Conventional Multidetector CT Research Articles

AAPM Task Group Report 261: Comprehensive quality control methodology and management of dental and maxillofacial cone beam computed tomography (CBCT) systems.

Cone-beam computed tomography (CBCT) systems specifically designed and manufactured for dental, maxillofacial imaging (MFI) and otolaryngology (OLR) applications have been commercially available in the United States since 2001 and have been in widespread clinical use since. Until recently, there has been a lack of professional guidance available for medical physicists about how to assess and evaluate the performance of these systems and about the establishment and management of quality control (QC) programs. The owners and users of dental CBCT systems may have only a rudimentary understanding of this technology, including how it differs from conventional multidetector CT (MDCT) in terms of acceptable radiation safety practices. Dental CBCT systems differ from MDCT in several ways and these differences are described. This report provides guidance to medical physicists and serves as a basis for stakeholders to make informed decisions regarding how to manage and develop a QC program for dental CBCT systems. It is important that a medical physicist with experience in dental CBCT serves as a resource on this technology and the associated radiation protection best practices. The medical physicist should be involved at the pre-installation stage to ensure that a CBCT room configuration allows for a safe and efficient workflow and that structural shielding, if needed, is designed into the architectural plans. Acceptance testing of new installations should include assessment of mechanical alignment of patient positioning lasers and x-ray beam collimation and benchmarking of essential image quality performance parameters such as image uniformity, noise, contrast-to-noise ratio (CNR), spatial resolution, and artifacts. Several approaches for quantifying radiation output from these systems are described, including simply measuring the incident air-kerma (Kair) at the entrance surface of the image receptor. These measurements are to be repeated at least annually as part of routine QC by the medical physicist. QC programs for dental CBCT, at least in the United States, are often driven by state regulations, accreditation program requirements, or manufacturer recommendations.

Musculoskeletal CT Imaging: State-of-the-Art Advancements and Future Directions.

CT is one of the most widely used modalities for musculoskeletal imaging. Recent advancements in the field include the introduction of four-dimensional CT, which captures a CT image during motion; cone-beam CT, which uses flat-panel detectors to capture the lower extremities in weight-bearing mode; and dual-energy CT, which operates at two different x-ray potentials to improve the contrast resolution to facilitate the assessment of tissue material compositions such as tophaceous gout deposits and bone marrow edema. Most recently, photon-counting CT (PCCT) has been introduced. PCCT is a technique that uses photon-counting detectors to produce an image with higher spatial and contrast resolution than conventional multidetector CT systems. In addition, postprocessing techniques such as three-dimensional printing and cinematic rendering have used CT data to improve the generation of both physical and digital anatomic models. Last, advancements in the application of artificial intelligence to CT imaging have enabled the automatic evaluation of musculoskeletal pathologies. In this review, the authors discuss the current state of the above CT technologies, their respective advantages and disadvantages, and their projected future directions for various musculoskeletal applications.

Metal artifact reduction in ultra-high-resolution cone-beam CT imaging with a twin robotic X-ray system

Cone-beam computed tomography (CBCT) has been shown to be a powerful tool for 3D imaging of the appendicular skeleton, allowing for detailed visualization of bone microarchitecture. This study was designed to compare artifacts in the presence of osteosynthetic implants between CBCT and multidetector computed tomography (MDCT) in cadaveric wrist scans. A total of 32 scan protocols with varying tube potential and current were employed: both conventional CBCT and MDCT studies were included with tube voltage ranging from 60 to 140 kVp as well as additional MDCT protocols with dedicated spectral shaping via tin prefiltration. Irrespective of scanner type, all examinations were conducted in ultra-high-resolution (UHR) scan mode. For reconstruction of UHR-CBCT scans an additional iterative metal artifact reduction algorithm was employed, an image correction tool which cannot be used in combination with UHR-MDCT. To compare applied radiation doses between both scanners, the volume computed tomography dose index for a 16 cm phantom (CTDIvol) was evaluated. Images were assessed regarding subjective and objective image quality. Without automatic tube current modulation or tube potential control, radiation doses ranged between 1.3 mGy (with 70 kVp and 50.0 effective mAs) and 75.2 mGy (with 140 kVp and 383.0 effective mAs) in UHR-MDCT. Using the pulsed image acquisition method of the CBCT scanner, CTDIvol ranged between 2.3 mGy (with 60 kVp and 0.6 mean mAs per pulse) and 61.0 mGy (with 133 kVp and 2.5 mean mAs per pulse). In essence, all UHR-CBCT protocols employing a tube potential of 80 kVp or more were found to provide superior overall image quality and artifact reduction compared to UHR-MDCT (all p < .050). Interrater reliability of seven radiologists regarding image quality was substantial for tissue assessment and moderate for artifact assessment with Fleiss kappa of 0.652 (95% confidence interval 0.618–0.686; p < 0.001) and 0.570 (95% confidence interval 0.535–0.606; p < 0.001), respectively. Our results demonstrate that the UHR-CBCT scan mode of a twin robotic X-ray system facilitates excellent visualization of the appendicular skeleton in the presence of metal implants. Achievable image quality and artifact reduction are superior to dose-comparable UHR-MDCT and even MDCT protocols employing spectral shaping with tin prefiltration do not achieve the same level of artifact reduction in adjacent soft tissue.

