Multidetector Computed Tomography System Research Articles

Spatial resolution measurement for iterative reconstruction by use of image-averaging techniques in computed tomography.

The purpose of our study was to investigate the validity of a spatial resolution measuring method that uses a combination of a bar-pattern phantom and an image-averaging technique, and to evaluate the spatial resolution property of iterative reconstruction (IR) images with middle-contrast (50 HU) objects. We used computed tomography (CT) images of the bar-pattern phantom reconstructed by the IR technology Adaptive Iterative Dose Reduction 3D (AIDR 3D), which was installed in the multidetector CT system Aquilion ONE (Toshiba Medical Systems, Otawara, Japan). The contrast of the bar-pattern image was set to 50 HU, which is considered to be a middle contrast that requires higher spatial resolution clinically. We employed an image-averaging technique to eliminate the influence of image noise, and we obtained averaged images of the bar-pattern phantom with sufficiently low noise. Modulation transfer functions (MTFs) were measured from the images. The conventional wire method was also used for comparison; in this method, AIDR 3D showed MTF values equivalent to those of filtered back projection. For the middle-contrast condition, the results showed that the MTF of AIDR 3D decreased with the strength of IR processing. Further, the MTF of AIDR 3D decreased with dose reduction. The image-averaging technique used was effective for correct evaluation of the spatial resolution for middle-contrast objects in IR images. The results obtained by our method clarified that the resolution preservation of AIDR 3D was not sufficient for middle-contrast objects.

High-Resolution Bone Imaging for Osteoporosis Diagnostics and Therapy Monitoring Using Clinical MDCT and MRI

Osteoporosis is classified as a public health problem due to its increased risk for fragility fractures. Osteoporotic fractures, in particular spine and hip fractures, are associated with a high morbidity and mortality, and generate immense financial cost. The World Health Organisation (WHO) based the diagnosis of osteoporosis on the measurement of bone mineral density (BMD) using dual-energy X-ray absorptiometry (DXA). However, BMD values of subjects with versus without osteoporotic fractures overlap. Furthermore, it was reported that the anti-fracture effects of drugs could be only partially explained by their effects on BMD. Bone strength reflects the integration of BMD and bone quality. The later can be partly determined by measurements of bone microstructure. Therefore, substantial research efforts have been undertaken to assess bone microstructure by using high-resolution imaging techniques, including high-resolution peripheral quantitative computed tomography (hr-pQCT), high-resolution multi-detector computed tomography (MDCT), and high-resolution magnetic resonance imaging (MRI). Clinical MDCT and MRI systems are broadly available and allow an adequate depiction of the bone microstructure at the clinically most important fracture sites, i.e. radius, spine and hip. Bone microstructure parameters and finite element models can be computed in high-resolution MDCT and MR images. These measurements improved the prediction of bone strength beyond the DXA-derived BMD and revealed pharmacotherapy effects, which are partly not captured by BMD. Therefore, high-resolution bone imaging using clinical MDCT and MRI may be beneficial for osteoporosis diagnostics and allow a highly sensitive monitoring of drug treatment, which plays an important role in the prevention of fragility fractures.

Retromolar trigone squamous cell cancers: A reappraisal of 16 section MDCT for assessing mandibular invasion

To reinvestigate the accuracy of 16 section multidetector computed tomography (MDCT) in assessing mandibular invasion in retromolar trigone (RMT) squamous cell cancers (SCC). A search for diagnosed cases of early RMT SCC that were both imaged and treated at Tata Memorial Centre, Mumbai, India, between 2007 and 2010, was undertaken and yielded 37 patients. The average tumour size was 2.6 cm. All patients had undergone segmental, marginal, or hemimandibulectomy within 2 weeks of imaging. Imaging records archived on the picture archiving and communication system (PACS) were analysed. Contrast-enhanced CT had been performed using a 16 section MDCT system using the puffed-cheek technique. Image acquisition was at 2.5 mm section thickness, but axial images and isotropic coronal and sagittal multiplanar reformations were generated ad hoc from 0.625 mm retro-reconstructed images. Optimal oblique reformations were generated at will by the radiologist to depict the RMT in its entirety. The soft-tissue algorithm and bone window or bone algorithm reformations and axial images were analysed on a volume viewer integrated within the PACS using triangulation. Two investigators independently studied the images and these were compared with the findings at histopathology. The sensitivity, specificity, and accuracy of 16 section MDCT for mandibular cortical and marrow invasion was 94, 90, and 91.8% and 83, 92, and 89%, respectively. Use of ad hoc generated oblique reformation contributed to the enhanced sensitivity and specificity. The accuracy for inferior alveolar canal invasion was 100%. There was excellent agreement between the two observers. Sixteen-section MDCT used to its full potential has high accuracy for the detection of mandibular invasion in RMT SCC.

