Standardized Regions Of Interest Research Articles

Abstract 18873: Microvascular Calcification Varies Across Brain Regions in Humans With and Without Dementia at Death

Background: Vascular calcification (VC) is an independent predictor of cardiovascular and cerebrovascular events. While the clinical significance of coronary VC is well recognized, less is known about the prevalence and implications of VC in brain microcirculation. Aims: In this exploratory study, we aimed to compare calcification volume (CV) across brain regions in subjects with and without dementia documented at death. Methods: In a cohort of human donor cadavers (n=14, 57% female, all >70 y/o), brain tissue was sampled bilaterally from basal ganglia (BG), substantia nigra (SN), subventricular zone (SVZ), hippocampus (Hc), and posterior cingulate cortex (PCC), and scanned by microCT at 10 μm resolution. Reconstructed images were segmented into standardized regions of interest (ROI). CV was defined as voxel quantity ≥130 Hounsfield units within each ROI. Findings were confirmed by histologic evaluation. Results: By two-way ANOVA, CV differed significantly by region (p=0.0006) and condition (p=0.0104). Hc and PCC CVs were significantly greater in subjects with dementia compared to age-matched subjects (9.3х10e7 μm 3 vs 1.4х10e7μm 3 , p=0.007; 2.6х10e7 μm 3 vs 4.7х10e6 μm 3 , p=0.017). Conclusions: All subjects in our cohort exhibited VC in at least one brain region, indicating that the prevalence of intracranial VC exceeds published estimates. Subjects with dementia exhibited significantly higher Hc and PCC CVs than age-matched subjects without documented dementia. Although limited by small sample size, our findings support recent reports of hippocampal and BG calcification in post-mortem brain samples from humans with Alzheimer disease.

Can SGRT be a Substitute for Plan Verification Procedure?

Verification of plan (VP) has been part of our pre-treatment workflow for treatment isocenter verification. Currently, our center uses simulator for VP procedure for all our patients before the treatment. We would like to investigate if SGRT could be a good substitute for VP procedure to simplify our pre-treatment workflow. In Group A (A-c, A-t, A-a), 20 patients of each treatment site (cranial, thorax and abdomen) were selected randomly. Patients did not go through VP procedure. During the first fraction of treatment, the therapists were guided by SGRT system (Vision RT, UK) and aligned the patient to 3mm and 1°using a standard region of interest (ROI). First CBCT was taken as a reference to customize the ROI for better suitability. Next, the patient was re-aligned to 1mm and 1°using the new ROI. Second CBCT was acquired, and 6 degrees of freedoms shifts were recorded. In Group B (B-c, B-t, B-a), 20 patients of each treatment site (cranial, thorax and abdominal) that were assigned for VP over the same period as Group A patients. Group B patients were aligned based on the skin markings drawn during VP procedure. CBCTs were taken at the first fraction of treatment and shifts were recorded. A total of 60 CBCT images were analyzed for each group of patients. The absolute mean and standard deviations were shown in Table 1. The results indicated that Group A is superior, if not comparable, to Group B. Table 1: The absolute mean and standard deviations of first fraction of CBCT positioning errors for Group A and B patients. With appropriate ROI, SGRT is a good or superior substitute for plan verification procedure. Localization verification can be done during day one of treatment which ease the pre-treatment workflow to both patients and clinical team. Analysis of customized ROI will be further studied in the future.

Influence of binarization methods on the fractal dimension of alveolar bone using digital radiographs

The aim of this study was to evaluate the influence of binarization methods (BnMs) on the fractal dimension (FD) of the alveolar bone in digital radiographic images. Five identical periapical radiographs were obtained from each of 20 anatomic regions. Using ImageJ/Fiji software, a standardized region of interest was positioned in the trabecular bone of all radiographs, 14 BnMs were independently applied, and FD was calculated. The Friedman test and Dunn post hoc tests were used to evaluate the influence of BnMs on FD (α=0.05). The intraclass correlation coefficient (ICC) was used to assess correlation among BnMs. No significant differences were observed in the threshold value between the BnMs. No significant differences in FD were observed among 9 BnMs (Default, Huang, Iso Data, Li, Mean, Min Error[I], Moments, Otsu, and Shanbhag). These methods presented significantly higher FDs than those from 3 other BnMs (Max Entropy, Renyi Entropy, and Yen), which did not significantly differ from each other. The Triangle method significantly differed from all BnMs, and the Percentile method produced significantly higher FDs than Huang, IsoData, Li, Moments, Otsu, and Shanbhag. Most BnMs presented good or excellent correlation (ICC ≥ 0.76). Binarization methods influence FD of the alveolar bone from digital periapical radiographs; thus, this technical aspect is relevant for comparison purposes and should be standardized. For comparison of published FD research, the Default method is recommended.

