Incidental findings on routine preoperative noncontrast chest computed tomography and chest radiography prior to cardiac surgery in the multicenter randomized controlled CRICKET study.

OBJECTIVE: To describe the prevalence and consequences of incidental findings when implementing routine noncontrast CT prior to cardiac surgery. METHODS: In the multicenter randomized controlled CRICKET study, 862 adult patients scheduled for cardiac surgery were randomized 1:1 to undergo standard of care (SoC), which included a chest-radiograph, or an additional preoperative noncontrast chest CT-scan (SoC+CT). In this subanalysis, all incidental findings detected on the chest radiograph and CT-scan were analyzed. The influence of smoking status on incidental findings was also evaluated, adjusting for sex, age, and group allocation. RESULTS: Incidental findings were observed in 11.4% (n = 49) of patients in the SoC+CT group and in 3.7% (n = 16) of patients in the SoC-group (p < 0.001). The largest difference was observed in findings requiring follow-up (SoC+CT 7.7% (n = 33) vs SoC 2.3% (n = 10), p < 0.001). Clinically relevant findings changing the surgical approach or requiring specific treatment were observed in 10 patients (1.2%, SoC+CT: 1.6% SoC: 0.7%), including lung cancer in 0.5% of patients (n = 4) and aortic dilatation requiring replacement in 0.2% of patients (n = 2). Incidental findings were more frequent in patients who stopped smoking (OR 1.91, 1.03-3.63) or who actively smoked (OR 3.91, 1.85-8.23). CONCLUSIONS: Routine CT-screening increases the rate of incidental findings, mainly by identifying more pulmonary findings requiring follow-up. Incidental findings are more prevalent in patients with a history of smoking, and preoperative CT might increase the yield of identifying lung cancer in these patients. Incidental findings, but not specifically the use of routine CT, are associated with delay of surgery. KEY POINTS: • Clinically relevant incidental findings are identified more often after a routine preoperative CT-scan, when compared to a standard of care workup, with some findings changing patient management. • Patients with a history of smoking have a higher rate of incidental findings and a lung cancer rate comparable to that of lung cancer screening trials. • We observed no clear delay in the time to surgery when adding routine CT screening.

Effect of routine preoperative screening for aortic calcifications using noncontrast computed tomography on stroke rate in cardiac surgery: the randomized controlled CRICKET study.

OBJECTIVES: To evaluate if routine screening for aortic calcification using unenhanced CT lowers the risk of stroke and alters the surgical approach in patients undergoing general cardiac surgery compared with standard of care (SoC). METHODS: In this prospective, multicenter, randomized controlled trial, adult patients scheduled for cardiac surgery from September 2014 to October 2019 were randomized 1:1 into two groups: SoC alone, including chest radiography, vs. SoC plus preoperative noncontrast CT. The primary endpoint was in-hospital perioperative stroke. Secondary endpoints were preoperative change of the surgical approach, in-hospital mortality, and postoperative delirium. The trial was halted halfway for expected futility, as the conditional power analysis showed a chance < 1% of finding the hypothesized effect. RESULTS: A total of 862 patients were evaluated (SoC-group: 433 patients (66 ± 11 years; 74.1% male) vs. SoC + CT-group: 429 patients (66 ± 10 years; 69.9% male)). The perioperative stroke rate (SoC + CT: 2.1%, 9/429 vs. SoC: 1.2%, 5/433, p = 0.27) and rate of changed surgical approach (SoC + CT: 4.0% (17/429) vs. SoC: 2.8% (12/433, p = 0.35) did not differ between groups. In-hospital mortality and postoperative delirium were comparable between groups. In the SoC + CT group, aortic calcification was observed on CT in the ascending aorta in 28% (108/380) and in the aortic arch in 70% (265/379). CONCLUSIONS: Preoperative noncontrast CT in cardiac surgery candidates did not influence the surgical approach nor the incidence of perioperative stroke compared with standard of care. Aortic calcification is a frequent finding on the CT scan in these patients but results in major surgical alterations to prevent stroke in only few patients. KEY POINTS: • Aortic calcification is a frequent finding on noncontrast computed tomography prior to cardiac surgery. • Routine use of noncontrast computed tomography does not often lead to a change of the surgical approach, when compared to standard of care. • No effect was observed on perioperative stroke after cardiac surgery when using routine noncontrast computed tomography screening on top of standard of care.

