Preliminary Results: Can Dual-Energy Computed Tomography Help Distinguish Cardiogenic Pulmonary Edema and Acute Interstitial Lung Disease?

OBJECTIVE: We compared iodine concentration in pulmonary ground-glass opacity on iodine density images of contrast-enhanced chest dual-energy computed tomography (DECT) between patients with cardiogenic pulmonary edema (CPE) and acute interstitial lung disease (AILD). METHODS: Five of 12 patients who underwent contrast-enhanced chest DECT to exclude pulmonary embolism were clinically diagnosed with CPE and 7, with AILD. We compared the mean CT value on monochromatic images at 65 keV and iodine concentration on iodine density images between the affected and normal areas. RESULTS: The mean iodine concentrations were comparable between the affected and normal areas (P = 0.3048) in patients with CPE and were significantly higher in the affected than in the normal areas in those with AILD (P < 0.0001). CONCLUSIONS: Measurement of iodine concentration in pulmonary ground-glass opacity of contrast-enhanced chest DECT has the potential to help distinguish CPE and AILD.

Clinical application of effective atomic number for classifying non-calcified coronary plaques by dual-energy computed tomography.

BACKGROUND AND AIMS: Coronary computed tomography (CT) angiography allows non-invasive classification of non-calcified coronary plaques (NCCPs) based on Hounsfield unit (HU) values. This methodology, however, is somewhat limited for reliable classification of NCCPs. Therefore, we evaluated the effective atomic number (EAN) for classifying NCCPs by single-source dual-energy CT with fast tube voltage switching (SSDECT). METHODS: We prospectively enrolled 18 patients undergoing both SSDECT and intravascular ultrasonography (IVUS). Monochromatic images at 70 keV and EAN images were reconstructed from SSDECT data sets. Regions of interest (ROIs) within NCCPs were placed on IVUS-matched SSDECT images, and mean HU values and EANs for soft and fibrous plaques, classified using IVUS, were compared with an unpaired t-test. RESULTS: We placed 96 ROIs in 29 soft plaques and 37 ROIs in 15 fibrous plaques in 12 coronary arteries of 11 patients. The mean HU value in soft plaques (58.2 ± 32.8 HU) was significantly lower than that in fibrous plaques (103.9 ± 48.3 HU) (p < 0.001). The mean EAN in soft plaques (8.7 ± 0.5) was also significantly lower than that in fibrous plaques (9.6 ± 0.5) (p < 0.0001). Area under the curve for EAN (0.91) was significantly higher than that for HU value (0.79) in receiver operating characteristic curve analysis (p = 0.046). With a cutoff EAN of 9.3, sensitivity was 90% and specificity, 87%; whereas with a cutoff HU value of 55.0 HU, sensitivity was 62% and specificity, 93%. CONCLUSIONS: EAN measurement by SSDECT can be clinically useful for accurately classifying soft and fibrous coronary plaques.

Dual-Energy Spectral CT: Various Clinical Vascular Applications.

Single-source dual-energy (DE) computed tomography (CT) with fast switching of tube voltage allows projection-based image reconstruction, substantial reduction of beam-hardening effects, reconstruction of accurate monochromatic images and material decomposition images (MDIs), and detailing of material composition by using x-ray spectral information. In vascular applications, DE CT is expected to overcome limitations of standard single-energy CT angiography, including patient exposure to nephrotoxic contrast medium and carcinogenic radiation, insufficient contrast vascular enhancement, interference from metallic and beam-hardening artifacts and severe vessel calcification, and limited tissue characterization and perfusion assessment. Acquisition of low-energy monochromatic images and iodine/water MDIs can reasonably reduce contrast agent dose and improve vessel enhancement. Acquisition of virtual noncontrast images, such as water/iodine MDIs, can reduce overall radiation exposure by replacing true noncontrast CT in each examination. Acquisition of monochromatic images by using metal artifact reduction software or acquisition of iodine/water MDIs can reduce metal artifacts with preserved or increased vessel contrast, and subtraction of monochromatic images between two energy levels can subtract coils composed of dense metallic materials. Acquisition of iodine/calcium (ie, hydroxyapatite) MDIs permits subtraction of vessel calcification and improves vessel lumen delineation. Sensitive detection of lipid-rich plaque can be achieved by using fat/water MDIs, the spectral Hounsfield unit curve (energy level vs CT attenuation), and a histogram of effective atomic numbers included in an image. Various MDIs are useful for accurate differentiation among materials with high attenuation values, including contrast medium, calcification, and fresh hematoma. Iodine/water MDIs are used to assess organ perfusion, such as in the lungs and myocardium. Understanding these DE CT techniques enhances the value of CT for vascular applications. (©)RSNA, 2016.