Heart Rate-Dependent Degree of Motion Artifacts in Coronary CT Angiography Acquired by a Novel Purpose-Built Cardiac CT Scanner.

Although reaching target heart rate (HR) before coronary CT angiography (CCTA) is still of importance, adequate HR control remains a challenge for many patients. Purpose-built cardiac scanners may provide optimal image quality at higher HRs by further improving temporal resolution. We aimed to compare the amount of motion artifacts on CCTA acquired using a dedicated cardiac CT (DCCT) compared to a conventional multidetector CT (MDCT) scanner. We compared 80 DCCT images to 80 MDCT scans matched by sex, age, HR, and coronary dominance. Image quality was graded on a per-patient, per-vessel and per-segment basis. Motion artifacts were assessed using Likert scores (1: non-diagnostic, 2: severe artifacts, 3: mild artifacts, 4: no artifacts). Patients were stratified into four groups according to HR (<60/min, 60–65/min, 66–70/min and >70/min). Overall, 2328 coronary segments were evaluated. DCCT demonstrated superior overall image quality compared to MDCT (3.7 ± 0.4 vs. 3.3 ± 0.7, p < 0.001). DCCT images yielded higher Likert scores in all HR ranges, which was statistically significant in the 60–65/min, 66–70/min and >70/min ranges (3.9 ± 0.2 vs. 3.7 ± 0.2, p = 0.008; 3.5 ± 0.5 vs. 3.1 ± 0.6, p = 0.048 and 3.5 ± 0.4 vs. 2.7 ± 0.7, p < 0.001, respectively). Using a dedicated cardiac scanner results in fewer motion artifacts, which may allow optimal image quality even in cases of high HRs.

A novel use of cone beam CT: flexion and extension weight-bearing imaging to assess spinal stability

To assess spinal stability in different physiological positions whilst weight-bearing. A cone beam CT scanner (CBCT) was used to identify any abnormal motion in the spine in different physiological positions whilst weight-bearing. The lumbar spine was assessed in 6 different patients with a comfortable neutral standing position and standing flexion and extension images in selected patients. Seated, weight-bearing flexion and extension images of the cervical spine were obtained in a further patient. Clinical indications included stability assessment post-trauma, post-surgical fusion and back pain. The projection images were reconstructed using bone and soft tissue algorithms to give isotropic CT images which could be viewed as per conventional multi-detector CT images. The flexion and extension CBCT data were fused to give a representation of any spinal movement between the extremes of motion. The flexion and extension weight-bearing images gave anatomical detail of the spine. Detail of the surgical constructs was possible. Dynamic structural information about spinal alignment, facet joints, exit foramina and paraspinal musculature was possible. The effective dose from the neutral position was equal to that of supine, multi-detector CT. CBCT can be used to image the lumbar and cervical spine in physiological weight-bearing positions and at different extremes of spinal motion. This novel application of an existing technology can be used to aid surgical decision making to assess spinal stability and to investigate occult back and leg pain. Its use should be limited to specific clinical indications, given the relatively high radiation dose.

Diagnostic performance of dual-energy CT in nonspecific terminal ileitis.