Perivascular Macrophages Mediate Microvasospasms After Experimental Subarachnoid Hemorrhage.

Subarachnoid hemorrhage (SAH) is characterized by acute and delayed reductions of cerebral blood flow (CBF) caused, among others, by spasms of cerebral arteries and arterioles. Recently, the inactivation of perivascular macrophages (PVM) has been demonstrated to improve neurological outcomes after experimental SAH, but the underlying mechanisms of protection remain unclear. The aim of our exploratory study was, therefore, to investigate the role of PVM in the formation of acute microvasospasms after experimental SAH. PVMs were depleted in 8- to 10-week-old male C57BL/6 mice (n=8/group) by intracerebroventricular application of clodronate-loaded liposomes and compared with mice with vehicle liposome injections. Seven days later, SAH was induced by filament perforation under continuous monitoring of CBF and intracranial pressure. Results were compared with sham-operated animals and animals who underwent SAH induction but no liposome injection (n=4/group each). Six hours after SAH induction or sham surgery, numbers of microvasospasms per volume of interest and % of affected pial and penetrating arterioles were examined in 9 standardized regions of interest per animal by in vivo 2-photon microscopy. Depletion of PVMs was proven by quantification of PVMs/mm3 identified by immunohistochemical staining for CD206 and Collagen IV. Statistical significance was tested with t tests for parametric data and Mann-Whitney U test for nonparametric data. PVMs were located around pial and intraparenchymal arterioles and were effectively depleted by clodronate from 671±28 to 46±14 PVMs/mm3 (P<0.001). After SAH, microvasospasms was observed in pial arteries and penetrating and precapillary arterioles and were accompanied by an increase to 1405±142 PVMs/mm3. PVM depletion significantly reduced the number of microvasospasms from 9 IQR 5 to 3 IQR 3 (P<0.001). Our results suggest that PVMs contribute to the formation of microvasospasms after experimental SAH.

Diffusion-weighted Breast MRI at 3 Tesla: Improved Lesion Visibility and Image Quality with a Combination of Water-excitation and Spectral Fat Saturation

In breast MRI with diffusion-weighted imaging (DWI), fat suppression is essential for eliminating the dominant lipid signal. This investigation evaluates a combined water-excitation-spectral-fatsat method (WEXfs) versus standard spectral attenuated inversion recovery (SPAIR) in high-resolution 3-Tesla breast MRI. Multiparametric breast MRI with 2 echo-planar DWI sequences was performed in 83 patients (50.1 ± 12.6 years) employing either WEXfs or SPAIR for fat signal suppression. Three radiologists assessed overall DWI quality and delineability of 88 focal lesions (28 malignant, 60 benign) on images with b values of 800 and 1600 s/mm2, as well as apparent diffusion coefficient (ADC) maps. For each fat suppression method and b value, the longest lesion diameter was determined in addition to measuring the signal intensity in DWI and ADC value in standardized regions of interest. Regardless of b values, image quality (all p < 0.001) and lesion delineability (all p ≤ 0.003) with WEXfs-DWI were deemed superior compared to SPAIR-DWI in benign and malignant lesions. Irrespective of lesion characterization, WEXfs-DWI provided superior signal-to-noise, contrast-to-noise and signal-intensity ratios with 1600 s/mm2 (all p ≤ 0.05). The lesion size difference between contrast-enhanced T1 subtraction images and DWI was smaller for WEXfs compared to SPAIR fat suppression (all p ≤ 0.007). The mean ADC value in malignant lesions was lower for WEXfs-DWI (p < 0.001), while no significant ADC difference was ascertained between both techniques in benign lesions (p=0.947). WEXfs-DWI provides better subjective and objective image quality than standard SPAIR-DWI, resulting in a more accurate estimation of benign and malignant lesion size.