A fatal condition in the thoracic aorta

A fatal condition in the thoracic aorta

Effective dose estimates for cone beam computed tomography in interventional radiology

To compare radiation doses in cone beam computed tomography (CBCT) with those of multi-detector computed tomography (MDCT) using manufacturers' standard protocols. Dose-levels in head and abdominal imaging were evaluated using a dosimetric phantom. Effective dose estimates were performed by placing thermoluminescent dosimeters in the phantom. Selected protocols for two CBCT systems and comparable protocols for one MDCT system were evaluated. Organ doses were measured and effective doses derived by applying the International Commission on Radiological Protection 2007 tissue weighting factors. Effective doses estimated for the head protocol were 4.4 and 5.4 mSv for the two CBCT systems respectively and 4.3 mSv for MDCT. Eye doses for one CBCT system and MDCT were comparable (173.6 and 148.4 mGy respectively) but significantly higher compared with the second CBCT (44.6 mGy). Two abdominal protocols were evaluated for each system; the effective doses estimated were 15.0 and 18.6 mSv, 25.4 and 37.0 mSv, and 9.8 and 13.5 mSv, respectively, for each of the CBCT and MDCT systems. The study demonstrated comparable dose-levels for CBCT and MDCT systems in head studies, but higher dose levels for CBCT in abdominal studies. There was a significant difference in eye doses observed between the CBCT systems. • Cone beam computed tomography (CBCT) is increasingly utilised in interventional radiology. • Effective doses for selected CBCT and MDCT protocols were estimated and compared. • Dose levels in CBCT and MDCT were comparable for head studies. • Dose levels were higher in CBCT for abdominal studies.

Revised protocol for whole-body CT for multi-trauma patients applying triphasic injection followed by a single-pass scan on a 64-MDCT

To evaluate a revised protocol for whole-body computed tomography (CT) for multi-trauma patients in an emergency department and compare it to conventional protocols. Forty-two of 82 multi-trauma patients underwent unenhanced CT examinations of the head, cervical spine, and upper abdomen, followed by an arterial-phase contrast-enhanced CT examination of the thorax and a porto-venous scan of the abdomen and pelvis (conventional protocol). The other 40 patients underwent unenhanced CT examinations of the head, cervical spine, and upper abdomen, followed by a one-step acquisition of the thorax, abdomen, and pelvis using a 64-section multidetector CT (MDCT) system following a triphasic injection (revised protocol). Contrast enhancement was measured in the ascending, descending, and abdominal aorta, common iliac arteries, inferior vena cava (IVC), liver, spleen, and kidneys. Image count, radiation dose, total acquisition time, mediastinal artefacts, and image quality of each area were reviewed. Mean enhancement values in the ascending and descending aorta were significantly greater with the conventional protocol. Enhancement of the abdominal aorta, iliac arteries, IVC, liver, spleen, and kidneys was significantly greater with the revised protocol. Mediastinal streak artefacts were present in all conventional protocol images and absent in all revised protocol images. Image quality using the revised protocol was significantly better (p<0.002). The mean effective radiation dose was significantly lower (p=0.005), and image number reduced (p<0.001). The revised triphasic injection single-pass whole-body imaging protocol was superior to the conventional protocol using 64-MDCT. It enabled better vascular and abdominal parenchymal imaging with reduction in radiation dose and image overload.

