Vessel size measurements in angiograms: manual measurements

A novel intravascular bioartificial pancreas device shows safety and islet functionality over 30 days in nondiabetic swine

In this study using a discordant, xenogeneic, transplant model we demonstrate the functionality and safety of the first stent-based bioartificial pancreas (BAP) device implanted endovascularly into an artery, harnessing the high oxygen content in blood to support islet viability. The device is a self-expanding nitinol stent that is coated with a bilayer of polytetrafluoroethylene that forms channels to hold islets embedded in a hydrogel. We completed a 1-month study in the nondiabetic swine model (N = 3) to test the safety of the device and to assess islet functionality after device recovery. The luminal diameter of the devices from 3 animals on day 0 and day 30 was 10.01 ± 0.408 mm and 10.05 ± 0.25 mm, respectively. The stimulation index of the control and endovascular BAP devices explanted at day 30 were 3.35 ± 0.97 and 4.83 ±1.20, respectively, and the islets stained positively for insulin and glucagon after 30 days in vivo. This pilot study shows that BAP implantation into a peripheral artery is safe and supports islet functionality over 30 days, providing the groundwork for future work assessing the in vivo function of the device in diabetic swine.

Myocardial strain assessment by cine cardiac magnetic resonance imaging using non-rigid registration

AIMS

To evaluate a novel post-processing method for assessment of longitudinal mid-myocardial strain in standard cine cardiac magnetic resonance (CMR) imaging sequences.

METHODS AND RESULTS

Cine CMR imaging and tagged cardiac magnetic resonance imaging (TMRI) were performed in 15 patients with acute myocardial infarction (AMI) and 15 healthy volunteers served as control group. A second group of 37 post-AMI patients underwent both cine CMR and late gadolinium enhancement (LGE) CMR exams. Speckle tracking echocardiography (STE) was performed in 36 of these patients. Cine CMR, TMRI and STE were analyzed to obtain longitudinal strain. LGE-CMR datasets were analyzed to evaluate scar extent. Comparison of peak systolic strain (PSS) measured from CMR and TMRI yielded a strong correlation (r=0.86, p<0.001). PSS measured from CMR and STE correlated well (r=0.75, p<0.001). A cutoff longitudinal PSS value of -13.14% differentiated non-infarction from any infarcted myocardium, with a sensitivity of 93% and a specificity of 89% (area under curve (AUC) 0.95). PSS value of -9.39% differentiated non-transmural from transmural infarcted myocardium, with a sensitivity of 75% and a specificity of 67% (AUC 0.78).

CONCLUSION

The present study showed a novel off-line post-processing method for segmental longitudinal strain analysis in mid-myocardium layer based on cine CMR data. The method was found to be highly correlated with strain measurements obtained by TMRI and STE. This tool allows accurate discrimination between different transmurality states of myocardial infarction.

Intracranial atherosclerotic disease: medical, biomechanical, imaging, and flow dynamics perspective

INTRODUCTION

Intracranial stenosis is one of the most common disease entities encountered by neurointerventionists. The physical and hemodynamic properties of the lesion are determined by the experience of the clinician. Computerized analysis may provide more accurate values of these parameters which can be used during the procedure for improving patient care.

MATERIALS AND METHODS

We present a case of a 55-year-old man who was having ischemic symptoms related to severe middle cerebral artery stenosis. Intralesional stent placement normalized the diameter of the vessel leading to cessation of the episodes of neurological events.

DISCUSSION

Discussants include a neurointerventionist, a neurovascular image analyst, and a neurovascular flow and hemodynamic analyst. Questions discussed included qualitative and quantitative analysis of stenosis; comparison of angiographic perfusion studies including analysis of delay in opacification, transit times and time density curves; role of automation in analysis of "emboli tolerance" and "no re-flow" phenomenon; and relationship of compliance and recoil in normal and diseased segments of a vessel during angioplasty or stent placement.

