The impact and challenges of implementing CTCA according to the 2019 ESC guidelines on chronic coronary syndromes: a survey and projection of CTCA services in the Netherlands

Background

The 2019 ESC-guidelines on chronic coronary syndromes (ESC-CCS) recommend computed tomographic coronary angiography (CTCA) or non-invasive functional imaging instead of exercise ECG as initial test to diagnose obstructive coronary artery disease. Since impact and challenges of these guidelines are unknown, we studied the current utilisation of CTCA-services, status of CTCA-protocols and modeled the expected impact of these guidelines in the Netherlands.

Methods and results

A survey on current practice and CTCA utilisation was disseminated to every Dutch hospital organisation providing outpatient cardiology care and modeled the required CTCA capacity for implementation of the ESC guideline, based on these national figures and expert consensus. Survey response rate was 100% (68/68 hospital organisations). In 2019, 63 hospital organisations provided CTCA-services (93%), CTCA was performed on 99 CTCA-capable CT-scanners, and 37,283 CTCA-examinations were performed. Between the hospital organisations, we found substantial variation considering CTCA indications, CTCA equipment and acquisition and reporting standards. To fully implement the new ESC guideline, our model suggests that 70,000 additional CTCA-examinations would have to be performed in the Netherlands.

Conclusions

Despite high national CTCA-services coverage in the Netherlands, a substantial increase in CTCA capacity is expected to be able to implement the 2019 ESC-CCS recommendations on the use of CTCA. Furthermore, the results of this survey highlight the importance to address variations in image acquisition and to standardise the interpretation and reporting of CTCA, as well as to establish interdisciplinary collaboration and organisational alignment.

Diagnostic accuracy of contrast-enhanced diffusion-weighted MRI for liver metastases of pancreatic cancer: towards adequate staging and follow-up of pancreatic cancer - DIA-PANC study: study protocol for an international, multicenter, diagnostic trial

BACKGROUND

At the time of surgery, approximately 10-20% of the patients with pancreatic cancer are considered unresectable because of unexpected liver metastasis, peritoneal carcinomatosis or locally advanced disease. This leads to futile surgical treatment with all the associated morbidity, mortality and costs. More than 50% of all liver metastases develop in the first six months postoperatively. These (subcentimeter) liver metastases are most likely already present at the time of diagnosis and have not been identified pre-operatively, due to the poor sensitivity of routine preoperative contrast-enhanced CT (CECT).

METHODS

The DIA-PANC study is a prospective, international, multicenter, diagnostic cohort study investigating diffusion-weighted, contrast-enhanced MRI for the detection of liver metastases in patients with all stages of pancreatic cancer. Indeterminate or malignant liver lesions on MRI will be further investigated histopathologically. For patients with suspected liver lesions without histopathological proof, follow up imaging with paired CT and MRI at 3-, 6- and 12-months will serve as an alternative reference standard.

DISCUSSION

The DIA-PANC trial is expected to report high-level evidence of the diagnostic accuracy of MRI for the detection of liver metastases, resulting in significant value for clinical decision making, guideline development and improved stratification for treatment strategies and future trials. Furthermore, DIA-PANC will contribute to our knowledge of liver metastases regarding incidence, imaging characteristics, their number and extent, and their change in time with or without treatment. It will enhance the worldwide implementation of MRI and consequently improve personalized treatment of patients with suspected pancreatic ductal adenocarcinoma.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT03469726 . Registered on March 19th 2018 - Retrospectively registered.

Scanning gate microscopy mapping of edge current and branched electron flow in a transition metal dichalcogenide nanoribbon and quantum point contact

We study scanning gate microscopy conductance mapping of a [Formula: see text] zigzag ribbon exploiting tight-binding and continuum models. We show that, even though the edge modes of a pristine nanoribbon are robust to backscattering on the potential induced by the tip, the conductance mapping reveals presence of both the edge modes and the quantized spin- and valley-current carrying modes. By inspecting the electron flow from a split gate quantum point contact (QPC) we find that the mapped current flow allows to determine the nature of the quantization in the QPC as spin-orbit coupling strength affects the number of branches in which the current exits the constriction. The radial conductance oscillation fringes found in the conductance mapping reveal the presence of two possible wavevectors for the charge carriers that correspond to spin and valley opposite modes. Finally, we show that disorder induced valley mixing leads to a beating pattern in the radial fringes.