Non-invasive diagnosis of brain gliomas by histological type using neuroradiomics in standardized regions of interest: towards digital biopsy

To introduce a standardized method for identification of regions of interest when analyzing MR images using radiomics; to test the hypothesis that this approach is effective for distinguishing different histological types of gliomas. We analyzed preoperative MR data in 83 adults with various gliomas (WHO classification, 2016), i.e. oligodendroglioma, anaplastic oligodendroglioma, anaplastic astrocytoma, and glioblastoma. Radiomic features were computed for T1, T1-enhanced, T2 and T2-FLAIR modalities in four standardized volumetric regions of interest by 356 voxels (46.93 mm3): 1) contrast enhancement; 2) edema-infiltration; 3) area adjacent to edema-infiltration; 4) reference area in contralateral hemisphere. Subsequently, mathematical models were trained to classify MR-images of glioma depending on histological type and quantitative features. Mean accuracy of differential diagnosis of 4 histological types of gliomas in experiments with machine learning was 81.6%, mean accuracy of identification of tumor types - from 94.1% to 99.5%. The best results were obtained using support vector machines and random forest model. In a pilot study, the proposed standardization of regions of interest demonstrated high effectiveness for MR-based differential diagnosis of oligodendroglioma, anaplastic oligodendroglioma, anaplastic astrocytoma and glioblastoma. There are grounds for applying and improving this methodology in further studies.

Definition of the Region of Interest for the Assessment of Alveolar Bone Repair Using Micro-computed Tomography.

The objective of this study was to evaluate the influence of the extraction socket (distal or lingual root) and the type of region of interest (ROI) definition (manual or predefined) on the assessment of alveolar repair following tooth extraction using micro-computed tomography (micro-CT). The software package used for scanning, reconstruction, reorientation, and analysis of images (NRecon®, DataViewer®, CT-Analyzer®) was acquired through Bruker < https://www.bruker.com > . The sample comprised the micro-CT volumes of seven Wistar rat mandibles, in which the right first molar was extracted. The reconstructed images were analyzed using the extraction sockets, i.e., the distal and intermediate lingual root and the method of ROI definition: manual (MA), central round (CR), and peripheral round (PR). The bone volume fraction (BV/TV) values obtained were analyzed by two-way ANOVA with Tukey's post hoc test (α = 5%). The distal extraction socket resulted in significantly lower BV/TV values than the intermediate lingual socket for MA (P = 0.001), CR (P < 0.001), and PR (P < 0.001). Regarding the ROI, when evaluating the distal extraction socket, the BV/TV was significantly higher (P < 0.001) for MA than for CR and PR, with a lower BV/TV for CR. However, no significant difference was observed for MA (P = 0.855), CR (P = 0.769), or PR (P = 0.453) in the intermediate lingual extraction socket. The bone neoformation outcome (BV/TV) for alveolar bone repair after tooth extraction is significantly influenced by the ROI and the extraction socket. Using the predefined method with a standardized ROI in the central region of the distal extraction socket resulted in the assessment of bone volume, demonstrating the most critical region of the bone neoformation process.

Volumetric tissue changes following combined surgical therapy of peri‐implantitis: A 2‐year follow‐up analysis. A prospective case series

To assess volumetric tissue changes following combined surgical therapy of peri-implantitis over a follow-up period of 24 months. A total of 20 patients (n=28 implants) were diagnosed with peri-implantitis and underwent access flap surgery, implantoplasty, and augmentative therapy at intrabony components (ie, combined therapy) using a natural bone mineral and a native collagen membrane. The peri-implant region of interest (ROI) was intraorally scanned pre-operatively (S0), and after 12 (S3) and 24 (S4) months. Digital files were superimposed for the assessment of volumetric changes between the referred time points. The change in thickness was assessed at a standardized ROI, segmented into two equidistant sections (ie, marginal and apical). Peri-implant tissues exhibited a nonsignificant mean thickness loss of 0.16 (95% CI: -4 to 0.06) and 0.17 mm (95% CI: -0.05 to 0.4) at S3 and S4, respectively. S0-S3 dimensional thickness changes at marginal and apical areas were -0.24 (95% CI: -0.48 to 0.002) and -0.19 mm (95% CI: -0.36 to -0.2), respectively. Dimensional changes from S0 to S4 amounted to -0.22 mm (95% CI: -0.46 to 0.02) and -0.07 mm (95% CI: -0.09 to 0.2), respectively. The thickness changes at marginal and apical ROIs were significant from S0 to S3. Clinical parameters (ie, plaque index, bleeding on probing, and probing depth) significantly improved over the 24-month follow-up period. Linear regression analyses revealed no significant association between baseline bone loss (%), width of keratinized mucosa, and mucosal recession scores and thickness changes. Peri-implant tissues revealed minor volumetric changes at 12 and 24 months after combined surgical therapy.