Reduction of Coronary Motion Artifacts in Prospectively Electrocardiography-Gated Coronary Computed Tomography Angiography Using Monochromatic Imaging at Various Energy Levels in Combination With a Motion Correction Algorithm on Single-Source Fast Tube Voltage Switching Dual-Energy Computed Tomography: A Phantom Experiment.

OBJECTIVES: The aim of this study was to assess the effect of monochromatic imaging at various energy levels in combination with a motion correction algorithm (MCA) in single-source dual-energy coronary computed tomography angiography (CCTA) with fast switching of tube voltage on the reduction of coronary motion artifacts (CMA) in a phantom setting. MATERIALS AND METHODS: Using this dual-energy computed tomography technique with a phantom comprising models of coronary vessels filled with contrast medium and pulsating at constant heart rates of 60 to 100 beats per minute, we reconstructed monochromatic images of CCTA obtained at 50 to 90 keV with and without use of MCA. Cardiac motion was modeled by simulating the in vivo time-volume curve of the left ventricle. Two independent readers graded CMA in 9 coronary segments using a 5-point scale (1, poor; 3 to 5, interpretable; 5, excellent). At each heart rate, we compared the average score of CMA between images obtained at 50 to 90 keV with and without use of MCA using Wilcoxon signed rank test, and we compared the score among images obtained at 50 to 90 keV with use of MCA using Kruskal-Wallis and post hoc tests. We also compared the percentages of image interpretability and improvement in image interpretability among images obtained at 50 to 90 keV with use of MCA. RESULTS: With the use of MCA, the average score of CMA was significantly higher for images obtained at each energy level from 50 to 70 keV (P < 0.05) and was comparable at 80 and 90 keV, and it was comparable among those obtained at 50 to 70 keV. With its use, the percentages of image interpretability were similarly high at 50 to 70 keV at 60 to 80 beats per minute (78%-100%), and they were higher at 50 to 60 keV (72%-83%) than at 70 keV at 90 to 100 beats per minute (50%-56%). The percentages of improved image interpretability with MCA were similarly high at 50 to 70 keV at 60 to 80 beats per minute (56%-100%), and they were higher at 50 to 60 keV (62%-77%) than at 70 keV at 90 to 100 beats per minute (36%-43%). The percentages of image interpretability and improved image interpretability with MCA were insufficient at 80 and 90 keV. CONCLUSIONS: Coronary motion artifacts were significantly reduced in images of monochromatic CCTA obtained at 50 to 70 keV in combination with MCA compared with those obtained without MCA, and the percentages of image interpretability and improved image interpretability with use of MCA were relatively high at 50 to 70 keV, and particularly at 50 to 60 keV, even at 90 to 100 beats per minute.

Whole-Body Clinical Applications of Digital Tomosynthesis.

With flat-panel detector mammography, radiography, and fluoroscopy systems, digital tomosynthesis (DT) has been recently introduced as an advanced clinical application that removes overlying structures, enhances local tissue separation, and provides depth information about structures of interest by providing high-quality tomographic images. DT images are generated from projection image data, typically using filtered back-projection or iterative reconstruction. These low-dose x-ray projection images are easily and swiftly acquired over a range of angles during a single linear or arc sweep of the x-ray tube assembly. DT is advantageous in a variety of clinical contexts, including breast, chest, head and neck, orthopedic, emergency, and abdominal imaging. Specifically, compared with conventional mammography, radiography, and fluoroscopy, as a result of reduced tissue overlap DT can improve detection of breast cancer, pulmonary nodules, sinonasal mucosal thickening, and bone fractures and delineation of complex anatomic structures such as the ostiomeatal unit, atlantoaxial joint, carpal and tarsal bones, and pancreatobiliary and gastrointestinal tracts. Compared with computed tomography, DT offers reduced radiation exposure, better in-plane resolution to improve assessment of fine bony changes, and less metallic artifact, improving postoperative evaluation of patients with metallic prostheses and osteosynthesis materials. With more flexible patient positioning, DT is also useful for functional, weight-bearing, and stress tests. To optimize patient management, a comprehensive understanding of the clinical applications and limitations of whole-body DT applications is important for improvement of diagnostic quality, workflow, and cost-effectiveness. Online supplemental material is available for this article. (©)RSNA, 2016.