Color-Mapping of 4D-CTA for the Detection of Cranial Arteriovenous Shunts

BACKGROUND AND PURPOSE

4D CT angiography is increasingly used in clinical practice for the assessment of different neurovascular disorders. Optimized processing of 4D-CTA is crucial for diagnostic interpretation because of the large amount of data that is generated. A color-mapping method for 4D-CTA is presented for improved and enhanced visualization of the cerebral vasculature hemodynamics. This method was applied to detect cranial AVFs.

MATERIALS AND METHODS

All patients who underwent both 4D-CTA and DSA in our hospital from 2011 to 2018 for the clinical suspicion of a cranial AVF or carotid cavernous fistula were retrospectively collected. Temporal information in the cerebral vasculature was visualized using a patient-specific color scale. All color-maps were evaluated by 3 observers for the presence or absence of an AVF or carotid cavernous fistula. The presence or absence of cortical venous reflux was evaluated as a secondary outcome measure.

RESULTS

In total, 31 patients were included, 21 patients with and 10 without an AVF. Arterialization of venous structures in AVFs was accurately visualized using color-mapping. There was high sensitivity (86%-100%) and moderate-to-high specificity (70%-100%) for the detection of AVFs on color-mapping 4D-CTA, even without the availability of dynamic subtraction rendering. The diagnostic performance of the 3 observers in the detection of cortical venous reflux was variable (sensitivity, 43%-88%; specificity, 60%-80%).

CONCLUSIONS

Arterialization of venous structures can be visualized using color-mapping of 4D-CTA and proves to be accurate for the detection of cranial AVFs. This finding makes color-mapping a promising visualization technique for assessing temporal hemodynamics in 4D-CTA.

Incidental perifissural nodules on routine chest computed tomography: lung cancer or not?

Objectives

Perifissural nodules (PFNs) are a common finding on chest CT, and are thought to represent non-malignant lesions. However, data outside a lung cancer-screening setting are currently lacking.

Methods

In a nested case-control design, out of a total cohort of 16,850 patients ≥ 40 years of age who underwent routine chest CT (2004-2012), 186 eligible subjects with incident lung cancer and 511 controls without were investigated. All non-calcified nodules ≥ 4 mm were semi-automatically annotated. Lung cancer location and subject characteristics were recorded.

Results

Cases (56 % male) had a median age of 64 years (IQR 59–70). Controls (60 % male) were slightly younger (p<0.01), median age of 61 years (IQR 51–70). A total of 262/1,278 (21 %) unique non-calcified nodules represented a PFN. None of these were traced to a lung malignancy over a median follow-up of around 4.5 years. PFNs were most often located in the lower lung zones (72 %, p<0.001). Median diameter was 4.6 mm (range: 4.0–8.1), volume 51 mm³ (range: 32–278). Some showed growth rates < 400 days.

Conclusions

Our data show that incidental PFNs do not represent lung cancer in a routine care, heterogeneous population. This confirms prior screening-based results.

Key Points

• One-fifth of non-calcified nodules represented a perifissural nodule in our non-screening population.

• PFNs fairly often show larger size, and can show interval growth.

• When morphologically resembling a PFN, nodules are nearly certainly not a malignancy.

• The assumed benign aetiology of PFNs seems valid outside the screening setting.

Corrigendum: Towards automatic pulmonary nodule management in lung cancer screening with deep learning

This corrects the article DOI: 10.1038/srep46479.

The Kissing Balloons Technique

Whereas dilatation of a single stenosis of the main renal artery is a routine intervention, a narrowing of the renal artery at its bifurcation extending into the branch arteries poses a more complex problem. The procedural risks of renal artery dilatation are compounded by the danger of occlusion of one of the branch arteries during maneuvers to dilate the other. Long-term results of surgical vascular reconstruction at a renal artery bifurcation are not satisfactory. Untreated, these stenoses lead to intractable hypertension and impairment or loss of renal function. We present a patient with hypertension and impaired function of the right kidney on account of a renal arterial bifurcation stenosis. Using a bilateral transfemoral arterial approach 2 balloon catheters were simultaneously placed into the origins of the renal artery branches and both arteries were successfully dilated by the kissing balloons technique. This method provides an elegant alternative to difficult surgery to save an endangered kidney.