To investigate the value of dual-energy CT (DECT) imaging in the diagnosis of nonspecific terminal ileitis (NTI). This is a retrospective study, enrolling patients with symptomatic terminal ileitis that underwent conventional multidetector CT (MDCT) enterography or DECT enterography. The sensitivity of the diagnosis of NTI between MDCT images and different kinds of DECT images (40-70 kev virtual monoenergetic images (VMIs) and iodine density images) was compared. The iodine concentrations of lesion bowel wall among NTI, Crohn's disease (CD) and intestinal tuberculosis (ITB) in DECT group and the value of lesion-to-non-lesion contrast ratios of all patients were measured. Receiver operator characteristic (ROC) curves for normalized iodine concentration (NIC) for differentiating among the three kinds of disease were drawn. The sensitivity for the diagnosis of NTI in DECT group (including 40 kev, 50keV VMIs, and iodine density images) were all 89.7%, significantly higher than that in MDCT group (65.1%) (P = 0.026). Statistical analysis did not reveal marked differences between 60 kev, 70 kev VMIs (86.2%) and MDCT images (65.1%) (P = 0.059). The NIC of NTI was (0.15 ± 0.04)100µg/cm3 and (0.45 ± 0.08)100µg/cm3, significantly lower than that of CD (0.34 ± 0.09) 100µg/cm3, (0.85 ± 0.06) 100µg/cm3 and that of ITB (0.29 ± 0.07) 100µg/cm3, (0.88 ± 0.07) 100µg/cm3 at the enteric phase (EP) and portal venous phase (PVP) (P < 0.001, wholly). The area under the ROC curves (AUROCs) of NICEP and NICPVP were 0.910 and 0.980, respectively, for differentiating between NTI and CD. The value of lesion-to-non-lesion contrast ratios is maximum on the 40keV VMI both EP and PVP. The value of lesion-to-non-lesion contrast ratios of NTI was lower than that of CD and ITB on each image. The AUROCs of NICEP and NICPVP were 0.875 and 0.940, respectively, for differentiating between NTI and ITB. DECT has higher sensitivity in the diagnosis of NTI than MDCT. Low-keV VMI and iodine density images of DECT can clearly show the NTI. DECT imaging can help to differentiate NTI from CD or ITB by comparing the NIC.

A dose–neutral image quality comparison of different CBCT and CT systems using paranasal sinus imaging protocols and phantoms

PurposeTo compare the image quality produced by equivalent low-dose and default sinus imaging protocols of a conventional dental cone-beam computed tomography (CBCT) scanner, an extremity CBCT scanner and a clinical multidetector computed tomography (MDCT) scanner.MethodsThree different phantoms were scanned using dose–neutral ultra-low-dose and low-dose sinus imaging protocols, as well as default sinus protocols of each device. Quantified parameters of image quality included modulation transfer function (MTF) to characterize the spatial response of the imaging system, contrast-to-noise ratio, low contrast visibility, image uniformity and Hounsfield unit accuracy. MTF was calculated using the line spread and edge spread functions (LSF and ESF).ResultsThe dental CBCT had superior performance over the extremity CBCT in each studied parameter at similar dose levels. The MDCT had better contrast-to-noise ratio, low contrast visibility and image uniformity than the CBCT scanners. However, the CBCT scanners had better resolution compared to the MDCT. Accuracy of HU values for different materials was on the same level between the dental CBCT and MDCT, but substantially poorer performance was observed with the extremity CBCT.ConclusionsThe studied dental CBCT scanner showed superior performance over the studied extremity CBCT scanner when using dose–neutral imaging protocols. In case a dental CBCT is not available, the given extremity CBCT is still a viable option as it provides the benefit of high resolution over a conventional MDCT.

Prognostic Implication of Bone Marrow Abnormality of Appendicular Skeletons Detected By Low-Dose Multidetector Computed Tomography in Patients with Myelodysplastic Syndrome

