Differentiation of Cerebral Neoplasms with Vessel Size Imaging (VSI)

Purpose Cerebral neoplasms of various histological origins may show comparable appearances on conventional Magnetic Resonance Imaging (MRI). Vessel size imaging (VSI) is an MRI technique that enables noninvasive assessment of microvasculature by providing quantitative estimates of microvessel size and density. In this study, we evaluated the potential of VSI to differentiate between brain tumor types based on their microvascular morphology. Methods Using a clinical 3T MRI scanner, VSI was performed on 25 patients with cerebral neoplasms, 10 with glioblastoma multiforme (GBM), 8 with primary CNS lymphoma (PCNSL) and 7 with cerebral lung cancer metastasis (MLC). Following the postprocessing of VSI maps, mean vessel diameter (vessel size index, vsi) and microvessel density (Q) were compared across tumors, peritumoral areas, and healthy tissues. Results The MLC tumors have larger and less dense microvasculature compared to PCNSLs in terms of vsi and Q (p = 0.0004 and p < 0.0001, respectively). GBM tumors have higher yet non-significantly different vsi values than PCNSLs (p = 0.065) and non-significant differences in Q. No statistically significant differences in vsi or Q were present between GBMs and MLCs. GBM tumor volume was positively correlated with vsi (r = 0.502, p = 0.0017) and negatively correlated with Q (r = −0.531, p = 0.0007). Conclusion Conventional MRI parameters are helpful in differentiating between PCNSLs, GBMs, and MLCs. Additionally incorporating VSI parameters into the diagnostic protocol could help in further differentiating between PCNSLs and metastases and potentially between PCNSLs and GBMs. Future studies in larger patient cohorts are required to establish diagnostic cut-off values for VSI.

Vessel diameter and close surveillance helps predict early patency in native arteriovenous fistulas

Introduction: Arteriovenous fistulas are the preferred method of vascular access for haemodialysis. Data suggests patency rates can be low and may be related to vessel diameters prior to creation. We use specific size criteria for fistula selection. We aimed to establish patency rates in relation to vessel size and whether other factors affect fistula patency. Methods: Consecutive patients undergoing radiocephalic (RCF) or brachiocephalic (BCF) creation between 2016 and 2018 were analysed. Preoperative arterial and venous diameters were collected. Six-week and six-month primary and secondary patency rates were analysed to establish any impact of vessel size on patency and re-intervention rates between groups. A univariate analysis was performed. Results: Ninety four RCFs and 101 BCFs were created. Median artery and vein size for RCF were 2.7 and 3.0 mm respectively. For BCF, they were 4.6 and 4.3 mm respectively. At 6-weeks, overall satisfactory patency for RCF and BCF combined was 91.8%. 89.7% demonstrated primary patency; 2.1% secondary patency. At 6-months, overall patency was 78.7%; 58.5% demonstrated primary patency, 20.2% secondary patency. A univariate analysis, for both groups, revealed vein size was a significant predictor of overall satisfactory patency at 6-weeks, with larger veins more likely to remain patent ( p = 0.025 RCF, p = 0.007 BCF). However, artery size was not predictive ( p = 0.1 RCF, p = 0.5 BCF). At 6-months, neither artery nor vein diameter were predictive in either group. When comparing size of vessel based on fistula type, vessels used to create RCFs were smaller than those for BCFs ( p < 0.001). RCFs were more likely to receive endovascular intervention or occlude when compared to BCFs ( p = 0.014). Discussion: Excellent patency and maturation rates can be achieved using fairly strict vessel size criteria. Vein size might be the more important predictor of early success. RCFs can be challenging due to smaller vessels, but maturation rates can be optimised by close surveillance and aggressive re-intervention.