Single-source dual-energy spectral multidetector CT of pancreatic adenocarcinoma: Optimization of energy level viewing significantly increases lesion contrast

To evaluate lesion contrast in pancreatic adenocarcinoma patients using spectral multidetector computed tomography (MDCT) analysis. The present institutional review board-approved, Health Insurance Portability and Accountability Act of 1996 (HIPAA)-compliant retrospective study evaluated 64 consecutive adults with pancreatic adenocarcinoma examined using a standardized, multiphasic protocol on a single-source, dual-energy MDCT system. Pancreatic phase images (35 s) were acquired in dual-energy mode; unenhanced and portal venous phases used standard MDCT. Lesion contrast was evaluated on an independent workstation using dual-energy analysis software, comparing tumour to non-tumoural pancreas attenuation (HU) differences and tumour diameter at three energy levels: 70 keV; individual subject-optimized viewing energy level (based on the maximum contrast-to-noise ratio, CNR); and 45 keV. The image noise was measured for the same three energies. Differences in lesion contrast, diameter, and noise between the different energy levels were analysed using analysis of variance (ANOVA). Quantitative differences in contrast gain between 70 keV and CNR-optimized viewing energies, and between CNR-optimized and 45 keV were compared using the paired t-test. Thirty-four women and 30 men (mean age 68 years) had a mean tumour diameter of 3.6 cm. The median optimized energy level was 50 keV (range 40-77). The mean ± SD lesion contrast values (non-tumoural pancreas - tumour attenuation) were: 57 ± 29, 115 ± 70, and 146 ± 74 HU (p = 0.0005); the lengths of the tumours were: 3.6, 3.3, and 3.1 cm, respectively (p = 0.026); and the contrast to noise ratios were: 24 ± 7, 39 ± 12, and 59 ± 17 (p = 0.0005) for 70 keV, the optimized energy level, and 45 keV, respectively. For individuals, the mean ± SD contrast gain from 70 keV to the optimized energy level was 59 ± 45 HU; and the mean ± SD contrast gain from the optimized energy level to 45 keV was 31 ± 25 HU (p = 0.007). Significantly increased pancreatic lesion contrast was noted at lower viewing energies using spectral MDCT. Individual patient CNR-optimized energy level images have the potential to improve lesion conspicuity.

A Computed Tomography (CT) wish list, from a medical physicist’s perspective

Significant advances in computed tomography (CT) technology have been made since the first clinical images were published in 1973. The initial clinical applications were brain scans where the patient’s head was immobilised by a water bag that compensated for the large changes in flux adjacent to the head. Body imaging became feasible as improvements led to better image quality and reduced scan times. Improved computing technology has allowed for image reconstruction, including rendering and 3D reconstruction, to all occur in real time. Perfusion studies, cardiac imaging and CT angiography are now common and interventional procedures can be performed using CT fluoroscopy guidance. Some of the major scanner developments that have contributed to this progress are slip-ring technology, which facilitated helical scanning, and multidetector CT systems with capabilities for volume scanning. In addition, increasingly complex X-ray tube designs and novel CT detector materials and configurations have also contributed to changes in CT imaging. Dose reporting began to address concerns raised regarding the risks from radiation exposure and other practical dose reduction measures such as the adaptation of parameters to the patient size were implemented. This included modulating the tube current throughout the scan. More recent CT developments include dual-energy imaging and iterative reconstruction techniques, which are used instead of or in combination with traditional filtered back-projection image formation. All of these improvements in technologies combined have resulted in dose reductions for some CT procedures in the order of 90 %! The changes to image quality, dose and the way in which CT scans are performed have been extensive. However, there are always further enhancements that can be made, especially as user requirements or objectives change. For diagnostic medical physicists, there will always be a wish list of what we would like on a CT scanner. This is largely driven by the work that we undertake and the needs of our colleagues, who request, perform or interpret CT scans. Inevitably, achieving the best health outcome for the patient is the primary concern. The wish list is also influenced by current opinions and attitudes towards CT imaging. Hence, the desirable features for a CT scanner are discussed below, with the rationale for these first explored. A small straw poll of radiologists and radiographers from a variety of workplaces was also undertaken to gauge opinions. Z. Brady (&) Radiology Department, The Alfred, P.O. Box 315, Prahran, VIC 3181, Australia e-mail: z.brady@alfred.org.au

Evaluation der Strahlendosis bei Polytrauma-CT-Untersuchungen eines 64-Zeilen-CT im Vergleich zur 4-Zeilen-CT