Timing-Invariant CT Angiography Derived from CT Perfusion Imaging in Acute Stroke: A Diagnostic Performance Study

BACKGROUND AND PURPOSE

Timing-invariant (or delay-insensitive) CT angiography derived from CT perfusion data may obviate a separate cranial CTA in acute stroke, thus enhancing patient safety by reducing total examination time, radiation dose, and volume of contrast material. We assessed the diagnostic accuracy of timing-invariant CTA for detecting intracranial artery occlusion in acute ischemic stroke, to examine whether standard CTA can be omitted.

MATERIALS AND METHODS

Patients with suspected ischemic stroke were prospectively enrolled and underwent CTA and CTP imaging at admission. Timing-invariant CTA was derived from the CTP data. Five neuroradiologic observers assessed all images for the presence and location of intracranial artery occlusion in a blinded and randomized manner. Sensitivity and specificity of timing-invariant CTA and standard CTA were calculated by using an independent expert panel as the reference standard. Interrater agreement was determined by using κ statistics.

RESULTS

We included 108 patients with 47 vessel occlusions. Overall, standard CTA and timing-invariant CTA provided similar high diagnostic accuracy for occlusion detection with a sensitivity of 96% (95% CI, 90%-100%) and a specificity of 100% (99%-100%) for standard CTA and a sensitivity of 98% (95% CI, 94%-100%) and a specificity of 100% (95% CI, 100%-100%) for timing-invariant CTA. For proximal large-vessel occlusions, defined as occlusions of the ICA, basilar artery, and M1, the sensitivity and specificity were 100% (95% CI, 100%-100%) for both techniques. Interrater agreement was good for both techniques (mean κ value, 0.75 and 0.76).

CONCLUSIONS

Timing-invariant CTA derived from CTP data provides diagnostic accuracy similar to that of standard CTA for the detection of artery occlusions in acute stroke.

4D-CTA in neurovascular disease: a review

CT angiography is a widely used technique for the noninvasive evaluation of neurovascular pathology. Because CTA is a snapshot of arterial contrast enhancement, information on flow dynamics is limited. Dynamic CTA techniques, also referred to as 4D-CTA, have become available for clinical practice in recent years. This article provides a description of 4D-CTA techniques and a review of the available literature on the application of 4D-CTA for the evaluation of intracranial vascular malformations and hemorrhagic and ischemic stroke. Most of the research performed to date consists of observational cohort studies or descriptive case series. These studies show that intracranial vascular malformations can be adequately depicted and classified by 4D-CTA, with DSA as the reference standard. In ischemic stroke, 4D-CTA better estimates thrombus burden and the presence of collateral vessels than conventional CTA. In intracranial hemorrhage, 4D-CTA improves the detection of the "spot" sign, which represents active ongoing bleeding.

MRA versus DSA for follow-up of coiled intracranial aneurysms: a meta-analysis

MR angiography is proposed as a safer and less expensive alternative to the reference standard, DSA, in the follow-up of intracranial aneurysms treated with endovascular coil occlusion. We performed a systematic review and meta-analysis to evaluate the accuracy of TOF-MRA and contrast-enhanced MRA in detecting residual flow in the follow-up of coiled intracranial aneurysms. Literature was reviewed through the PubMed, Cochrane, and EMBASE data bases. In comparison with DSA, the sensitivity of TOF-MRA was 86% (95% CI: 82-89%), with a specificity of 84% (95% CI: 81-88%), for the detection of any recurrent flow. For contrast-enhanced MRA, the sensitivity and specificity were 86% (95% CI: 82-89%) and 89% (95% CI: 85-92%), respectively. Both TOF-MRA and contrast-enhanced MRA are shown to be highly accurate for detection of any recanalization in intracranial aneurysms treated with endovascular coil occlusion.

Inter- and intraobserver reliability for diagnosing levator ani changes on magnetic resonance imaging

OBJECTIVES

To assess the inter- and intraobserver reliability of the diagnosis of pubovisceral muscle avulsions and measurements of the levator hiatus on magnetic resonance imaging (MRI).

