A Novel and Generic Workflow of Indocyanine Green Perfusion Assessment Integrating Standardization and Quantification Toward Clinical Implementation.

OBJECTIVE: This study aims to generate a reproducible and generalizable Workflow model of ICG-angiography integrating Standardization and Quantification (WISQ) that can be applied uniformly within the surgical innovation realm independent of the user. SUMMARY BACKGROUND DATA: Tissue perfusion based on indocyanine green (ICG)-angiography is a rapidly growing application in surgical innovation. Interpretation of results has been subjective and error-prone due to the lack of a standardized and quantitative ICG-workflow and analytical methodology. There is a clinical need for a more generic, reproducible, and quantitative ICG perfusion model for objective assessment of tissue perfusion. METHODS: In this multicenter, proof-of-concept study, we present a generic and reproducible ICG-workflow integrating standardization and quantification for perfusion assessment. To evaluate our model's clinical feasibility and reproducibility, we assessed the viability of parathyroid glands after performing thyroidectomy. Biochemical hypoparathyroidism was used as the postoperative endpoint and its correlation with ICG quantification intraoperatively. Parathyroid gland is an ideal model as parathyroid function post-surgery is only affected by perfusion. RESULTS: We show that visual subjective interpretation of ICG-angiography by experienced surgeons on parathyroid perfusion cannot reliably predict organ function impairment postoperatively, emphasizing the importance of an ICG quantification model. WISQ was able to standardize and quantify ICG-angiography and provided a robust and reproducible perfusion curve analysis. A low ingress slope of the perfusion curve combined with a compromised egress slope was indicative for parathyroid organ dysfunction in 100% of the cases. CONCLUSION: WISQ needs prospective validation in larger series and may eventually support clinical decision-making to predict and prevent postoperative organ function impairment in a large and varied surgical population.

Radiation dose reduction and static image quality assessment using a channelized hotelling observer on an angiography system upgraded with clarity IQ.

The goal of this paper was the comparison of radiation dose and imaging quality before and after the Clarity IQ technology installation in a Philips AlluraXper FD20/20 angiography system using a Channelized Hotelling Observer model (CHO). The core characteristics of the Allura Clarity IQ technology are its real-time noise reduction algorithms (NRT) combined with state-of-the-art hardware; this technology allows to implement acquisition protocols able to significantly reduce patient entrance dose. To measure the system performances in terms of image quality we used a contrast detail phantom in a clinical scatter condition. A Leeds TO10 phantom has been imaged between two 10 cm thick homogeneous solid water slabs. Fluoroscopy images were acquired using a cerebral protocol at 3 dose levels (low, medium and high) with a field- of view (FOV) of 31 cm. Cineangiography images were acquired using a cerebral protocol at 2 fps. Thus, 4 acquisitions were obtained for the conventional technology and 4 acquisitions were taken after the Clarity IQ upgrade, for a total of 8 different image sets. A validated 40 Gabor channels CHO with an internal noise model compared the image sets. Human observers' studies were carried out to tune the internal noise parameter. We showed that the CHO did not detect any significant difference between any of the image sets acquired using the two technologies. Consequently, this x-ray imaging technology provides a non-inferior image quality with an average patient dose reduction of 57% and 28% respectively in cineangiography and fluoroscopy. The Clarity IQ installation has certainly allowed a considerable improvement in patient and staff safety, while maintaining the same image quality.

The Assessment of Carbon Dioxide Automated Angiography in Type II Endoleaks Detection: Comparison with Contrast-Enhanced Ultrasound.