Normal imaging findings after aortic valve implantation on 18F-Fluorodeoxyglucose positron emission tomography with computed tomography.

BACKGROUND: To determine the normal perivalvular 18F-Fluorodeoxyglucose (18F-FDG) uptake on positron emission tomography (PET) with computed tomography (CT) within one year after aortic prosthetic heart valve (PHV) implantation. METHODS: Patients with uncomplicated aortic PHV implantation were prospectively included and underwent 18F-FDG PET/CT at either 5 (± 1) weeks (group 1), 12 (± 2) weeks (group 2) or 52 (± 8) weeks (group 3) after implantation. 18F-FDG uptake around the PHV was scored qualitatively (none/low/intermediate/high) and quantitatively by measuring the maximum Standardized Uptake Value (SUVmax) and target to background ratio (SUVratio). RESULTS: In total, 37 patients (group 1: n = 12, group 2: n = 12, group 3: n = 13) (mean age 66 ± 8 years) were prospectively included. Perivalvular 18F-FDG uptake was low (8/12 (67%)) and intermediate (4/12 (33%)) in group 1, low (7/12 (58%)) and intermediate (5/12 (42%)) in group 2, and low (8/13 (62%)) and intermediate (5/13 (38%)) in group 3 (P = 0.91). SUVmax was 4.1 ± 0.7, 4.6 ± 0.9 and 3.8 ± 0.7 (mean ± SD, P = 0.08), and SUVratio was 2.0 [1.9 to 2.2], 2.0 [1.8 to 2.6], and 1.9 [1.7 to 2.0] (median [IQR], P = 0.81) for groups 1, 2, and 3, respectively. CONCLUSION: Non-infected aortic PHV have similar low to intermediate perivalvular 18F-FDG uptake with similar SUVmax and SUVratio at 5, 12, and 52 weeks after implantation.

Vascular uptake on 18F-sodium fluoride positron emission tomography: precursor of vascular calcification?

BACKGROUND: Microcalcifications cannot be identified with the present resolution of CT; however, 18F-sodium fluoride (18F-NaF) positron emission tomography (PET) imaging has been proposed for non-invasive identification of microcalcification. The primary objective of this study was to assess whether 18F-NaF activity can assess the presence and predict the progression of CT detectable vascular calcification. METHODS AND RESULTS: The data of two longitudinal studies in which patients received a 18F-NaF PET-CT at baseline and after 6 months or 1-year follow-up were used. The target to background ratio (TBR) was measured on PET at baseline and CT calcification was quantified in the femoral arteries at baseline and follow-up. 128 patients were included. A higher TBR at baseline was associated with higher calcification mass at baseline and calcification progression (ß = 1.006 [1.005-1.007] and ß = 1.002 [1.002-1.003] in the studies with 6 months and 1-year follow-up, respectively). In areas without calcification at baseline and where calcification developed at follow-up, the TBR was .11-.13 (P < .001) higher compared to areas where no calcification developed. CONCLUSION: The activity of 18F-NaF is related to the amount of calcification and calcification progression. In areas where calcification formation occurred, the TBR was slightly but significantly higher.

Osteoarthritis in Pseudoxanthoma Elasticum Patients: An Explorative Imaging Study.