METHODS

Women with recurrent pelvic organ prolapse or in whom there was a discrepancy between clinical signs and symptoms of pelvic floor dysfunction underwent MRI and were eligible for inclusion. MRI datasets of the pelvic floor of 262 women were obtained and evaluated by two observers, who scored the presence and extent of pubovisceral muscle avulsions on each side using a scale from 0 to 3 and obtained measurements of the anteroposterior and transverse diameters and area of the levator hiatus. A random sample of 100 patients was reviewed a second time by one of the observers. Intraclass correlation coefficients (ICCs) with their 95% CI were calculated for all measurements. Mean differences with accompanying limits of agreement were calculated to estimate agreement between pairs of measurements and to detect possible systematic bias.

RESULTS

Good interobserver reliability was found for the assessment of pubovisceral muscle avulsions (ICC = 0.76-0.79) and excellent agreement for measurements of the levator hiatus (ICC = 0.85-0.89). The intraobserver reliability for pubovisceral muscle avulsions and other levator hiatus measurements was also excellent (ICC = 0.80-0.97). A significant interobserver systematic bias was observed in the measurement of levator hiatus transverse diameter; however, narrow limits of agreement were observed.

CONCLUSIONS

Pubovisceral muscle avulsions and levator hiatus measurements can be assessed with good to excellent reliability on MRI.

A national survey on radiation dose in CT in The Netherlands

Objectives

To assess radiation exposure due to CT in the Netherlands.

Methods

Twenty-one hospitals participated in a dose survey for the 21 most frequently used CT protocols. Hospitals completed a Web survey with detailed parameters for one patient per protocol, including the dose length product (DLP) from the scanner dose report. Only standard-sized patients (1.74 m and 77 kg and BMI 25.4 kg/m² ± 15 %) for each protocol and available scanner were considered. Effective dose (E) per protocol was estimated using ICRP-103-based E/DLP coefficients. Dose levels were compared to surveys from other countries and to diagnostic reference levels.

Results

Data of 186 patients (247 scan phases) from 14 hospitals and 19 scanners were used for final analysis of DLP and E. Effective doses varied from 0.2 mSv in sinus CT to 19.4 mSv for multiphase liver. The most frequent exams were brain (1.5 mSv), abdomen (8.0 mSv), and thorax-abdomen (11.5 mSv). These results are lower than in Germany and comparable to those in the UK, and are within reference levels. Results between hospitals varied, with per protocol minimum/maximum E ratios ranging from 1.1–5.4.

Conclusions

Compared to surrounding countries, CT in the Netherlands is associated with relatively low radiation doses in standard patients. Important differences remain between hospitals.

Main Messages

• A national dose survey providing updated, detailed data for patient dose in the most frequently used CT protocols.

• CT in the Netherlands is associated with relatively low individual radiation doses in standard patients compared to surrounding European countries.

• Considerable differences remain between hospitals for the most frequently used CT protocols, indicating the need for further optimisation.

Improved arterial visualization in cerebral CT perfusion-derived arteriograms compared with standard CT angiography: a visual assessment study

BACKGROUND AND PURPOSE

Invasive cerebral DSA has largely been replaced by CTA, which is noninvasive but has a compromised arterial view due to superimposed bone and veins. The purpose of this study was to evaluate whether arterial visualization in CTPa is superior to standard CTA, which would eliminate the need for an additional CTA scan to assess arterial diseases and therefore reduce radiation dose.

MATERIALS AND METHODS

In this study, we included 24 patients with subarachnoid hemorrhage for whom CTA and CTP were available. Arterial quality and presence of superimposed veins and bone in CTPa were compared with CTA and scored by 2 radiologists by using a VAS (0%-100%). Average VAS scores were determined and VAS scores per patient were converted to a 10-point NRS. Arterial visualization was considered to be improved when the highest rate (NRS 10, VAS > 90%) was scored for arterial quality, and the lowest rate (NRS 1, VAS < 10%), for the presence of superimposed veins and bone. A sign test with continuity correction was used to test whether the number of cases with these rates was significant.

RESULTS

Average VAS scores in the proximal area were 94% (arterial quality), 4% (presence of bone), and 7% (presence of veins). In this area, the sign test showed that a significant number of cases scored NRS 10 for arterial quality (P < .02) and NRS 1 for the presence of superimposed veins and bone (P < .01).

CONCLUSIONS

Cerebral CTPa shows improved arterial visualization in the proximal area compared with CTA, with similar arterial quality but no superimposed bone and veins.

