Optimizing Coronary Computed Tomography Angiography Using a Novel Deep Learning-Based Algorithm.

Coronary computed tomography angiography (CCTA) is an essential part of the diagnosis of chronic coronary syndrome (CCS) in patients with low-to-intermediate pre-test probability. The minimum technical requirement is 64-row multidetector CT (64-MDCT), which is still frequently used, although it is prone to motion artifacts because of its limited temporal resolution and z-coverage. In this study, we evaluate the potential of a deep-learning-based motion correction algorithm (MCA) to eliminate these motion artifacts. 124 64-MDCT-acquired CCTA examinations with at least minor motion artifacts were included. Images were reconstructed using a conventional reconstruction algorithm (CA) and a MCA. Image quality (IQ), according to a 5-point Likert score, was evaluated per-segment, per-artery, and per-patient and was correlated with potentially disturbing factors (heart rate (HR), intra-cycle HR changes, BMI, age, and sex). Comparison was done by Wilcoxon-Signed-Rank test, and correlation by Spearman's Rho. Per-patient, insufficient IQ decreased by 5.26%, and sufficient IQ increased by 9.66% with MCA. Per-artery, insufficient IQ of the right coronary artery (RCA) decreased by 18.18%, and sufficient IQ increased by 27.27%. Per-segment, insufficient IQ in segments 1 and 2 decreased by 11.51% and 24.78%, respectively, and sufficient IQ increased by 10.62% and 18.58%, respectively. Total artifacts per-artery decreased in the RCA from 3.11 ± 1.65 to 2.26 ± 1.52. HR dependence of RCA IQ decreased to intermediate correlation in images with MCA reconstruction. The applied MCA improves the IQ of 64-MDCT-acquired images and reduces the influence of HR on IQ, increasing 64-MDCT validity in the diagnosis of CCS.

Glymphatic System in Ocular Diseases: Evaluation of MRI Findings.

BACKGROUND AND PURPOSE: There is growing evidence of leakage of gadolinium in an impaired blood-retina barrier. We investigated gadolinium enhancement in different eye compartments and correlated the enhancement with specific ophthalmologic diseases. MATERIALS AND METHODS: In a prospective clinical study (ClinicalTrials.gov Identifier: NCT05035251), 95 patients (63 with and 32 without ophthalmologic disease) were examined before and after gadolinium administration (20 and 120 minutes) with heavily T2-weighted FLAIR. The cohort was divided according to the location of pathology into anterior and posterior eye compartment groups. Relative signal intensity increase in the anterior eye chamber, vitreous body with retina, optic nerve sheath, and the Meckel cave was analyzed and correlated with the final clinical diagnosis. RESULTS: In patients with a disorder in the anterior eye compartment, significant signal intensity increases were found in the central anterior eye chamber (P 20 minutes = .000, P 120 minutes = .000), lateral anterior eye chamber (P 20 minutes = .001, P 120 minutes = .005), and vitreous body with retina (P 20 minutes = .02) compared with the control group. Patients with pathologies in the posterior eye compartment showed higher signal intensity levels in the central anterior eye compartment (P 20 minutes = .041) and vitreous body with retina (P 120 minutes = .006). CONCLUSIONS: Increased gadolinium enhancement was found in the central and lateral anterior eye compartments and the vitreous body with retina in patients with anterior eye compartment disorders 20 and 120 minutes after contrast application, suggesting impairment of the blood-aqueous barrier. In patients with a disorder in the posterior eye compartment, pathologic enhancement indicated disruption of the blood-retinal barrier that allows gadolinium to diffuse into the vitreous body with retina from posterior to anterior, opposite to the known physiologic glymphatic pathway.

Corrigendum to "Improving contrast enhancement in pulmonary CTA: The value of breathing maneuvers" [Eur J Radiol Open 7 (2020) 100280].

[This corrects the article DOI: 10.1016/j.ejro.2020.100280.].

[Current diagnostic imaging and treatment planning for laryngeal cancer]. / Aktuelle Bildgebung bei Diagnostik und Therapieplanung des Larynxkarzinoms.

