Assessment of computed tomography perfusion software in predicting spatial location and volume of infarct in acute ischemic stroke patients: a comparison of Sphere, Vitrea, and RAPID.

BACKGROUND: CT perfusion (CTP) infarct and penumbra estimations determine the eligibility of patients with acute ischemic stroke (AIS) for endovascular intervention. This study aimed to determine volumetric and spatial agreement of predicted RAPID, Vitrea, and Sphere CTP infarct with follow-up fluid attenuation inversion recovery (FLAIR) MRI infarct. METHODS: 108 consecutive patients with AIS and large vessel occlusion were included in the study between April 2019 and January 2020 . Patients were divided into two groups: endovascular intervention (n=58) and conservative treatment (n=50). Intervention patients were treated with mechanical thrombectomy and achieved successful reperfusion (Thrombolysis in Cerebral Infarction 2b/2 c/3) while patients in the conservative treatment group did not receive mechanical thrombectomy or intravenous thrombolysis. Intervention and conservative treatment patients were included to assess infarct and penumbra estimations, respectively. It was assumed that in all patients treated conservatively, penumbra converted to infarct. CTP infarct and penumbra volumes were segmented from RAPID, Vitrea, and Sphere to assess volumetric and spatial agreement with follow-up FLAIR MRI. RESULTS: Mean infarct differences (95% CIs) between each CTP software and FLAIR MRI for each cohort were: intervention cohort: RAPID=9.0±7.7 mL, Sphere=-0.2±8.7 mL, Vitrea=-7.9±8.9 mL; conservative treatment cohort: RAPID=-31.9±21.6 mL, Sphere=-26.8±17.4 mL, Vitrea=-15.3±13.7 mL. Overlap and Dice coefficients for predicted infarct were (overlap, Dice): intervention cohort: RAPID=(0.57, 0.44), Sphere=(0.68, 0.60), Vitrea=(0.70, 0.60); conservative treatment cohort: RAPID=(0.71, 0.56), Sphere=(0.73, 0.60), Vitrea=(0.72, 0.64). CONCLUSIONS: Sphere proved the most accurate in patients who had intervention infarct assessment as Vitrea and RAPID overestimated and underestimated infarct, respectively. Vitrea proved the most accurate in penumbra assessment for patients treated conservatively although all software overestimated penumbra.

Can fully iterative reconstruction technique enable routine abdominal CT at less than 1 mSv?

OBJECTIVE: We assessed the effect of the forward projected model-based reconstruction technique (FIRST) on lesion detection of routine abdomen CT at <1 mSv. MATERIALS AND METHODS: Thirty-seven adult patients gave written informed consent for acquisition of low-dose CT (LDCT) immediately after their clinically-indicated, standard of care dose (SDCT), routine abdomen CT on a 640-slice MDCT (Aquillion One, Canon Medical System). The LDCT series were reconstructed with FIRST (at STD (Standard) and STR (Strong) levels), and SDCT series with filtered back projection (FBP). Two radiologists assessed lesions in LD-FBP and FIRST images followed by SDCT images. Then, SDCT and LDCT were compared for presence of artifacts in a randomized and blinded fashion. Patient demographics, size and radiation dose descriptors (CTDIvol, DLP) were recorded. Descriptive statistics and inter-observer variability were calculated for data analysis. RESULTS: Mean CTDIvol for SDCT and LDCT were 13 ± 4.7 mGy and 2.2 ± 0.8 mGy, respectively. There were 46 true positive lesions detected on SDCT. Radiologists detected 38/46 lesions on LD-FIRST-STD compared to 26/46 lesions on LD-FIRST-STR. The eight lesions (liver and kidney cysts, pancreatic lesions, sub-cm peritoneal lymph node) missed on LD-FIRST-STD were seen in patients with BMI > 25.8 kg/m2. Diagnostic confidence for lesion assessment was optimal in LD-FIRST-STD setting in most patients regardless of their size. The inter-observer agreement (kappa-value) for overall image quality were 0.98 and 0.84 for LD-FIRST-STD and STR levels, respectively. CONCLUSION: FIRST enabled optimal lesion detection in routine abdomen CT at less than 1 mSv radiation dose in patients with body mass less than ≤25.8 kg/m2.

Molecular alterations associated with aneurysmal remodeling are localized in the high hemodynamic stress region of a created carotid bifurcation.