NIMG-14. RESTING STATE EXECUTIVE CONTROL AND SALIENCE NETWORK CONNECTIVITY IN CLINICALLY STABLE LOWER GRADE GLIOMA COVARIES WITH COGNITIVE PERFORMANCE

Abstract BACKGROUND Survival outcomes for patients with lower grade gliomas (LrGG) are improving. However, injury from tumor growth and consequences of treatment often leads to impaired cognition, particularly in cognitive domains reliant on distributed functional networks and intact white-matter tracts. Resting state functional MRI (rsfMRI) is a method of investigating the integrity of these functional networks. METHODS This study investigated rsfMRI connectivity in 21 patients with clinically stable LrGG compared to age- and gender-matched healthy controls, and associated imaging measures with cognitive outcomes. Data were acquired for 12 cognitive tests administered within one week of imaging. RsfMRI and T1-weighted images for 21 research controls were acquired from OpenNeuro datasets. RsfMRI data were processed and analyzed using the CONN toolbox using CONN’s standard regions of interest (ROI) for the 8 canonical networks as seeds, and cognitive test scores as covariates, with a threshold for T tests of p&amp;lt; .001 uncorrected. RESULTS Median age was 48 years old (range 27-67). There were 6 astrocytomas, IDHmut; 3 astrocytomas IDH-wt, 8 oligodendrogliomas, and 4 NOS. Thirteen had left hemisphere tumors (8 frontal, 3 parietal, 2 temporal), and 6 right (5 frontal, 1 temporal). Fourteen had previously recieved radiotherapy. There was significantly lower connectivity in frontoparietal executive control and the salience networks in LrGG patients versus controls. Within patients, lower executive control network connectivity covaried with worse performance on executive measures (FAS, Tower of London, Trails-A, Animal Naming, FrSBe), and attention and working memory measures (Digit Symbol, HVLT). Lower salience network connectivity covaried with poorer performance on executive measures (FrSBe, FAS) and attention and working memory measures (Digit Span, HVLT, WAIS-WM). CONCLUSION In clinically stable LrGG, rsfMRI measures of network connectivity are potentially useful markers to monitor and track, given the concordance with cognition, and could help guide cognitive assessment and rehabilitation.

Carotid webs produce greater hemodynamic disturbances than atherosclerotic disease: a DSA time–density curve study

BackgroundCarotid webs (CaWs) are associated with ischemic strokes in younger patients without degrees of stenosis that are traditionally considered clinically significant.ObjectiveTo compare the hemodynamic parameters in the internal carotid artery...

Structural changes in the trabecular bone of the mandibular condyle of growing patients with sagittal jaw discrepancy treated with the twin-block appliance.

The objective of this study was to evaluate the structural changes in the trabecular bone of the mandibular condyles in patients treated with the Twin-block functional orthopaedic appliance that act by promoting condylar growth and to compare the fractal dimension (FD) of condylar trabecular bone structure prior to treatment (T0) and after orthopaedic functional treatment (T1). This retrospective study included panoramic images of 112 individuals with a mean age of 11.04±1.30years in the study group (32 girls and 24 boys) and 11.6±.80years in the control group (29 girls and 27 boys). The standardized region of interest was selected as the right and left condylar areas close to the articulation surfaces from the twin-block (TB) group, which included patients who completed functional orthopaedic treatment and the control group, which included untreated individuals. FD values in the condylar region were analysed from the panoramic radiographs of both groups using a box-counting method with ImageJ software (version 1.52a, US National Institutes of Health). There was a significant decrease in the FD values of the right (-.038) and left (-.022) condylar region at T0 and T1 in the TB group. Between-group FD comparisons demonstrated that the TB group showed changes in the condylar region (right, P=.004; left, P=.022) compared to the control group. Functional orthopaedic forces caused a decrease in the trabecular structure of the condylar area examined.