Introduction: Iodinated contrast media completion angiography (ICM-A) may underestimate the presence of type II endoleak (ELII) after endovascular aortic repair (EVAR), particularly if they are at low flow. Contrast-enhanced ultrasound (CEUS) has been proposed as the gold standard in ELII detection during EVAR follow-up. Intraprocedural carbon dioxide (CO2) angiography has been shown to be useful in this setting; however no comparative studies including these three techniques are currently available. Our aim was to investigate the accuracy of a new automated CO2 angiographic (CO2-A) system in the detection of ELII, by comparing it with ICM-A and CEUS. Methods: A series of consecutive patients undergoing EVAR for abdominal aortic aneurysm (AAA) were enrolled and submitted to ICM-A and CO2-A during the procedure. The iodinated contrast media were delivered through an automatic injector connected to a pigtail catheter in the suprarenal aorta. CO2 was delivered through a recently available automatic injector connected to a 10 F sheath positioned in the external iliac artery. All patients were blindly evaluated by CEUS within postoperative day 1. The ICM-A and CO2-A ability to detect ELII was compared with that of CEUS through Cohen's concordance Index (K). Results: Twenty-one patients were enrolled in the study. One (5%), seven (33%), and four (19%) ELII were detected by ICM-A, CO2-A, and CEUS, respectively. The only ELII detected by ICM-A was also detected by CO2-A and CEUS. Three cases of ELII detected by CO2-A were not detected by CEUS. All ELII detected by CEUS were visualized by CO2-A. CEUS and ICM-A showed a poor agreement (Cohen's K: 0.35) while CEUS and CO2-A showed a substantial agreement (Cohen's K: 0.65) for ELII detection. Conclusion: CO2-A is safe and effective method for ELII detection in EVAR, with a significantly higher agreement with CEUS if compared with ICM-A. This trial is registered with 155/2015/U/Oss.

Different Imaging Strategies in Patients With Possible Basilar Artery Occlusion: Cost-Effectiveness Analysis.

BACKGROUND AND PURPOSE: This study evaluated the cost-effectiveness of different noninvasive imaging strategies in patients with possible basilar artery occlusion. METHODS: A Markov decision analytic model was used to evaluate long-term outcomes resulting from strategies using computed tomographic angiography (CTA), magnetic resonance imaging, nonenhanced CT, or duplex ultrasound with intravenous (IV) thrombolysis being administered after positive findings. The analysis was performed from the societal perspective based on US recommendations. Input parameters were derived from the literature. Costs were obtained from United States costing sources and published literature. Outcomes were lifetime costs, quality-adjusted life-years (QALYs), incremental cost-effectiveness ratios, and net monetary benefits, with a willingness-to-pay threshold of $80,000 per QALY. The strategy with the highest net monetary benefit was considered the most cost-effective. Extensive deterministic and probabilistic sensitivity analyses were performed to explore the effect of varying parameter values. RESULTS: In the reference case analysis, CTA dominated all other imaging strategies. CTA yielded 0.02 QALYs more than magnetic resonance imaging and 0.04 QALYs more than duplex ultrasound followed by CTA. At a willingness-to-pay threshold of $80,000 per QALY, CTA yielded the highest net monetary benefits. The probability that CTA is cost-effective was 96% at a willingness-to-pay threshold of $80,000/QALY. Sensitivity analyses showed that duplex ultrasound was cost-effective only for a prior probability of ≤0.02 and that these results were only minimally influenced by duplex ultrasound sensitivity and specificity. Nonenhanced CT and magnetic resonance imaging never became the most cost-effective strategy. CONCLUSIONS: Our results suggest that CTA in patients with possible basilar artery occlusion is cost-effective.

Comparing the diagnostic accuracy of contrast-enhanced computed tomographic angiography and gadolinium-enhanced magnetic resonance angiography for the assessment of hemodynamically significant transplant renal artery stenosis.

To compare diagnostic accuracy of contrast-enhanced computed tomographic angiography (CTA) and gadolinium-enhanced magnetic resonance angiography (MRA) for the assessment of hemodynamically significant transplant renal artery stenosis (TRAS). After institutional review board approval, records of 27 patients with TRAS confirmed on digital subtraction angiography (DSA) were retrospectively reviewed. A total of 13 patients had MRA and 14 had CTA before DSA. Two board-certified fellowship-trained radiologists, one each from interventional radiology and body imaging blindly reviewed the DSA and CTA or MRA data, respectively. Sensitivity (SN), specificity (SP), positive predictive value, and negative predictive value of MRA and CTA were estimated using 50% stenosis as the detection threshold for significant TRAS. These parameters were compared between modalities using the Fisher exact test. Bias between MRA or CTA imaging and DSA was tested using the Wilcoxon signed-rank test. Two patients were excluded from the MRA group owing to susceptibility artifacts obscuring the TRAS. The correlation between MRA and DSA measurements of stenosis was r = 0.57 (95% CI:-0.02, 0.87; P = 0.052) and between CTA and DSA measurements was r = 0.63 (95% CI: 0.14, 0.87; P = 0.015); the difference between the 2 techniques was not significant (P = 0.7). Both imaging modalities tended to underestimate the degree of stenosis when compared with DSA. MRA group (SN and SP: 56% and 100%, respectively) and CTA group (SN and SP: 81% and 67%, respectively). There were no significant differences in detection performance between modalities (P>0.3 for all measures). We did not find that either modality had any advantage over the other in terms of measuring or detecting significant stenosis. Accordingly, MRA may be preferred over CTA after positive color Doppler ultrasound screening when not contraindicated owing to lack of ionizing radiation or nephrotoxic iodinated contrast. However, susceptibility of artifacts owing to surgical clips at the anastomosis may limit diagnostic utility of MRA as found in 2 of 13 patients. Trend towards no significant difference between the CTA and enhanced MRA in the detection of hemodynamically significant TRAS.