To evaluate radiation exposure in whole-body CT (WBCT) of multiple injured patients comparing 4-row multidetector computed tomography (MDCT) to 64-row MDCT. 200 WBCT studies were retrospectively evaluated: 92 4-row MDCT scans and 108 64-row MDCT scans. Each CT protocol was optimized for the particular CT system. The scan length, CT dose index (CTDI), and dose length product (DLP) were recorded and analyzed for radiation exposure. The mean effective dose was estimated based on conversion factors. Student's t-test was used for statistical analysis. The mean CTDIvol values (mGy) of the thorax and abdomen were significantly reduced with 64-row MDCT (10.2±2.5 vs. 11.4±1.4, p<0.001; 14.2±3.7 vs. 16.1±1.7, p<0.001). The DLP values (mGy×cm) of the head and thorax were significantly increased with 64-row MDCT (1305.9±201.1 vs. 849.8±90.9, p<0,001; 504.4±134.4 vs. 471.5±74.1, p=0.030). The scan lengths (mm) were significantly increased with 64-row MDCT: head 223.6±35.8 vs. 155.5±12.3 (p<0.001), thorax 427.4±44.5 vs. 388.3±57.5 (p<0.001), abdomen 520.3±50.2 vs. 490.8±51.6 (p<0.001). The estimated mean effective doses (mSv) were 22.4±2.6 (4-row MDCT) and 24.1±4.6 (64-row MDCT; p=0.001), resulting in a percentage increase of 8%. The radiation dose per slice of the thorax and abdomen can be significantly decreased by using 64-row MDCT. Due to the technical advances of modern 64-row MDCT systems, the scan field can be adapted to the clinical demands and, if necessary, enlarged without time loss. As a result, the estimated mean effective dose might be increased in WBCT.

Image Quality Evaluation of New Image Reconstruction Methods Applying the Iterative Reconstruction

The purpose of this study was to evaluate the image quality of an iterative reconstruction method, the iterative reconstruction in image space (IRIS), which was implemented in a 128-slices multi-detector computed tomography system (MDCT), Siemens Somatom Definition Flash (Definition). We evaluated image noise by standard deviation (SD) as many researchers did before, and in addition, we measured modulation transfer function (MTF), noise power spectrum (NPS), and perceptual low-contrast detectability using a water phantom including a low-contrast object with a 10 Hounsfield unit (HU) contrast, to evaluate whether the noise reduction of IRIS was effective. The SD and NPS were measured from the images of a water phantom. The MTF was measured from images of a thin metal wire and a bar pattern phantom with the bar contrast of 125 HU. The NPS of IRIS was lower than that of filtered back projection (FBP) at middle and high frequency regions. The SD values were reduced by 21%. The MTF of IRIS and FBP measured by the wire phantom coincided precisely. However, for the bar pattern phantom, the MTF values of IRIS at 0.625 and 0.833 cycle/mm were lower than those of FBP. Despite the reduction of the SD and the NPS, the low-contrast detectability study indicated no significant difference between IRIS and FBP. From these results, it was demonstrated that IRIS had the noise reduction performance with exact preservation for high contrast resolution and slight degradation of middle contrast resolution, and could slightly improve the low contrast detectability but with no significance.

Characteristics of x-ray beams in two commercial multidetector computed tomography simulators: Monte Carlo simulations

As multidetector computed tomography (MDCT) scanning is routinely performed for treatment planning in radiation oncology, understanding the characteristics of the MDCT x-ray beam is essential to accurately estimate patient dose. The purpose of this study is to characterize the x-ray beams of two commercial MDCT simulators widely used in radiation oncology by Monte Carlo (MC) simulations. X-ray tube systems of two wide bore MDCT scanners (GE LightSpeed RT 4 and Philips Brilliance Big Bore) were modeled in the BEAMNRC/EGSNRC MC system. All the tube components were modeled from targets to bowtie filters. To validate our MC models, the authors measured half-value layers (HVL) using aluminum sheets and multifunctional radiation detectors and compared them to those obtained from MC simulations for 120 kVp beams. The authors also compared x-ray spectra obtained from MC simulation to the data provided by manufacturers. Additionally, lateral/axial beam profiles were measured in-air using radiochromic films and compared to the MC results. To understand the scatter effect, the authors also derived the scatter-to-primary energy fluence ratio (SPR) profiles and calculated the total SPR for each CT system with the CT dose index (CTDI) head and body phantoms using the BEAMNRC system. The authors found that the HVL, x-ray spectrum and beam profiles of the MC simulations agreed well with the manufacturer-specified data within 1%-10% on average for both scanners. The total SPR were ranged from 7.8 to 13.7% for the head phantom and from 10.7 to 18.9% for the body phantom. The authors demonstrate the full MC simulations of two commercial MDCT simulators to characterize their x-ray beams. This study may be useful to establish a patient-specific dosimetry for the MDCT systems.