CLINICAL/METHODICAL ISSUE: Laryngeal cancer is the third most common malignancy in the head and neck region. Endoscopic laryngoscopy with assessment of vocal fold function, microlaryngoscopy with biopsy and computed tomography (CT)/magnetic resonance imaging (MRI) remain the cornerstones of diagnostic workup. Thus, in the context of therapy planning, consideration of individual functional and socioeconomic aspects is of major importance. STANDARD RADIOLOGICAL METHODS: Due to the short acquisition time and the possibility to perform functional maneuvers, CT is the tool of choice. MRI allows better soft tissue differentiation, but is more susceptible to movement artifacts and is complicated by disease-specific symptoms. The choice of examination method therefore depends on the patient's physical resilience. PERFORMANCE: Depending on the study, the information on the sensitivity of CT with regard to the question of cartilage infiltration varies between 62 and 87% with a specificity between 75 and 98%. For MRI, sensitivity between 64 and 95% and specificity between 56 and 88% are stated. ACHIEVEMENTS: The synthesis of the findings from endoscopy, biopsy and imaging is prerequisite for initiation of stage-appropriate treatment. For image interpretation, knowledge of the anatomical landmarks is essential. However, the assessment of posttherapeutic changes also poses a challenge for the radiologist. PRACTICAL RECOMMENDATIONS: Regular interdisciplinary dialogue between radiologists, otorhinolaryngologists and radiotherapists in the context of primary diagnostics, therapy planning and aftercare is essential.

Improving Contrast Enhancement in Pulmonary CTA: The value of breathing maneuvers.

PURPOSE: To investigate contrast dynamics and artifacts associated with different breathing maneuvers during pulmonary computed tomography angiography (pCTA) in a prospective randomized clinical trial. METHOD: Three different breathing maneuvers (inspiration, expiration, Mueller) were randomly assigned to 146 patients receiving pCTA for suspected pulmonary embolism (PE). Contrast enhancement of central and peripheral arteries and imaging quality of lung parenchyma were compared and analyzed. Results were compared by using the analysis of variances (ANOVA) and Kruskal-Wallis-Test. RESULTS: Mean enhancement in the pulmonary trunk was highest during breath-hold in inspiration (293 HU, range 195-460 HU) compared to Mueller (259 HU, range 136-429 HU, p = 0022) and expiration (267 HU, range 115-376 HU). This was similar for the right pulmonary artery (inspiration 289 HU, range 173-454 HU; Mueller 250 HU, range 119-378 HU; p = 0.007; expiration 257 HU, range 114-366 HU; p = 0.032) and left pulmonary artery (inspiration 280.3 HU, range 170-462 HU; Mueller 245 HU, range 111-371 HU; p = 0.016; expiration 252 HU, range 110-371 HU).Delineation of peripheral arteries was significantly better in inspiration vs Mueller (p = 0.006) and expiration (p = 0.049). Assessment of the lung parenchyma was significantly better in inspiration vs Mueller (p = 0.013) or expiration (p < 0.001). CONCLUSIONS: Resting inspiratory position achieved the highest enhancement levels in central and peripheral pulmonary arteries and best image quality of the pulmonary parenchyma in comparison to other breathing maneuvers. It is necessary to train the maneuver prior to the examination in order to avoid deep inspiration with the risk of suboptimal opacification of the pulmonary arteries.

Cardiac MRI in Children and Adolescents Who Have Undergone Surgical Repair of Right-Sided Congenital Heart Disease: Automated Left Ventricular Volumes and Function Analysis and Effects of Different Manual Adjustments.