OBJECTIVE: Although elevated hemodynamics has been speculated to play a key role in intracranial aneurysm (IA) initiation, little is known about the specific hemodynamic microenvironment that triggers aneurysmal vascular degradation. We previously demonstrated maladaptive remodeling characteristic of IA initiation occurring in hemodynamic regions of combined high wall shear stress (WSS) and high WSS gradient near the apex of an experimentally created carotid bifurcation. This study examines whether this remodeling recapitulates the molecular changes found in IAs and whether molecular changes also correspond to specific hemodynamic environments. METHODS: De novo bifurcations were surgically created using both native common carotid arteries in each of 6 dogs. Bifurcations were imaged 2 weeks or 2 months after surgery by high-resolution 3-dimensional angiography, from which flow fields were obtained by computational fluid dynamics simulations. Subsequently, harvested tissues, demonstrating early aneurysmal changes near the apex, were immunostained for interleukin-1beta, endothelial and inducible nitric oxide synthases, nitrotyrosine, and matrix metalloproteinase-2 and -9. Spatial distributions of these molecules were comapped with computational fluid dynamics results. RESULTS: The aneurysmal wall showed decreased endothelial nitric oxide synthase expression compared with surrounding segments, the feeding artery, and native controls, whereas all other markers increased. Anti-CD68 staining indicated the absence of inflammatory cells in the aneurysmal wall. Comapping molecular marker distributions with flow fields revealed confinement of these molecular changes within the hemodynamic region of high WSS and high, positive WSS gradient. CONCLUSION: Aneurysm-initiating remodeling induced by combined high WSS and high, positive WSS gradient is associated with molecular changes implicated in IAs.

In vivo assessment of rapid cerebrovascular morphological adaptation following acute blood flow increase.

OBJECT: Pathological extremes in cerebrovascular remodeling may contribute to basilar artery (BA) dolichoectasia and fusiform aneurysm development. Factors regulating cerebrovascular remodeling are poorly understood. To better understand hemodynamic influences on cerebrovascular remodeling, we examined BA remodeling following common carotid artery (CCA) ligation in an animal model. METHODS: Rabbits were subjected to sham surgery (3 animals), unilateral CCA ligation (3 animals), or bilateral CCA ligation (5 animals). Transcranial Doppler ultrasonography and rotational angiography were used to compute BA flow, diameter, wall shear stress (WSS), and a tortuosity index on Days 0, 1, 4, 7, 14, 28, 56, and 84. Basilar artery tissues were stained and analyzed at Day 84. Statistical analysis was performed using orthogonal contrast analysis, repeated measures analysis of variance, or mixed regression analysis of repeated measures. Statistical significance was defined as a probability value < 0.05. RESULTS: Basilar artery flow and diameter increased significantly after the procedure in both ligation groups, but only the bilateral CCA ligation group demonstrated significant differences between groups. Wall shear stress significantly increased only in animals in the bilateral CCA ligation group and returned to baseline by Day 28, with 52% of WSS correction occurring by Day 7. Only the bilateral CCA ligation group developed significant BA tortuosity, occurring within 7 days postligation. Unlike the animals in the sham and unilateral CCA ligation groups, the animals in the bilateral CCA ligation group had histological staining results showing a substantial internal elastic lamina fragmentation. CONCLUSIONS: Increased BA flow results in adaptive BA remodeling until WSS returns to physiological baseline levels. Morphological changes occur rapidly following flow alteration and do not require chronic insult to affect substantial and significant structural transformation. Additionally, it appears that there exists a flow-increase threshold that, when surpassed, results in significant tortuosity.

Nascent aneurysm formation at the basilar terminus induced by hemodynamics.

BACKGROUND AND PURPOSE: Hemodynamic insults at arterial bifurcations are hypothesized to play a key role in intracranial aneurysm formation. This study investigates aneurysm-initiating vascular responses at the rabbit basilar terminus subsequent to common carotid artery ligation. METHODS: Nine adult female New Zealand white rabbits were subjected to sham, unilateral, or bilateral common carotid artery ligation to produce varying degrees of compensatory basilar artery flow increase. Basilar artery flow velocity and geometry were monitored by transcranial Doppler and rotational angiography, respectively, for 12 weeks after surgery. Bifurcation tissues were harvested at 12 weeks and examined histologically. From the histological sections, we quantified the destructive structural changes at the basilar terminus and correlated them with the basilar artery flow rate increase. RESULTS: Subsequent to common carotid artery ligation, basilar artery flow rate increased by 105% to 900% at the maximum. All common carotid artery-ligated rabbits presented nascent aneurysm formation characterized by a bulge with thinned media and absent internal elastic lamina near the basilar terminus. We defined a nascent aneurysm index based on a multiplicative combination of the local destructive remodeling lengths measured at the nascent aneurysm. The nascent aneurysm index strongly correlated with the increase in basilar artery flow rate with R(2)=0.91. CONCLUSIONS: Without other known predisposition, flow increase alone at the basilar bifurcation can lead to a nascent aneurysm. This nascent aneurysm formation is dose-dependent on basilar artery flow increase.