Age-dependent microstructural changes of the intervertebral disc: a validation of proteoglycan-sensitive spectral CT

ObjectiveTo analyze the two major components of the intervertebral disc (IVD) in an ex vivo phantom, as well as age-related changes in patients.MethodsCollagen and chondroitin sulfate were imaged at different concentrations in agar solution. Age-related changes in disc density were retrospectively analyzed in normal-appearing discs in dual-energy computed tomography (DECT) images from a patient cohort with various spinal pathologies (n = 136). All computed tomography (CT) scans were acquired using single-source DECT at 80 and 135 kVp with automatic exposure calculation. In 136 patients, the attenuation of normal-appearing discs on collagen/chondroitin maps (cMaps) correlated with the patients’ age with Pearson’s r using standardized regions of interest in the anterior anulus fibrosus (AAF) and nucleus pulposus (NP).ResultsDECT collagen mapping revealed concentration-dependent Hounsfield units (HU) of IVD components. For collagen, we found Pearson’s r = 0.9610 (95% CI 0.6789–0.9959), p = 0.0023 at 120 kVe, and r = 0.8824 (95% CI 0.2495–0.9871), p = 0.0199 in cMap. For chondroitin sulfate, Pearson’s r was 0.9583 (95% CI 0.6603–0.9956), p = 0.0026 at 120 kVp, and r = 0.9646 (95% CI 0.7044–0.9963), p = 0.0019 in cMap. Analysis of normal-appearing IVDs revealed an inverse correlation of density with age in the AAF: Pearson’s r = − 0.2294 at 135 kVp (95% CI − 0.4012 to − 0.04203; p=0.0141) and r = − 0.09341 in cMap (95% CI − 0.2777 to 0.09754; p = 0.0003). In the NP, age and density did not correlate significantly at 135 kVp (p = 0.9228) and in cMap (p = 0.3229).ConclusionsDECT-based collagen mapping allows microstructural analysis of the two main intervertebral disc components—collagen and chondroitin sulfate. IVD density declines with age, presumably due to a reduction in collagen and chondroitin sulfate content. Age-related alterations of disc microstructure appear most pronounced in the AAF.Key Points• DECT-based collagen mapping allows precise analysis of the two main intervertebral disc components—collagen and chondroitin sulfate.• Intervertebral disc (IVD) density declines with age, presumably due to a reduction in collagen and chondroitin sulfate content.• Age-related alterations of disc microstructure are most pronounced in the anterior anulus fibrosus (AAF).

Ordinal classification of the affectation level of 3D-images in Parkinson diseases

Parkinson’s disease is characterised by a decrease in the density of presynaptic dopamine transporters in the striatum. Frequently, the corresponding diagnosis is performed using a qualitative analysis of the 3D-images obtained after the administration of ^{123}I-ioflupane, considering a binary classification problem (absence or existence of Parkinson’s disease). In this work, we propose a new methodology for classifying this kind of images in three classes depending on the level of severity of the disease in the image. To tackle this problem, we use an ordinal classifier given the natural order of the class labels. A novel strategy to perform feature selection is developed because of the large number of voxels in the image, and a method for generating synthetic images is proposed to improve the quality of the classifier. The methodology is tested on 434 studies conducted between September 2015 and January 2019, divided into three groups: 271 without alteration of the presynaptic nigrostriatal pathway, 73 with a slight alteration and 90 with severe alteration. Results confirm that the methodology improves the state-of-the-art algorithms, and that it is able to find informative voxels outside the standard regions of interest used for this problem. The differences are assessed by statistical tests which show that the proposed image ordinal classification could be considered as a decision support system in medicine.

Pharmacokinetic Analysis of Dynamic Contrast-Enhanced Magnetic Resonance Imaging at 7T for Breast Cancer Diagnosis and Characterization.