Current and Novel Imaging Techniques in Coronary CT.

Multidetector coronary computed tomography (CT), which is widely performed to assess coronary artery disease noninvasively and accurately, provides excellent image quality. Use of electrocardiography (ECG)-controlled tube current modulation and low tube voltage can reduce patient exposure to nephrotoxic contrast media and carcinogenic radiation when using standard coronary CT with a retrospective ECG-gated helical scan. Various imaging techniques are expected to overcome the limitations of standard coronary CT, which also include insufficient spatial and temporal resolution, beam-hardening artifacts, limited coronary plaque characterization, and an inability to allow functional assessment of coronary stenosis. Use of a step-and-shoot scan, iterative reconstruction, and a high-pitch dual-source helical scan can further reduce radiation dose. Dual-energy CT can improve contrast medium enhancement and reasonably reduce the contrast dose when combined with noise reduction with the use of iterative reconstruction. High-definition CT can improve spatial resolution and diagnostic evaluation of small or peripheral coronary vessels and coronary stents. Dual-source CT and a motion correction algorithm can improve temporal resolution and reduce coronary motion artifacts. Whole-heart coverage with 320-detector CT and an intelligent boundary registration algorithm can eliminate stair-step artifacts. By decreasing beam hardening and enabling material decomposition, dual-energy CT is expected to remove or reduce the depiction of coronary calcification to improve intraluminal evaluation of calcified vessels and to provide detailed analysis of coronary plaque components and accurate qualitative and quantitative assessment of myocardial perfusion. Fractional flow reserve derived from coronary CT is a state-of-the-art noninvasive technique for accurately identifying myocardial ischemia beyond coronary CT. Understanding these techniques is important to enhance the value of coronary CT for assessment of coronary artery disease.

Iterative image reconstruction that includes a total variation regularization for radial MRI.

This paper presents an iterative image reconstruction method for radial encodings in MRI based on a total variation (TV) regularization. The algebraic reconstruction method combined with total variation regularization (ART_TV) is implemented with a regularization parameter specifying the weight of the TV term in the optimization process. We used numerical simulations of a Shepp-Logan phantom, as well as experimental imaging of a phantom that included a rectangular-wave chart, to evaluate the performance of ART_TV, and to compare it with that of the Fourier transform (FT) method. The trade-off between spatial resolution and signal-to-noise ratio (SNR) was investigated for different values of the regularization parameter by experiments on a phantom and a commercially available MRI system. ART_TV was inferior to the FT with respect to the evaluation of the modulation transfer function (MTF), especially at high frequencies; however, it outperformed the FT with regard to the SNR. In accordance with the results of SNR measurement, visual impression suggested that the image quality of ART_TV was better than that of the FT for reconstruction of a noisy image of a kiwi fruit. In conclusion, ART_TV provides radial MRI with improved image quality for low-SNR data; however, the regularization parameter in ART_TV is a critical factor for obtaining improvement over the FT.

Analysis of coronary arterial calcification components with coronary CT angiography using single-source dual-energy CT with fast tube voltage switching.

Clinical cardiac applications of single-source dual-energy computed tomography (DECT) have recently been introduced. This study aimed to analyze the components of coronary arterial calcification (CAC) in vivo by material decomposition achieved with DECT. We reconstructed computed tomography (CT) angiography images for 51 consecutive patients with CACs who had undergone electrocardiography-gated coronary CT angiography by single-source DECT with fast tube voltage switching. We placed regions of interest (ROIs) within the CAC with margins of at least 0.5 mm to minimize partial volume averaging. We compared histograms for the effective atomic number (EAN) and the median, mean, and maximum EANs for each CAC with the theoretical EANs for possible CAC components, including hydroxyapatite (HA), calcium oxalate monohydrate (COM), and dicalcium phosphate dehydrate. We also investigated the in vivo EAN for COM and in vitro EAN for HA by our phantom experiment. Analysis of the CAC components was feasible in 177 ROIs from 28 patients. The median EAN was 13.8 ± 0.8 (95% confidence interval 13.7-13.9), which is similar to the theoretical EAN for COM (13.8). The EAN for HA in vitro was 16.5 ± 0.1, which was slightly higher than the theoretical EAN value for HA (16.1). Notably, the median EAN in 144 ROIs (81.4%) was between 11.2 and 14.4, which is the reported range of the in vivo EAN for COM. Our results suggest that COM might be a more frequent CAC component than previously reported.