Effect of stenting on cerebral CT perfusion in symptomatic and asymptomatic patients with carotid artery stenosis

BACKGROUND AND PURPOSE

The introduction of CAS has led to increased treatment of both symptomatic and asymptomatic patients with internal carotid stenosis. This study was performed to compare the effect of stent placement on cerebral perfusion in symptomatic and asymptomatic patients using CT perfusion.

MATERIALS AND METHODS

We included 45 patients with carotid artery stenosis of ≥70% who underwent arterial stent placement. Thirty-one patients were treated because of symptoms; 14 asymptomatic patients were treated before coronary artery bypass grafting. Patients underwent CTP before and after stent placement. We calculated MTT, CBV, and CBF, and derived relative numbers that compared treated with untreated hemispheres: ratios of CBV and CBF and difference in MTT. We compared the effect of carotid stent placement on cerebral perfusion in symptomatic and asymptomatic patients.

RESULTS

All perfusion parameters changed significantly after treatment in symptomatic patients: rCBF increased from 0.81 to 0.93 (P < .001), rCBV decreased from 1.02 to 0.95 (P < .05), and dMTT decreased from 1.29 to 0.14 (P < .001). In asymptomatic patients only, rCBF changed significantly with an increase from 0.92 to 1.03 (P < .05). When we compared symptomatic and asymptomatic patients before treatment, rCBF in symptomatic patients was significantly lower. The decrease of rCBV after treatment in symptomatic patients resulted in a significantly lower value than in asymptomatic patients.

CONCLUSIONS

Carotid artery stent placement improves blood flow in the affected hemisphere in symptomatic and asymptomatic patients. CBF before treatment is more strongly impaired in patients with symptomatic carotid stenosis. Compensatory hyperemia on the symptomatic side before treatment (rCBV > 1) turns into hypoxemia after treatment, suggesting impaired autoregulation in these patients.

The relationship between lung function impairment and quantitative computed tomography in chronic obstructive pulmonary disease

OBJECTIVES

To determine the relationship between lung function impairment and quantitative computed tomography (CT) measurements of air trapping and emphysema in a population of current and former heavy smokers with and without airflow limitation.

METHODS

In 248 subjects (50 normal smokers; 50 mild obstruction; 50 moderate obstruction; 50 severe obstruction; 48 very severe obstruction) CT emphysema and CT air trapping were quantified on paired inspiratory and end-expiratory CT examinations using several available quantification methods. CT measurements were related to lung function (FEV(1), FEV(1)/FVC, RV/TLC, Kco) by univariate and multivariate linear regression analysis.

RESULTS

Quantitative CT measurements of emphysema and air trapping were strongly correlated to airflow limitation (univariate r-squared up to 0.72, p < 0.001). In multivariate analysis, the combination of CT emphysema and CT air trapping explained 68-83% of the variability in airflow limitation in subjects covering the total range of airflow limitation (p < 0.001).

CONCLUSIONS

The combination of quantitative CT air trapping and emphysema measurements is strongly associated with lung function impairment in current and former heavy smokers with a wide range of airflow limitation.

Stand-alone performance of a computer-assisted detection prototype for detection of acute pulmonary embolism: a multi-institutional comparison

OBJECTIVE

To assess whether the performance of a computer-assisted detection (CAD) algorithm for acute pulmonary embolism (PE) differs in pulmonary CT angiographies acquired at various institutions.

METHODS

In this retrospective study, we included 40 consecutive scans with and 40 without PE from 3 institutions (n = 240) using 64-slice scanners made by different manufacturers (General Electric; Philips; Siemens). CAD markers were classified as true or false positive (FP) using independent evaluation by two readers and consultation of a third chest radiologist in discordant cases. Image quality parameters were subjectively scored using 4/5-point scales. Image noise and vascular enhancement were measured. Statistical analysis was done to correlate image quality of the three institutions with CAD stand-alone performance.

RESULTS

Patient groups were comparable with respect to age (p = 0.22), accompanying lung disease (p = 0.12) and inpatient/outpatient ratio (p = 0.67). The sensitivity was 100% (34/34), 97% (37/38) and 92% (33/36), and the specificity was 18% (8/44), 15% (6/41) and 13% (5/39). Neither significantly differed between the institutions (p = 0.21 and p = 0.820, respectively). The mean number of FP findings (4.5, 6.2 and 3.7) significantly varied (p = 0.02 and p = 0.03), but median numbers (2, 3 and 3) were comparable. Image quality parameters were significantly associated with the number of FP findings (p<0.05) but not with sensitivity. After correcting for noise and vascular enhancement, the number of FPs did not significantly differ between the three institutions (p = 0.43).

