Acquired CT Images Research Articles

Effect of replanning boost radiotherapy plan in locally advanced unresectable middle to lower thoracic esophageal cancer

Thoracic bulky esophageal cancer shrinks during radiotherapy, changing the location and shape of the surrounding heart and lungs. The current study aimed to explore how replanning by volumetric-modulated arc radiotherapy (VMAT) and three-dimensional conformal radiotherapy (3DCRT) influences the target coverage and dose to organs at risk in locally advanced unresectable middle to lower thoracic esophageal cancer. We retrospectively collected CT simulation images of initial and boost radiotherapy plans for locally advanced unresectable thoracic esophageal cancer in 17 consecutive patients. First, we created boost plans of 20 Gy using 3DCRT and VMAT on the initially acquired CT images. Second, we replicated the process on CT images acquired after 20–40 Gy of radiotherapy. We then compared non-replanned boost radiotherapy plans with replanned boost plans. Replanned radiotherapy delivered more conformal doses to the target and reduced heart and lung doses. VMAT reduced more irradiated mean doses to the heart than 3DCRT in the case of replanning (1.7 and 1.1 Gy, p < 0.001). Replanning to accommodate tumor shrinkage during radiotherapy effectively lowers the irradiated doses to the heart and lungs in patients with locally advanced unresectable middle to lower thoracic esophageal cancer, especially those treated with VMAT.

The impact of muscle mass and myosteatosis on mortality in critically ill patients with Sars-Cov2-related pneumonia

Sars-Cov-2 pneumonia can lead to severe complications, requiring invasive mechanical ventilation and admission to the intensive care unit (ICU). Low muscle quantity and quality (the latter evaluated by the amount of ectopic fat infiltration in the muscle [myosteatosis]) at ICU admission are associated with worse outcomes in critically ill patients. The purpose of the present study is to assess muscle mass and myosteatosis of paravertebral skeletal muscle, in critically ill patients with Sars-Cov2 pneumonia and its association with mortality. We conducted a retrospective observational study in 110 critically ill patients with severe Sars-Cov-2 pneumonia that had a high - resolution chest Computerized Tomography (HR-CT) at ICU admission. We acquired CT images at the level of the thoracic 12 (T12) vertebral body and measured skeletal muscle area (SMA), intermuscular adipose tissue (IMAT), and low attenuation muscle area (LAMA). Patients were followed until ICU mortality or discharge. Patients were 59.8±8.1 years old, 77% were male. Seventy-nine percent of patients were considered at nutritional risk, and 22% were obese. Average Acute Physiology and Chronic Health Evaluation II (APACHE II) score was 17±5.4, and the overall ICU mortality was 48,2% (53/110). At ICU admission, both parameters of myosteatosis were associated with higher mortality (IMAT [per 10% increase] HR: 2.01 (95% Confidence Interval [CI] 1.27 to 3.17), P=0.003; LAMA HR [per 10% increase]: 1.53 (95% CI 1.10 to 2.13), P=0.012). Myosteatosis as assessed by CT scans plays a relevant role as a prognostic marker in critically ill patients with Sars-Cov2 severe pneumonia.

Self-adaption and texture generation: A hybrid loss function for low-dose CT denoising.

Deep learning has been successfully applied to low-dose CT (LDCT) denoising. But the training of the model is very dependent on an appropriate loss function. Existing denoising models often use per-pixel loss, including mean abs error (MAE) and mean square error (MSE). This ignores the difference in denoising difficulty between different regions of the CT images and leads to the loss of large texture information in the generated image. In this paper, we propose a new hybrid loss function that adapts to the noise in different regions of CT images to balance the denoising difficulty and preserve texture details, thus acquiring CT images with high-quality diagnostic value using LDCT images, providing strong support for condition diagnosis. We propose a hybrid loss function consisting of weighted patch loss (WPLoss) and high-frequency information loss (HFLoss). To enhance the model's denoising ability of the local areas which are difficult to denoise, we improve the MAE to obtain WPLoss. After the generated image and the target image are divided into several patches, the loss weight of each patch is adaptively and dynamically adjusted according to its loss ratio. In addition, considering that texture details are contained in the high-frequency information of the image, we use HFLoss to calculate the difference between CT images in the high-frequency information part. Our hybrid loss function improves the denoising performance of several models in the experiment, and obtains a higher peak signal-to-noise ratio (PSNR) and structural similarity index (SSIM). Moreover, through visual inspection of the generated results of the comparison experiment, the proposed hybrid function can effectively suppress noise and retain image details. We propose a hybrid loss function for LDCT image denoising, which has good interpretation properties and can improve the denoising performance of existing models. And the validation results of multiple models using different datasets show that it has good generalization ability. By using this loss function, high-quality CT images with low radiation are achieved, which can avoid the hazards caused by radiation and ensure the disease diagnosis for patients.