PURPOSE: To evaluate automated segmentation and the effects of different manual adjustments regarding left ventricular parameter quantification in cardiac magnetic resonance (MR) data on children and adolescents who have undergone surgical repair of right-sided congenital heart disease (CHD). MATERIALS AND METHODS: Dedicated software (syngo.via, Siemens AG) was used to automatically segment and/or manually adjust the end-diastolic volume (EDV), end-systolic volume (ESV), stroke volume (SV), myocardial mass (MM) and ejection fraction (EF) before/after manual apex/base adjustment (ADJ-step 1) and after manual apex/base/myocardial contour adjustment (ADJ-step 2; reference standard). MR data of 40 patients (13.1 ± 3. y, 4 - 17 y) with repaired CHD with decreased pulmonary blood flow (CHD-DPBF) were evaluated. Intra- and inter-rater reliability was determined for 10 randomly selected patients. RESULTS: The software correctly detected the left ventricle in 38/40 (95%) patients. EDV after automated segmentation: 119.1 ± 44.0 ml; after ADJ-step 1: 115.8 ± 9.5 ml; after ADJ-step 2: 116.2 ± 39.4 ml. The corresponding results for ESV were 52.0 ± 18.5/49.6 ± 6.9/49.7 ± 16.4 ml; for SV 67.1 ± 28.5/66.2 ± 25.4/66.5 ± 25. ml; for EF 55.5 ± 7.3/56.7 ± 6.6/56.7 ± 6.3%; for MM 83.7 ± 35.9/76.2 ± 8.3/74.6 ± 27.2 g. Significant differences were found for ESV/MM/EF comparing the automated segmentation results with these after ADJ-step 1 and ADJ-step 2. No significant differences were found when comparing all results of ADJ-step 1 and ADJ-step 2 or when comparing EDV/SV results. Intra- and inter-rater reliability was excellent. The mean time effort was 63.4 ± 6.9 s for the automated segmentation, 74.2 ± 8.9 s for ADJ-step 1 and 269.5 ± 39.4 s for ADJ-step 2. CONCLUSION: Automated left ventricular volumes and function analysis in children and adolescents with surgically treated CHD proved to be feasible with excellent intra- and inter-rater reliability. Automated segmentation with manual apex/base adjustment provided clinically acceptable results. KEY POINTS: Automated left ventricular volume and function analysis in children and adolescents with surgically treated right-sided heart disease is feasible with excellent intra- and inter-rater reliability. Automated segmentation with manual apex/base adjustment provides clinically acceptable results. Additional manual myocardial contour adjustment does not significantly improve the results.

Imaging the Parasinus Region with a Third-Generation Dual-Source CT and the Effect of Tin Filtration on Image Quality and Radiation Dose.

BACKGROUND AND PURPOSE: CT is the imaging technique of choice in the evaluation of midface trauma or inflammatory disease. We performed a systematic evaluation of scan protocols to optimize image quality and radiation exposure on third-generation dual-source CT. MATERIALS AND METHODS: CT protocols with different tube voltage (70-150 kV), current (25-300 reference mAs), prefiltration, pitch value, and rotation time were systematically evaluated. All images were reconstructed with iterative reconstruction (Advanced Modeled Iterative Reconstruction, level 2). To individually compare results with otherwise identical factors, we obtained all scans on a frozen human head. Conebeam CT was performed for image quality and dose comparison with multidetector row CT. Delineation of important anatomic structures and incidental pathologic conditions in the cadaver head was evaluated. RESULTS: One hundred kilovolts with tin prefiltration demonstrated the best compromise between dose and image quality. The most dose-effective combination for trauma imaging was Sn100 kV/250 mAs (volume CT dose index, 2.02 mGy), and for preoperative sinus surgery planning, Sn100 kV/150 mAs (volume CT dose index, 1.22 mGy). "Sn" indicates an additional prefiltration of the x-ray beam with a tin filter to constrict the energy spectrum. Exclusion of sinonasal disease was possible with even a lower dose by using Sn100 kV/25 mAs (volume CT dose index, 0.2 mGy). CONCLUSIONS: High image quality at very low dose levels can be achieved by using a Sn100-kV protocol with iterative reconstruction. The effective dose is comparable with that of conventional radiography, and the high image quality at even lower radiation exposure favors multidetector row CT over conebeam CT.

Dose reduction in computed tomography of the chest: image quality of iterative reconstructions at a 50% radiation dose compared to filtered back projection at a 100% radiation dose.

