Noninvasive vascular imaging with computed tomography (CT) has become the clinical mainstay for many indications and body regions. The recent introduction of photon-counting detector (PCD)-CT into ...clinical routine has further broadened the spectrum of vascular applications. Technical improvements of PCD-CT, such as the decreased noise levels, improved contrast-to-noise ratio, and full spectral multienergy data information from every acquisition, have the potential to further impact on clinical decision making and ultimately on outcome of vascular patients. Early experience with the new PCD-CT technology demonstrates these improvements in various aspects. This review summarizes the main advantages of PCD-CT for vascular imaging a discussion of the PureLumen and PureCalcium algorithms.
Since its development in the 1970s, X-ray CT has emerged as a landmark diagnostic imaging modality of modern medicine. Technological advances have been crucial to the success of CT imaging, as they ...have increasingly enabled improvements in image quality and diagnostic value at increasing radiation dose efficiency. With recent advances in engineering and physics, a novel technology has emerged with the potential to surpass several shortcomings and limitations of current CT systems. Photon-counting detector (PCD)-CT might substantially improve and expand the applicability of CT imaging by offering intrinsic spectral capabilities, increased spatial resolution, reduced electronic noise and improved image contrast. In this review we sought to summarize the first clinical experience of PCD-CT. We focused on most recent prototype and first clinically approved PCD-CT systems thereby reviewing initial publications and presenting corresponding clinical cases.
Summary Background Intravenous saline is recommended in clinical practice guidelines as the cornerstone for preventing contrast-induced nephropathy in patients with compromised renal function. ...However, clinical-effectiveness and cost-effectiveness of this prophylactic hydration treatment in protecting renal function has not been adequately studied in the population targeted by the guidelines, against a group receiving no prophylaxis. This was the aim of the AMACING trial. Methods AMACING is a prospective, randomised, phase 3, parallel-group, open-label, non-inferiority trial of patients at risk of contrast-induced nephropathy according to current guidelines. High-risk patients (with an estimated glomerular filtration rate eGFR of 30–59 mL per min/1·73 m2 ) aged 18 years and older, undergoing an elective procedure requiring iodinated contrast material administration at Maastricht University Medical Centre, the Netherlands, were randomly assigned (1:1) to receive intravenous 0·9% NaCl or no prophylaxis. We excluded patients with eGFR lower than 30 mL per min/1·73 m2 , previous dialysis, or no referral for intravenous hydration. Randomisation was stratified by predefined risk factors. The primary outcome was incidence of contrast-induced nephropathy, defined as an increase in serum creatinine from baseline of more than 25% or 44 μmol/L within 2–6 days of contrast exposure, and cost-effectiveness of no prophylaxis compared with intravenous hydration in the prevention of contrast-induced nephropathy. We measured serum creatinine immediately before, 2–6 days, and 26–35 days after contrast-material exposure. Laboratory personnel were masked to treatment allocation. Adverse events and use of resources were systematically recorded. The non-inferiority margin was set at 2·1%. Both intention-to-treat and per-protocol analyses were done. This trial is registered with ClinicalTrials.gov , number NCT02106234. Findings Between June 17, 2014, and July 17, 2016, 660 consecutive patients were randomly assigned to receive no prophylaxis (n=332) or intravenous hydration (n=328). 2–6 day serum creatinine was available for 307 (92%) of 332 patients in the no prophylaxis group and 296 (90%) of 328 patients in the intravenous hydration group. Contrast-induced nephropathy was recorded in eight (2·6%) of 307 non-hydrated patients and in eight (2·7%) of 296 hydrated patients. The absolute difference (no hydration vs hydration) was −0·10% (one-sided 95% CI −2·25 to 2·06; one-tailed p=0·4710). No hydration was cost-saving relative to hydration. No haemodialysis or related deaths occurred within 35 days. 18 (5·5%) of 328 patients had complications associated with intravenous hydration. Interpretation We found no prophylaxis to be non-inferior and cost-saving in preventing contrast-induced nephropathy compared with intravenous hydration according to current clinical practice guidelines. Funding Stichting de Weijerhorst.
To assess the impact of low kilo-electronvolt (keV) virtual monoenergetic image (VMI) energies and iterative reconstruction on image quality of clinical photon-counting detector coronary CT ...angiography (CCTA).
CCTA with PCD-CT (prospective ECG-triggering, 120 kVp, automatic tube current modulation) was performed in a high-end cardiovascular phantom with dynamic flow, pulsatile heart motion, and including different calcified plaques with various stenosis grades and in 10 consecutive patients. VMI at 40,50,60 and 70 keV were reconstructed without (QIR-off) and with all quantum iterative reconstruction (QIR) levels (QIR-1 to 4). In the phantom, noise power spectrum, vessel attenuation, contrast-to-noise-ratio (CNR), and vessel sharpness were measured. Two readers graded stenoses in the phantom and graded overall image quality, subjective noise, vessel sharpness, vascular contrast, and coronary artery plaque delineation on 5-point Likert scales in patients.