Enhancing the target visibility with synthetic target specific digitally reconstructed radiograph for intrafraction motion monitoring: A proof-of-concept study.

Intrafraction motion monitoring in External Beam Radiation Therapy (EBRT) is usually accomplished by establishing a correlation between the tumor and the surrogates such as an external infrared reflector, implanted fiducial markers, or patient skin surface. These techniques either have unstable surrogate-tumor correlation or are invasive. Markerless real-time onboard imaging is a noninvasive alternative that directly images the target motion. However, the low target visibility due to overlapping tissues along the X-ray projection path makes tumor tracking challenging. To enhance the target visibility in projection images, a patient-specific model was trained to synthesize the Target Specific Digitally Reconstructed Radiograph (TS-DRR). Patient-specific models were built using a conditional Generative Adversarial Network (cGAN) to map the onboard projection images to TS-DRR. The standard Pix2Pix network was adopted as our cGAN model. We synthesized the TS-DRR based on the onboard projection images using phantom and patient studies for spine tumors and lung tumors. Using previously acquired CT images, we generated DRR and its corresponding TS-DRR to train the network. For data augmentation, random translations were applied to the CT volume when generating the training images. For the spine, separate models were trained for an anthropomorphic phantom and a patient treated with paraspinal stereotactic body radiation therapy (SBRT). For lung, separate models were trained for a phantom with a spherical tumor insert and a patient treated with free-breathing SBRT. The models were tested using Intrafraction Review Images (IMR) for the spine and CBCT projection images for the lung. The performance of the models was validated using phantom studies with known couch shifts for the spine and known tumor deformation for the lung. Both the patient and phantom studies showed that the proposed method can effectively enhance the target visibility of the projection images by mapping them into synthetic TS-DRR (sTS-DRR). For the spine phantom with known shifts of 1 mm, 2 mm, 3 mm, and 4 mm, the absolute mean errors for tumor tracking were 0.11 ± 0.05 mm in the x direction and 0.25 ± 0.08 mm in the y direction. For the lung phantom with known tumor motion of 1.8 mm, 5.8 mm, and 9 mm superiorly, the absolute mean errors for the registration between the sTS-DRR and ground truth are 0.1 ± 0.3 mm in both the x and y directions. Compared to the projection images, the sTS-DRR has increased the image correlation with the ground truth by around 83% and increased the structural similarity index measure with the ground truth by around 75% for the lung phantom. The sTS-DRR can greatly enhance the target visibility in the onboard projection images for both the spine and lung tumors. The proposed method could be used to improve the markerless tumor tracking accuracy for EBRT.

On the effect of training database size for MR-based synthetic CT generation in the head.