Pseudoxanthoma elasticum (PXE) is a systemic disease affecting the skin, eyes, and cardiovascular system of patients. Cardiovascular disease is associated with osteoarthritis (OA), which is the most common cause of joint pain. There is a lack of systematic investigations on joint manifestations in PXE in the literature. In this explorative study, we aimed to investigate whether patients with PXE are more at risk for developing osseous signs of OA. Patients with PXE and hospital controls with whole-body low-dose CT examinations available were included. OA was assessed using the OsteoArthritis Computed Tomography (OACT)-score, which is a 4-point Likert scale, in the acromioclavicular (AC), glenohumeral (GH), facet, hip, knee, and ankle joints. Additionally, intervertebral disc degeneration was scored. Data were analyzed using ordinal logistic regression adjusted for age, body mass index (BMI), and smoking status. In total, 106 PXE patients (age 56 (48-64), 42% males, BMI 25.3 (22.7-28.2)) and 87 hospital controls (age 55 (43-67), 46% males, BMI 26.0 (22.5-29.2)) were included. PXE patients were more likely to have a higher OA score for the AC joints (OR 2.00 (1.12-3.61)), tibiofemoral joint (OR 2.63 (1.40-5.07)), and patellofemoral joint (2.22 (1.18-4.24)). For the other joints, the prevalence and severity of OA did not differ significantly. This study suggests that patients with PXE are more likely to have structural OA of the knee and AC joints, which needs clinical confirmation in larger groups and further investigation into the mechanism.

Intracranial Arterial Calcification: Prevalence, Risk Factors, and Consequences: JACC Review Topic of the Week.

Intracranial large and small arterial calcifications are a common incidental finding on computed tomography imaging in the general population. Here we provide an overview of the published reports on prevalence of intracranial arterial calcifications on computed tomography imaging and histopathology in relation to risk factors and clinical outcomes. We performed a systematic search in Medline, with a search filter using synonyms for computed tomography scanning, (histo)pathology, different intracranial arterial beds, and calcification. We found that intracranial calcifications are a frequent finding in all arterial beds with the highest prevalence in the intracranial internal carotid artery. In general, prevalence increases with age. Longitudinal studies on calcification progression and intervention studies are warranted to investigate the possible causal role of calcification on clinical outcomes. This might open up new therapeutic directions in stroke and dementia prevention and the maintenance of the healthy brain.

Etidronate halts systemic arterial calcification in pseudoxanthoma elasticum.

BACKGROUND AND AIMS: In pseudoxanthoma elasticum (PXE), low levels of inorganic pyrophosphate result in extensive arterial calcification. Recently, the treatment of ectopic mineralization in the PXE (TEMP) trial showed that one year of treatment with etidronate halts progression of femoral artery calcification in PXE patients. The aim of this study was to test the efficacy of etidronate on calcification in different vascular beds. METHODS: In this prespecified post-hoc analysis of the TEMP trial, arterial calcification mass was quantified in the carotid siphon, common carotid artery, thoracic and abdominal aorta, coronary arteries, iliac arteries, and the femoropopliteal and crural arteries using CT at baseline and after one year of etidronate treatment or placebo. In addition, a total arterial calcification score was calculated. The difference in calcification progression was compared between the etidronate and placebo group. RESULTS: 74 PXE patients were enrolled and randomized. Etidronate significantly halted progression of calcification in all vascular beds except for the coronary arteries. For the total arterial calcification score, the median absolute increase in mass score was -63.6 (-438.4-42.2) vs. 113.7 (9.4-377.1) (p < 0.01) and the median relative increase was -2.4% (-10.3-3.8) vs. 6.3% (0.2-15.8) (p < 0.01) in the etidronate and placebo arm, respectively. CONCLUSIONS: Etidronate treatment halts systemic arterial calcification in PXE. Further research must assess the long term safety and efficacy of etidronate on clinical outcomes in PXE.

Emphysema quantification using chest CT: influence of radiation dose reduction and reconstruction technique.

BACKGROUND: Computed tomography (CT) emphysema quantification is affected by both radiation dose (i.e. image noise) and reconstruction technique. At reduced dose, filtered back projection (FBP) results in an overestimation of the amount of emphysema due to higher noise levels, while the use of iterative reconstruction (IR) can result in an underestimation due to reduced noise. The objective of this study was to determine the influence of dose reduction and hybrid IR (HIR) or model-based IR (MIR) on CT emphysema quantification. METHODS: Twenty-two patients underwent inspiratory chest CT scan at routine radiation dose and at 45%, 60% and 75% reduced radiation dose. Acquisitions were reconstructed with FBP, HIR and MIR. Emphysema was quantified using the 15th percentile of the attenuation curve and the percentage of voxels below -950 HU. To determine whether the use of a different percentile or HU threshold is more accurate at reduced dose levels and with IR, additional measurements were performed using different percentiles and HU thresholds to determine the optimal combination. RESULTS: Dose reduction resulted in a significant overestimation of emphysema, while HIR and MIR resulted in an underestimation. Lower HU thresholds with FBP at reduced dose and higher HU thresholds with HIR and MIR resulted in emphysema percentages comparable to the reference. The 15th percentile quantification method showed similar results as the HU threshold method. CONCLUSIONS: This within-patients study showed that CT emphysema quantification is significantly affected by dose reduction and IR. This can potentially be solved by adapting commonly used thresholds.