In the phantom, noise texture was only slightly affected by keV and QIR while noise increased by 69% from 70 keV QIR-4 to 40 keV QIR-off. Reconstructions at 40 keV QIR-4 exhibited the highest CNR (46.1 ± 1.8), vessel sharpness (425 ± 42 ∆HU/mm), and vessel attenuation (1098 ± 14 HU). Stenosis measurements were not affected by keV or QIR level (
> 0.12) with an average error of 3%/6% for reader 1/reader 2, respectively. In patients, across all subjective categories and both readers, 40 keV QIR-3 and QIR-4 images received the best scores (
< 0.001).
Forty keV VMI with QIR-4 significantly improved image quality of CCTA with PCD-CT.
PCD-CT at 40 keV and QIR-4 improves image quality of CCTA.
Radiomics, the high-throughput mining of quantitative image features from standard-of-care medical imaging that enables data to be extracted and applied within clinical-decision support systems to ...improve diagnostic, prognostic, and predictive accuracy, is gaining importance in cancer research. Radiomic analysis exploits sophisticated image analysis tools and the rapid development and validation of medical imaging data that uses image-based signatures for precision diagnosis and treatment, providing a powerful tool in modern medicine. Herein, we describe the process of radiomics, its pitfalls, challenges, opportunities, and its capacity to improve clinical decision making, emphasizing the utility for patients with cancer. Currently, the field of radiomics lacks standardized evaluation of both the scientific integrity and the clinical relevance of the numerous published radiomics investigations resulting from the rapid growth of this area. Rigorous evaluation criteria and reporting guidelines need to be established in order for radiomics to mature as a discipline. Herein, we provide guidance for investigations to meet this urgent need in the field of radiomics.
ABSTRACTThe advent of computed tomography (CT) has revolutionized radiology. Starting as head-only scanners, modern CT systems are now capable of performing whole-body examinations within a couple of ...seconds in isotropic resolution. Technical advancements of scanner hardware and image reconstruction techniques are reviewed and discussed in their clinical context. These improvements have led to a steady increase of CT examinations in all age groups for a number of reasons. On the one hand, it is very easy today to obtain whole-body data for oncologic staging and follow-up or for trauma imaging. On the other hand, new examinations such as cardiac imaging, virtual colonoscopy, gout imaging, and whole-organ perfusion imaging have widened the application profile of CT. The increasing awareness of risks associated with radiation exposure triggered the development of a variety of dose reduction techniques. Effective dose values below 1 mSv, less than the annual natural background radiation (3.1 mSv/year on average in the United States), are now routinely possible for a number of dedicated examinations, even for coronary CT angiography.
Interestingly, increases in serum creatinine akin to those in contrast-associated acute kidney injury definitions have been reported in patients who did not receive contrast at all.1–3 To further ...complicate matters, serum creatinine is directly affected by a large number of factors, many of which are encountered in the setting of contrast procedures, leading some to speculate that we are seeing signal where there is mostly noise.4 Despite these uncertainties, reports of associations between contrast-associated acute kidney injury and increased morbidity, longer hospital stays, and mortality risk are consistent, especially in patients with cardiac disease.5 Whether the relationship is causal or coincidental remains unclear, but the general assumption is that preventing contrast-associated acute kidney injury will prevent associated risks of adverse outcomes. To date, the only risk factor to be widely agreed upon is severe renal insufficiency, and even for this risk factor conflicting evidence exists.6–8 Nevertheless, current international guideline consensus is that patients at high risk are those with severe and end-stage chronic kidney disease, without other risk factor-based screening.9,10 In The Lancet, Roxana Mehran and colleagues11 propose a novel risk score based on only pre-procedural variables (Model 1) or both pre-procedural and procedural variables (Model 2) in a large database of patients undergoing percutaneous coronary intervention (derivation cohort n=14 616; validation cohort n=5606). ...congestive heart failure and reduced left ventricular ejection fraction are themselves risk factors for complications of the only accepted prophylaxis to date, namely intravenous hydration.12 Kansas City Star/Getty Images It is difficult to distinguish between effects of population characteristics, comorbidities, and procedure characteristics (eg, catheter manipulation), and effects of the contrast itself.