To investigate the performance of unsupervised training using a large number of unpaired data sets as well as the potential gain in performance after fine-tuning with supervised training using spatially registered data sets in generation of synthetic computed tomography (sCT) from magnetic resonance (MR) images. A cycleGAN method consisting of two generators (residual U-Net) and two discriminators (patchGAN) was used for unsupervised training. Unsupervised training utilized unpaired T1-weighted MR and CT images (2061 sets for each modality). Five supervised models were then fine-tuned starting with the generator of the unsupervised model for 1, 10, 25, 50, and 100 pairs of spatially registered MR and CT images. Four supervised training models were also trained from scratch for 10, 25, 50, and 100 pairs of spatially registered MR and CT images using only the residual U-Net generator. All models were evaluated on a holdout test set of spatially registered images from 253 patients, including 30 with significant pathology. sCT images were compared against the acquired CT images using mean absolute error (MAE), Dice coefficient, and structural similarity index (SSIM). sCT images from 60 test subjects generated by the unsupervised, and most accurate of the fine-tuned and supervised models were qualitatively evaluated by a radiologist. While unsupervised training produced realistic-appearing sCT images, addition of even one set of registered images improved quantitative metrics. Addition of more paired data sets to the training further improved image quality, with the best results obtained using the highest number of paired data sets (n=100). Supervised training was found to be superior to unsupervised training, while fine-tuned training showed no clear benefit over supervised learning, regardless of the training sample size. Supervised learning (using either fine tuning or full supervision) leads to significantly higher quantitative accuracy in the generation of sCT from MR images. However, fine-tuned training using both a large number of unpaired image sets was generally no better than supervised learning using registered image sets alone, suggesting the importance of well registered paired data set for training compared to a large set of unpaired data.

AB-453070-1 NOVEL INSIGHTS OF GANGLIONATED PLEXI ABLATION FOR ATRIAL FIBRILLATION: FINDINGS FROM RECURRENCE CASES

Epicardial adipose tissue (EAT) containing ganglionated plexi (GP) plays an important role in the presence of atrial fibrillation (AF), but the effect of GP ablation remains controversial. This study aimed to investigate whether the effect of GP ablation on eliminated vagal response and EAT volume persisted after ablation. In 17 patients (70.7± 6.5years, 11 males, 13 persistent AF) who had AF recurrence after 1st pulmonary vein isolation (PVI) and GP ablation, high-frequency stimulation (HFS) at 5 major left atrial (LA)-GP sites (i.e., superior left, inferior left, anterior right, inferior right, and Marshall tract GP) was again performed to detect a vagal response at the 2nd session. The 320-row multidetector CT was performed within 2 weeks before each ablation. The acquired CT images were transferred to a workstation. EAT was defined as -50 to -200 Hounsfield units. The CT-derived EAT volume (around the whole heart and LA) at the 1st session was compared to that at the 2nd session. Despite the elimination of vagal response in all 5 LA-GP sites by GP ablation at the 1st ablation, the percentage of patients in whom a vagal response was elicited was significantly increased in IRGP at 2nd session compared to at 1st session (IRGP; 1st, 42% [7/17] vs. 2nd, 76% [13/17], P=0.009), and there was no significant difference in the other GP sites between initial ablation and the 2nd session (Marshal tract GP; 53% [9/17] vs. 47% [8/17], P=0.79, SLGP; 65% [11/17] vs. 41% [7/17], P=0.16, ILGP; 24% [4/17] vs. 53% [9/17], P=0.06, ARGP; 82% [14/17] vs. 65% [11/17], P=0.27). There was no significant difference in the maximum R-R intervals recorded during HFS between 1st ablation and the 2nd session in all GP sites (Marshal tract GP; 1296 [792-1806] vs. 1020 [772-1294] ms, P=0.12, SLGP; 1064 [760-1560] vs. 1244 [738-1444] ms, P=0.47, ILGP; 1000 [930-1472] vs. 1124 [748-1412] ms, P=0.92, ARGP; 1872 [1128-2880] vs. 1284 [960-1886] ms, P=0.24, IRGP; 1064 [808-1424] vs. 1280 [886-1736] ms, P=0.34). EAT volume increased significantly from the 1st ablation to the 2nd session (whole EAT: 143±78 ml vs. 165±94 ml; P=0.029, LA-EAT: 38± 21 ml vs. 46±28 ml; P=0.007). The elimination of vagal response by GP ablation did not persist and EAT volume increased in AF recurrence cases, suggesting that the effect of GP ablation is transient and GP ablation does not have any favorable effect on EAT in those cases.

