Photon-counting detector CT - first experiences in the field of musculoskeletal radiology.

The introduction of photon-counting detector CT (PCD-CT) marks a remarkable leap in innovation in CT imaging. The new detector technology allows X-rays to be converted directly into an electrical signal without an intermediate step via a scintillation layer and allows the energy of individual photons to be measured. Initial data show high spatial resolution, complete elimination of electronic noise, and steady availability of spectral image data sets. In particular, the new technology shows promise with respect to the imaging of osseous structures. Recently, PCD-CT was implemented in the clinical routine. The aim of this review was to summarize recent studies and to show our first experiences with photon-counting detector technology in the field of musculoskeletal radiology.We performed a literature search using Medline and included a total of 90 articles and reviews that covered recent experimental and clinical experiences with the new technology.In this review, we focus on (1) spatial resolution and delineation of fine anatomic structures, (2) reduction of radiation dose, (3) electronic noise, (4) techniques for metal artifact reduction, and (5) possibilities of spectral imaging. This article provides insight into our first experiences with photon-counting detector technology and shows results and images from experimental and clinical studies. · This review summarizes recent experimental and clinical studies in the field of photon-counting detector CT and musculoskeletal radiology.. · The potential of photon-counting detector technology in the field of musculoskeletal radiology includes improved spatial resolution, reduction in radiation dose, metal artifact reduction, and spectral imaging.. · PCD-CT enables imaging at lower radiation doses while maintaining or even enhancing spatial resolution, crucial for reducing patient exposure, especially in repeated or prolonged imaging scenarios.. · It offers promising results in reducing metal artifacts commonly encountered in orthopedic or dental implants, enhancing the interpretability of adjacent structures in postoperative and follow-up imaging.. · With its ability to routinely acquire spectral data, PCD-CT scans allow for material classification, such as detecting urate crystals in suspected gout or visualizing bone marrow edema, potentially reducing reliance on MRI in certain cases.. Bette S, Risch F, Becker J et al. Photon-counting detector CT - first experiences in the field of musculoskeletal radiology. Fortschr Röntgenstr 2024; DOI 10.1055/a-2312-6914.

Automated image quality assessment for selecting among multiple magnetic resonance image acquisitions in the German National Cohort study.

In magnetic resonance imaging (MRI), the perception of substandard image quality may prompt repetition of the respective image acquisition protocol. Subsequently selecting the preferred high-quality image data from a series of acquisitions can be challenging. An automated workflow may facilitate and improve this selection. We therefore aimed to investigate the applicability of an automated image quality assessment for the prediction of the subjectively preferred image acquisition. Our analysis included data from 11,347 participants with whole-body MRI examinations performed as part of the ongoing prospective multi-center German National Cohort (NAKO) study. Trained radiologic technologists repeated any of the twelve examination protocols due to induced setup errors and/or subjectively unsatisfactory image quality and chose a preferred acquisition from the resultant series. Up to 11 quantitative image quality parameters were automatically derived from all acquisitions. Regularized regression and standard estimates of diagnostic accuracy were calculated. Controlling for setup variations in 2342 series of two or more acquisitions, technologists preferred the repetition over the initial acquisition in 1116 of 1396 series in which the initial setup was retained (79.9%, range across protocols: 73-100%). Image quality parameters then commonly showed statistically significant differences between chosen and discarded acquisitions. In regularized regression across all protocols, 'structured noise maximum' was the strongest predictor for the technologists' choice, followed by 'N/2 ghosting average'. Combinations of the automatically derived parameters provided an area under the ROC curve between 0.51 and 0.74 for the prediction of the technologists' choice. It is concluded that automated image quality assessment can, despite considerable performance differences between protocols and anatomical regions, contribute substantially to identifying the subjective preference in a series of MRI acquisitions and thus provide effective decision support to readers.

Image Characteristics of Virtual Non-Contrast Series Derived from Photon-Counting Detector Coronary CT Angiography-Prerequisites for and Feasibility of Calcium Quantification.

In photon-counting detector CT (PCD-CT), coronary artery calcium scoring (CACS) can be performed using virtual non-contrast (VNC) series derived from coronary CT angiography (CCTA) datasets. Our study analyzed image characteristics of VNC series in terms of the efficacy of virtual iodine "removal" and image noise to determine whether the prerequisites for calcium quantification were satisfied. We analyzed 38 patients who had undergone non-enhanced CT followed by CCTA on a PCD-CT. VNC reconstructions were performed at different settings and algorithms (conventional VNCConv; PureCalcium VNCPC). Virtual iodine "removal" was investigated by comparing histograms of heart volumes. Noise was assessed within the left ventricular cavity. Calcium was quantified on the true non-contrast (TNC) and all VNC series. The histograms were comparable for TNC and all VNC. Image noise between TNC and all VNC differed slightly but significantly. VNCConv CACS showed a significant underestimation regardless of the reconstruction setting, while VNCPC CACS were comparable to TNC. Correlations between TNC and VNC were excellent, with a higher predictive accuracy for VNCPC. In conclusion, the iodine contrast can be effectively subtracted from CCTA datasets. The remaining VNC series satisfy the requirements for CACS, yielding results with excellent correlation compared to TNC-based CACS and high predicting accuracy.