Comparison of maximum intensity projection and digitally reconstructed radiographic projection for carotid artery stenosis measurement

Digital subtraction angiography is being supplanted by three-dimensional imaging techniques in many clinical applications, leading to extensive use of maximum intensity projection (MIP) images to depict volumetric vascular data. The MIP algorithm produces intensity profiles that are different than conventional angiograms, and can also increase the vessel-to-tissue contrast-to-noise ratio. We evaluated the effect of the MIP algorithm in a clinical application where quantitative vessel measurement is important: internal carotid artery stenosis grading. Three-dimensional computed rotational angiography (CRA) was performed on 26 consecutive symptomatic patients to verify an internal carotid artery stenosis originally found using duplex ultrasound. These volumes of data were visualized using two different postprocessing projection techniques: MIP and digitally reconstructed radiographic (DRR) projection. A DRR is a radiographic image simulating a conventional digitally subtracted angiogram, but it is derived computationally from the same CRA dataset as the MIP. By visualizing a single volume with two different projection techniques, the postprocessing effect of the MIP algorithm is isolated. Vessel measurements were made, according to the NASCET guidelines, and percentage stenosis grades were calculated. The paired t-test was used to determine if the measurement difference between the two techniques was statistically significant. The CRA technique provided an isotropic voxel spacing of 0.38 mm. The MIPs and DRRs had a mean signal-difference-to-noise-ratio of 30:1 and 26:1, respectively. Vessel measurements from MIPs were, on average, 0.17 mm larger than those from DRRs (P < 0.0001). The NASCET-type stenosis grades tended to be underestimated on average by 2.4% with the MIP algorithm, although this was not statistically significant (P=0.09). The mean interobserver variability (standard deviation) of both the MIP and DRR images was 0.35 mm. It was concluded that the MIP algorithm slightly increased the apparent dimensions of the arteries, when applied to these intra-arterial CRA images. This subpixel increase was smaller than both the voxel size and interobserver variability, and was therefore not clinically relevant.

Magnetic resonance angiography shows dilatation of the middle cerebral artery after infusion of glyceryl trinitrate in healthy volunteers

Previous studies have reported dilatation of the middle cerebral artery (MCA) during acute glyceryl trinitrate (GTN)-induced headache, using imaging techniques such as transcranial Doppler (TCD), positron emission tomography (PET) and single photon emission computerized tomography (SPECT). In the present study we aimed to evaluate whether magnetic resonance angiography (MRA) may be used to examine the effect of GTN on the MCA, with respect to changes in diameter and cross-sectional area in healthy volunteers. In addition, we wanted to determine the intra- and inter-observer variation of the method. In a randomized, double blind, crossover study 12 healthy volunteers received intravenous infusion of GTN (0.5 microg/kg/min for 20 min) or placebo. Using 1.5 Tesla MRA, we recorded changes in the diameter and cross-sectional area of MCA before, during and after infusion of GTN. The MRA images were evaluated by two blinded, independent observers/neuroradiologists. The primary endpoints were the differences in the AUC for diameter and cross-sectional area of the MCA between the two experimental conditions and the intra- and inter-observer variation. The areas under the curve (AUC) of the MCA diameter and cross-sectional area were significantly greater after GTN than after placebo (P < 0.05). The intra-observer variation (day-to-day) at baseline was 8.3% and 10.9% for the two observers. The mean inter-observer variation of the cross-sectional MCA area was 15.5% and for the diameter measurements 8%. The present study shows that the MRA method gives a reliable semi-quantitative index of the vascular changes in the intra-cerebral arteries after infusion of GTN and may be useful for headache research.

Changes in lumen width of nasolacrimal drainage system after adrenergic and cholinergic stimulation

PURPOSE

To determine the effect of an adrenergic agonist and a cholinergic agonist on the lumen width of the nasolacrimal drainage system.

DESIGN

Prospective, nonrandomized, clinical trial.

METHODS

The asymptomatic sides of 33 patients (23 women, 10 men) with unilateral stenosis/obstruction of the nasolacrimal drainage system were studied. The tear meniscus height of the asymptomatic side was normal, with a patent lacrimal system as revealed by dacryocystography. The nasolacrimal drainage system of the asymptomatic side was infused with 100 microL of 5% phenylephrine hydrochloride (an alpha-1 adrenoceptor agonist) or 100 microL of 2% pilocarpine hydrochloride (a cholinergic agonist), and dacryocystography was performed to determine the lumen width of the nasolacrimal drainage system.