Commonly available hematological biomarkers are associated with the extent of coronary calcifications.

BACKGROUND AND AIMS: We aimed to improve the understanding of potential associations between commonly available hematological biomarkers and the coronary artery calcification (CAC) score, which may help unravel the pathophysiology of coronary calcifications and subclinical coronary artery disease. METHODS: A cross-sectional study was performed within the Utrecht Patient Oriented Database (UPOD). Patients with suspected or known coronary artery disease who underwent CT CAC scoring as well as standard hematology analysis that was part of routine clinical care (within 3 months of CT acquisition) were included. Complete hematology datasets were extracted from hematology analyzers. Linear regression adjusted for potential confounders was used to assess if hematological biomarkers were related to the CAC score. RESULTS: In total, 1504 patients were included, of whom 43% (n = 647) had a CAC score of 0. Mean age (±SD) was 53 ±â€¯13 years, and 34% of patients were women. Red blood cell distribution width (RDW, ß = 0.20 [0.05-0.36], p=0.007), the fraction of immature reticulocytes (ß = 0.97 [0.10-6.43], p=0.004), coefficient of variation of neutrophil lobularity (ß = 0.13 [0.01-0.25], p=0.040) and mean lymphocyte cell size (ß = 0.21 [0.08-0.34], p=0.001) were positively associated with the CAC score after adjustment for age, sex, body mass index (BMI), diabetes, glomerular filtration rate (GFR) and high-density lipoprotein (HDL). CONCLUSIONS: This study confirms the known association of RDW with the CAC score, and presents the fraction of immature reticulocytes, coefficient of variation of neutrophil lobularity, and mean lymphocyte cell size as new markers associated with a higher CAC score.

Brock malignancy risk calculator for pulmonary nodules: validation outside a lung cancer screening population.

OBJECTIVE: To assess the performance of the Brock malignancy risk model for pulmonary nodules detected in routine clinical setting. METHODS: In two academic centres in the Netherlands, we established a list of patients aged ≥40 years who received a chest CT scan between 2004 and 2012, resulting in 16 850 and 23 454 eligible subjects. Subsequent diagnosis of lung cancer until the end of 2014 was established through linking with the National Cancer Registry. A nested case-control study was performed (ratio 1:3). Two observers used semiautomated software to annotate the nodules. The Brock model was separately validated on each data set using ROC analysis and compared with a solely size-based model. RESULTS: After the annotation process the final analysis included 177 malignant and 695 benign nodules for centre A, and 264 malignant and 710 benign nodules for centre B. The full Brock model resulted in areas under the curve (AUCs) of 0.90 and 0.91, while the size-only model yielded significantly lower AUCs of 0.88 and 0.87, respectively (p<0.001). At 10% malignancy risk, the threshold suggested by the British Thoracic Society, sensitivity of the full model was 75% and 81%, specificity was 85% and 84%, positive predictive values were 14% and 10% at negative predictive value (NPV) of 99%. The optimal threshold was 6% for centre A and 8% for centre B, with NPVs >99%. DISCUSSION: The Brock model shows high predictive discrimination of potentially malignant and benign nodules when validated in an unselected, heterogeneous clinical population. The high NPV may be used to decrease the number of nodule follow-up examinations.

Etidronate for Prevention of Ectopic Mineralization in Patients With Pseudoxanthoma Elasticum.