Dosimetric Influence of Normalization Points on Post Mastectomy Chest Wall Teletherapy

Background: Many advanced radiotherapy techniques had been employed in breast cancer teletherapy, purposely to significantly reduce dose to organs at risk (heart and lungs) with marginal or no compromise in planning target volume (PTV). Majority of used techniques yielded rewarding results in developed countries where facilities, manpower and skills are available. In Nigeria, significant number of post mastectomy breast cancer patients received chest wall irradiation using manual hand planning, therefore, the dose distributions to target volume and organs at risk (OAR) were uncertain. Sokoto centre being the first in the country to use treatment planning system (TPS) focused on identifying planning skills (normalization points) with good 95% dose coverage to PTV, and minimizing dose to OAR. Methods: Eighteen post mastectomy patients (ten rights and eight lefts chest walls) were simulated via computed tomography scan (CT-scan) in supine position with breast board and fudicial markers to demarcate tumour bed borders. Planning target volume (PTV chest walls) and OAR were contoured from the acquired CT images and bi-tangential portals were applied. The energy used from Elekta précised Linac was 6 MV, and dose of 50Gy in 25# was prescribed to each patient. The Upper 1/3rd normalization point (UNP), Lower 1/3rd (LNP) and Inter-field (INP) were sequentially applied as dose normalization points on each planning CT image, dose to PTV and OAR were evaluated using Clarkson and pencil beam calculation algorithms. Statistical analysis was conducted using SPSS Software to study dose distributions of the normalization points. Results: Patients simulated were between the ages of 29-56yrs with mean age of 42yrs. The mean percentage doses from normalization points on left chest walls ranged between 81.7-107.7% to PTV, 13.3-17.8% to the lung and 5.5-6.8% to the heart, the reported hot spots were between 110.7 to 141.5%. Similarly, the mean doses from normalization points on the right chest walls ranged between 81.5-108.8% for PTV, 17.8-23.5% to the lung and 2.7-3.7% to the heart, with hot spots of 108.8-137.9%. The statistical differences using independent-t- test for the normalization points on both left and right chest walls shows p-value &lt; 5%. Conclusion: The three normalization points influenced dose distribution to PTV and OAR differently. The UNP and LNP showed a desired dosimetry with marginal compromise in 95% PTV coverage compared to INP.

Retrospective Study on the Prevalence of Gastro-esophageal Reflux in Brachycephalic and Non-Brachycephalic Dogs Anesthetized for CT Examination

Gastro-esophageal reflux is the return of gastric contents in the esophagus, phenomenon that can be identified in dogs under general anesthesia, but also in dogs without anesthesia, due to disorders of the distal esophageal sphincter. The aim of the present study was the comparative assessment of the incidence of gastro-esophageal reflux in brachycephalic and non-brachycephalic dogs. The medical records were evaluated for 98 dogs, presented with different pathologies of the spine. The animals were subjected to a standardized anesthetic protocol and CT scan. Following the analysis of the acquired CT images, it was found that gastro-esophageal reflux was present in 31 brachycephalic dogs (31/46; 67.39%) and in 9 non-brachycephalic dogs (9/52; 17.31%), respectively. There was an increased predisposition of the brachycephalic breeds regarding the occurrence of gastro-esophageal reflux, using identical anesthesia and positioning protocols.

Scanner-specific validation of a CT simulator using a COPD-emulated anthropomorphic phantom.

Traditional methods of quantitative analysis of CT images typically involve working with patient data, which is often expensive and limited in terms of ground truth. To counter these restrictions, quantitative assessments can instead be made through Virtual Imaging Trials (VITs) which simulate the CT imaging process. This study sought to validate DukeSim (a scanner-specific CT simulator) utilizing clinically relevant biomarkers for a customized anthropomorphic chest phantom. The physical phantom was imaged utilizing two commercial CT scanners (Siemens Somatom Force and Definition Flash) with varying imaging parameters. A computational version of the phantom was simulated utilizing DukeSim for each corresponding real acquisition. Biomarkers were computed and compared between the real and virtually acquired CT images to assess the validity of DukeSim. The simulated images closely matched the real images both qualitatively and quantitatively, with the average biomarker percent difference of 3.84% (range 0.19% to 18.27%). Results showed that DukeSim is reasonably well validated across various patient imaging conditions and scanners, which indicates the utility of DukeSim for further VIT studies where real patient data may not be feasible.