RESULTS

Phenylephrine caused a significant increase of the lumen width of the nasolacrimal drainage system, and the changes were more marked in the nasolacrimal duct (NLD), especially the upper and middle regions, than in the lacrimal sac. In contrast, pilocarpine reduced the lumen width of the NLD significantly, especially in the middle and lower regions, and the lumen width of the lacrimal sac was not significantly changed.

CONCLUSION

The alterations of the lumen width of the nasolacrimal drainage system, especially the lumen width of the NLD by adrenergic and cholinergic agonists, suggest that the lumen width can be changed by the autonomic nervous system.

New microangiography system development providing improved small vessel imaging, increased contrast to noise ratios, and multi-view 3D reconstructions

A new microangiographic system (MA) integrated into a c-arm gantry has been developed allowing precise placement of a MA at the exact same angle as the standard x-ray image intensifier (II) with unchanged source and object position. The MA can also be arbitrarily moved about the object and easily moved into the field of view (FOV) in front of the lower resolution II when higher resolution angiographic sequences are needed. The benefits of this new system are illustrated in a neurovascular study, where a rabbit is injected with contrast media for varying oblique angles. Digital subtraction angiographic (DSA) images were obtained and compared using both the MA and II detectors for the same projection view. Vessels imaged with the MA appear sharper with smaller vessels visualized. Visualization of ~100 μm vessels was possible with the MA whereas not with the II. Further, the MA could better resolve vessel overlap. Contrast to noise ratios (CNR) were calculated for vessels of varying sizes for the MA versus the II and were found to be similar for large vessels, approximately double for medium vessels, and infinitely better for the smallest vessels. In addition, a 3D reconstruction of selected vessel segments was performed, using multiple (three) projections at oblique angles, for each detector. This new MA/II integrated system should lead to improved diagnosis and image guidance of neurovascular interventions by enabling initial guidance with the low resolution large FOV II combined with use of the high resolution MA during critical parts of diagnostic and interventional procedures.

Accurate and objective infarct sizing by contrast-enhanced magnetic resonance imaging in a canine myocardial infarction model

OBJECTIVES

To identify an accurate and reproducible method to define myocardial infarct (MI) size, we conducted a study in a closed-chest canine model of acute myocardial infarction, in which MI size was measured using different thresholding techniques and by imaging at different delay times after contrast administration.

BACKGROUND

The MI size by contrast-enhanced magnetic resonance imaging (CE-MRI) is directly related to long-term prognosis. However, previous measurements were done using nonuniform methods and tended to overestimate nonviable areas.

METHODS

Thirteen animals underwent 90 min of coronary artery occlusion, followed by reperfusion. The CE-MRI data were acquired within 24 h after reperfusion and compared with triphenyltetrazolium chloride pathology. In the first nine animals, images were obtained approximately 15 min after gadolinium diethylene triamine penta-acetic acid (Gd-DTPA) using an inversion-recovery gradient-echo pulse sequence. To identify the most accurate method, MI size by CE-MRI was measured visually and by semi-automatic thresholding techniques, using different criteria. In four additional animals, images were acquired every 6 min until 30 min after Gd-DTPA.

RESULTS

Postmortem MI size was 13.5 +/- 2.6% of left ventricular volume. Semi-automatic techniques, using full-width at half-maximum (FWHM) criterion, correlated best with postmortem data (r(2) = 0.94, p < 0.001; results confirmed by Bland-Altman plots). Using FWHM, there was no difference in MI size between different delay times after contrast (15.2 +/- 2.9% to 14.5 +/- 4.2% at 6 and 30 min, respectively; p = NS).

CONCLUSIONS

When an objective technique is used to define MI size by CE-MRI, accurate infarct size measurements can be obtained from images obtained up to 30 min after contrast administration.