BackgroundA number of prognostic systems have been developed and validated in patients with myelodysplastic syndrome (MDS). However, the use of the current scoring systems including international prognostic scoring system (IPSS) in determining the prognosis among MDS patient has various conflicting views pertaining to the inclusion of patients with different outcomes. Abnormal red marrow distribution in appendicular skeletons (AS) based on magnetic resonance imaging (MRI) has been described in the literature; however, these findings have not been confirmed. We examined the prognostic implication of medullary abnormalities of AS detected by low-dose whole-body multidetector computed tomography (MDCT) in patients with MDS.Patients and methods147 consecutive patients with MDS diagnosed between January 2009 and May 2017 at Kameda Medical Center were recruited. Diagnosis and classification of MDS were made per 2008 WHO criteria. MDCT studies were performed at the diagnosis of MDS and before the start of any chemotherapy. MDCT images were acquired as previously reported. Medullary pattern of AS were categorized into three groups: (1) Fatty marrow pattern; (2) Focal/scattered marrow pattern; (3) diffuse marrow pattern. To examine if the value of MDCT findings on appendicular marrow has incremental predictive value when the conventional risk factors were controlled, we constructed a receiver operating characteristics (ROC) curve for two logistic regression models. Model 1 was constructed with only conventional risk factors while Model 2 was constructed with conventional risk factors plus MDCT findings.ResultsOf the 147 patients with MDS, there were 47 (32.0%) with fatty, 51 (34.7%) with focal/scattered and 49 (33.3%) with diffuse marrow patterns. Fatty pattern was seen more among non-RAEB patients (76.5%), focal/scattered pattern was about equal while diffuse pattern was more in RAEB patients with 65.3% (P<0.001). The development of AML differed significantly between groups and the highest occurred with diffuse pattern, 30 (61.2%), (P<0.001). Among those with AML, death occurred among 28 (93.3%) . The median LFS was not reached (NR) for fatty pattern, but was 29.2 and 11.1 months for the focal/scattered and diffuse marrow patterns respectively (P<0.001). Similarly, the median OS was NR for fatty pattern but was 40.9 and 14.6 months for the focal/scattered and diffuse marrow patterns respectively (P<0.001). Among the 82 low-risk patients, median survivals of fatty, focal/scattered, and diffuse pattern differed significantly and were NR, 35.2 and 18.2 months respectively for LFS (P<0.001), and NR, 50.9 and 26.3 months respectively for OS (P<0.001). Similarly, for the 65 patients with high-risk MDS, median time were NR, 11.2 and 8.3 months for LFS (P<0.001), and NR, 19.1 and 11.4 months for OS (P<0.001), respectively for fatty, focal/scattered, and diffuse patterns. At multivariate analysis, both focal/scattered and diffuse patterns of medullary marrow of AS remained independently associated with shorter LFS and OS. ROC curve was developed based on the conventional risk model as well as the conventional risk model plus MDCT findings for LFS and OS. Although AUC comparisons showed statistical significance in neither LFS (P=0.108) nor OS (P=0.138), net reclassification improvement (NRI) and integrated discrimination improvement (IDI) were significant for both LFS (NRI 0.43 [95% CI;0.12-0.74], P=0.007 and IDI 0.06 [95% CI; 0.02-0.10], P=0.002) and OS (NRI 0.52 [95% CI; 0.21-0.83], P<0.001 and IDI 0.07 [95% CI; 0.03-0.11], P<0.001).ConclusionOur findings showed a novel method for prognostication of MDS using the medullary findings of AS using MDCT. The prognostic impact of medullary abnormality of AS detected by MDCT has not been described previously. Our findings indicate that the MDCT of appendicular bone marrow is predictive of the prognosis in patients with MDS and has a potential for improving the risk stratification of MDS in conjunction with preexisting scoring systems. [Display omitted] DisclosuresKitadate:Pfizer: Research Funding; Fujimoto: Research Funding; Otsuka: Research Funding; Novartis: Research Funding; Toyama kagaku: Research Funding; Chugai: Research Funding; Asahi Kasei: Research Funding; Eisai: Research Funding; Kyowa Kirin: Research Funding.

Multidetector CT and cone-beam CT have substantial agreement in detecting dental and sinus abnormalities in equine cadaver heads.

The performance of cone-beam CT (CBCT) systems compared to conventional helical multidetector CT (MDCT) imaging of the equine head is unknown. The aim of this prospective, method-comparison study was to compare the ability of CBCT and MDCT to detect abnormalities in equine cadaver heads. Eleven equine cadaver heads were scanned using a CBCT scanner and a 64-slice MDCT scanner. Consensus evaluations for CBCT and MDCT scans were performed by three observers. Identified abnormalities were grouped into subcategories with a focus on dental abnormalities. Kappa agreement values between detected abnormalities for CBCT and MDCT methods were calculated. Of 468 teeth evaluated, 122 (26.1%) were found to have abnormalities (including in 58 infundibula and 7 pulps) using MDCT and 105 (22.4%) were found to have abnormalities (including in 52 infundibula and 2 pulps) using CBCT. The agreement between CBCT and MDCT was almost perfect for overall detection of dental abnormalities (k=0.90) with k=1 for diastema k=0.95 for clinical crown abnormalities, and k=0.93 for infundibular abnormalities. However, the detection of pulp changes by CBCT was only moderate k=0.44. Increased scatter radiation, non-calibrated Hounsfield Unit and artefacts in CBCT images made accurate identification of the pulp density difficult. In conclusion, CBCT results were similar to conventional MDCT for the majority of dental abnormalities, however, pulp abnormalities were not reliably identified using CBCT, potentially limiting its clinical use for detecting endodontic disease in its current form. Further comparison with more cases with confirmed dental disease and studies in clinical cases are warranted.