Influence of the motion correction algorithm on the quality and interpretability of images of single-source 64-detector coronary CT angiography among patients grouped by heart rate.

PURPOSE: We retrospectively investigated the effect of the motion correction algorithm (MCA) on image quality and interpretability by heart rate (HR) in coronary CT angiography (CCTA). MATERIALS AND METHODS: For 105 patients (6 HR groups) undergoing CCTA, 2 readers independently graded the image quality of the 4 major coronary arteries reconstructed with and without MCA at diastole with HR ≤64 bpm and at systole and diastole ≥65 bpm using a 5-point scale. For each HR group and cardiac phase, we compared per-vessel and per-segment image quality using Wilcoxon signed rank test and percentages of interpretable image quality (scores 3-5) among without MCA at diastole with HR ≤64 bpm, as a reference, with MCA at diastole ≤69 bpm and at systole 70-79 bpm using the chi-square test. RESULTS: The motion correction algorithm reconstruction provided similar or better image quality and interpretability in all groups, with 96-100 % per-vessel (P = 0.008 for the right coronary artery; otherwise, P > 0.05) and 99 % per-segment interpretable image quality (P = 0.0002) at diastole with HR ≤69 bpm and at systole 70-79 bpm compared to the reference (88-100 and 97 %, respectively). CONCLUSION: MCA reconstruction preserved image quality and interpretability of CCTA with HR ≤79 bpm.

CT of the pancreas: comparison of image quality and pancreatic duct depiction among model-based iterative, adaptive statistical iterative, and filtered back projection reconstruction techniques.

The purpose of this study is to compare CT images of the pancreas reconstructed with model-based iterative reconstruction (MBIR), adaptive statistical iterative reconstruction (ASiR), and filtered back projection (FBP) techniques for image quality and pancreatic duct (PD) depiction. Data from 40 patients with contrast-enhanced abdominal CT [CTDIvol: 10.3 ± 3.0 (mGy)] during the late arterial phase were reconstructed with FBP, 40% ASiR-FBP blending, and MBIR. Two radiologists assessed the depiction of the main PD, image noise, and overall image quality using 5-point scale independently. Objective CT value and noise were measured in the pancreatic parenchyma, and the contrast-to-noise ratio (CNR) of the PD was calculated. The Friedman test and post-hoc multiple comparisons with Bonferroni test following one-way ANOVA were used for qualitative and quantitative assessment, respectively. For the subjective assessment, scores for MBIR were significantly higher than those for FBP and 40% ASiR (all P < 0.001). No significant differences in CT values of the pancreatic parenchyma were noted among FBP, 40% ASiR, and MBIR images (P > 0.05). Objective image noise was significantly lower and CNR of the PD was higher with MBIR than with FBP and 40% ASiR (all P < 0.05). Our results suggest that pancreatic CT images reconstructed with MBIR have lower image noise, better image quality, and higher conspicuity and CNR of the PD compared with FBP and ASiR.

A method for selecting a protocol for routine body CT scan using Gemstone Spectral Imaging with or without adaptive statistical iterative reconstruction: phantom experiments.

PURPOSE: To investigate a method for selecting a protocol for body CT scan to acquire monochromatic images (MIs) by gemstone spectral imaging (GSI) with or without adaptive statistical iterative reconstruction (ASiR). MATERIALS AND METHODS: We subjected a phantom to conventional scanning at 120 kVp and 50-700 mAs and GSI at 165-600 mAs; reconstructed MIs at 65 keV with ASiR 0-100 % for GSI; placed 5 regions of interest on each of 3 consecutive reconstructed slices to obtain the averaged standard deviation (SD) as image noise for conventional scan and GSI. Linear regression analysis yielded the mAs by conventional scan that could be used to achieve similar image noise by GSI. RESULTS: To achieve similar noise, we found excellent linear correlation of mAs between GSI with ASiR 0-100 % and conventional scan (r = 1.00, P < 0.0001), and obtained a table of equivalent mAs between MIs at 65 keV and conventional CT at 120 kVp. CONCLUSIONS: We can select a protocol for body CT scan for MIs at 65 keV with or without ASiR with results comparable to those of conventional CT at 120 kVp.