SU‐E‐I‐26: A Monte Carlo Based Study on X‐Ray Characteristics of Two Commercial Multi‐Detector CT Simulators

Purpose: As multi‐detector computed tomography (MDCT) scan is routinely performed for treatment planning in radiation oncology, understanding the characteristics of MDCT x‐ray beam is essential to optimize scan protocols as well as to estimate patient dose. The purpose of this study was to characterize the x‐ray beams of two commercial MDCT simulators with Monte Carlo (MC) simulations. Methods: X‐ray tube systems of two wide bore MDCT scanners (GE LightSpeed RT, LS and Philips Brilliance Big Bore, BB) were modeled in the BEAMnrc/EGSnrc systems. All the tube components were modeled: tungsten target, inherent filter, bowtie filter, and beam collimators. Three benchmark processes were performed to validate the MC models. (1) X‐ray spectra comparison between MC and manufacturersˈ data, (2) Half‐value layers (HVLs) between MC and measurements using aluminum sheets and multi‐functional radiation detectors, (3) Lateral and axial beam profiles between MC and radiochromic film measurements To understand the scatter effect of the MDCT beams, scatter‐to‐primary energy fluence ratios (SPRs) were derived and the total SPR for each CT system was calculated with CTDI head and body phantoms.. Results: MC generated x‐ray spectra agreed well with the manufacturer‐specified data over the entire energy range. Effective photon beam energies for 120kVp beam were found to be (MC, vendor‐specified): (60.8, 60.2keV) for LS scatter, and (65.4, 64.9keV) for BB scanner. MC‐computed HVLs were found to be within 1% of the ion chamber measurements on average. The lateral and axial profiles between film and MC showed overall good agreement within 10% on average. The total SPR ranged from 3.5 to 4.9% for head phantom and from 7.1 to 11.1% for body phantom. Conclusion: Complete characterizations of two MDCT scanners have been performed using the BEAMnrc/EGSnrc MC system. This information can be utilized to optimize scan protocols as well as patient‐specific dosimetry for the MDCT systems.

Evaluation of image quality and radiation dose at prospective ECG-triggered axial 256-slice multi-detector CT in infants with congenital heart disease

There are a limited number of reports on the technical and clinical feasibility of prospective electrocardiogram (ECG)-gated multi-detector computed tomography (MDCT) in infants with congenital heart disease (CHD). To evaluate image quality and radiation dose at weight-based low-dose prospectively gated 256-slice MDCT angiography in infants with CHD. From November 2009 to February 2010, 64 consecutive infants with CHD referred for pre-operative or post-operative CT were included. All were scanned on a 256-slice MDCT system utilizing a low-dose protocol (80 kVp and 60-120 mAs depending on weight: 60 mAs for ≤ 3 kg, 80 mAs for 3.1-6 kg, 100 mAs for 6.1-10 kg, 120 mAs for 10.1-15 kg). No serious adverse events were recorded. A total of 174 cardiac deformities, confirmed by surgery or heart catheterization, were studied. The sensitivity of MDCT for cardiac deformities was 97.1%; specificity, 99.4%; accuracy, 95.9%. The mean heart rate during scan was 136.7 ± 14.9/min (range, 91-160) with a corresponding heart rate variability of 2.8 ± 2.2/min (range, 0-8). Mean scan length was 115.3 ± 11.7 mm (range, 93.6-143.3). Mean volume CT dose index, mean dose-length product and effective dose were 2.1 ± 0.4 mGy (range, 1.5-2.8), 24.7 ± 5.9 mGy·cm (range, 14.7-35.8) and 1.6 ± 0.3 mSv (range, 1.1-2.5), respectively. Diagnostic-quality images were achieved in all cases. Satisfactory diagnostic quality for visualization of all/proximal/distal coronary artery segments was achieved in 88.4/98.8/80.0% of the scans. Low-dose prospectively gated axial 256-slice CT angiography is a valuable tool in the routine clinical evaluation of infants with CHD, providing a comprehensive three-dimensional evaluation of the cardiac anatomy, including the coronary arteries.