Novel flat-panel cone-beam CT compared to multi-detector CT for assessment of acute ischemic stroke: A prospective study

PurposeCone beam CT (CBCT) imaging assessment of acute ischemic stroke (AIS) patients with large-vessel occlusion (LVO) in the angiosuite may improve stroke workflow and decrease time to recanalization. In order for this workflow to gain widespread acceptance, current CBCT imaging needs further development to improve image quality. Our study aimed to compare the image quality of a new CBCT protocol performed directly in the angiosuite with imaging from multidetector CT as a gold standard. MethodsAIS patients with an LVO who were candidates for endovascular treatment were prospectively included in this study. Following conventional multidetector CT (MDCT), patients underwent unenhanced cone beam CT (XperCT, Philips) imaging in the angiosuite, using two different protocols: a standard 20.8 s XperCT and/or an improved 10.4 s XperCT protocol. Images were evaluated using both qualitative and quantitative methods. ResultsWe included 65 patients in the study. Patients received CBCT imaging prior to endovascular treatment; 18 patients were assessed with a standard 20.8 s protocol scans and 47 with a newer 10.4 s scan. The quantitative analysis showed that the mean contrast-to-noise ratio (CNR) was significantly higher for the newer 10.4 s protocol compared with the 20.8 s protocol (2.08 +/- 0.64 vs. 1.15 +/- 0.27, p < 0.004) and the mean image noise was significantly lower for the 10.4 s XperCTs when compared with the 20.8 s XperCTs (6.30 +/- 1.34 vs. 7.82 +/- 2.03, p=<0.003). Qualitative analysis, including 6 measures of image quality, demonstrated that 74.1 % of the 10.4 s XperCT scans were ranked as ‘Acceptable’ for assessing parenchymal imaging in AIS patients(scoring 3–5 points on a 5-point Likert-scale), compared with 32.4 % of the standard 20.8 s XperCT and 100 % of the MDCT scans. Compared to the MDCT studies, 83 % of the 10.4 s XperCT scans were deemed sufficient image quality for a direct-to-angiosuite selection, compared to only 11 % for the standard 20.8 s scans. The largest image quality improvements included grey/white matter differentiation (59 % improvement), and reduction of image noise and artefacts (63 % & 50 % improvement, respectively). ConclusionsContinued advances in cone-beam CT allow marked improvements in image quality for the assessment of brain parenchyma, which supports a direct-to-angiosuite approach for AIS patients eligible for thrombectomy treatment.

CT Findings of Central Airway Lesions Causing Airway Stenosis-Visualization and Quantification: A Pictorial Essay.

The tracheobronchial tree is a system of airways that allows the passage of air to aerate the lungs and entire body. Several pathological conditions can affect this anatomical region. Multidetector CT (MDCT) helps identify and characterize various large airway diseases. Post-processing tools, such as virtual bronchoscopy and automatic lung analysis, can help enhance the performance of imaging studies. In this pictorial essay review, we provide imaging findings of various bronchial lesions manifested as wall thickening and endoluminal nodules on conventional MDCT and advanced image visualization and analysis.

Improved image quality of temporal bone CT with an ultrahigh-resolution CT scanner: clinical pilot studies

PurposeUltrahigh-resolution CT (UHRCT) with slice collimation of 0.25 mm × 160 and matrix size of 1024 × 1024 has become clinically available. We compared the image quality of temporal bone CT (TBCT) between UHRCT and conventional multidetector CT (MDCT).Materials and methodsWe retrospectively enrolled 20 patients who underwent TBCT by MDCT (matrix size, 512 × 512) and subsequently by UHRCT (matrix size, 1024 × 1024). Two independent reviewers subjectively graded delineation of normal stapes, oval window, facial nerve canal, incudostapedial joint, and tympanic tegmen. We also quantified image noise in the cerebellar hemisphere. Between MDCT and UHRCT, we compared mean subjective grades using the Wilcoxon signed-rank test and the image noise using paired t test.ResultsGrades were significantly higher with UHRCT than with MDCT for all the anatomies (P < 0.001), whereas noise was significantly higher with UHRCT than with MDCT (P = 0.002).ConclusionFor TBCT, UHRCT shows better delineation of the fine anatomical structures compared with MDCT.

Advanced imaging techniques for chronic pancreatitis.

