impact of the correction strategy and its individual components was evaluated by simulations on a virtual prostate phantom. This heterogeneous reference phantom was systematically subjected to population based prostate transformations to simulate interfraction variations. Additionally, a patient example illustrated the clinical practice. The correction strategy was evaluated using both dosimetric (CTV mean dose, conformity index) and clinical (tumor control probability, and normal tissue complication probability) measures. Results: Based on the current experiments, the intended target dose and tumor control probability could be assured by the proposed method (TCP ≥ TCP{sub intended}). Additionally, the conformity index error was more than halved compared to the current clinical practice (ΔCI{sub 95%} from 40% to 16%) resulting in improved organ at risk protection. All the individual correction steps had an added value to the full correction. Conclusions: A limited number of fiducial points (no organ contours required) and an in-room (CB)CT are sufficient to perform a full dosimetric correction for IMRT plans. In the presence of interfraction variation, the corrected plans show superior dose distributions compared to our current clinical practice.« less

Purpose: To use the new EBT3 Gafchromic films for large modulated field dosimetry, a lateral scan correction needs to be performed. We propose a lateral correction built in in the calibration curve. The feasibility of this calibration methodology is evaluated. Methods: The relative scan value (Transmittance, T) is associated with the dose using a rational function with three parameters: T0 the unirradiated transmittance, Tmax the maximal transmittance, and b3 a parameter scaling the impact of the dose. Because, the lateral scan effect is inherent to the scanner transmission system, a parabolic correction is implemented in the calibration function itself, instead of a post calibration correction. To assess a sufficient sampling of both the dose and the lateral dependency in the calibration procedure, eight dose levels are irradiated to two lateral locations on two uncut calibration films (one location per film). The resulting calibration function is validated by delivering known uniform doses on eight strips a single film. The central pixel line of each validation strip is converted to dose for the three (RGB) color channels. To show lateral independence of the measured dose, the central pixel line is divided in five 2 inch ROIs, subsequently, the root mean square error (RMSE) of these ROIs is calculated. Results: The dose errors (1SD) are 2%, 2.2%, and 2% for the red, green, and blue color channel respectively. The red channel dose, without lateral correction, has a maximal RMSE >2.5%, for the outer ROI. The proposed methodology results in a maximal RMSE < 0.5% for all ROIs and all three color channels in a [0.57,4.16]Gy dose range. Conclusions: The scanner‐transmission system with the new EBT3 gafchromic films is calibrated with a calibration protocol incorporating the lateral scan effect. This method reduces the RMSE from 2.5% to 0.5%. Research was supported Ashland Specialty Ingredients Wayne, New Jersey 07470, and PEO Radiation Technology bvba, 2320 Hoogstraten, Belgium. The authors acknowledge David Lewis and Andre Micke for their fruitful discussions.

Purpose: To estimate intrafracional motion of the prostate in a routine clinical setting and its impact on margin reduction and treatment time. Method and Materials: External beam treatment for cancer of the prostate using an IMRT technique was evaluated. Fifteen patients underwent a marker match procedure ensuring correct positioning at time of treatment. For all fields intra‐treatment images were obtained, yielding 5 to 7 images per fraction. IMRT was delivered using a dynamic sliding window technique. The obtained images were processed to remove IMRT information. The markers were detected in the image using an automated methodology. Every image was timestamped and chronologically adjacent images were backprojected to yield 3D marker coordinates. Allowing to calculate the position of the prostate during the treatment delivery at specific time instances. Using a Poisson model for the probability of movement we can determine the maximal allowable time frame within which to perform this treament. Results: The maximal treament time measured was 1460s, the shortest lasted 343s. The times were measured starting from the last image in the marker‐match procedure and includes the decision and adjustment process. Depending on the elapsed time we noticed an increase in positional confidence level from 5.8mm to 7.6mm. The delivery of the fields are of the order of 250s. Conclusion: We note a significant increase in probability of prostate movement in our treaments as time elapses. This limits the amount of margin reduction possible. There are two strategies possible to reduce this time. 1) Increase the marker match speed, or 2) increase the delivery speed. A good candidate to do this is the use of a volumetric Arc technique (VMAT) which is implemented in our department with RapidArc™. The latter is able to deliver the same or even better dose distribution in under 2 minutes (8 patients).

Purpose: We wish to achieve maximum registration performance in the region around the tumor for patients with rectal cancer to assess the changes in PET signal due to radiotherapy.Method and Materials: A nonrigid registration was performed on nine PET‐CT images of three patients with rectal cancer. We use a B‐spline transformation model with mutual information as similarity criterion. The registration is performed in a multiresolution framework. To exclude the influence of differences in bladder filling, registration was limited to the mesorectum, delineated at planning time, by only calculating the similarity criterion for the control points inside the mesorectum. In the last multiresolution stages of the registration, a small, local volume constraint was used to regularize the deformation field inside the tumor region. Validation was performed by comparing volume overlap (Dice Similarity Coefficient or DSC), centroid distance and volume change of the manually delineated rectum contour for all slices where tumor was actually seen on the FDG‐PET. Results: When using the region of interest, volume overlap increases while centroid distance decreases for all registrations. The mean DSC when using the entire image for registrations was 0.68 compared to 0.79 when only registering inside the mesorectum. The mean centroid distance decreased from 4.40mm to 3.30mm. The mean volume difference decreased from 28.11% to 14.09%. Conclusion: Results show that by limiting the registration to the mesorectum, a much higher volume overlap for the rectum can be seen. Also, by regularizing the deformation field around the tumor in the last stages of the registration, a slight increase in rectum correspondence is found. The results of these registrations can be used to evaluate the PET signal around the tumor over time.

Maximization of mutual information (MMI) is a popular similarity measure for medical image registration. Although its accuracy and robustness has been demonstrated for rigid body image registration, extending MMI to nonrigid image registration is not trivial and an active field of research. We propose conditional mutual information (cMI) as a new similarity measure for nonrigid image registration. cMI starts from a 3-D joint histogram incorporating, besides the intensity dimensions, also a spatial dimension expressing the location of the joint intensity pair. cMI is calculated as the expected value of the cMI between the image intensities given the spatial distribution. The cMI measure was incorporated in a tensor-product B-spline nonrigid registration method, using either a Parzen window or generalized partial volume kernel for histogram construction. cMI was compared to the classical global mutual information (gMI) approach in theoretical, phantom, and clinical settings. We show that cMI significantly outperforms gMI for all applications.