Clinical application of 320-row multidetector computed tomography for a dynamic three-dimensional vascular study: Imaging findings and initial experience

The 320-row multidetector computed tomography (MDCT) is now used by both cardiologists and neurosurgeons. It enables dynamic 3D-CT angiography, because the wide-area detector eliminates helical scanning, thus achieving very fast scanning times for single 3D-CT volume data. Some microvascular surgeons are familiar with 64-row MDCT for perforator studies, but there are few reports of studies using 320-row MDCT. This MDCT system was used to follow the dynamic blood flow of small vessels. It is considered to have a great potential in the clinical field of microvascular surgery.

A case report of a normal aorta misdiagnosed as type A dissection by modern multidetector computed tomography

Computed tomography (CT) is generally considered the investigation of choice to exclude acute aortic syndrome. We report an important potentially disastrous misdiagnosis using a modern 32 slice multidetector CT system.

Evaluation of pericardial sinuses and recesses with 2-, 4-, 16-, and 64-row multidetector CT

The aim of this study was to describe visualisation rate and appearance of all pericardial sinuses and recesses and to evaluate whether there is a significant difference between visualisation of these sinuses and recesses on 2-, 4-, 16- and 64-slice multidetector computed tomography (MDCT). We retrospectively analysed 588 MDCT scans of the chest obtained with a protocol for pulmonary embolism. The visualisation rate of any pericardial recess was 85.2%. The rates on 2-, 4-, 16- and 64-slice MDCT were 74.7%, 90.6%, 90.3% and 88.7%, respectively. There was a statistically significant difference in visualisation rates of pericardial recesses between 2-slice MDCT and other MDCT systems (p<0.01). Age, and 4-, 16- and 64-slice MDCT versus 2-slice MDCT and the presence of pleural effusion appeared as significant predictors of the presence of any recess. Visualisation rates of pericardial recesses are higher with 4-, 16- and 64-slice MDCT than with 2-slice MDCT. Therefore, radiologists need to be familiar with the different appearances of pericardial recesses on MDCT to avoid misdiagnosis.

Diffuse Liver Disease: Strategies for Hepatic CT and MR Imaging

The liver plays several complex but essential roles in the metabolism of amino acids, carbohydrates, and lipids, as well as synthesis of proteins. The basic pathophysiology of diffuse parenchymal hepatic diseases usually represents a failure in one of these metabolic pathways. Specific parenchymal diseases can be categorized as storage, vascular, and inflammatory diseases. Cross-sectional hepatic imaging techniques, specifically multidetector computed tomography (CT) and magnetic resonance (MR) imaging, have roles in evaluation of diffuse liver disease. The prominent role of multidetector CT is primarily defined by its excellent morphologic visualization capabilities, in particular of diffuse or focal intrahepatic lesions as well as of anatomic relationships between the liver and adjacent organs. The variety of available multidetector CT scanners covers a huge spectrum of detector configurations ranging from equally sized and equally spaced detector arrays to asymmetric detector configurations, resulting in imaging protocols with unique parameters for almost each multidetector CT system. In addition to 64-detector row imaging, hepatic multidetector CT can be performed with emerging techniques such as dual-energy CT. Hepatic MR imaging has been proved to be a comprehensive modality for assessing the morphology and functional characteristics of the liver. Concurrent technical improvements as well as implementation of advanced imaging sequence designs permit high-quality examination of the liver with T1-, T2-, and diffusion-weighted pulse sequences. Three basic demands remain if MR imaging is chosen for hepatic imaging: to improve parenchymal contrast, to suppress respiratory motion, and to ensure complete anatomic coverage. Supplemental material available at http://radiographics.rsna.org/content/29/6/1591/suppl/DC1.