[Radiologic evaluation of lymph nodes in cancer patients]. / Bildgebende Diagnostik von Lymphknoten bei Verdacht auf Tumorbefall.

BACKGROUND: In solid tumors, the detection of locoregional lymph node metastases is of decisive importance not only for the prognosis but also for selecting the correct treatment. Various noninvasive imaging methods or, classically, lymph node dissection are available for this purpose. OBJECTIVE: This article presents the general principles of noninvasive lymph node diagnostics and discusses the value of the clinically available imaging modalities, ultrasound (US), computed tomography (CT), magnetic resonance imaging (MRI) and positron emission tomography (PET). In addition, recent new technical developments of each modality are highlighted. MATERIAL AND METHODS: Literature search and summary of the clinical and scientific experience of the authors. RESULTS: The available imaging procedures are divided into (1) morphological (US, CT, MRI) and (2) functional modalities (PET, special MRI). The former capture structural lymph node parameters, such as size and shape, while the latter address properties that go beyond morphology (e.g. glucose metabolism). The high diagnostic accuracy required for future treatment algorithms will require a combination of both aspects. DISCUSSION/CONCLUSION: Currently, none of the available modalities have sufficient accuracy to replace lymph node dissection in all oncological scenarios. One of the major challenges for interdisciplinary oncological research is to define the optimal interaction between imaging and lymph node dissection for different malignancies and tumor stages.

Spontaneous Iliopsoas Muscle Hemorrhage-Predictors of Associated Mortality.

RATIONALE AND OBJECTIVES: Spontaneous iliopsoas muscle hemorrhage (SIPH) is a rare clinical condition associated with high mortality. In this work we aimed to retrospectively investigate the predictors of mortality in a single-institution cohort of consecutive SIPH patients. MATERIALS AND METHODS: Consecutive patients (n = 61, 30 men, 76 years [range 51-93]) with computed tomography (CT) confirmed diagnosis of SIPH were retrospectively included between January 2010 and April 2020. CT studies were assessed for signs of active bleeding, extramuscular retroperitoneal hematoma, visible sedimentation, and hematoma volume. Medication history, laboratory parameters, comorbidities, and disease management were also recorded. All parameters were subsequently examined with regard to their impact on outcome and survival. Univariate and multivariate Cox regressions were performed to identify variables associated with time to death. RESULTS: The overall mortality was 22.9%. A total of 77% of patients received anticoagulant therapy prior to the onset of SIPH. Active bleeding in contrast enhanced CT (CECT) was the only independent variable associated with shorter survival (p = 0.01, hazard ratio 7.05 [1.45-34.20]). Hematoma volume or extramuscular retroperitoneal hematoma had no significant influence on short-term mortality. CONCLUSION: Only active bleeding but not hematoma volume or extra-muscular bleeding is an independent risk factor for short-term mortality in patients with SIPH.

Typical Imaging Patterns in COVID-19 Infections of the Lung on Plain Chest Radiographs to Aid Early Triage.