Objectives The purpose of this study was to investigate whether the use of a semiautomated plaque quantification algorithm (reporting volumetric and geometric plaque properties) provides additional ...prognostic value for the development of acute coronary syndromes (ACS) as compared with conventional reading from cardiac computed tomography angiography (CCTA). Background CCTA enables the visualization of coronary plaque characteristics, of which some have been shown to predict ACS. Methods A total of 1,650 patients underwent 64-slice CCTA and were followed up for ACS for a mean 26 ± 10 months. In 25 patients who had ACS and 101 random controls (selected from 993 patients with coronary artery disease but without coronary event), coronary artery disease was evaluated using conventional reading (calcium score, luminal stenosis, morphology), and then independently quantified using semiautomated software (plaque volume, burden area plaque area divided by vessel area times 100%, noncalcified percentage, attenuation, remodeling). Clinical risk profile was calculated with Framingham risk score (FRS). Results There were no significant differences in conventional reading parameters between controls and patients who had ACS. Semiautomated plaque quantification showed that compared to controls, ACS patients had higher total plaque volume (median: 94 mm3 vs. 29 mm3 ) and total noncalcified volume (28 mm3 vs. 4 mm3 , p ≤ 0.001 for both). In addition, per-plaque maximal volume (median: 56 mm3 vs. 24 mm3 ), noncalcified percentage (62% vs. 26%), and plaque burden (57% vs. 36%) in ACS patients were significantly higher (p < 0.01 for all). A receiver-operating characteristic model predicting for ACS incorporating FRS and conventional CCTA reading had an area under the curve of 0.64; a second model also incorporating semiautomated plaque quantification had an area under the curve of 0.79 (p < 0.05). Conclusions The semiautomated plaque quantification algorithm identified several parameters predictive for ACS and provided incremental prognostic value over clinical risk profile and conventional CT reading. The application of this tool may improve risk stratification in patients undergoing CCTA.
This study aimed to determine the diagnostic accuracy of the 3 most commonly used noninvasive myocardial perfusion imaging modalities, single-photon emission computed tomography (SPECT), cardiac ...magnetic resonance (CMR), and positron emission tomography (PET) perfusion imaging for the diagnosis of obstructive coronary artery disease (CAD). Additionally, the effect of test and study characteristics was explored.
Accurate detection of obstructive CAD is important for effective therapy. Noninvasive myocardial perfusion imaging is increasingly being applied to gauge the severity of CAD.
Studies published between 1990 and 2010 identified by PubMed search and citation tracking were examined. A study was included if a perfusion imaging modality was used as a diagnostic test for the detection of obstructive CAD and coronary angiography as the reference standard (≥50% diameter stenosis).
Of the 3,635 citations, 166 articles (n = 17,901) met the inclusion criteria: 114 SPECT, 37 CMR, and 15 PET articles. There were not enough publications on other perfusion techniques such as perfusion echocardiography and computed tomography to include these modalities into the study. The patient-based analysis per imaging modality demonstrated a pooled sensitivity of 88% (95% confidence interval CI: 88% to 89%), 89% (95% CI: 88% to 91%), and 84% (95% CI: 81% to 87%) for SPECT, CMR, and PET, respectively; with a pooled specificity of 61% (95% CI: 59% to 62%), 76% (95% CI: 73% to 78%), and 81% (95% CI: 74% to 87%). This resulted in a pooled diagnostic odds ratio (DOR) of 15.31 (95% CI: 12.66 to 18.52; I(2) 63.6%), 26.42 (95% CI: 17.69 to 39.47; I(2) 58.3%), and 36.47 (95% CI: 21.48 to 61.92; I(2) 0%). Most of the evaluated test and study characteristics did not affect the ranking of diagnostic performances.
SPECT, CMR, and PET all yielded a high sensitivity, while a broad range of specificity was observed. SPECT is widely available and most extensively validated; PET achieved the highest diagnostic performance; CMR may provide an alternative without ionizing radiation and a similar diagnostic accuracy as PET. We suggest that referring physicians consider these findings in the context of local expertise and infrastructure.
Acute aortic syndromes comprise a group of potentially fatal conditions that result from weakening of the aortic vessel wall. Pre-emptive surgical intervention is currently reserved for patients with ...severe aortic dilatation, although abundant evidence describes the occurrence of dissection and rupture in aortas with diameters below surgical thresholds. Modern imaging techniques (such as hybrid PET-CT and 4D flow MRI) afford the non-invasive assessment of anatomic, hemodynamic, and molecular features of the aorta, and may provide for a more accurate selection of patients who will benefit from preventative surgical intervention. In the current review, we summarize evidence and considerations regarding predictive aortic imaging and highlight evolving imaging modalities that have shown promise to improve risk assessment for the occurrence of dissection and rupture.
Key Points
• Guidelines for the preventative management of aortic disease depend on maximal vessel diameters, while these have shown to be poor predictors for the occurrence of catastrophic acute aortic events.
• Evolving imaging modalities (such as 4D flow MRI and hybrid PET-CT) afford a more comprehensive insight into anatomic, hemodynamic, and molecular features of the aorta and have shown promise to detect vessel wall instability at an early stage.
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