Simple SummaryConfirming whether a breast lesion is benign or malignant usually involves an invasive tissue sample with an image-guided breast biopsy, which may cause substantial inconvenience to the patient. The purpose of this study was to investigate whether imaging biomarkers obtained from noninvasive dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) of the breast can help differentiate benign from malignant lesions and characterize breast cancers to the same extent as a biopsy. In a sample of 37 patients with suspicious findings on mammography or ultrasound, we found that the radiologists’ diagnostic accuracy was improved when subjective Breast Imaging-Reporting and Data System (BI-RADS) evaluation was augmented with the use of pharmacokinetic markers. This study serves as a starting point for future collaborative research with the potential of providing valuable noninvasive tools for improved breast cancer diagnosis.The purpose of this study was to investigate whether ultra-high-field dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) of the breast at 7T using quantitative pharmacokinetic (PK) analysis can differentiate between benign and malignant breast tumors for improved breast cancer diagnosis and to predict molecular subtypes, histologic grade, and proliferation rate in breast cancer. In this prospective study, 37 patients with 43 lesions suspicious on mammography or ultrasound underwent bilateral DCE-MRI of the breast at 7T. PK parameters (KTrans, kep, Ve) were evaluated with two region of interest (ROI) approaches (2D whole-tumor ROI or 2D 10 mm standardized ROI) manually drawn by two readers (senior reader, R1, and R2) independently. Histopathology served as the reference standard. PK parameters differentiated benign and malignant lesions (n = 16, 27, respectively) with good accuracy (AUCs = 0.655–0.762). The addition of quantitative PK analysis to subjective BI-RADS classification improved breast cancer detection from 88.4% to 97.7% for R1 and 86.04% to 97.67% for R2. Different ROI approaches did not influence diagnostic accuracy for both readers. Except for KTrans for whole-tumor ROI for R2, none of the PK parameters were valuable to predict molecular subtypes, histologic grade, or proliferation rate in breast cancer. In conclusion, PK-enhanced BI-RADS is promising for the noninvasive differentiation of benign and malignant breast tumors.

An Automated Method for Quality Control in MRI Systems: Methods and Considerations

Objective: The purpose of this study was to develop an automated method for performing quality control (QC) tests in magnetic resonance imaging (MRI) systems, investigate the effect of different definitions of QC parameters and its sensitivity with respect to variations in regions of interest (ROI) positioning, and validate the reliability of the automated method by comparison with results from manual evaluations. Materials and Methods: Magnetic Resonance imaging MRI used for acceptance and routine QC tests from five MRI systems were selected. All QC tests were performed using the American College of Radiology (ACR) MRI accreditation phantom. The only selection criterion was that in the same QC test, images from two identical sequential sequences should be available. The study was focused on four QC parameters: percent signal ghosting (PSG), percent image uniformity (PIU), signal-to-noise ratio (SNR), and SNR uniformity (SNRU), whose values are calculated using the mean signal and the standard deviation of ROIs defined within the phantom image or in the background. The variability of manual ROIs placement was emulated by the software using random variables that follow appropriate normal distributions. Results: Twenty-one paired sequences were employed. The automated test results for PIU were in good agreement with manual results. However, the PSG values were found to vary depending on the selection of ROIs with respect to the phantom. The values of SNR and SNRU also vary significantly, depending on the combination of the two out of the four standard rectangular ROIs. Furthermore, the methodology used for SNR and SNRU calculation also had significant effect on the results. Conclusions: The automated method standardizes the position of ROIs with respect to the ACR phantom image and allows for reproducible QC results.

Determination of Diagnostic Reference Levels for Chest Examination for Windhoek, Namibia