An analysis of the meso-structural damage evolution of coal using X-ray CT and a gray-scale level co-occurrence matrix method

To study the meso-damage evolution in coal under loading conditions, the industrial CT scanning tests under the uniaxial compression condition were carried out using an industrial CT scanner equipped with a loading control system. The gray level co-occurrence matrix (GLCM) theory was applied to quantitatively analyze the meso-damage evolution and the fracturing characteristics using the acquired CT images at each scanning stage. Four statistical features (i.e., contrast, energy, correlation, and homogeneity) of the CT images were extracted to evaluate the internal damage evolution in coal. The results show that the contrast generally took a changing trend of first decreasing and then increasing with the closure, initiation, and expansion of the fractures, that is, it decreased slowly at the compaction stage, slightly increased at the elasticity stage, and drastically increased at the post-peak stage. On the contrary, the energy, correlation, and homogeneity showed a changing trend opposite to that of the contrast. The changing tendency of mean values of the four statistical features could be depicted by the Boltzmann function, and in addition, the statistical features followed Gaussian distribution during the complete stress-strain process. The maximum damage cross-section of the coal sample could be transferred with the increase of deformation in the coal sample, indicating that the final failure location may not be the maximum initial damage location. The fracture ratio measured by the binarization and K-Means clustering algorithm methods typical showed three changing stages (i.e., a slow reduction process, a slight increase process, and a dramatic increase process) and could be used to reflect the meso-damage development process in coal at different deformation stages.

Please Place Your Seat in the Full Upright Position: A Technical Framework for Landing Upright Radiation Therapy in the 21st Century.

Delivering radiotherapy to patients in an upright position can allow for increased patient comfort, reduction in normal tissue irradiation, or reduction of machine size and complexity. This paper gives an overview of the requirements for the delivery of contemporary arc and modulated radiation therapy to upright patients. We explore i) patient positioning and immobilization, ii) simulation imaging, iii) treatment planning and iv) online setup and image guidance. Treatment chairs have been designed to reproducibly position seated patients for treatment and can be augmented by several existing immobilisation systems or promising emerging technologies such as soft robotics. There are few solutions for acquiring CT images for upright patients, however, cone beam computed tomography (CBCT) scans of upright patients can be produced using the imaging capabilities of standard Linacs combined with an additional patient rotation device. While these images will require corrections to make them appropriate for treatment planning, several methods indicate the viability of this approach. Treatment planning is largely unchanged apart from translating gantry rotation to patient rotation, allowing for a fixed beam with a patient rotating relative to it. Rotation can be provided by a turntable during treatment delivery. Imaging the patient with the same machinery as used in treatment could be advantageous for online plan adaption. While the current focus is using clinical linacs in existing facilities, developments in this area could also extend to lower-cost and mobile linacs and heavy ion therapy.

A moving liver phantom in an anthropomorphic thorax for SPECT MP imaging

Cranio-caudal respiratory motion and liver activity cause a variety of complex myocardial perfusion (MP) artifacts, especially in the inferior myocardial wall, that may also mask cardiac defects. To assess and characterise such artifacts, an anthropomorphic thorax with moving thoracic phantoms can be utilised in SPECT MP imaging. In this study, a liver phantom was developed and anatomically added into an anthropomorphic phantom that also encloses an ECG beating cardiac phantom and breathing lungs’ phantom. A cranio-caudal respiratory motion was also developed for the liver phantom and it was synchronised with the corresponding ones of the other thoracic phantoms. This continuous motion was further divided into isochronous dynamic respiratory phases, from end-exhalation to end-inspiration, to perform SPECT acquisitions in different respiratory phases. The new motions’ parameters and settings were measured by mechanical means and also validated in a clinical environment by acquiring CT images and by using two imaging software packages. To demonstrate the new imaging capabilities of the phantom assembly, SPECT/CT MP acquisitions were performed and compared to previous phantom and patients studies. All thoracic phantoms can precisely perform physiological motions within the anthropomorphic thorax. The new capabilities of the phantom assembly allow to perform SPECT/CT MP acquisitions for different cardiac-liver activity ratios and cardiac-liver proximities in supine and, for first time, in prone position. Thus, MP artifacts can be characterised and motion correction can be performed due to these new capabilities. The impact of artifacts and motion correction on defect detection can be also investigated.