Diameter measurement of vascular model on CT angiography using model-based iterative reconstruction: effect of tube current on accuracy.

OBJECTIVE: The purpose of this study was to evaluate the effect of tube current on the accuracy of vascular diameter measurements on CT angiography using model-based iterative reconstruction (MBIR). MATERIALS AND METHODS: We constructed a physical phantom composed of nine vascular models of three wall thicknesses filled with contrast material of three densities and scanned the phantom using a 64-MDCT unit with tube currents of 80, 40, 20, and 10 mA. We reconstructed raw data using MBIR and filtered back projection (FBP) algorithms and examined image sharpness by edge rise distance using four tube currents in each of the two reconstruction methods. We measured the mean inner diameter for each model for each set of image data using MBIR with the four tube currents (80, 40, 20, and 10 mA) and FBP with tube current of 80 mA. RESULTS: Sharpness decreased as tube current decreased using MBIR (p < 0.0001) but did not differ significantly among the four tube currents using FBP (p = 0.0506). Sharpness using MBIR with 10 mA tube current was comparable to or significantly worse than that with FBP. The measurement error using MBIR tended to increase as tube current decreased. The measurement errors using MBIR with 10 mA tube current were comparable to or significantly larger than those using FBP for eight of the nine vascular models. CONCLUSION: By decreasing spatial resolution, MBIR with lower tube current can enhance errors in measurement of vascular diameter and should be applied carefully in evaluating vessel diameter.

Origin of sylvian hematoma in patients with subarachnoid hemorrhage: findings of extravasation on multiphase contrast-enhanced computed tomography.

OBJECTIVE: Sylvian hematoma in subarachnoid hemorrhage (SAH) is associated with a poor prognosis. Although active bleeding can be detected by multiphase dynamic enhanced computed tomography (CT), bleeding from vessels in the Sylvian fissure has also been found in Sylvian hematoma. We investigated possible origins of Sylvian hematoma based on novel imaging findings of multiphase enhanced CT. METHODS: We investigated a series of SAH patients with or without Sylvian hematoma. The existence of active bleeding in a Sylvian hematoma was evaluated using multiphase dynamic enhancement CT perfusion scans. The location of the aneurysm as well as regional cerebral blood volume and flow were also recorded. RESULTS: Among 71 SAH patients, 8 were found to have a Sylvian hematoma (11.3%), 3 of which showed multiple extravasations from small vessels apart from the ruptured aneurysms. No extravasations were found in the remaining patients in other cerebral artery territories, even those associated with Sylvian hematoma. No severe perfusion disturbance was observed in patients with extravasation in a Sylvian hematoma. CONCLUSIONS: Sylvian hematomas may be caused secondarily by multiple bleeds from small vessels together with aneurysm rupture.

Dual-energy subtraction radiography improves laryngeal delineation in patients with moderate to severe cervical spondylosis.

PURPOSE: To investigate the feasibility of dual-energy subtraction (DES) in patients with moderate-severe cervical spondylosis for improving delineation of the larynx on flat panel detector (FPD) radiography. MATERIALS AND METHODS: For 118 patients, we graded conventional/DES anterior-posterior views for delineation of the vocal cords, subglottis, and pyriform sinus using a 5-point scale and lateral views from conventional laryngeal FPD radiography to determine cervical spondylosis severity on a scale from 0 (none) to 3 (severe). We compared the delineation of each anatomical structure in both groups of grades 0-1 and grades 2-3 of spondylosis severity between conventional and DES methods and the improved delineation rate for each anatomical structure by DES compared to the conventional method between both groups. RESULTS: With DES, the delineation of each anatomical structure was significantly better than with conventional radiography for both groups (P < 0.0001). The improved delineation rate of the vocal cord and subglottis using DES was significantly higher in grades 2-3 than in grades 0-1 (P < 0.05), although there was no significant difference in the delineation rate of the pyriform sinus between the groups (P = 0.847). CONCLUSION: DES provides better delineation of the laryngeal anatomy than conventional FPD radiography predominantly in patients with moderate-severe cervical spondylosis.

Reproducibility of scan prescription in follow-up brain MRI: manual versus automatic determination.