BACKGROUND: In pseudoxanthoma elasticum (PXE), low pyrophosphate levels may cause ectopic mineralization, leading to skin changes, visual impairment, and peripheral arterial disease. OBJECTIVES: The authors hypothesized that etidronate, a pyrophosphate analog, might reduce ectopic mineralization in PXE. METHODS: In the Treatment of Ectopic Mineralization in Pseudoxanthoma Elasticum trial, adults with PXE and leg arterial calcifications (n = 74) were randomly assigned to etidronate or placebo (cyclical 20 mg/kg for 2 weeks every 12 weeks). The primary outcome was ectopic mineralization, quantified with 18fluoride positron emission tomography scans as femoral arterial wall target-to-background ratios (TBRfemoral). Secondary outcomes were computed tomography arterial calcification and ophthalmological changes. Safety outcomes were bone density, serum calcium, and phosphate. RESULTS: During 12 months of follow-up, the TBRfemoral increased 6% (interquartile range [IQR]: -12% to 25%) in the etidronate group and 7% (IQR: -9% to 32%) in the placebo group (p = 0.465). Arterial calcification decreased 4% (IQR: -11% to 7%) in the etidronate group and increased 8% (IQR: -1% to 20%) in the placebo group (p = 0.001). Etidronate treatment was associated with significantly fewer subretinal neovascularization events (1 vs. 9, p = 0.007). Bone density decreased 4% ± 12% in the etidronate group and 6% ± 9% in the placebo group (p = 0.374). Hypocalcemia (<2.20 mmol/l) occurred in 3 versus 1 patient (8.1% vs. 2.7%, p = 0.304). Eighteen patients (48.6%) treated with etidronate, compared with 0 patients treated with placebo (p < 0.001), experienced hyperphosphatemia (>1.5 mmol/l) and recovered spontaneously. CONCLUSIONS: In patients with PXE, etidronate reduced arterial calcification and subretinal neovascularization events but did not lower femoral 18fluoride sodium positron emission tomography activity compared with placebo, without important safety issues. (Treatment of Ectopic Mineralization in Pseudoxanthoma elasticum; NTR5180).

Frequency of abnormal findings on routine chest radiography before cardiac surgery.

OBJECTIVE: Preoperative chest radiograph screening is widely used before cardiac surgery. The objective of this study was to investigate the frequency of abnormal findings on a routine chest radiograph before cardiac surgery. METHODS: In this retrospective cohort study, 1136 patients were included. Patients were scheduled for cardiac surgery and underwent a preoperative chest radiograph. The primary outcome was the frequency of abnormalities on the chest radiograph. Secondary outcome was the effect of those abnormalities on surgery. RESULTS: One half of the patients (570/1136; 50%) had 1 or more abnormalities on the chest radiograph. Most frequent abnormalities were cardiomegaly, aortic elongation, signs of chronic obstructive pulmonary disease, vertebral fractures or height loss, possible pulmonary or mediastinal mass, pleural effusion, and atelectasis. In 2 patients (2/1136; 0.2%), the chest radiograph led to postponement of surgery, whereas in none of the patients the surgery was cancelled. In 1 patient (1/1136; 0.1%) the surgical approach was altered and in 15 patients (15/1136; 1.3%) further analysis was performed without having an impact on the planned surgical approach. CONCLUSIONS: Although abnormalities are frequently found on preoperative chest radiographs before cardiac surgery, change in clinical management with regard to planned surgery or surgical approach occurs infrequently.

Computed tomography image quality of aortic stents in patients with aortic coarctation: a multicentre evaluation.

BACKGROUND: Stents are commonly used to treat aortic coarctation. The objective of this study was to evaluate the post-implantation computed tomography (CT) image quality of different stent types used to treat aortic coarctation. METHODS: Adult and paediatric patients with stent-treated aortic coarctation who underwent contrast-enhanced CT were retrospectively included from three tertiary care centres. CT scans were subjectively scored for image quality using a 4-point scale (1 = unacceptable; 2 = poor; 3 = good; 4 = excellent). Furthermore, the amount of stent-induced blooming artefacts was measured as the percentage of the difference between outer and inner stent diameters over the outer stent diameter. RESULTS: A total of 35 children and 34 adults implanted with 71 stents of six different types were included. The most commonly used stent type was the Cheatham Platinum stent (52 stents, 73%). The subjective image quality of the Cheatham Platinum stents was moderate with a score of 2.0±0.8 (mean ± standard deviation) in children and 2.3±0.6 in adults. The image quality in patients with Formula stents was 2.3±1.2. The Cheatham Platinum stents induced 34-48% blooming, the Formula stents 44-55%. The image quality in patients with the less commonly used Atrium Advanta V12, IntraStent, AndraStent and Palmaz stents was scored 3 (good) to 4 (excellent) with less blooming. The electrocardiographic gating and tube voltage (kVp) did not affect image quality. CONCLUSIONS: There is a substantial variation in CT image quality and blooming artefacts for different stent types used to treat aortic coarctation.