MRI and MRCP play an important role in the diagnosis of chronic pancreatitis (CP) by imaging pancreatic parenchyma and ducts. MRI/MRCP is more widely used than computed tomography (CT) for mild to moderate CP due to its increased sensitivity for pancreatic ductal and gland changes; however, it does not detect the calcifications seen in advanced CP. Quantitative MR imaging offers potential advantages over conventional qualitative imaging, including simplicity of analysis, quantitative and population-based comparisons, and more direct interpretation of detected changes. These techniques may provide quantitative metrics for determining the presence and severity of acinar cell loss and aid in the diagnosis of chronic pancreatitis. Given the fact that the parenchymal changes of CP precede the ductal involvement, there would be a significant benefit from developing MRI/MRCP-based, more robust diagnostic criteria combining ductal and parenchymal findings. Among cross-sectional imaging modalities, multi-detector CT (MDCT) has been a cornerstone for evaluating chronic pancreatitis (CP) since it is ubiquitous, assesses primary disease process, identifies complications like pseudocyst or vascular thrombosis with high sensitivity and specificity, guides therapeutic management decisions, and provides images with isotropic resolution within seconds. Conventional MDCT has certain limitations and is reserved to provide predominantly morphological (e.g., calcifications, organ size) rather than functional information. The emerging applications of radiomics and artificial intelligence are poised to extend the current capabilities of MDCT. In this review article, we will review advanced imaging techniques by MRI, MRCP, CT, and ultrasound.

Cone-Beam Computed Tomography Allows Accurate Registration to Surgical Navigation Systems: A Multidevice Phantom Study.

Background Cone-beam computed tomography (CBCT) is a fast imaging technique with a substantially lower radiation dosage than conventional multidetector computed tomography (MDCT) for sinus imaging. Surgical navigation systems are increasingly being used in endoscopic sinus and skull base surgery, reducing perioperative morbidity. Objective To investigate CBCT as a low-radiation imaging modality for use in surgical navigation. Methods The required field of view was measured from the tip of the nose to the posterior clinoid process anteroposteriorly and the nasolabial angle to the roof of the frontal sinus superoinferiorly on 50 consecutive MDCT scans (male = 25; age = 17–85 years). A phantom head was manufactured by 3-dimensional printing and imaged using 3 CBCT scanners (Carestream, J Morita, and NewTom), a conventional MDCT scanner (Siemens), and highly accurate laser scanner (FARO). The phantom head was registered to 3 surgical navigation systems (Brainlab, Stryker, and Medtronic) using scans from each system. Results The required field of view (mean ± standard deviation) was measured as 107 ± 7.6 mm anteroposteriorly and 90.3 ± 9.6 mm superoinferiorly. Image error deviations from the laser scan (median ± interquartile range) were comparable for MDCT (0.19 ± 0.09 mm) and CBCT (CBCT 1: 0.15 ± 0.11 mm; CBCT 2: 0.33 ± 0.18 mm; and CBCT 3: 0.13 ± 0.13 mm) scanners. Fiducial registration error and target registration error were also comparable for MDCT- and CBCT-based navigation. Conclusion CBCT is a low-radiation preoperative imaging modality suitable for use in surgical navigation.

Multimodality Imaging, including Dual-Energy CT, in the Evaluation of Gallbladder Disease.

Imaging of the gallbladder has a key role in the examination of patients with abdominal pain-especially pain localized to the right upper quadrant. Pathologic conditions that affect the gallbladder include cholelithiasis and associated complications such as acute and chronic cholecystitis, choledocholithiasis, gallstone pancreatitis, and cancer. Modalities used to image the gallbladder include ultrasonography (US), computed tomography (CT), magnetic resonance (MR) imaging, and nuclear scintigraphy. US is the primary imaging modality used to evaluate entities suspected of being gallbladder disease, as it is both sensitive and specific for demonstrating gallstones, biliary duct dilatation, and inflammatory features. However, CT is often the first imaging examination performed in patients who present to the emergency department with acute abdominal pain. Because the CT appearance of gallstones is variable, depending on the composition of the stone, pattern of calcification, and presence of gas, gallstones and other gallbladder conditions can be difficult to detect at conventional multidetector CT, with which data are acquired by using a single x-ray energy spectrum. Dual-energy CT, with which one takes advantage of the material-dependent x-ray absorption behavior of concurrently acquired high- and low-kilovolt-peak data, can add value by increasing the conspicuity of noncalcified gallstones and improving the detection of acute cholecystitis and gallbladder malignancy. In addition, MR cholangiopancreatography can be helpful for assessing choledocholithiasis and complicated biliary duct disease. ©RSNA, 2018.