PURPOSE: The aim of this study was to evaluate the potential of iterative reconstruction (IR) in chest computed tomography (CT) to reduce radiation exposure. The qualitative and quantitative image quality of standard reconstructions with filtered back projection (FBP) and half dose (HD) chest CT data reconstructed with FBP and IR was assessed. MATERIALS AND METHODS: 52 consecutive patients underwent contrast-enhanced chest CT on a dual-source CT system at 120 kV and automatic exposure control. The tube current was equally split on both tube detector systems. For the HD datasets, only data from one tube detector system was utilized. Thus, FD and HD data was available for each patient with a single scan. Three datasets were reconstructed from the raw data: standard full dose (FD) images applying FBP which served as a reference, HD images applying FBP and IR. Objective image quality analysis was performed by measuring the image noise in tissue and air. The subjective image quality was evaluated by 2 radiologists according to European guidelines. Additional assessment of artifacts, lesion conspicuity and edge sharpness was performed. RESULTS: Image noise did not differ significantly between HD-IR and FD-FBP (p = 0.254) but increased substantially in HD-FBP (p < 0.001). No statistically significant differences were found for the reproduction of anatomical and pathological structures between HD-IR and FD-FBP, subsegmental bronchi and bronchioli. The image quality of HD-FBP was rated inferior because of increased noise. CONCLUSION: A 50 % dose reduction in contrast-enhanced chest CT is feasible without a loss of diagnostic confidence if IR is used for image data reconstruction. Iterative reconstruction is another powerful tool to reduce radiation exposure and can be combined with other dose-saving techniques. KEY POINTS: • Iterative reconstructions allow for image noise and artifact reduction.• Comparable image data can thus be attained even at 50 % radiation dose.• Diagnostic confidence remains unaffected.

Carotid CTA: radiation exposure and image quality with the use of attenuation-based, automated kilovolt selection.

BACKGROUND AND PURPOSE: CTA is considered the imaging modality of choice in evaluating the supraaortic vessels in many institutions, but radiation exposure remains a matter of concern. The objective of the study was to evaluate a fully automated, attenuation-based kilovolt selection algorithm in carotid CTA in respect to radiation dose and image quality compared with a standard 120-kV protocol. MATERIALS AND METHODS: Ninety-eight patients were included: 53 examinations (patient age, 66 ± 12 years) were performed by use of automated adaption of tube potential (80-140 kV) on the basis of the attenuation profile of the scout scan (study group), and 45 examinations (patient age, 67 ± 11 years) were performed by use of a standard 120-kV protocol (control group). CT dose index volume and dose-length product were recorded from the examination protocol. Image quality was assessed by ROI measurements and calculations of SNR and contrast-to-noise ratio. Subjective image quality was evaluated by 2 observers with the use of a 4-point scale (3, excellent; 0, not diagnostic). RESULTS: Subjective image quality was rated as "excellent" or "good" in all examinations (study group, 2.8; control group, 2.8). The algorithm automatically selected 100 kV in 47% and 80 kV in 34%; 120 kV was retained in 19%. An elevation to 140 kV did not occur. Compared with the control group, overall CT dose index volume reduction was 33.7%; overall dose-length product reduction was 31.5%. In the low-kilovolt scans, image noise and mean attenuation of ROIs inside the carotid arteries were significantly higher than in 120-kV scans, resulting in a constant or increased (80-kV group) contrast-to-noise ratio. CONCLUSIONS: The attenuation-based, kilovolt selection algorithm enables a dose reduction of >30% in carotid artery CTA while maintaining contrast-to-noise ratio and subjective image quality at adequate levels.

[Anesthesiological time requirements and reasons for delayed processes in MRI examinations of children undergoing sedation or general anesthesia]. / Magnetresonanztomografie bei Kindern in Sedierung--anästhesiologisches Prozedere, Zeitbedarf und Determinanten verzögerter Prozessabläufe.