Variability of redundant scan coverages along the Z-axis and dose implications for common computed tomography examinations

BackgroundScan length optimization is a method of optimization which ensures that, imaging is performed to cover just the area of interest without unnecessarily exposing structures that would not add value to answer a given clinical question. PurposeThis study assessed the variability and degree of redundant scan coverages along the z-axis of CT examinations of common indications and the associated radiation dose implications in CT facilities in Ghana for optimization measures to be recommended. MethodsOn reconstructed acquired CT images, the study measured extra distances covered above and below anatomical targets for common indications with calibrated calipers across 25 CT facilities. The National Cancer Institute Dosimetry System for CT (NCICT) (Monte Carlo-based-software) was used to simulate the scanning situations and organ dose implications for scans with and without the inclusion of the redundant scan areas. ResultsA total of 1,640 patients’ CT data sets were used in this study. The results demonstrated that CT imaging utilized varying scan lengths (16.45±21.0–45.99±4.3 cm), and 70.6% of the scans exceeded their pre-defined anatomic boundaries by a mean range of 2.86±1.07–5.81±1.66 cm, thereby resulting in extra patient radiation dose. Hence, scanning without the redundant coverages could generate a dose length product (DLP) reduction of 17.5%, 18.8%, 15.5% and 9.0% without degrading image quality for brain lesion, lung lesion, pulmonary embolism and abdominopelvic lesion CT imaging, respectively, whilst ensuring organ dose reduction of0.8%–79.1%. ConclusionThe study strongly recommends that radiographers should avoid the inclusion of redundant areas in CT examinations to reduce organ doses.

P.169 Reduced radiation CT imaging for augmented reality spinal surgery applications

Background: There is growing evidence for the use of augmented reality (AR) in pedicle screw placement in spinal surgery to increase surgical accuracy, improve clinical outcomes and reduce the radiation exposure required for intraoperative navigation. Auto-segmentation is the cornerstone of AR applications because it correlates patient-specific anatomy to structures segmented from preoperative computed tomography (pCT) images. These AR techniques allow for a reduction in the radiation dose required to acquire CT images while maintaining accurate segmentation. Methods: In this study, we methodically increase the noise that is introduced into CT images to determine the image quality threshold that is required for auto-segmentation on pCT. We then enhance the images with denoising algorithms to evaluate the effect on the segmentation. Results: The pCT radiation dose is decreased to below the current lowest clinical threshold and the resulting images still produce segmentations that are appropriate for input into AR applications. The application of denoising algorithms to the images resulted in increased artifacts and decreased bone density. Conclusions: The CT image quality that is required for successful AR auto-segmentation is lower than that which is currently employed in spine surgery. Future research is required to identify the specific, clinically relevant radiation dose thresholds.

B-PO04-087 EFFECT OF OBESITY ON LEFT ATRIAL WALL SUBSTRATE IN PATIENTS WITH ATRIAL FIBRILLATION: INSIGHT INTO EPICARDIAL ADIPOSE TISSUE AND FATTY INFILTRATION

Obesity and epicardial adipose tissue fat (EAT) contributes to the progression of atrial fibrillation (AF). But, its effect on the left atrial (LA) wall substate is clinically unknown. This study aimed to assess the effect of obesity on the LA substrate. Of 23 AF patients who underwent an initial pulmonary vein isolation (PVI) were enrolled. The 320-row multidetector CT was performed within 2 weeks before PVI. The acquired CT images were transferred to a workstation. EAT was defined as -50 to -200 Hounsfield units (HU). We measured LA EAT volume, EAT thickness adjacent to the LA roof, CT values on the LA roof wall, and LA roof wall thickness using workstation (figure). We compared these parameters between AF patients with and without obesity (≥BMI 25 kg/m2). Both LA EAT volume and EAT thickness were significantly greater in obese group than in non-obese group (LA EAT volume, 50±13 vs. 24±9 ml, P<0.01; EAT thickness, 8.8±2.7 vs. 5.5±1.7 mm, P<0.01). There was a strong positive correlation with LA EAT volume and EAT thickness (r=0.89, P<0.01). The CT value on the LA roof wall was significantly lower in obese group than in non-obese group (21±7 vs. 36±12 HU, P<0.01). The CT value on the LA roof wall correlated negatively with both LA EAT volume (r=-0.80, P<0.01) and EAT thickness (r=-0.72, P<0.01). The LA roof wall thickness did not differ between two groups (2.5±0.5 vs. 2.5±0.3 mm, P=0.88). Our data disclosed different LA wall substrates in obese AF patients. Lower CT values adjacent to thickened EAT may reflect fatty infiltration from EAT, which may explain the pathogenesis of AF in obesity.