The widespread use of X-ray examination has improved lives worldwide and this evolution of imaging has also resulted in a significant increase in the population’s exposure to ionizing radiation. This exposure can be minimised by the setting up Diagnostic Reference Levels (DRLs). DRLs are exposure level that serve as guide for standard regions of interest and are recommended by the International Atomic Energy Agency for member states to apply within the context of the national legislation. Namibia Radiation Protection and Waste Disposal Regulations also mandate the National Radiation Protection Authority to determine guidance levels as a condition of a license. Management of patient dose and determination of DRLs are important part of quality control programsin X-ray diagnostic departments as it forms an efficient and powerful standard for minimising radiation dosage to patients. Since Namibia has not yet established DRLs, the aim of this study was to develop DRLs for posterior anterior (PA) chest examinationin Windhoek, Namibia. Quality control tests were done on the X-ray machines using a Xi-Unfors radiation meter. Entrance skin doses (ESDs) were obtained from 120 patients that were referred for chest examination at the six selected facilities in Windhoek. The following parameters were measured: kilovoltage peak (kVp), milliampere seconds (mAs), the focus to bucky distance (FBD) and focus to surface distance (FSD). The ESDs were then calculated. The average ESD was found to be 0.47 mGy, ranging from 0.14 to 1.3 mGy. The study provided baseline information on ESD’s for PA chest radiography. The ESD’s in this study was above the ESD’s recommended by the IAEA which is 0.2mGy. This was attributed to the use of high kVp and mAs and a short FBD at some facilities. The results of this study, with more data expected to be collected by the National Radiation Protection Authority (NRPA) will provide a useful baseline to establish Namibia’s DRLs.

QUANTIFICATION OF TMJ RHEUMATOID ARTHRITIS ON POSITRON EMISSION TOMOGRAPHY SCANS USING ROVER SOFTWARE

<h3>Background</h3> Inflammation of the temporomandibular joint (TMJ) has a relatively high correlation (> 17%) to the late stages of rheumatoid arthritis (RA). RA is a chronic inflammatory autoimmune disease that causes cartilage and bone destruction. Cell activity of TMJ was measured by using 2 radiotracers, [18 F]-fluoro-2-deoxy-D-glucose (FDG) and [18 F]-sodium fluoride (NaF), for staging and surveillance of RA. <h3>Objective</h3> The aim of this study was to quantify the region of interest (ROI) volumes of FDG- and NaF-based TMJ positron emission tomography (PET) images by using the ROVER software. <h3>Materials and Methods</h3> Institutional review board (IRB) approval was obtained for 20 previously diagnosed patients with RA. From this cohort, 17 anonymized patients with NaF and FDG-PET/CT scans were reviewed by 3 calibrated investigators. When there was disagreement, a fourth investigator who is an expert in PET/CT, was used. The standardized uptake values corrected (SUV-Mean Cor) were calculated and recorded on ROVER. The collected data and literature review findings were collated and analyzed to provide a holistic comparison table. The clinical applications, advantages, and disadvantages of 8 imaging techniques were reviewed. <h3>Results</h3> The average ROI volumes differed between FDG- and NaF-based PET images in every case, showing a higher quantification for NaF-based scans. In 1 case, ROI mean total corrected value was 23.25 when NaF-PET was used, as opposed to 6.7 when FDG-PET was used. There was a similar trend among other cases included in the study. The NaF-PET ROI values appeared higher than the standard FDG-PET ROI values in the cases where the RA activity was quantified. SUV can be obtained by dividing the ROI activity concentration (KBq/L) by the decay-corrected amount of injected FDG (KBq/L) times the weight of the patient in grams. ROVER automatically calculates the average and maximum SUVs for all patients. <h3>Discussion</h3> With the use of ROVER, it is possible to collect accurate measurements of TMJ disease activity from both FDG-PET and NaF-PET images. NaF-PET appeared to be a more sensitive technique.

Volumetric assessment of tissue changes following combined surgical therapy of peri-implantitis: A pilot study.

To assess volumetric tissue changes at peri-implantitis sites following combined surgical therapy of peri-implantitis over a 6-month follow-up period. Twenty patients (n=28 implants) diagnosed with peri-implantitis underwent access flap surgery, implantoplasty at supracrestally or bucally exposed implant surfaces and augmentation at intra-bony components using a natural bone mineral and application of a native collagen membrane during clinical routine treatments. The peri-implant region of interest (ROI) was intra-orally scanned pre-operatively (S0), and after 1 (S1) and 6 (S2) months following surgical therapy. Digital files were converted to standard tessellation language (STL) format for superimposition and assessment of peri-implant volumetric variations between time points. The change in thickness was assessed at a standardized ROI, subdivided into three equidistant sections (i.e. marginal, medial and apical). Peri-implant soft tissue contour area (STCA) (mm2 ) and its corresponding contraction rates (%) were also assessed. Peri-implant tissues revealed a mean thickness change (loss) of -0.11 and -0.28mm at 1 and 6months. S0 to S1 volumetric variations pointed to a thickness change of -0.46, 0.08 and 0.4mm at marginal, medial and apical regions, respectively. S0 to S2 analysis exhibited corresponding thickness changes of -0.61, -0.25 and -0.09mm, respectively. The thickness differences between the areas were statistically significant at both time periods. The mean peri-implant STCA totalled to 189.2, 175 and 158.9mm2 at S0, S1 and S2, showing a significant STCA contraction rate of 7.9% from S0 to S1 and of 18.5% from S0 to S2. Linear regression analysis revealed a significant association between the pre-operative width of keratinized mucosa (KM) and STCA contraction rate. The peri-implant mucosa undergoes considerable volumetric changes after combined surgical therapy. However, tissue contraction appears to be influenced by the width of KM.