PURPOSE: MRI examinations in children under sedation or general anesthesia are a multidisciplinary challenge for pediatric, radiology and anesthesiology departments. This article presents findings about patient population, anesthesiology procedures and process times in pediatric MRI procedures under sedation or general anesthesia. The analysis is focused on the potential to optimize process times. MATERIALS AND METHODS: Retrospectively over a 5-year period, data from diagnostic radiology procedures in children requiring sedation or general anesthesia were retrieved from anesthesia records and analyzed statistically. RESULTS: The median anesthesia time in patients without an airway device was 6 min. In patients with a laryngeal mask (19 min) and in patients receiving endotracheal intubation (20 min), the anesthesia time was significantly longer (p < 0.001). The need for airway management in the age groups was 67 % for neonates, 25 % for infants, 8 % for toddlers and 7 % for school children. Improved clinical pathways could potentially save additional time up to 69 hours in our period of investigation. CONCLUSION: In relation to older children, toddlers, infants and neonates had the longest process times in diagnostic radiology procedures, caused by the need to secure the airway. Improved pre-MRI processes have an enormous potential to generate additional examination time.

Frequency split metal artefact reduction in pelvic computed tomography.

OBJECTIVES: Artefacts from total hip replacement affect image quality and the visualisation of pelvic lesions on computed tomography (CT). We propose a frequency split (FS) approach in addition to the normalised metal artefact reduction (NMAR) algorithm that aims to suppress artefacts and improves image quality in patients with orthopaedic hardware. METHODS: Data from ten consecutive patients with metal artefacts from uni- (n = 5) and bilateral (n = 4) total hip replacement or osteosynthesis (n = 1) were reconstructed with filtered back projection (FBP), linear interpolation MAR (LIMAR), NMAR, FSLIMAR and FSNMAR and analysed for image quality and severity of artefacts. RESULTS: NMAR and FSNMAR significantly improved the assessment of the pelvic organs, lymph nodes and vessels compared with FBP, LIMAR or FSLIMAR (P < 0.05). Assessment of the metal hardware, joint and capsule was improved with the addition of FS (FSLIMAR, FSNMAR). No algorithm-related artefacts were detected in regions that did not contain metal. CONCLUSIONS: NMAR, FSLIMAR and FSNMAR have the potential to improve image quality in patients with artefacts from metal hardware and to improve the diagnostic accuracy of CT of the organs of the pelvis. Although introducing some algorithm-related artefacts, FSNMAR most accurately displayed adjacent bone and tissue next to metal implants. KEY POINTS: • Orthopaedic metallic hardware often creates serious artefacts in computed tomography, hindering diagnosis. • The normalised metal artefact reduction (NMAR) algorithm was developed to suppress such artefacts. • NMAR improves CT assessment of pelvic organs in patients with orthopaedic hardware. • Addition of the frequency split technique (FSNMAR) helps assess tissue near metal hardware. • NMAR and FSNMAR are robust and computationally effective sinogram interpolation algorithms.

[Current strategies for dosage reduction in computed tomography]. / Aktuelle Strategien zur Dosisreduktion in der Computertomographie.

The potential risks of radiation exposure associated with computed tomography (CT) imaging are reason for ongoing concern for both medical staff and patients. Radiation dose reduction is, according to the as low as reasonably achievable principle, an important issue in clinical routine, research and development. The complex interaction of preparation, examination and post-processing provides a high potential for optimization on the one hand but on the other a high risk for errors. The radiologist is responsible for the quality of the CT examination which requires specialized and up-to-date knowledge. Most of the techniques for radiation dose reduction are independent of the system and manufacturer. The basic principle should be radiation dose optimization without loss of diagnostic image quality rather than just reduction.

CT perfusion in acute ischemic stroke: a comparison of 2-second and 1-second temporal resolution.

