Petr Ourednicek

Phantom-less QCT BMD system as screening tool for osteoporosis without additional radiation

PURPOSE Phantom-less bone mineral density (PLBMD) systems are easily integrated into the CT workflow for non-dedicated Quantitative CT (QCT) BMD measurements in thoracic and abdominal scans. This in vivo retrospective study aims to determine accuracy and precision of the PLBMD option located on the Extended Brilliance Workspace (Philips Medical Systems, Cleveland, OH, US) from both cross-sectional and longitudinal image data. MATERIALS AND METHODS The cross-sectional comparison with phantom-based QCT BMD was performed for 82 patients (61 female, 21 male) with a mean age of (63.0±11.8 SD) years on 197 vertebrae. This was followed by an interobserver variability analysis on 71 vertebrae. The longitudinal PLBMD study was carried out on 45 vertebrae from 10 patients (5 female, 5 male) with a mean age of (64.4±11.5 SD) years. They were re-scanned with standardized scan and contrast-injection protocols within a mean and median of (33±41 SD) and 8 days, respectively. All CT scans were acquired on an Mx8000 Quad (Philips) at Florence-Nightingale Hospital, Kaiserswerth, Germany, in a spiral acquisition mode. RESULTS A negligible BMD bias of -0.9mg/cm(3) for the PLBMD option was observed with respect to phantom-based QCT BMD. Applying CT number matching of muscle and fat ROIs, the analysis of cross-sectional interobserver and of longitudinal variability yielded precision values of 3.1mg/cm(3) (CV%=4.0) and 4.2mg/cm(3) (CV%=5.3), respectively. CONCLUSION Although the precision is inferior to phantom-based BMD systems, PLBMD is a robust clinical utility for the detection of lowered BMD in a large patient population. This can be achieved without additional radiation exposure from non-contrasted CT scans, to perform an ancillary diagnosis of osteopenia or osteoporosis.

Submilisievert ultralow-dose CT colonography using iterative reconstruction technique: a feasibility study

Background Computed tomography (CT) colonography is a well established modality for the examination of symptomatic patients as well as in screening. Recent technical advances in improving image quality by iterative reconstruction contribute to the reduction of the radiation dose which is a major concern in CT imaging. Purpose To evaluate image quality of ultralow-dose submilisievert CT colonography using hybrid iterative reconstruction technique. Material and Methods Sixteen patients underwent contrast-enhanced CT colonography with standard protocol in supine position and ultralow-dose protocol in prone position. Ultralow-dose datasets were reconstructed with filtered back projection and an advanced hybrid iterative reconstruction technique. Two radiologists independently evaluated 96 colonic segments for image quality in the endoluminal view and axial thin sections. Colonic distension, smoothness of colonic wall and distortion of folds in the endoluminal view, sharpness of colonic wall delineation, perceived image noise, and presence of photon starvation artifact were rated on a five-point scale. Intraluminal noise expressed as standard deviation of Hounsfield density was measured in all segments. Results The mean radiation dose was 0.42 mSv and 5.48 mSv in prone and supine scans, respectively. All distended segments were rated evaluable in standard dose and ultralow-dose series reconstructed with the iterative reconstruction technique, whereas in 61% segments image quality was rated poor or unacceptable in ultralow-dose series where filtered back projection was used with worst ratings in the rectum and the sigmoid colon. Conclusion This pilot study shows that iterative reconstruction technique is a feasible method to decrease the radiation dose from CT colonography for both positions below 1mSv. Further investigations of larger scale need to be done to clarify, whether such a low radiation dose would influence the detection of polyps.