Developing patient-centered outcome measures for evaluating vasospasm in aneurysmal subarachnoid hemorrhage.

RATIONALE AND OBJECTIVES: Patient-centered outcome measures have become an essential focus in research methodology in recent years. This may be particularly challenging in imaging research at the technology assessment level to incorporate patient-centeredness. A primary issue in this field is designing a reference standard that is applicable to the entire study population. MATERIALS AND METHODS: This important element is necessary for translation of findings into clinical practice. In our work, computed tomographic perfusion imaging is being evaluated as a new technology used in aneurysmal subarachnoid hemorrhage patients to detect cerebral vasospasm. We have developed a new reference standard employing a multistage hierarchical design incorporating both clinical and imaging criteria to determine a diagnosis of vasospasm. RESULTS: A flowchart of the reference standard levels is provided for illustration. The limitations and potential biases that may occur using this reference standard are discussed. CONCLUSIONS: This reference standard will be applicable to the entire study population, including those with and without symptoms or further imaging with digital subtraction angiography.

An automatic calibration approach for left ventricular volume assessment.

The development of interventional procedures in the catheterisation laboratory drives the introduction of simple, fast and accurate quantification methods. Quantification is used to evaluate the volume of the left ventricle but also for choosing the size of a balloon or a stent during the percutaneous coronary angioplasty procedure. The objective of the calibration procedure is to establish the relation between the true size of the analyzed organ and its apparent size in the image. This calibration step aims at measuring the pixel size in mm. Traditional approach measures a known object on the image, but suffers from several limitations and constraints; in particular, the size of the reference object is often not exactly known. Besides, the therapeutic procedures are done in the continuity of the diagnosis and the physician has a very little amount of time to spend on the determination of the quantitative information like the chosen reference size. A new approach has been proposed [1], allowed by the introduction of the flat-panel technology and modern positioning systems. With the absence of distortion in the image and accurate knowledge of the system geometry, a model can be used to automatically identify the calibration factor using an additional input provided by the operator: the target organ height above the table top. The objective of our study was to estimate this input parameter in the particular case of the Left Ventricle (LV) volume angiographic computation.

The role of CT pulmonary angiography in patients with suspected pulmonary embolism admitted to general medicine.

BACKGROUND: CT pulmonary angiography (CTPA), D-dimer testing, and pre-test probability scoring have greatly improved the ability to manage patients with suspected pulmonary embolism. International guidelines suggest combining these investigations for the best yield. We have been investigating the use of CTPA in patients with suspected pulmonary embolism (PE) admitted to the Department of General Medicine at Christchurch Hospital, New Zealand. METHODS: A retrospective audit of 100 patients with suspected pulmonary embolism who had a CTPA performed between October 2003 and April 2004. RESULTS: CTPA was positive for PE in 31% of admissions. The pre-test probability was documented in only 4% of admissions. All patients with PE had a significantly elevated D-dimer (> 499 ng/mL). Wells score calculated by the investigators showed 59 (59%) to have a low, 33 (33%) a moderate, and 8 (8%) a high risk for PE. Of these, PE was diagnosed in 9 (15%), 15 (45%), and 7 (88%) respectively; 93% of patients had a blood gas performed, yet only 77% had the D-dimer measured. No patient with a measured and negative D-dimer had a diagnosis of a PE; 32 CTPAs were performed on 32 patients out of hours. CONCLUSION: There was a very low uptake of the formal use of pre-test probability scores by medical registrars. This audit confirms that, in patients with low or moderate risk of PE and a negative D-dimer, an alternative diagnosis should be considered. The management of suspected venous thromboembolism (VTE) could be improved; it is likely that after hours CTPA could be reduced.

Effective doses in angiography and interventional radiology: calculation of conversion coefficients for angiography of the lower limbs.