Assessment of trabecular bone structure using MDCT: comparison of 64- and 320-slice CT using HR-pQCT as the reference standard

ObjectivesThe aim of our study was to perform trabecular bone structure analysis with images from 64- and 320-slice multidetector computed tomography (MDCT) and to compare these with high-resolution peripheral computed tomography (HR-pQCT).Materials and methodsTwenty human cadaver distal forearm specimens were imaged on a 64- and 320-slice MDCT system at 120 kVp, 200 mA and 135 kVp, 400 mA (in-plane pixel size 234 µm; slice thickness 500 µm). HR-pQCT imaging was performed at an isotropic voxel size of 41 µm. Bone volume fraction (BV/TV), trabecular number (Tb.N), thickness (Tb.Th) and separation (Tb.Sp) were computed.ResultsMDCT-derived BV/TV and Tb.Sp were highly correlated (r = 0.92–0.96, p < 0.0001) with the corresponding HR-pQCT parameters. Tb.Th was the only structure measure that did not yield any significant correlation.ConclusionThe 64- and 320-slice MDCT systems both perform equally well in depicting trabecular bone architecture. However, because of constrained resolutions accurate derivation of trabecular bone measures is limited to only a subset of microarchitectural parameters.

Low radiation dose ECG-gated chest CT angiography on a 256-slice multidetector CT scanner

Computed tomography angiography (CTA) of the thorax other than cardiac CTA, is utilized for a multitude of conditions and ranges in application from a diagnostic test, to presurgical planning and postsurgical follow-up. Helical CTA without electrocardiogram (ECG) gating has been routinely utilized for the evaluation of thoracic vasculature. However, its applicability can be limited in the evaluation of the thoracic aorta and pulmonary vasculature because of the artifacts resulting from cardiac motion. Traditional retrospective ECG-gated helical scans address this issue but at the price of a high radiation dose to the patient. In this paper we review CTA dose reduction strategies for non-coronary indications, examine field of view requirements, and discuss breath hold challenges for ECG-gated acquisitions. In addition, we present clinical examples performed using low-dose prospective gating technique for evaluation of the aorta acquired on a 256-slice multidetector computed tomography system.

State-Of-The-Art Cardiac CT At The Methodist Hospital

The last decade has witnessed dramatic improvements in computed tomography (CT) technology. Developments have included increasing gantry speeds, addition of multiple thin detector arrays, and more sophisticated software processing for informative image displays. The results have been improved temporal resolution, near isotropic voxels for submillimeter spatial resolution, reduced image acquisition times, and lower radiation exposures with fast scan times.1 As a result, cardiac CT has evolved into a robust technology used to noninvasively assess cardiac structure and function, determine the presence and extent of coronary artery calcification (CAC) and noncalcified plaque, hunt for coronary anomalies, and provide a noninvasive coronary angiogram for diagnosing significant coronary artery disease (CAD} in native vessels or coronary artery bypass grafts (Figures 1-3).Accompanying research literature has evolved at an equally dizzying pace. Whether experimenting with newer CT technologies, comparing them to other cardiac imaging modalities, learning to better characterize plaque, or changing acquisition parameters to reduce radiation exposures, CT is currently generating a level of excitement that is reminiscent of the 1970s, when echocardiography rapidly came into common clinical use.2 Cardiac computed tomography has the potential to revolutionize the current practice of cardiology for CAD detection and treatment, and it is expected that its use and development will continue to accelerate in the upcoming years.The Methodist DeBakey Heart &amp; Vascular Center (MDHVC) is actively committed to the research, clinical activity, and teaching of cardiac CT. Under the leadership of the center's medical director of nuclear cardiology John J. Mahmarian, M.D., two board-certified nuclear-CT cardiologists have come on board and two state-of-the-art multidetector CT (MDCI) systems dedicated to cardiac imaging are now place. Also, under Mahmarian, the clinical volumes have rapidly expanded to more than 400 cardiac cases per year. Every effort is being made to design, coordinate, and participate in research trials to advance this promising field while at the same time showcasing this robust tool to clinicians.