Body size and tube voltage dependent corrections for Hounsfield Unit in medical X-ray computed tomography: theory and experiments

The purpose of this work is to present a body size and tube voltage dependent correction scheme for the Hounsfield Unit, HU, in medical X-ray Computed Tomography imaging. Boltzmann photon transport equation was employed to study X-ray interaction with bulk water in CT imaging. Experimentally measured X-ray output in body of phantoms and attenuation cross sections of water were employed in the derivation of beam intensity in X-ray imaging. A Somatom Emotion CT scanner from Siemens and electron density phantoms from CIRS were employed to acquire CT images of different body sizes and different tissue materials located at different depths from body’s surface. Tube voltage and depth dependent effective attenuation of bulk water was found from theoretical analysis in agreement with measured size-specific correction factors for CTDIvol under different tube voltages. A size and tube voltage dependent correction scheme for the Hounsfield Unit is established. For the same tissue material, body size has much larger impact on the CT number variations than that of depth from the body surface in phantom measurements. Good results were achieved by applying the established correction scheme on the experimentally measured CT number variations under different tube voltages and body sizes.

Tarsal Morphology Differs in Plano Valgus Feet

Category:HindfootIntroduction/Purpose:While there are established associated conditions, the intrinsic cause of symptomatic adult flatfoot is not known. There are published data suggesting that the relationship of the hindfoot bones in acquired flatfoot are subluxated. And there is some support in 2 D for the concept that the bones are shaped differently in flatfoot but the complexity of bone shape and human variation makes comparisons difficult. The purpose of this study was to utilize principal component analysis (PCA) to determine whether morphology of the hind- and midfoot bones differs in neutral and plano-valgus feet.Methods:Forty subjects (23 male and 17 Female, average age 52.6 +/- 8.9) with no history of injury or surgery underwent bilateral foot WB CT scan for another study. The talus, calcaneus, navicular and cuboid were segmented into bone models from these previously acquired CT images. Morphometric Shape analysis software (Geomorph) was used to assess shape variations among foot types using Principal component analysis (PCA). PCA is a statistical modelling technique used to study variation in the shape of structures that are difficult to compare and bring out strong patterns in a dataset objectively. Forty feet had been classified into 4 foot groups prior to this study; neutral, cavus, asymptomatic flatfoot and symptomatic flatfoot. This study included the painful flatfeet and neutral feet. Each bone was compared between the feet that were flat and those that were neutral. Comparisons were made between men and women as well.Results:There were no differences between groups in age or sex. There were 38 principle components identified. The first two PC accounted for 38% of the calcaneal variation and 33% of the talar variation. Subtle differences between men and women were found only at the talus and navicular. The cuboid did not exhibit any differences between foot types. The navicular in symptomatic planus had a more posteriorly positioned tuberosity (tuber wrapped around the medial side of the talus) and were wider than neutral feet. The calcaneus showed planus feet to have calcanei that have decreased height and increased length compared to neutrally aligned feet. The cross -sectional area of the calcaneus was reduced compared to neutral feet. The talar shape was not different in the PC.Conclusion:A flat foot is present in over 20% of the population and most often not symptomatic. The root cause of symptomatic adult plano valgus foot is not known and is likely multi factorial. The study demonstrates that there is intrinsic difference in the shape of the calcaneus and navicular bones in flat foot. it is possible that the catalyst for collapse is bony rather than soft tissue.