CONCLUSIONS

CAD stand-alone performance is independent of scanner type but strongly related to image quality and thus scanning protocols.

Case report: low circulating IGF-I levels due to Acid-Labile Subunit deficiency in adulthood are not associated with early development of atherosclerosis and impaired heart function

OBJECTIVE

Decreased insulin-like growth factor-I (IGF-I) levels in adults have been associated with an increased risk of ischemic heart disease and heart failure. It is currently unknown whether patients with low circulating IGF-I levels due to a homozygous acid-labile subunit (IGFALS) gene mutation also have increased risk of cardiovascular disease. Therefore, we evaluated atherosclerotic burden in a 27 year old male patient who was diagnosed with a homozygous IGFALS mutation and consequently had extremely low circulating IGF-I levels.

METHODS

Ten year's cardiovascular risk was calculated using the Framingham risk score. Presence of (subclinical) atherosclerosis was assessed using a 64-slice CT scan of the coronary arteries. Cardiac performance was measured by conventional echocardiographic measurements, three dimensional (3D)-echocardiography, and tissue deformation imaging.

RESULTS

Despite his extremely low circulating IGF-I levels due to Acid-Labile Subunit (ALS) deficiency, our patient had a low Framingham risk score and no signs of coronary atherosclerosis. Adjusted for physical height, cardiac performance was not impaired compared with healthy subjects.

CONCLUSION

The present case report does not lend support to routine cardiovascular screening in patients with extremely low circulating IGF-I levels due to a homozygous IGFALS mutation, when cardiovascular risk is low.

Radiological evidence of lymphangioleiomyomatosis in female and male patients with tuberous sclerosis complex

AIM

To determine the gender-specific prevalence of pulmonary cysts typical for lymphangioleiomyomatosis (LAM) in adult patients with known tuberous sclerosis complex (TSC).

MATERIALS AND METHODS

A retrospective, cross-sectional study in a cohort of 206 adult TSC patients was performed. Institutional review board approval was obtained, and patient informed consent was waived. Patients had routinely undergone abdominal CT scanning between 1996 and 2006. All 186 patients (mean age 38 years; range 19-72 years; 91 (49%) male patients) in whom at least the lung bases were depicted on computed tomography (CT) were included. Images were reviewed for the presence of pulmonary thin-walled cysts. Descriptive statistics, two sample t-test to compare means, and χ(2)-test to compare proportions were applied.

RESULTS

CT demonstrated pulmonary thin-walled cysts in the lung bases in 52 (28%) of 186 patients. Size varied from 2mm in diameter to more than 2 cm. Pulmonary cysts were detected in 40 (42%) of 95 female patients and in 12 (13%) of 91 male patients (p<0.001). In general, cysts were larger and more numerous in women than in men. Only minimal cystic changes were found in four women and two men, moderate cystic changes were seen in three women and seven men, but considerable cystic changes were seen almost exclusively in women (33 women versus three men).

CONCLUSION

CT demonstrated thin-walled pulmonary cysts in the lung bases in 28% of 186 included patients with tuberous sclerosis complex. Female patients were more affected than male patients.

Calcium scoring with prospectively ECG-triggered CT: using overlapping datasets generated with MPR decreases inter-scan variability

OBJECTIVE

To examine the feasibility of reducing the inter-scan variability of prospectively ECG-triggered calcium-scoring scans by using overlapping 3-mm datasets generated from multiplanar reformation (MPR) instead of non-overlapping 3-mm or 1.5-mm datasets.

PATIENTS AND METHODS

Seventy-five women (59-79 years old) underwent two sequential prospectively ECG-triggered calcium-scoring scans with 16 mm×1.5mm collimation in one session. Between the two scans patients got off and on the table. We performed calcium scoring (Agatston and mass scores) on the following datasets: contiguous 3-mm sections reconstructed from the raw data (A), contiguous 3-mm sections from MPR (B), overlapping 3-mm sections from MPR (C) and contiguous 1.5-mm sections from the raw data (D). To determine the feasibility of the MPR approach, we compared MPR (B) with direct raw data reconstruction (A). Inter-scan variability was calculated for each type of dataset (A-D).