Spatial Frequency Analysis Identifies Altered Local Micromorphology In Adolescent Athletes With Achilles Tendinopathy

Site specific intratendinous Achilles morphology measured with ultrasound image spatial frequency analysis (SFA), quantifies the degree of collagen fiber density and organization. As tendon pain varies in location, and is not always related to hypoechogenicity, it is of interest to establish if spatial frequency parameters discriminate regions of tendon pain where hypoechoic alterations are not readily observable. PURPOSE: This study aims to analyze intratendinous micromorphology in adolescent athletes (AA) with Achilles tendinopathy and without sonographic evidence of tendinosis. METHODS: 22 AA (14m/8f, 13.2±1.4 y, 161±11 cm, 47±11 kg) with Achilles tendinopathy (history of tendon pain and pain on palpation) and no visible sonographic hypoechogenicity or focal tendon thickening were included in this analysis. Longitudinal ultrasound scans of the Achilles tendon were acquired. SFA was performed on regions of interest (ROI) corresponding to tendon pre-insertion and midportion, as well as the site of subjectively-reported tendon pain on palpation. Higher values of SFA parameters suggest greater collagen fiber density and alignment. Calculated SFA parameter values were compared using a one-factorial or Wilcoxon ANOVA (α<0.05). RESULTS: Significantly lower values for three SFA parameters were found at the symptomatic area as compared to tendon pre-insertion ROI, and for two parameters at the symptomatic area as compared to tendon midportion ROI (Table 1). CONCLUSION: As indicated by SFA, intratendinous morphology was altered at the painful area, whereas standard ROIs reveal comparable values to previous findings in healthy AA. These results indicate that painful, yet sonographically inconspicuous regions of tendons, have lower fiber density and alignment.Table 1:: SF parameters at tendon pre-insertion (I), midportion (M), and pain site (P) [mean ± SD]

Adaptive segmentation of knee radiographs for selecting the optimal ROI in texture analysis

The purposes of this study were to investigate: 1) the effect of placement of region-of-interest (ROI) for texture analysis of subchondral bone in knee radiographs, and 2) the ability of several texture descriptors to distinguish between the knees with and without radiographic osteoarthritis (OA). Bilateral posterior-anterior knee radiographs were analyzed from the baseline of Osteoarthritis Initiative (OAI) (9012 knee radiographs) and Multicenter Osteoarthritis Study (MOST) (3,644 knee radiographs) datasets. A fully automatic method to locate the most informative region from subchondral bone using adaptive segmentation was developed. Subsequently, we built logistic regression models to identify and compare the performances of several texture descriptors and each ROI placement method using 5-fold cross validation. Importantly, we also investigated the generalizability of our approach by training the models on OAI and testing them on MOST dataset. We used area under the receiver operating characteristic curve (ROC AUC) and average precision (AP) obtained from the precision-recall (PR) curve to compare the results. We found that the adaptive ROI improves the classification performance (OA vs non-OA) over the commonly-used standard ROI (up to 9% percent increase in AUC). We also observed that, from all texture parameters, Local Binary Pattern (LBP) yielded the best performance in all settings with the best AUC of 0.840 [0.825, 0.852] and associated AP of 0.804 [0.786, 0.820]. Compared to the current state-of-the-art approaches, our results suggest that the proposed adaptive ROI approach in texture analysis of subchondral bone can increase the diagnostic performance for detecting the presence of radiographic OA.