The next era of renal radionuclide imaging: novel PET radiotracers

Although single-photon-emitting radiotracers have long been the standard for renal functional molecular imaging, recent years have seen the development of positron emission tomography (PET) agents for this application. We provide an overview of renal radionuclide PET radiotracers, in particular focusing on novel 18F-labelled and 68Ga-labelled agents. Several reported PET imaging probes allow assessment of glomerular filtration rate, such as [68Ga]ethylenediaminetetraacetic acid ([68Ga]EDTA), [68Ga]IRDye800-tilmanocept and 2-deoxy-2-[18F]fluorosorbitol ([18F]FDS)). The diagnostic performance of [68Ga]EDTA has already been demonstrated in a clinical trial. [68Ga]IRDye800-tilmanocept shows receptor-mediated binding to glomerular mesangial cells, which in turn may allow the monitoring of progression of diabetic nephropathy. [18F]FDS shows excellent kidney extraction and excretion in rats and, as has been shown in the first study in humans. Further, due to its simple one-step radiosynthesis via the most frequently used PET radiotracer 2-deoxy-2-[18F]fluoro-d-glucose, [18F]FDS could be available at nearly every PET centre. A new PET radiotracer has also been introduced for the effective assessment of plasma flow in the kidneys: Re(CO)3-N-([18F]fluoroethyl)iminodiacetic acid (Re(CO)3([18F]FEDA)). This compound demonstrates similar pharmacokinetic properties to its 99mTc-labelled analogue [99mTc](CO)3(FEDA). Thus, if there is a shortage of molybdenum-99, Re(CO)3([18F]FEDA would allow direct comparison with previous studies with 99mTc. The PET radiotracers for renal imaging reviewed here allow thorough evaluation of kidney function, with the tremendous advantage of precise anatomical coregistration with simultaneously acquired CT images and rapid three-dimensional imaging capability.

Adaptive Fruitfly Based Modified Region Growing Algorithm for Cardiac Fat Segmentation Using Optimal Neural Network.

Epicardial adipose tissue is a visceral fat that has remained an entity of concern for decades owing to its high correlation with coronary heart disease. It continues to stump medical practitioners on the pretext of its relevance with pericardial fat and its dependence on a numerous other parameters including ethnicity and physique of an individual. This calls for a fool-proof algorithm that promises accurate classification and segmentation, hence an immaculate prediction. CT is immensely popular and widely preferred for diagnosis. Implementation of an improvised algorithm in CT would be a natural necessity. This research work proposes a Fruitfly Algorithm based Modified region growing algorithm is applied to the acquired CT images to segment fat accurately. The proposed methodology promises image registration and classification in order to segment two cardiac fats namely epicardial, pericardial and mediastinal. The main contributions are (1) Fat feature extraction: Construction of GLCM features CT image (2) Development of GWO based optimal neural network for classification; (3) Modeling the fat segmentation using modified region growing algorithm with Fruitfly optimization. The entire experimentation has been implemented in MATLAB simulation environment and final result is expected to flaunt a definite distinction between cardiac mediastinal and epicardial fats. Parallely, the accuracy, sensitivity, specificity, FPR and FNR have been stated and contrasted methodically with the existing methodology. This venture aims at spurring the healthcare industry towards smarter computational techniques that multiplies efficiency manifold.

Development of an In-house Couch Model to Improve Dose Attenuation Correction Accuracy for a Couch with Different Thickness in the Superior-inferior Direction

As the couch used in external radiation therapy attenuate radiation by interaction, it is necessary to correct attenuation of radiation by inserting a couch model in the treatment planning systems. For a couch whose thickness is different in the superior-inferior direction, it is possible to perform dose calculations with an error within ±1% by using separate different couch models provided by vendors. However, it is difficult to correct attenuation correction accurately with a single couch model. In this study, we created an in-house couch model which can set couch shape and physical density in detail by acquiring CT images of actual couch. When we performed dose calculation by optimizing the physical densities of in-house and vendor couch, it was found that the difference between the measured and the calculated values can be significantly reduced by using in-house couch model. Additionally, by using in-house couch model, it is found that the dose attenuation can be corrected within ±1% for a couch whose thickness is different in the superior-inferior direction.