Cochlear Implant Electrode Localization Using an Ultra-High Resolution Scan Mode on Conventional 64-Slice and New Generation 192-Slice Multi-Detector Computed Tomography.

A new generation 192-slice multi-detector computed tomography (MDCT) clinical scanner provides enhanced image quality and superior electrode localization over conventional MDCT. Currently, accurate and reliable cochlear implant electrode localization using conventional MDCT scanners remains elusive. Eight fresh-frozen cadaveric temporal bones were implanted with full-length cochlear implant electrodes. Specimens were subsequently scanned with conventional 64-slice and new generation 192-slice MDCT scanners utilizing ultra-high resolution modes. Additionally, all specimens were scanned with micro-CT to provide a reference criterion for electrode position. Images were reconstructed according to routine temporal bone clinical protocols. Three neuroradiologists, blinded to scanner type, reviewed images independently to assess resolution of individual electrodes, scalar localization, and severity of image artifact. Serving as the reference standard, micro-CT identified scalar crossover in one specimen; imaging of all remaining cochleae demonstrated complete scala tympani insertions. The 192-slice MDCT scanner exhibited improved resolution of individual electrodes (p < 0.01), superior scalar localization (p < 0.01), and reduced blooming artifact (p < 0.05), compared with conventional 64-slice MDCT. There was no significant difference between platforms when comparing streak or ring artifact. The new generation 192-slice MDCT scanner offers several notable advantages for cochlear implant imaging compared with conventional MDCT. This technology provides important feedback regarding electrode position and course, which may help in future optimization of surgical technique and electrode design.

Relationship between cone-beam CT technique and diagnostic usefulness in patients undergoing embolotherapy for hepatocellular carcinoma

To determine the effect of different numbers of projection images in C-arm cone-beam computed tomography (CBCT) on diagnostic content and image quality in patients undergoing angiographic embolotherapy for hepatocellular carcinoma (HCC). A total of 29 patients who underwent contrast-enhanced conventional multidetector CT (MDCT) within 6 weeks prior to CBCT acquired during embolotherapy for HCC between 2010 and 2013 were included in the study. CBCT was acquired in each patient using a 5-s (248 projection images) or 8-s (396 projection images) protocol. Anonymised images were reviewed independently by an interventional radiologist blinded to CBCT group. MDCT was used as a reference to the patient's anatomy, and performance of CBCT was compared to that of MDCT in each group. The level of concordance between CBCT and MDCT within each group was assessed for the following variables: number of foci >1 cm, largest tumour diameter, highest order branching vessel identified, image quality, diagnostic quality, signal-to-noise ratio, and contrast-to-noise ratio (CNR). CBCT radiation dose was recorded. There was no significant difference between MDCT and CBCT within each group in the number of tumour foci >1 cm identified or size of the largest focus measured. MDCT had superior image quality compared to both CBCT groups (p<0.01), but CBCT demonstrated subsegmental branches more often in each group than MDCT. Both CBCT groups demonstrated higher CNR than MDCT (p<0.01). The dose-area product (3675±1295 versus 6598±1252 μGy·m2; p<0.001) and skin dose (119±41 versus 212±38 mGy; p<0.001) were significantly lower with 5-s CBCT than with 8-s CBCT. The relationship between MDCT and CBCT in both groups was consistent. The information obtained with 5-s CBCT was equivalent to that obtained with 8-s CBCT but with a lower radiation dose.

Role of dynamic multidetector computed tomography using ′eee′ phonation in the diagnosis of various laryngeal lesions

Objective The aim of the study was to determine the effectiveness of dynamic multidetector computed tomography (MDCT) using 'eee' phonation in the detection and delineation of extension of various laryngeal lesions in comparison with conventional nonfunctional MDCT. Patients and methods The study included 60 patients with suspected laryngeal pathology who underwent precontrast and both prephonation and during-phonation contrast-enhanced MDCT. Each imaging study was evaluated for pyriform sinus and ventricle involvement, vocal cord mobility, and local tumor staging of malignant laryngeal lesions. All patients subsequently underwent direct laryngoscopy. Detailed endoscopic findings were reported and compared with MDCT findings. Results Dynamic MDCT using 'eee' phonation is effective in the assessment of pyriform sinus and ventricle involvement with high sensitivity (100% for both), high specificity (97.83 and 97.44%, respectively), and high accuracy (98.3% for both), compared with lower accuracy of conventional nonfunctional MDCT, which is 78.3% and 93.3%, respectively. It is also highly accurate in the assessment of vocal cord mobility (94.6%) and it increases the accuracy of MDCT in local tumor staging of malignant laryngeal lesions to 80.4% compared with 76.1% accuracy of conventional nonfunctional MDCT. Conclusion Dynamic MDCT using 'eee' phonation is effective in the detection and delineation of extension of various laryngeal lesions and is more accurate than conventional nonfunctional MDCT.