PURPOSE: To evaluate imaging patterns of a COVID-19 infection of the lungs on chest radiographs and their value in discriminating this infection from other viral pneumonias. MATERIALS AND METHODS: All 321 patients who presented with respiratory impairment suspicious for COVID-19 infection between February 3 and May 8, 2020 and who received a chest radiograph were included in this analysis. Imaging findings were classified as typical for COVID-19 (bilateral, peripheral opacifications/consolidations), non-typical (findings consistent with lobar pneumonia), indeterminate (all other distribution patterns of opacifications/consolidations), or none (no opacifications/consolidations). The sensitivity, specificity, as well as positive and negative predictive value for the diagnostic value of the category "typical" were determined. Chi² test was used to compare the pattern distribution between the different types of pneumonia. RESULTS: Imaging patterns defined as typical for COVID-19 infections were documented in 35/111 (31.5 %) patients with confirmed COVID-19 infection but only in 4/210 (2 %) patients with any other kind of pneumonia, resulting in a sensitivity of 31.5 %, a specificity of 98.1 %, and a positive and negative predictive value of 89.7 % or 73 %, respectively. The sensitivity could be increased to 45.9 % when defining also unilateral, peripheral opacifications/consolidations with no relevant pathology contralaterally as consistent with a COVID-19 infection, while the specificity decreases slightly to 93.3 %. The pattern distribution between COVID-19 patients and those with other types of pneumonia differed significantly (p < 0.0001). CONCLUSION: Although the moderate sensitivity does not allow the meaningful use of chest radiographs as part of primary screening, the specific pattern of findings in a relevant proportion of those affected should be communicated quickly as additional information and trigger appropriate protective measures. KEY POINTS: · COVID-19 infections show specific X-ray image patterns in 1/3 of patients.. · Bilateral, peripheral opacities and/or consolidations are typical imaging patterns.. · Unilateral, peripheral opacities and/or consolidations should also raise suspicion of COVID-19 infection.. CITATION FORMAT: · Kasper J, Decker J, Wiesenreiter K et al. Typical Imaging Patterns in COVID-19 Infections of the Lung on Plain Chest Radiographs to Aid Early Triage. Fortschr Röntgenstr 2021; 193: 1189 - 1196.

Visceral Artery Aneurysms and Pseudoaneurysms: Retrospective Analysis of Interventional Endovascular Therapy of 43 Aneurysms.

Purpose To evaluate the results of interventional endovascular therapy of incidental and symptomatic visceral artery aneurysms in the elective and emergency situation. Materials and Methods 43 aneurysms in 38 patients (19 female, 19 male, mean age: 57 ±â€Š16 years [18 - 82]) were treated between 2011 and 2015. The characteristics of the aneurysms (true vs. false aneurysm, size, etiology, location, symptoms) were considered. Furthermore, we evaluated the intervention with respect to technical success, embolic/occlusive agents used, therapy-associated complications and post-interventional follow-up.  Results 23 true aneurysms (maximum diameter: 22 ±â€Š18 mm [11 - 67 mm]) and 20 false aneurysms (maximum diameter: 9 ±â€Š33 mm [3 - 150 mm]) were evaluated. The splenic (n = 14) and renal arteries (n = 18) were most frequently affected. The etiology was most commonly degenerative-atherosclerotic (47 %) or iatrogenic post-operative (19 %). 18/48 interventions were performed due to active bleeding. False aneurysms were associated significantly more often with active bleeding (63 vs. 25 %, p = 0.012). 41/48 treatments were technically successful. Re-intervention was necessary 6 times. In 2 cases the endovascular approach did not succeed. There was a complication rate of 10 %, whereby only 4 minor and 1 major complications occurred. No patient suffered from permanent sequelae. Aneurysms were primarily treated by using coils and if necessary additional embolic agents (liquid embolic agent or vascular plugs) (75 %). In the follow-up period, reperfusion of treated aneurysms occurred at a rate of 7 % (n = 3). Conclusion Interventional endovascular therapy of visceral artery aneurysms is safe and effective in the elective treatment of incidental aneurysms as well as in significantly more frequent hemorrhaging false aneurysms in the emergency situation. Key points · Interventional endovascular therapy of visceral artery aneurysms is safe and effective.. · In more than 60 % of cases visceral artery pseudoaneurysms are associated significantly more often with a history of bleeding or acute bleeding. Hence, there is a need for (interventional) therapy even in small pseudoaneurysms.. · Follow-up seems to be useful to detect reperfusion as manifestation of treatment failure.. Citation Format · Ruhnke H, Kröncke TJ, . Visceral Artery Aneurysms and Pseudoaneurysms: Retrospective Analysis of Interventional Endovascular Therapy of 43 Aneurysms. Fortschr Röntgenstr 2017; 189: 632 - 639.

[Case Report: Recurrent postpartum haemorrhage after emergency caesarean section - Clipping, embolization and haemostaseological therapy]. / Kasuistik: Rezidivierende postpartale Blutung nach Notsectio - Clipping, Embolisation und hämostaseologische Therapie.

Immediately after emergency caesarean section a 37 yr old patient suffered severe atonic bleeding requiring different operating procedures (Clipping of the uterine arteries) in combination with an uterotonic and haemostaseological medication as well as massive transfusion of blood components and recombinant factor VIIa. After a period of 17 days without any bleeding the patient presented to the emergency room with recurrent massive uterine bleeding. Transarterial embolization of the anterior bundles of the iliac arteries in combination with a second uterotonic and haemostaseological medication stopped the haemorrhage. Reasons and risk factors of a recurrent postpartum bleeding are discussed and a multidisciplinary algorithm for treatment is proposed.