Radiation dose reduction for CT assessment of urolithiasis using iterative reconstruction: A prospective intra-individual study.

OBJECTIVE: To assess the performance of hybrid (HIR) and model-based iterative reconstruction (MIR) in patients with urolithiasis at reduced-dose computed tomography (CT). METHODS: Twenty patients scheduled for unenhanced abdominal CT for follow-up of urolithiasis were prospectively included. Routine dose acquisition was followed by three low-dose acquisitions at 40%, 60% and 80% reduced doses. All images were reconstructed with filtered back projection (FBP), HIR and MIR. Urolithiasis detection rates, gall bladder, appendix and rectosigmoid evaluation and overall subjective image quality were evaluated by two observers. RESULTS: 74 stones were present in 17 patients. Half the stones were not detected on FBP at the lowest dose level, but this improved with MIR to a sensitivity of 100%. HIR resulted in a slight decrease in sensitivity at the lowest dose to 72%, but outperformed FBP. Evaluation of other structures with HIR at 40% and with MIR at 60% dose reductions was comparable to FBP at routine dose, but 80% dose reduction resulted in non-evaluable images. CONCLUSIONS: CT radiation dose for urolithiasis detection can be safely reduced by 40 (HIR)-60 (MIR) % without affecting assessment of urolithiasis, possible extra-urinary tract pathology or overall image quality. KEY POINTS: • Iterative reconstruction can be used to substantially lower the radiation dose. • This allows for radiation reduction without affecting sensitivity of stone detection. • Possible extra-urinary tract pathology evaluation is feasible at 40-60% reduced dose.

Complications After Stent Placement for Aortic Coarctation: A Pictorial Essay of Computed Tomographic Angiography.

Stent placement is commonly used to treat aortic coarctation. Although invasive angiography remains the gold standard, follow-up is often performed using computed tomography, which allows rapid, noninvasive assessment of the aorta and surrounding tissues. The goal of this pictorial essay is to provide a guide to the interpretation of these examinations. Normal and abnormal computed tomographic appearance of different stent types is shown along with reconstructions that can help assess stent integrity and the stent position in relation to the aortic wall and branches. Furthermore, imaging findings of complications including aortic wall injuries, restenosis, and intimal hyperplasia are depicted.

Radiation dose reduction in pediatric great vessel stent computed tomography using iterative reconstruction: A phantom study.

BACKGROUND: To study dose reduction using iterative reconstruction (IR) for pediatric great vessel stent computed tomography (CT). METHODS: Five different great vessel stents were separately placed in a gel-containing plastic holder within an anthropomorphic chest phantom. The stent lumen was filled with diluted contrast gel. CT acquisitions were performed at routine dose, 52% and 81% reduced dose and reconstructed with filtered back projection (FBP) and IR. Objective image quality in terms of noise, signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) as well as subjective image quality were evaluated. RESULTS: Noise, SNR and CNR were improved with IR at routine and 52% reduced dose, compared to FBP at routine dose. The lowest dose level resulted in decreased objective image quality with both FBP and IR. Subjective image quality was excellent at all dose levels. CONCLUSION: IR resulted in improved objective image quality at routine dose and 52% reduced dose, while objective image quality deteriorated at 81% reduced dose. Subjective image quality was not affected by dose reduction.

Accuracy of bone mineral density quantification using dual-layer spectral detector CT: a phantom study.