The present study reports on investigations that we have performed to allow the calculation of effective doses (E) in interventional radiology. The use of published conversion tables might not allow sufficient guidance for the establishment of optimization strategies for procedures in interventional radiology. With the Monte Carlo N-Particle transport code (MCNP4B), conversion coefficients, linking dose-area product (DAP) measurements with E, are calculated for angiography of the lower limbs in six hospitals. The influence of various parameters on the calculation of these conversion coefficients is studied in a systematic way using the 2(n) factorial design. In this design the effect of different parameters and their pair-wise interactions on a certain variable is explored. In our study, the relevant parameters are tube potential, total filtration and field size and position. We concluded that the influence of radiation spectrum (kVp + filtration) is large and that the effect of field position and size is moderate, except when differences are observed in respect of the gonads. In that case, the variation in conversion coefficients is large. The results of this statistical analysis are then applied to the differences observed between the conversion coefficients, calculated for angiography of the lower limbs in the six hospitals. Recommendations for optimization of patient doses are given.

Impact of spiral computed tomography on the diagnosis of pulmonary embolism in a community hospital setting.

BACKGROUND: While the optimal role of spiral CT angiography (CTA) in the diagnosis of pulmonary embolism (PE) remains controversial, this technology is already being widely utilized in the community setting. OBJECTIVES: To assess the impact CTA has had on angiography utilization rates and the overall diagnostic rate of PE. METHODS: All patients evaluated for PE during a 4-year period were studied. PE was defined as either a high-probability V/Q scan, a positive conventional angiogram, or a CTA with emboli in the segmental or larger pulmonary vessels. Diagnostic rates of PE per 1,000 hospital admissions were determined and analyzed for time periods before and after the introduction of CTA. CT reports were compared with their concurrent chest radiograph (CXR) reports and additional findings that were not apparent on CXR were abstracted. RESULTS: The diagnostic rate of PE per 1,000 hospital admissions was 1.8 prior to the introduction of CTA and increased to 2.8 per 1,000 admissions after the introduction of CTA (p < 0.0001). Total costs for diagnostic testing per PE diagnosis made went from US 2,518 dollars to US 2,572 dollars. While the number of PE diagnosed by V/Q scan remained constant, the number of PE diagnosed by conventional angiography decreased while the number diagnosed by CTA increased. In patients with intermediate probability V/Q scan results, the percentage of patients receiving subsequent angiography (conventional or CTA) increased from 17 to 26% (p = 0.043). When conventional angiography was performed, CT imaging of the chest still had to be ordered for other reasons 38% of the time. Additional information was obtained in 78% of cases when CTA was performed. CONCLUSIONS: Increased utilization of CTA was associated with an increase in angiography utilization rates and diagnostic rates of PE, was cost effective, and often provided additional, useful, and unanticipated diagnostic information.

Vital signs for your cardiovascular services.

Current trends and "best practice" operating statistics can be vital to the success of today's cardiovascular programs. The findings from a recently published survey entitled, "Trends in Cardiovascular Programs: A National Benchmarking Study", provide the administrator with immediate and current knowledge of best ways to manage cardiovascular services to succeed in a competitive market. Study results provide some interesting and valuable information regarding non-invasive cardiology, cardiac catheterization, and peripheral vascular angiography program administration and provide insight into issues of cost, quality, and cardiovascular program concerns, interests and needs.

International differences in health care costs in Europe and the United States: Do these affect the cost-effectiveness of diagnostic strategies for pulmonary embolism?

The aim of this study was to assess whether potential differences in costs for diagnostic procedures and treatment of pulmonary embolism (PE) among European and U. S. hospitals alter the optimal cost-effective diagnostic strategy for PE. A standardized questionnaire was used to obtain cost data for the diagnosis and treatment of PE in participating European and U. S. hospitals. Costs for diagnostic tests and treatment of PE were then calculated in a standardized manner for all participating hospitals, from the hospital perspective. Costs were used in an existing cost-effectiveness analysis (CEA) model to determine the most cost-effective diagnostic strategy in participating hospitals. There were considerable differences in costs for diagnostic and therapeutic procedures for PE among the participating centers. These differences, however, did not affect the most cost-effective strategy based on incremental cost-effectiveness. In all hospitals the most cost-effective strategy appeared to be ultrasound followed by helical CT. International differences in cost of diagnostic and therapeutic procedures certainly exist and should be considered before applying a published CEA. Nevertheless, despite these cost differences, the diagnostic strategy for PE of ultrasound followed by helical CT appears most cost-effective.