BACKGROUND AND PURPOSE: CT perfusion data sets are commonly acquired using a temporal resolution of 1 image per second. To limit radiation dose and allow for increased spatial coverage, the reduction of temporal resolution is a possible strategy. The aim of this study was to evaluate the effect of reduced temporal resolution in CT perfusion scans with regard to color map quality, quantitative perfusion parameters, ischemic lesion extent, and clinical decision-making when using DC and MS algorithms. MATERIALS AND METHODS: CTP datasets from 50 patients with acute stroke were acquired with a TR of 1 second. Two-second TR datasets were created by removing every second image. Various perfusion parameters (CBF, CBV, MTT, TTP, TTD) and color maps were calculated by using identical data-processing settings for 2-second and 1-second TR. Color map quality, quantitative region-of-interest-based perfusion measurements, and TAR/NVT lesions (indicated by CBF/CBV mismatch) derived from the 2-second and 1-second processed data were statistically compared. RESULTS: Color map quality was similar for 2-second versus 1-second TR when using DC and was reduced when using MS. Regarding quantitative values, differences between 2-second and 1-second TR datasets were statistically significant by using both algorithms. Using DC, corresponding tissue-at-risk lesions were slightly smaller at 2-second versus 1-second TR (P < .05), whereas corresponding NVT lesions showed excellent agreement. With MS, corresponding tissue-at-risk lesions showed excellent agreement but more artifacts, whereas NVT lesions were larger (P < .001) compared with 1-second TR. Therapeutic decisions would have remained the same in all patients. CONCLUSIONS: CTP studies obtained with 2-second TR are typically still diagnostic, and the same therapy would have been provided. However, with regard to perfusion quantitation and image-quality-based confidence, our study indicates that 1-second TR is preferable to 2-second TR.

Perfusion CT in acute ischemic stroke: a qualitative and quantitative comparison of deconvolution and maximum slope approach.

BACKGROUND AND PURPOSE: PCT postprocessing commonly uses either the MS or a variant of the DC approach for modeling of voxel-based time-attenuation curves. There is an ongoing discussion about the respective merits and limitations of both methods, frequently on the basis of theoretic reasoning or simulated data. We performed a qualitative and quantitative comparison of DC and MS by using identical source datasets and preprocessing parameters. MATERIALS AND METHODS: From the PCT data of 50 patients with acute ischemic stroke, color maps of CBF, CBV, and various temporal parameters were calculated with software implementing both DC and MS algorithms. Color maps were qualitatively categorized. Quantitative region-of-interest-based measurements were made in nonischemic GM and WM, suspected penumbra, and suspected infarction core. Qualitative results, quantitative results, and PCT lesion sizes from DC and MS were statistically compared. RESULTS: CBF and CBV color maps based on DC and MS were of comparably high quality. Quantitative CBF and CBV values calculated by DC and MS were within the same range in nonischemic regions. In suspected penumbra regions, average CBF(DC) was lower than CBF(MS). In suspected infarction core regions, average CBV(DC) was similar to CBV(MS). Using adapted tissue-at-risk/nonviable-tissue thresholds, we found excellent correlation of DC and MS lesion sizes. CONCLUSIONS: DC and MS yielded comparable qualitative and quantitative results. Lesion sizes indicated by DC and MS showed excellent agreement when using adapted thresholds. In all cases, the same therapy decision would have been made.

High-resolution 3T MR angiography of the carotid arteries: comparison of manual and semiautomated quantification of stenosis.

BACKGROUND AND PURPOSE: High-resolution contrast-enhanced MR angiography (CE-MRA) acquired at 3T exquisitely depict carotid artery (CA) stenosis. In this study, we examined the agreement of different vessel-analysis tools with manual quantitative measurement by 2 readers using CE-MRA data. MATERIALS AND METHODS: Three vessel tools determining the trajectory of the vessel of interest and, subsequently, the vessel dimensions were tested against manual measurements. Diameter and area stenoses were calculated. CE-MRA data of 32 patients with CA stenosis were evaluated. The agreement between different measurements was assessed with kappa statistics after categorizing stenosis (<25%, 25%-49%, 50%-69%, 70%-99%, and 100%). RESULTS: The mean grades of stenosis based on diameter measurements were 59% (readers) and 60%/56%/59% based on the analysis with tools A/B/C (P = 0.2-0.7). kappa values for agreement between readers and the vessel tools were 0.73/0.77/0.77 (tools A/B/C for all CAs) and 0.66/0.74/0.75 (for the symptomatic side). The mean grades of stenoses based on area measurements for tools A/B/C were 68%/63%/69% versus 58% for readers. Values from readers differed significantly from those for tools A and C (P < 0.01). kappa values for agreement between readers and the vessel tools were 0.66/0.55/0.64 (for all CAs) and 0.53/0.44/0.57 (for the symptomatic side). CONCLUSIONS: The automated approach allows accurate assessment of vessel dimensions in MRA images at least for diameter measurements according to the North American Symptomatic Carotid Endarterectomy Trial criteria.