RESULTS

Calcium scores ranged from 0 to 1455 (Agatston) and 0 to 279 mg (mass) for overlapping 3-mm sections (C). Calcium scores (both Agatston and mass) were nearly identical for MPR (B) and raw data approaches (A), with inter-quartile ranges of 0-1% for inter-scan variability. Median inter-scan variability with contiguous 3-mm sections (B) was 13% (Agatston) and 11% (mass). Median variability was reduced to 10% (Agatston and mass) with contiguous 1.5-mm sections (D) and to 8% (Agatston) and 7% (mass) with overlapping 3-mm MPR (A).

CONCLUSION

Calcium scoring on MPR yields nearly identical results to calcium scoring on images directly reconstructed from raw data. Overlapping MPR from prospectively ECG-triggered scans improve inter-scan variability of calcium scoring without increasing patient radiation dose.

Simultaneous aortic and coronary assessment in abdominal aortic aneurysm patients by thoraco-abdominal 64-detector-row CT angiography: estimate of the impact on preoperative management: a pilot study

OBJECTIVES

To estimate the influence of information on the coronary arteries obtained from routine thoraco-abdominal CT angiography (CTA) on pre-operative clinical management in abdominal aortic aneurysm (AAA) patients.

METHODS

Twenty-eight AAA patients underwent pre-operative thoraco-abdominal electrocardiography (ECG)-gated 64-detector-row CTA to evaluate aortic pulsatility for prosthesis size matching. Retrospectively, the coronaries were reconstructed from the same data set and scored on a per segment basis for stenosis (0%, <or=50% or >50%) and grading confidence (poor, adequate or high). An experienced cardiologist was presented information on patient characteristics obtained from patient records and CTA findings. Suggested changes in European Society of Cardiology guidelines based patient management based on CTA information were scored.

RESULTS

On CTA, 17 patients (61%) had significant coronary disease (>50% stenosis) including left main (n=4), single (n=7) and multiple (n=6) vessel disease. Grading confidence was adequate or high in 86% of proximal and middle segments. Based on CTA findings, patient management would have been changed in 4 out of the 28 patients (14%; 95% CI 1-27%) by adding coronary angiography (n=4). In five patients who underwent coronary artery bypass grafting previously, CT did not change management but confirmed graft patency.

CONCLUSIONS

Information on coronary pathology and coronary bypass graft patency can be readily obtained from thoraco-abdominal CTA and may alter pre-operative patient management, as shown in 14% of AAA patients in our study.

Computer-aided detection (CAD) of lung nodules and small tumours on chest radiographs

Detection of focal pulmonary lesions is limited by quantum and anatomic noise and highly influenced by variable perception capacity of the reader. Multiple studies have proven that lesions - missed at time of primary interpretation - were visible on the chest radiographs in retrospect. Computer-aided diagnosis (CAD) schemes do not alter the anatomic noise but aim at decreasing the intrinsic limitations and variations of human perception by alerting the reader to suspicious areas in a chest radiograph when used as a 'second reader'. Multiple studies have shown that the detection performance can be improved using CAD especially for less experienced readers at a variable amount of decreased specificity. There seem to be a substantial learning process for both, experienced and inexperienced readers, to be able to optimally differentiate between false positive and true positive lesions and to build up sufficient trust in the capabilities of these systems to be able to use them at their full advantage. Studies so far focussed on stand-alone performance of the CAD schemes to reveal the magnitude of potential impact or on retrospective evaluation of CAD as a second reader for selected study groups. Further research is needed to assess the performance of these systems in clinical routine and to determine the trade-off between performance increase in terms of increased sensitivity and decreased inter-reader variability and loss of specificity and secondary indicated follow-up examinations for further diagnostic workup.

Prevalence of subependymal giant cell tumors in patients with tuberous sclerosis and a review of the literature

BACKGROUND AND PURPOSE

To investigate the prevalence of subependymal giant cell ependymomas (SEGA) in patients with tuberous sclerosis complex (TSC).

METHODS

We performed a retrospective cross-sectional study in a cohort of 285 patients with known TSC. Institutional review board approval was obtained. We included all 214 TSC-patients who had received a contrast-enhanced computed tomography (CT) scan of the brain. The most recent scan was evaluated for SEGA and presence of hydrocephalus. Additionally, a literature search was performed, and pooled estimates of SEGA prevalence in TSC were calculated. We used descriptive statistics, two sample t-test, chi-squared-test, and meta-analysis as appropriate.