MDCT in ARDS: A single center experience

Acute respiratory distress syndrome (ARDS) is a clinical condition first described by Ashbaugh et al in 1967 using the term ?adult respiratory distress syndrome?1. In order to establish a diagnosis of ARDS, radiological findings are necessary and they serve as one of the postulates. According to the latest definition, which was created by a panel of experts in 2011 in Berlin, thus termed the Berlin definition of ARDS, ARDS2 is a condition starting within 1 week of clinical insult with bilateral infiltrates detectable by chest imaging (either conventional radiography or multidetector computed tomography (MDCT) scan of lungs) and severe hypoxemia in the absence of evidence for cardiogenic pulmonary edema or fluid overload. It is necessary to explain the origin of edema, and to do that we need objective assessment (e.g., echocardiography) in order to exclude cardiogenic factors. Severity of ARDS is based on ratio between partial oxygen pressure in arterial blood and fraction of oxygen in the inspired air (PaO2 /FIO2) on 5 cm of continuous positive airway pressure (CPAP). The 3 categories are mild (PaO2/FIO2 200-300), moderate (PaO2/FIO2 100-200) and severe (PaO2/FIO2 =100). The definition itself says that in order to make a diagnosis we must do radiology imaging, although it does not say which one should be performed, the conventional radiography or MDCT. ARDS represents a stereotypic response to many different inciting insults and goes through a number of different phases, from alveolar capillary damage to lung resolution or a fibro-proliferative and fibrotic phase. The pulmonary epithelial and endothelial cellular damage is characterized by inflammation, apoptosis, necrosis and increased alveolar capillary permeability, which lead to development of alveolar edema. Purpose and role of radiographic methods is to assist in the visualization of above mentioned pathomorphological substrate. Because of the fact that sensitivity of conventional radiography is significantly lower than that of MDCT imaging, MDCT could be the primary method of choice in the initial diagnosis, but for the patient with ARDS it is most important that he has the best conditions concerning mechanical ventilation, which is very complicated to provide during the transportation of the patient from intensive care unit to MDCT diagnostic unit. As the disease evolves inside the lung area, some of the complications can be visualized only with MDCT. That is one of the main reasons MDCT is used for that period of disease evolution. Because of everything that is mentioned above, it is hard to decide whether and when MDCT scan should be performed.

Conventional and novel imaging modalities in osteoarthritis: current state of the evidence.

Imaging modalities are currently an inseparable part of osteoarthritis diagnosis. In this review, we describe the current state of evidence regarding conventional and novel imaging modalities in evaluation of osteoarthritis. Modalities including radiography (qualitative and semi-quantitative assessments), ultrasonography, computed tomography [CT; conventional multidetector CT (MDCT), cone-beam CT (CBCT) and four-dimensional CT (4DCT)], MRI (MRI; semi-quantitative, quantitative and compositional) and PET and their applications are reviewed. Radiography is the modality of choice for initial assessment of osteoarthritis. However, due to its low sensitivity and specificity, numerous recent investigations have proposed MRI as a powerful addition to detect and grade osteoarthritis features, which are not apparent in radiography. Semi-quantitative MRI measurements are feasible to perform in routine clinical practice. Quantitative and compositional MRI measurements have extended the amount of information an MRI examination can provide regarding the three-dimensional shape and tissue composition of articular cartilage. 4DCT and CBCT are introduced as imaging examinations that may reveal biomechanical cartilage abnormalities in osteoarthritis joint by dynamic and weight-bearing evaluations, respectively. Recent PET studies may unveil the underlying metabolic activities that can be associated with osteoarthritis. In addition to the established role of radiographs, MRI is the advanced modality of choice for detection and quantification of various osteoarthritis features. 4DCT and CBCT may have specified applications when diagnosis of underlying motion abnormality or dynamic changes in weight-bearing situation is suspected. Future studies should elucidate the specific clinical applications of ultrasonography and PET.