MR imaging: influence of imaging technique and postprocessing on measurement of internal carotid artery stenosis.

BACKGROUND AND PURPOSE: MR angiography (MRA) is increasingly used as an alternative to digital subtraction angiography (DSA) to evaluate internal carotid artery (ICA) stenosis. Because MRA is not standardized in data acquisition and postprocessing, we sought to evaluate the effects of different acquisition techniques (time-of-flight MRA [TOF-MRA]) and contrast-enhanced MRA [CE-MRA]) and postprocessing methods (maximum intensity projection [MIP], multiplanar reformation [MPR], and volume-rendering on stenosis grading. MATERIALS AND METHODS: Fifty patients (33 men, 17 women) with symptomatic ICA stenosis were examined at 1.5T. Two imaging techniques and 3 postprocessing methods resulted in 6 image datasets per patient. Two readers independently evaluated ICA stenosis according to the North American Symptomatic Carotid Endarterectomy Trial criteria. Interobserver variability was calculated with the Pearson correlation coefficient and simultaneous confidence intervals (CI). The relationship of the values of ICA stenosis between the techniques was assessed by means of simultaneous 95% Tukey CI. RESULTS: Interobserver agreement was high. Higher concordance was found for postprocessing techniques with TOF- than with CE-MRA; the mean difference between TOF-MPR and TOF-MIP was 0.4% (95% CI, -2.9%-3.8%). Stenosis values for CE-MPR differed significantly from those of CE volume-rendering (7.2%; 95% CI, 3.9%-10.6%). CONCLUSION: Stenosis grading was found to be independent of the postprocessing technique except for comparison of CE-MPR with CE volume-rendering, with the volume-rendering technique resulting in higher stenosis values. MPR seems to be best-suited for measurement of ICA stenosis. Parameter setting is critical with volume-rendering, in which stenosis values were consistently higher compared with the other methods.

Bone-subtraction CT angiography: evaluation of two different fully automated image-registration procedures for interscan motion compensation.

BACKGROUND AND PURPOSE: Bone-subtraction techniques have been shown to enhance CT angiography (CTA) interpretation, but motion can lead to incomplete bone removal. The aim of this study was to evaluate 2 novel registration techniques to compensate for patient motion. MATERIALS AND METHODS: Fifty-four patients underwent bone-subtraction CTA (BSCTA) for the evaluation of the neck vessels with 64-section CT. We tested 3 different registration procedures: pure rigid registration (BSCTA), slab-based registration (SB-BSCTA), and a partially rigid registration (PR-BSCTA) approach. Subtraction quality for the assessment of different vascular segments was evaluated by 2 examiners in a blinded fashion. The Cohen kappa test was applied for interobserver variability, and the Wilcoxon signed rank test, for differences between the procedures. Motion between the corresponding datasets was measured and plotted against image-quality scores. RESULTS: Algorithms with motion compensation revealed higher image-quality scores (SB-BSCTA, mean 4.31; PR-BSCTA, mean 4.43) than pure rigid registration (BSCTA, mean 3.88). PR-BSCTA was rated superior to SB-BSCTA for the evaluation of the cervical internal and external carotid arteries (P<.001), whereas there was no significant difference for the other vessels (P=.157-.655). Both algorithms were clearly superior to pure rigid registration for all vessels except the basilar and ophthalmic artery. Interobserver agreement was high (kappa=0.46-0.98). CONCLUSION: Bone-subtraction algorithms with motion compensation provided higher image-quality scores than pure rigid registration methods, especially in cases with complex motion. PR-BSCTA was rated superior to SB-BSCTA in the visualization of the internal and external carotid arteries.