RESULTS

Computed tomography showed radiological evidence of SEGA in 43 of the 214 TSC-patients (20%); 23 of 105 men (22%) and 20 of 109 women (18%; P = .52). Average maximum tumor size was 11.4 mm (range, 4-29 mm). Patients with SEGA (mean, 31 years; range, 16-58 years) were on average younger than patients without SEGA (mean, 37 years; range, 10-72 years; P = 0.007). No association between tumor size and patient age was detected. Nine patients had bilateral SEGA. Hydrocephalus was present in six of the 43 patients (14%). Meta-analysis of reported prevalence and our current study showed that studies using radiological evidence to diagnose SEGA gave a higher pooled estimate of the prevalence of SEGA in TSC (0.16; 95% CI: 0.12, 0.21) than studies using mainly histopathological evidence of SEGA (0.09; 95% CI: 0.07, 0.12).

CONCLUSIONS

In our cohort, CT demonstrated evidence of SEGA in 20% of TSC-patients. Prevalence of SEGA in TSC is higher in studies using radiological evidence to diagnose SEGA than in studies using histopathological evidence.

Supervised enhancement filters: application to fissure detection in chest CT scans

In medical image processing, many filters have been developed to enhance certain structures in 3-D data. In this paper, we propose to use pattern recognition techniques to design more optimal filters. The essential difference with previous approaches is that we provide a system with examples of what it should enhance and suppress. This training data is used to construct a classifier that determines the probability that a voxel in an unseen image belongs to the target structure(s). The output of a rich set of basis filters serves as input to the classifier. In a feature selection process, this set is reduced to a compact, efficient subset. We show that the output of the system can be reused to extract new features, using the same filters, that can be processed by a new classifier. Such a multistage approach further improves performance. While the approach is generally applicable, in this work the focus is on enhancing pulmonary fissures in 3-D computed tomography (CT) chest scans. A supervised fissure enhancement filter is evaluated on two data sets, one of scans with a normal clinical dose and one of ultra-low dose scans. Results are compared with those of a recently proposed conventional fissure enhancement filter. It is demonstrated that both methods are able to enhance fissures, but the supervised approach shows better performance; the areas under the receiver operating characteristic (ROC) curve are 0.98 versus 0.90, for the normal dose data and 0.97 versus 0.87 for the ultra low dose data, respectively.

Reproducibility of quantitative CT brain perfusion measurements in patients with symptomatic unilateral carotid artery stenosis

BACKGROUND AND PURPOSE

To establish intraobserver and interobserver variability for regional measurement of CT brain perfusion (CTP) and to determine whether reproducibility can be improved by calculating perfusion ratios.

MATERIALS AND METHODS

CTP images were acquired in 20 patients with unilateral symptomatic carotid artery stenosis (CAS). We manually drew regions of interest (ROIs) in the cortical flow territories of the anterior (ACA), middle (MCA), and posterior (PCA) cerebral arteries and the basal ganglia in each hemisphere; recorded cerebral blood volume (CBV), cerebral blood flow (CBF), and mean transit time (MTT); and calculated ratios of perfusion values between symptomatic and asymptomatic hemisphere. We assessed intraobserver and interobserver variability by performing a Bland-Altman analysis of the relative differences between 2 observations and calculated SDs of relative differences (SDD(rel)) as a measure of reproducibility. We used an F test to assess significance of differences between SDD(rel) of absolute CTP values and CTP ratios, and the Levine test to compare the 4 perfusion territories.

RESULTS

MTT was the most reproducible parameter (SDD(rel) <or= 10%). Intraobserver and interobserver variability were higher for absolute CTP values compared with CTP ratios for CBV (16%-17% versus 11%-16%) and CBF (18% versus 10%-13%) but not for MTT (5%-9%). Reproducibility was best in the MCA territory: SDD(rel) was <or=11% for perfusion ratios of all 3 parameters.

CONCLUSION

MTT is the most reproducible CTP parameter in patients with unilateral symptomatic CAS. Measurement variability in CBV and CBF can be improved if CTP ratios instead of CTP values are used. The MCA territory shows the least measurement variability.