OBJECTIVES: To investigate the accuracy of bone mineral density (BMD) quantification using dual-layer spectral detector CT (SDCT) at various scan protocols. METHODS: Two validated anthropomorphic phantoms containing inserts of 50-200 mg/cm3 calcium hydroxyapatite (HA) were scanned using a 64-slice SDCT scanner at various acquisition protocols (120 and 140 kVp, and 50, 100 and 200 mAs). Regions of interest (ROIs) were placed in each insert and mean attenuation profiles at monochromatic energy levels (90-200 keV) were constructed. These profiles were fitted to attenuation profiles of pure HA and water to calculate HA concentrations. For comparison, one phantom was scanned using dual energy X-ray absorptiometry (DXA). RESULTS: At both 120 and 140 kVp, excellent correlations (R = 0.97, P < 0.001) were found between true and measured HA concentrations. Mean error for all measurements at 120 kVp was -5.6 ± 5.7 mg/cm3 (-3.6 ± 3.2%) and at 140 kVp -2.4 ± 3.7 mg/cm3 (-0.8 ± 2.8%). Mean measurement errors were smaller than 6% for all acquisition protocols. Strong linear correlations (R2 ≥ 0.970, P < 0.001) with DXA were found. CONCLUSIONS: SDCT allows for accurate BMD quantification and potentially opens up the possibility for osteoporosis evaluation and opportunistic screening in patients undergoing SDCT for other clinical indications. However, patient studies are needed to extend and translate our findings. KEY POINTS: • Dual-layer spectral detector CT allows for accurate bone mineral density quantification. • BMD measurements on SDCT are strongly linearly correlated to DXA. • SDCT, acquired for several indications, may allow for evaluation of osteoporosis. • This potentially opens up the possibility for opportunistic osteoporosis screening.

Aortic Valve and Thoracic Aortic Calcification Measurements: How Low Can We Go in Radiation Dose?

OBJECTIVE: This study aimed to determine the lowest radiation dose and iterative reconstruction level(s) at which computed tomography (CT)-based quantification of aortic valve calcification (AVC) and thoracic aortic calcification (TAC) is still feasible. METHODS: Twenty-eight patients underwent a cardiac CT and 20 patients a chest CT at 4 different dose levels (routine dose and approximately 40%, 60%, and 80% reduced dose). Data were reconstructed with filtered back projection, 3 iDose levels, and 3 iterative model-based reconstruction levels. Two observers scored subjective image quality. The AVC and TAC were quantified using mass and compared to the reference scan (routine dose reconstructed with filtered back projection). RESULTS: In cardiac CT at 0.35 mSv (60% reduced), all scans reconstructed with iDose (all levels) were diagnostic, calcification detection errors occurred in only 1 patient, and there were no significant differences in mass scores compared to the reference scan. Similar results were found for chest CT at 0.48 mSv (75% reduced) with iDose levels 4 and 6 and iterative model reconstruction levels 1 and 2. CONCLUSIONS: Iterative reconstruction enables AVC and TAC quantification on CT at submillisievert dose.

Submillisievert coronary calcium quantification using model-based iterative reconstruction: A within-patient analysis.

PURPOSE: To determine the effect of model-based iterative reconstruction (IR) on coronary calcium quantification using different submillisievert CT acquisition protocols. METHODS: Twenty-eight patients received a clinically indicated non contrast-enhanced cardiac CT. After the routine dose acquisition, low-dose acquisitions were performed with 60%, 40% and 20% of the routine dose mAs. Images were reconstructed with filtered back projection (FBP), hybrid IR (HIR) and model-based IR (MIR) and Agatston scores, calcium volumes and calcium mass scores were determined. RESULTS: Effective dose was 0.9, 0.5, 0.4 and 0.2mSv, respectively. At 0.5 and 0.4mSv, differences in Agatston scores with both HIR and MIR compared to FBP at routine dose were small (-0.1 to -2.9%), while at 0.2mSv, differences in Agatston scores of -12.6 to -14.6% occurred. Reclassification of risk category at reduced dose levels was more frequent with MIR (21-25%) than with HIR (18%). CONCLUSIONS: Radiation dose for coronary calcium scoring can be safely reduced to 0.4mSv using both HIR and MIR, while FBP is not feasible at these dose levels due to excessive noise. Further dose reduction can lead to an underestimation in Agatston score and subsequent reclassification to lower risk categories. Mass scores were unaffected by dose reductions.