Abstract 1122‐000073: Influence of Catheter Tip Position and Aspiration Technique on ADAPT Revascularization Success with Various Catheters

Introduction : Previous studies demonstrated that both the location of the distal access catheter tip and angle of aspiration have a significant impact on revascularization outcomes 1,2 . A direct aspiration First‐Pass technique (ADAPT) with large‐bore aspiration catheters has emerged as a fast, safe, and effective thrombectomy technique. Maximizing the catheter‐to‐vessel size has previously been shown to enhance distal flow control resulting in improved in‐vitro revascularization rates for aspiration thrombectomy 3 . However, physicians differ in their preference for aspiration catheter tip placement, typically either positioning the catheter tip at the ‘face’ of the clot or advancing the catheter tip into the clot to engage it. We hypothesize that sizing the aspiration catheter outer diameter (OD) to the inner diameter (ID) of the vessel and embedding the catheter tip in the clot may result in ‘pinning’ fragments of clot between the catheter and vessel wall, thereby negatively affecting revascularization outcomes. Withdrawal of the aspiration catheter under continuous aspiration may mitigate this effect. We investigate the influence of catheter tip position and aspiration technique on ADAPT revascularization success with various sizes of aspiration catheters. Methods : Two clot analogues phenotypes (RBC‐Rich and Fibrin/Platelet‐Rich) were created from human blood and used to form occlusions in an In‐vitro thrombectomy model as previously described 4 . Two catheter tip positions and three techniques were investigated; 1). Catheter tip proximal to the face of the clot followed by conventional aspiration, 2). Catheter tip ‘embedded’ into the clot followed by conventional aspiration, and 3). Catheter tip ‘embedded’ into the clot followed by conventional aspiration and aspiration on catheter withdrawal even if clot ingestion occurred. Two aspiration catheters were investigated; Millipede 088’’ (Perfuze Ltd) and SOFIA Plus (Terumo). Multiple replicates of each test were performed. Endpoints were First‐Pass Effect and procedural‐related distal emboli from 200–1000µm. Results : Maximizing the catheter‐to‐vessel size increases success of the ADAPT approach when the tip is located proximal to the clot face (Fig 1 A&B); Millipede 088 achieves a higher First‐Pass Effect rate than SOFIA Plus. Sizing the catheter‐to‐vessel and embedding the catheter tip into the clot (Figure 1C) results in ‘pinning’ of clot fragments between the catheter and vessel wall (Figure 1D) resulting in lower rates of First‐Pass Effect. Withdrawing the catheter under continuous aspiration increases the success of the embedding method by capturing ‘pinned’ fragments. Conclusions : The position of the aspiration catheter tip and aspiration technique used both influence the success of ADAPT procedures. Sizing the catheter‐to‐vessel results in improved revascularization. However, embedding the tip into the clot when the vessel is similar in ID to the catheter OD may reduce First‐Pass Effect rates. To optimize the rates of First‐Pass Effect, aspiration catheters may be positioned at the proximal face of the clot or retracted under continuous aspiration if wedged into the clot.

Parametric Effects of Heater Size, Contact Angle, and Surrounding Vessel Size On Pool Boiling Critical Heat Flux From Horizontal Surfaces

Saturated water at one atmosphere pressure was boiled on horizontal copper discs of diameters 1.0,1.5 and 2.0 cm. respectively. The contact angle was varied from 10 to 80 degrees by controlling thermal oxidation of the discs, while the surrounding vessel size was changed by placing glass tubes of different inner diameters around the discs. Nucleate boiling heat transfer data were obtained up to critical heat flux (CHF), where vapor removal patterns were photographed. Dominant wavelengths at vapor jet interface and vapor jet diameters were measured from the photographs of the well wetted discs. For a well wetted surface, the magnitude of CHF increased when the heater size was reduced from 2.0 to 1.0 cm. Improving the wettability enhanced the CHF substantially, whereas the increased size of the liquid holding vessel had a smaller effect. The highest measured CHF is 233 W/cm2 or 2.11 times Zuber's CHF prediction for infinite horizontal flat plates. It was obtained on a 1.0 cm. disc of contact angle about 10 degrees surrounded by a large vessel. The CHF for this surface was increased from 201 to 233 W/cm2 when the ratio of heater size to surrounding vessel size was reduced from 1 to about 0.

Comparison of gray scale versus Doppler ultrasound to detect deep venous thrombosis in lower extremities.