Evaluation of left atrial function by multidetector computed tomography before left atrial radiofrequency-catheter ablation: Comparison of a manual and automated 3D volume segmentation method

INTRODUCTION The purpose of this study was to compare a manual and automated 3D volume segmentation tool for evaluation of left atrial (LA) function by 64-slice multidetector-CT (MDCT). METHODS AND MATERIALS In 33 patients with paroxysmal atrial fibrillation a MDCT scan was performed before radiofrequency-catheter ablation. Atrial function (minimal volume (LAmin), maximal volume (LAmax), stroke volume (SV), ejection fraction (EF)) was evaluated by two readers using a manual and an automatic tool and measurement time was evaluated. RESULTS Automated LA volume segmentation failed in one patient due to low LA enhancement (103HU). Mean LAmax, LAmin, SV and EF were 127.7 ml, 93 ml, 34.7 ml, 27.1% by the automated, and 122.7 ml, 89.9 ml, 32.8 ml, 26.3% by the manual method with no significant difference (p>0.05) and high Pearsons correlation coefficients (r=0.94, r=0.94, r=0.82 and r=0.85, p<0.0001), respectively. The automated method was significantly faster (p<0.001). Interobserver variability was low for both methods with Pearsons correlation coefficients between 0.98 and 0.99 (p<0.0001). CONCLUSIONS Evaluation of LA volume and function with 64-slice MDCT is feasible with a very low interobserver variability. The automatic method is as accurate as the manual method but significantly less time consuming permitting a routine use in clinical practice before RF-catheter ablation.

Whole‑body low‑dose computed tomography in multiple myeloma staging: Superior diagnostic performance in the detection of bone lesions, vertebral compression fractures, rib fractures and extraskeletal findings compared to radiography with similar radiation exposure

The primary objective of the present prospective study was to compare the diagnostic performance of conventional radiography (CR) and whole-body low-dose computed tomography (WBLDCT) with a comparable radiation dose reconstructed using hybrid iterative reconstruction technique, in terms of the detection of bone lesions, skeletal fractures, vertebral compressions and extraskeletal findings. The secondary objective was to evaluate lesion attenuation in relation to its size. A total of 74 patients underwent same-day skeletal survey by CR and WBLDCT. In CR and WBLDCT, two readers assessed the number of osteolytic lesions at each region and stage according to the International Myeloma Working Group (IMWG) criteria. A single reader additionally assessed extraskeletal findings and their significance, the number of vertebral compressions and bone fractures. The radiation exposure was 2.7±0.9 mSv for WBLDCT and 2.5±0.9 mSv for CR (P=0.054). CR detected bone involvement in 127 out of 486 regions (26%; P<0.0001), confirmed by WBLDCT. CR underestimated the disease stage in 16% and overestimated it in 8% of the patients (P=0.0077). WBLDCT detected more rib fractures compared with CR (188 vs. 47; P<0.0001), vertebral compressions (93 vs. 67; P=0.010) and extraskeletal findings (194 vs. 52; P<0.0001). There was no correlation observed between lesion size (≥5 mm) and its attenuation (r=-0.006; P=0.93). The inter-observer agreement for the presence of osteolytic lesions was κ=0.76 for WBLDCT, and κ=0.55 for CR. The present study concluded that WBLDCT with hybrid iterative reconstruction technique demonstrates superiority to CR with an identical radiation dose in the detection of bone lesions, skeletal fractures, vertebral compressions and extraskeletal findings, which results in up- or downstaging in 24% patients according to the IMWG criteria. The attenuation of osteolytic lesions can be measured with the avoidance of the partial volume effect.

3D CT spine data segmentation and analysis of vertebrae bone lesions

A method is presented aiming at detecting and classifying bone lesions in 3D CT data of human spine, via Bayesian approach utilizing Markov random fields. A developed algorithm for necessary segmentation of individual possibly heavily distorted vertebrae based on 3D intensity modeling of vertebra types is presented as well.

Novel registration-based framework for CT angiography in lower legs

Proper subtraction and visualization of contrast-enhanced blood vessels in lower extremities using computed tomography angiography (CTA) is based on precise masking of all non-contrasted structures in the area, and it is the main prerequisite for correct diagnosis and decision on treatment for peripheral arterial occlusive disease (PAOD). Because of possible motion of patients during the CTA examination, precise elimination of non-contrasted tissues, including bones, calcifications, and soft tissue, is still very challenging for lower legs, that is, from knees to toes. We propose novel registration-based framework for detection and correction of the motion in lower legs, which typically occurs between and during CTA pre-contrast and post-contrast acquisitions. Within the framework, two registration cores are proposed as alternatives, and resulting CTA subtraction images are compared with Advanced Vessel Analysis considered one of the reference commercial tools among clinical applications for CTA of lower extremities. The CTA subtraction images of 55 patients examined for PAOD are evaluated visually by four expert observers on the Philips Extended Brilliance Workspace using four criteria assessing the overall robustness of tested methods. According to the complex evaluation, the proposed framework enabled valuable improvements of CTA examination of lower legs.

