The Best of Both Worlds: Ultra-high-pitch Pulmonary Angiography with Free-Breathing Technique by Means of Photon-Counting Detector CT for Diagnosis of Acute Pulmonary Embolism.

RATIONALE AND OBJECTIVES: To assess image quality and radiation dose of ultra-high-pitch CT pulmonary angiography (CTPA) with free-breathing technique for diagnosis of pulmonary embolism using a photon-counting detector (PCD) CT compared to matched energy-integrating detector (EID)-based single-energy CTPA. MATERIALS AND METHODS: Fifty-one PCD-CTPAs were prospectively compared to 51 CTPAs on a third-generation dual-source EID-CT. CTPAs were acquired with an ultra-high-pitch protocol with free-breathing technique (40 mL contrast medium, pitch 3.2) at 140 kV (PCD) and 70-100 kV (EID). Iodine maps were reconstructed from spectral PCD-CTPAs. Image quality of CTPAs and iodine maps was assessed independently by three radiologists. Additionally, CT attenuation numbers within pulmonary arteries as well as signal-to-noise and contrast-to-noise ratios (SNR, CNR) were compared. Administered radiation dose was compared. RESULTS: CT attenuation was higher in the PCD-group (all P < 0.05). CNR and SNR were higher in lobar pulmonary arteries in PCD-CTPAs (P < 0.05), whereas no difference was ascertained within the pulmonary trunk (P > 0.05). Image quality of PCD-CTPA was rated best by all readers (excellent/good image quality in 96.1% of PCD-CTPAs vs. 50.9% of EID-CTPAs). PCD-CT produced no non-diagnostic scans vs. three non-diagnostic (5.9%) EID-CTPAs. Radiation dose was lower with PCD-CT than with EID-CT (effective dose 1.33 ± 0.47 vs. 1.80 ± 0.82 mSv; all P < 0.05). CONCLUSION: Ultra-high-pitch CTPA with free-breathing technique with PCD-CT allows for superior image quality with significantly reduced radiation dose and full spectral information. With the ultra-high pitch, only PCD-CTPA enables reconstruction of iodine maps containing additional functional information.

Imaging findings in Giant Cell Arteritis: Don't Turn A Blind Eye To The Obvious!

Giant cell arteritis (GCA) is the most common primary large vessel systemic vasculitis in the western world. Even though the involvement of scalp and intracranial vessels has received much attention in the neuroradiology literature, GCA, being a systemic vasculitis can involve multiple other larger vessels including aorta and its major head and neck branches. Herein, the authors present a pictorial review of the various cranial, extracranial and orbital manifestations of GCA. An increased awareness of this entity may help with timely and accurate diagnosis, helping expedite therapy and preventing serious complications.ABBREVIATIONS: ACR= American College of Rheumatology, AION= Anterior Ischemic Optic Neuropathy, EULAR= European League Against Rheumatism, GCA= Giant Cell Arteritis, LV-GCA= Large vessel GCA, PMR= Polymyalgia Rheumatica, US= Ultrasound, VWI= Vessel Wall Imaging.

Large vessel giant cell arteritis.

Giant cell arteritis is the principal form of systemic vasculitis affecting people over 50. Large-vessel involvement, termed large vessel giant cell arteritis, mainly affects the aorta and its branches, often occurring alongside cranial giant cell arteritis, but large vessel giant cell arteritis without cranial giant cell arteritis can also occur. Patients mostly present with constitutional symptoms, with localising large vessel giant cell arteritis symptoms present in a minority of patients only. Large vessel giant cell arteritis is usually overlooked until clinicians seek to exclude it with imaging by ultrasonography, magnetic resonance angiography (MRA), computed tomography angiography (CTA), or [18F]fluorodeoxyglucose-PET-CT. Although the role of imaging in treatment monitoring remains uncertain, imaging by MRA or CTA is crucial for identifying aortic aneurysm formation during patient follow up. In this Series paper, we define the large vessel subset of giant cell arteritis and summarise its clinical challenges. Furthermore, we identify areas for future research regarding the management of large vessel giant cell arteritis.

MRVAS Score-introducing a standardized magnetic resonance scoring system for assessing the extent of inflammatory burden in giant cell arteritis.