In follow-up brain magnetic resonance imaging (MRI), precise reproducibility of the scan prescription is important so that over- or underestimating changes in volumes of clinical interest is prevented. (The scan prescription is defined as the location and orientation of the head with respect to the scan planes of the three-dimensional MRI matrix.) In this study, the misregistration between the original and a second scan was calculated in the case of both manual positioning and automatic positioning. These calculations were carried out both for a healthy volunteer scanned repeatedly and, in a retrospective study, for 225 patients who had an original and at least one follow-up scan. The effects of the scan operator being the same for both scans or being different were also examined. A commercially available 1.5 Tesla MRI system and a six-element head-array coil were employed in all of the imaging. The reproducibility of the scan prescription was determined by the registration of the original scan image to the follow-up scan image by use of the Fourier phase correlation method. Our results showed that (1) the reproducibility by automatic positioning was superior to that by manual positioning (p < 0.05), and (2) there was no significant difference in the results between when the operator was the same or different (p > 0.05). We conclude that, in follow-up brain MRI, automatic positioning should be used, because manual positioning decreases the reproducibility of the scan prescription even if the same operator performs the second scan.

Detection of paranasal sinus opacification with digital tomosynthesis radiography: a clinical pilot study.

OBJECTIVE: We investigated the diagnostic accuracy of digital tomosynthesis (DT) radiography for detecting sinus opacification. METHODS: For 31 adult patients with signs suggestive of sinusitis who underwent both sinus multi-detector-row computed tomography and DT, 2 readers independently assessed opacification in the maxillary, ethmoid, frontal, and sphenoid sinuses by DT and in consensus determined the presence of opacification in each sinus by multi-detector-row computed tomography as a reference. We assessed the diagnostic accuracy of DT and interreader agreement with DT using Cohen κ statistics. RESULTS: For the maxillary, ethmoid, frontal, and sphenoid sinuses, opacification was identified in 81.7%, 75.9%, 59.3%, and 40.7%; the sensitivity/specificity for detecting opacification by DT were 93.9/72.7%, 79.5/71.4%, 93.8/72.7%, and 90.9/75.0% for reader 1 and 95.9/100.0%, 95.5/92.9%, 100.0/81.8%, and 81.8/75.0% for reader 2; the interreader agreement was 0.79, 0.42, 0.67, and 0.63, respectively. CONCLUSIONS: Digital tomosynthesis allows relatively accurate detection of sinus opacification with substantial interreader agreement for all the sinuses except the ethmoid sinuses.

Vascular diameter measurement in CT angiography: comparison of model-based iterative reconstruction and standard filtered back projection algorithms in vitro.

OBJECTIVE: The purpose of this study was to evaluate the performance of model-based iterative reconstruction (MBIR) in measurement of the inner diameter of models of blood vessels and compare performance between MBIR and a standard filtered back projection (FBP) algorithm. MATERIALS AND METHODS: Vascular models with wall thicknesses of 0.5, 1.0, and 1.5 mm were scanned with a 64-MDCT unit and densities of contrast material yielding 275, 396, and 542 HU. Images were reconstructed images by MBIR and FBP, and the mean diameter of each model vessel was measured by software automation. Twenty separate measurements were repeated for each vessel, and variance among the repeated measures was analyzed for determination of measurement error. For all nine model vessels, CT attenuation profiles were compared along a line passing through the luminal center on axial images reconstructed with FBP and MBIR, and the 10-90% edge rise distances at the boundary between the vascular wall and the lumen were evaluated. RESULTS: For images reconstructed with FBP, measurement errors were smallest for models with 1.5-mm wall thickness, except those filled with 275-HU contrast material, and errors grew as the density of the contrast material decreased. Measurement errors with MBIR were comparable to or less than those with FBP. In CT attenuation profiles of images reconstructed with MBIR, the 10-90% edge rise distances at the boundary between the lumen and vascular wall were relatively short for each vascular model compared with those of the profile curves of FBP images. CONCLUSION: MBIR is better than standard FBP for reducing reconstruction blur and improving the accuracy of diameter measurement at CT angiography.

Improved delineation of the anterior spinal artery with model-based iterative reconstruction in CT angiography: a clinical pilot study.