Objectives: The objective was to determine the accuracy of Gray Scale versus Doppler Ultrasound to Detect Deep Venous Thrombosis in Lower Extremities. Study Design: Cross Sectional Analytical study. Setting: The University of Lahore and Shalimar Hospital Lahore. Period: May to October 2020. Material & Methods: After a permission from the ethical committee and a written consent of the patients, on the basis of the clinical suspicions of deep vein thrombosis, A total of 140 patients of both the genders, aging from 20 to 90 years, were referred for Gray Scale & Doppler ultrasound examination. The convenient sampling technique and Statistical software for social sciences (SPSS version 22.0) were used for the analysis of data. Results: In 140 patients’ present study on Gray Scale ultrasound, 120 (85%) cases were observed with significantly increased blood vessel size, intraluminal echogenicity and a loss of compressibility However, on Doppler ultrasound, 130 (92%) cases were detected possessing significantly increased blood vessel size, intraluminal echogenicity, absence of blood flow and negative augmentation effect. Conclusions: From the result of present study, it is concluded that Doppler may be used as gold standard to diagnose the DVT in the lower extremities. This study concludes also that DVT detection accuracy difference between Doppler and Gray Scale ultrasound is minor i.e. 1:1.08. This minor difference encourages the radiology practitioners of periphery to screen DVT in lower extremities through Gray Scale ultrasound, if Doppler ultrasound is unavailable there.

Automated Detection and Diameter Estimation for Mouse Mesenteric Artery Using Semantic Segmentation

<b><i>Background:</i></b> Pressurized myography is useful for the assessment of small artery structures and function. However, this procedure requires technical expertise for sample preparation and effort to choose an appropriate sized artery. In this study, we developed an automatic artery/vein differentiation and a size measurement system utilizing machine learning algorithms. <b><i>Methods and Results:</i></b> We used 654 independent mouse mesenteric artery images for model training. The model yielded an Intersection-over-Union of 0.744 ± 0.031 and a Dice coefficient of 0.881 ± 0.016. The vessel size and lumen size calculated from the predicted vessel contours demonstrated a strong linear correlation with manually determined vessel sizes (<i>R</i> = 0.722 ± 0.048, <i>p</i> &#x3c; 0.001 for vessel size and <i>R</i> = 0.908 ± 0.027, <i>p</i> &#x3c; 0.001 for lumen size). Last, we assessed the relation between the vessel size before and after dissection using a pressurized myography system. We observed a strong positive correlation between the wall/lumen ratio before dissection and the lumen expansion ratio (<i>R</i> = 0.832, <i>p</i> &#x3c; 0.01). Using multivariate binary logistic regression, 2 models estimating whether the vessel met the size criteria (lumen size of 160–240 μm) were generated with an area under the receiver operating characteristic curve of 0.761 for the upper limit and 0.747 for the lower limit. <b><i>Conclusion:</i></b> The U-Net-based image analysis method could streamline the experimental approach.

Saphenous vein valve assessment utilizing upright CT to potentially improve graft assessment for bypass surgery

Saphenous veins (SVs) are frequently employed as bypass grafts. The SV graft failure is predominantly seen at the valve site. Avoiding valves during vein harvest would help reduce graft failure. We endeavored to detect SV valves, tributaries, and vessel size employing upright computed tomography (CT) for the raw cadaver venous samples and in healthy volunteers. Five cadaver legs were scanned. Anatomical analysis showed 3.0 (IQR: 2.0–3.0) valves and 13.50 (IQR: 10.00–16.25) tributaries. The upright CT completely detected, compared to 2.0 (IQR: 1.5–2.5, p = 0.06) valves and 9.5 (IQR: 7.5–13.0, p = 0.13) tributaries by supine CT. From a total of 190 volunteers, 138 (men:75, women:63) were included. The number of valves from the SF junction to 35 cm were significantly higher in upright CT than in supine CT bilaterally [upright vs. supine, Right: 4 (IQR: 3–5) vs. 2 (IQR:1–2), p < 0.0001, Left: 4 (IQR: 3–5) vs. 2 (IQR: 1–2), p < 0.0001]. The number of tributaries and vessel areas per leg were also higher for upright compared with supine CT. Upright CT enables non-invasive detection of SV valves, tributaries, and vessel size. Although not tested here, it is expected that upright CT may potentially improve graft assessment for bypass surgery.