OBJECTIVES: Our aim was to introduce a standardized system for assessing the extent of giant cell arteritis (GCA) on MRI, titled MRVAS (MR Vasculitis Activity score). To obtain a comprehensive view, we used an extensive MRI protocol including cranial vessels and the aorta with its branches. To test reliability, MRI was assessed by 4 readers with different levels of experience. METHODS: 80 patients with suspected GCA underwent MRI of cranial arteries and the aorta/branches (20 vessel segments). Every vessel was rated dichotomous [inflamed (coded as 1) or not 0], providing a summed score from 0 to 20. Blinded readers (two experienced radiologists [ExR], two inexperienced radiologists [InR]) applied the MRVAS on an individual vessel and an overall level (defined as the highest score of any of the individual vessel scores). To determine interrater agreement, Cohen's kappa was calculated for pairwise comparison of each reader for individual vessel segments. Intraclass correlation coefficients (ICC) were used for the MRVAS score. RESULTS: Concordance rates were excellent for both sub-cohorts on an individual vessel-based (GCA, ICC, 0.95; and non-GCA, ICC, 0.96) and Overall MRVAS score level (GCA, ICC, 0.96; and non-GCA, ICC, 1.0). Interrater agreement yielded significant concordance (p< 0.001) for all pairs (kappa range 0.78-0.98). No significant differences between ERs and IRs were observed (p= 0.38). CONCLUSION: The proposed MRVAS score allows standardized scoring of inflammation in GCA and achieved high agreement rates in a prospective setting.

Virtual non-iodine photon-counting CT-angiography for aortic valve calcification scoring.

Photon-counting detector (PCD)-CT allows for reconstruction of virtual non-iodine (VNI) images from contrast-enhanced datasets. This study assesses the diagnostic performance of aortic valve calcification scoring (AVCS) derived from VNI datasets generated with a 1st generation clinical dual-source PCD-CT. AVCS was evaluated in 123 patients (statistical analysis only comprising patients with aortic valve calcifications [n = 56; 63.2 ± 11.6 years]), who underwent contrast enhanced electrocardiogram-gated (either prospective or retrospective or both) cardiac CT on a clinical PCD system. Patient data was reconstructed at 70 keV employing a VNI reconstruction algorithm. True non-contrast (TNC) scans at 70 keV without quantum iterative reconstruction served as reference in all individuals. Subgroup analysis was performed in 17 patients who received both, prospectively and retrospectively gated contrast enhanced scans (n = 8 with aortic valve calcifications). VNI images with prospective/retrospective gating had an overall sensitivity of 69.2%/56.0%, specificity of 100%/100%, accuracy of 85.4%/81.0%, positive predictive value of 100%/100%, and a negative predictive value of 78.2%/75.0%. VNI images with retrospective gating achieved similar results. For both gating approaches, AVCSVNI showed high correlation (r = 0.983, P < 0.001 for prospective; r = 0.986, P < 0.001 for retrospective) with AVCSTNC. Subgroup analyses demonstrated excellent intra-individual correlation between different acquisition modes (r = 0.986, P < 0.001). Thus, VNI images derived from cardiac PCD-CT allow for excellent diagnostic performance in the assessment of AVCS, suggesting potential for the omission of true non-contrast scans in the clinical workup of patients with aortic calcifications.

High-resolution Magnetic Resonance Imaging visualizes intracranial large artery involvement in Giant Cell Arteritis.

OBJECTIVE: Giant Cell arteritis (GCA) is a large vessel vasculitis, typically involving the aorta and its branches with predilection for the scalp arteries. Intracranial involvement is still part of ongoing research. We assess inflammation of the intracranial arteries on 3D-black-blood magnetic resonance imaging (3D-CS-BB-MRI) in patients with GCA and age-matched controls. METHODS: 105 patients with 3D-CS-BB-MRI of the brain were included in this retrospective dual-center case-control study; 55 with diagnosed GCA and 50 age-matched controls. High-resolution 3D-CS-BB-MRI was performed on a 3 Tesla MR scanner with a post-contrast 3D-compressed-sensing (CS) MR pulse sequence, specifically a T1-weighted sampling perfection, application-optimized contrasts using different flip angle evolution (SPACE) pulse sequence with whole-brain coverage and isotropic resolution of 0.55 mm3. Two neuroradiologists blinded to clinical data independently scored the cerebral arteries qualitatively for inflammation; circumferential vessel wall thickening and contrast enhancement were scored positive for vasculitis. RESULTS: 8 of 55 GCA patients (14.5%) showed inflammation of at least one intracranial artery. The internal carotid artery (ICA) was affected in 6/55 (10.9%), the vertebral artery in 4/55 (7.3%) and the basilar artery and posterior cerebral artery in 1/55 (1.8%). All patients with inflammatory changes reported headaches and none showed any focal neurological deficit. Besides headache and general weakness, there was no significant correlation between inflammation of the intracranial arteries and clinical symptoms. No age-matched control patient showed inflammatory changes of the intracranial arteries. CONCLUSION: High-resolution 3D-CS-BB-MRI revealed inflammatory changes of intracranial arteries in 14.5% of GCA patients with the intradural ICA as the most frequently affected vessel.