OBJECTIVE: The purpose of this study was to investigate the utility of model-based iterative reconstruction (MBIR) for improving delineation of the anterior spinal artery (ASA) during routine-dose CT angiography. MATERIALS AND METHODS: For imaging of 10 patients (six men, four women; mean age, 73.9 ± 7.5 years) consecutively undergoing CT angiography of the whole aorta with a 12-HU noise index, we used filtered back projection with a standard kernel, adaptive statistical iterative reconstruction of 40% with a detail kernel, and MBIR to reconstruct axial and oblique coronal multiplanar reformation images to delineate the ASA. We measured objective noise in the spinal cord and contrast-to-noise ratio (CNR) between the aorta and spinal cord on axial images at the T12 level. Two radiologists independently graded subjective noise and ASA delineation on the multiplanar reformation images from 1 (poor) to 4 (excellent). We compared results among the three reconstructions using one-way analysis of variance and Tukey-Kramer significance tests. RESULTS: Objective noise, CNR, and subjective image noise and ASA delineation improved significantly with MBIR. Image noise was 18.4 ± 3.6 HU and CNR, 23.4 ± 8.6 (reader 1 scores, 3.9 ± 0.3 and 3.7 ± 0.5; reader 2, 3.9 ± 0.3 and 3.5 ± 0.7). With filtered back projection, image noise was 34.7 ± 8.3 HU and CNR 12.1 ± 4.0 (reader 1 scores, 2.0 ± 0.0 and 2.2 ± 0.4; reader 2, 2.2 ± 0.4 and 2.5 ± 0.7), and with ASIR, 33.0 ± 8.1 HU and 12.7 ± 4.3 (reader 1 scores, 2.0 ± 0.0 and 2.2 ± 0.4; reader 2, 2.2 ± 0.4 and 2.5 ± 0.7) (p < 0.05). Results between filtered back projection and adaptive statistical iterative reconstruction were comparable. CONCLUSION: Use of MBIR can improve delineation of the ASA during CT angiography.

Usefulness of left ventricular diastolic function assessed by magnetic resonance imaging over invasive coronary flow reserve measurement for detecting cardiac allograft vasculopathy in heart transplant recipients.

Heart transplant recipients undergo annual screening of early-stage cardiac allograft vasculopathy (CAV) by invasive coronary flow reserve (CFR) measurement. We compared the sensitivity for CAV detection between the CFR measurement and noninvasive magnetic resonance (MR) assessment of left ventricular (LV) diastolic function. In 46 asymptomatic recipients (29 men, aged 35.2 ± 16.1 years) 7.9 ± 4.3 years after transplantation, we measured LV peak filling rate (PFR) using cine MR and CFR in the left anterior descending artery by Doppler guidewire; classified recipients of class 0-2 as negative for CAV and class 3-4, positive, according to Stanford classification assessed by IVUS; compared those values between the 2 groups; and calculated receiver operating characteristic curve in the relationship between PFR value and CAV. We classified 20 recipients (43%) positive and 26 (57%) negative for CAV. Although there was no significant difference in CFR value, the PFR value was significantly lower in the positive (3.54 ± 0.84 EDV/s) than in negative group (4.39 ± 0.85 EDV/s, P = 0.002). Area under the curve was 0.78, and the sensitivity was 78% and specificity, 61%, when PFR cut-off value was 4.20. MR PFR measurement provides noninvasive prediction of CAV, preceding impaired CFR in asymptomatic recipients.

Depicting the semicircular canals with inner-ear MRI: a comparison of the SPACE and TrueFISP sequences.

PURPOSE: To assess the ability of magnetic resonance imaging (MRI) to depict the semicircular canals of the inner ear by comparing results from the sampling perfection with application-optimized contrasts by using different flip angle evolutions (SPACE) sequence with those from the true free induction with steady precession (TrueFISP) sequence. MATERIALS AND METHODS: A 1.5-T MRI system was used to perform an in vivo study of 10 healthy volunteers and 17 patients. A three-point visual score was employed for assessing the depiction of the semicircular canals and facial and vestibulocochlear nerves and the contrast-to-noise ratio (CNR) was computed for the vestibule and pons on images with the SPACE and TrueFIPS sequences. RESULTS: There were no susceptibility artifact-related filling defects with the SPACE sequence. However, the TrueFISP sequence showed filling defects for at least one semicircular canal on both sides in seven cases for healthy subjects and in 10 cases for patients. The CNR with the SPACE sequence was significantly higher than with the TrueFISP sequence (P < 0.05). There was no statistically significant difference in depicting the facial and the vestibulocochlear nerves (P = 0.32). CONCLUSION: For the depiction of the semicircular canal, the SPACE sequence is superior to the TrueFISP sequence.