Sub-milliSievert ultralow-dose CT colonography with iterative model reconstruction technique

Purpose. The purpose of this study was to evaluate the technical and diagnostic performance of sub-milliSievert ultralow-dose (ULD) CT colonograpy (CTC) in the detection of colonic and extracolonic lesions. Materials and Methods. CTC with standard dose (SD) and ULD acquisitions of 64 matched patients, half of them with colonic findings, were reconstructed with filtered back projection (FBP), hybrid (HIR) and iterative model reconstruction techniques (IMR). Image noise in six colonic segments, in the left psoas muscle and aorta were measured. Image quality of the left adrenal gland and of the colon in the endoscopic and 2D view was rated on a five point Likert scale by two observers, who also completed the reading of CTC for colonic and extracolonic findings. Results. The mean radiation dose estimate was 4.1 ± 1.4 mSv for SD and 0.86 ± 0.17 mSv for ULD for both positions (p < 0.0001). In ULD-IMR, SD-IMR and SD-HIR, the endoluminal noise was decreased in all colonic segments compared to SD-FBP (p < 0.001). There were 27 small (6–9 mm) and 17 large (≥10 mm) colonic lesions that were classified as sessile polyps (n = 38), flat lesions (n = 3), or as a mass (n = 3). Per patient sensitivity and specificity were 0.82 and 0.93 for ULD-FBP, 0.97 and 0.97 for ULD-HIR, 0.97 and 1.0 for ULD-IMR. Per polyp sensitivity was 0.84 for ULD-FBP, 0.98 for ULD-HIR, 0.98 for ULD-IMR. Significantly less extracolonic findings were detected in ULD-FBP and ULD-HIR, but in the E4 category by C-RADS (potentially important findings), the detection was similar. Conclusion. Both HIR and IMR are suitable for sub-milliSievert ULD CTC without sacrificing diagnostic performance of the study.

Combined bone lesion analysis in 3D CT data of vertebrae.

Two novel statistically based methods for bone lesion detection and classification are presented. Together with the previously published MRF method [15], they form a triad of mutually complementary methods that promise, when fused, to enable higher reliability of bone lesion assessment.

Fully Automatic CAD System for Segmentation and Classification of Spinal Metastatic Lesions in CT Data

Our contribution presents a research progress in our long-term project that deals with spine analysis in computed tomography (CT) data. A fully automatic computer-aided diagnosis (CAD) system is presented, enabling the simultaneous segmentation and classification of metastatic tissues that can occur in the vertebrae of oncological patients. The task of the proposed CAD system is to segment metastatic lesions and classify them into two categories: osteolytic and osteoblastic. These lesions, especially osteolytic, are ill defined and it is difficult to detect them directly with only information about voxel intensity. The use of several local texture and shape features turned out to be useful for correct classification, however the exact determination of relevant image features is a difficult task. For this reason, the feature determination has been solved by automatic feature extraction provided by a deep convolutional neural network (CNN). The achieved mean sensitivity of detected lesions is greater than 92% with approximately three false positive detections per lesion for both types.

Fully Automatic CAD System for Spine Localisation and Vertebra Segmentation in CT Data

In this paper, we describe a fully automatic CAD system for spine detection in CT data followed by vertebra identification and segmentation. There are several basic problems: spine detection including the determination of spinal axis in spinal CT data, a localisation of individual vertebrae and identification of their types (order in spine) in case of incomplete scans of spine and also the final vertebra segmentation. By a subjective strict expert validation, the algorithm provides 82.6% of fully correct vertebra segmentations. Based on that, it seems to be routinely usable and fully applicable in preparation for the following automatic spine bone lesion analysis.