Outcomes of one-stage and two-stage aneurysm repair in arteriovenous fistulae.

OBJECTIVE: Maintenance of long-term arteriovenous access is important in long-term care for patients with end-stage renal disease. Arteriovenous access is associated in the long term with the development of fistula aneurysms (FAs). This study aims to evaluate the outcomes of staged FA treatment in dialysis access arteriovenous fistulae (AVF). METHODS: A retrospective review of all patients over a 12-year period with primary autogenous AVF was undertaken at a single center. Patients undergoing elective open aneurysm repair were identified and were categorized into three groups: single FA repair (single, control group) and staged and unstaged repair of two FAs (staged and unstaged). A staged repair was a procedure in which the initial intent was to treat both aneurysms in the AVF and in which the most symptomatic aneurysm was treated first. When the incision from the first surgery had healed, the second symptomatic aneurysm in the AVF was treated. An unstaged repair was a procedure in which the initial intent was to repair both symptomatic aneurysms simultaneously. All patients had a fistulogram before the FA repair. Thirty-day outcomes, cannulation failure, line placement, reintervention, and functional dialysis (continuous hemodialysis for 3 consecutive months) were examined. RESULTS: Five hundred twenty-seven patients presented with FA that met requirements for open intervention; 44% underwent single FA repair, whereas the remaining 34% and 22% underwent staged and unstaged repair of two FAs, respectively. The majority of patients were diabetic and Hispanic. Ninety-one percent of the patients required percutaneous interventions of the outflow tract (37%) and the central veins (54%). Thirty-day major adverse cardiovascular events were equivalent across all modalities. Thirty-day morbidity and early thrombosis (<18 days) were significantly higher in the unstaged group (4.3%) compared with the two other groups (1.3% and 2.1%, single and staged, respectively), which led to an increased need for a short-term tunneled catheter (8.9%) compared with the two other groups (3.4% and 4.4%, single and staged, respectively), Unstaged repair resulted in an increased incidence of secondary procedures (5.0%) compared with the two other groups (2.6% and 3.1%, single and staged, respectively). Functional dialysis at 5 years was equivalent in the single and staged groups but was significantly decreased in the unstaged group. CONCLUSIONS: Open interventions are successful therapeutic modalities for FAs, but unstaged rather than staged repair of two concurrent FAs results in a higher early thrombosis, an increased secondary intervention rate, and a need for a short-term tunneled central line. Staged and single FA repairs have equivalent results. In the setting of two symptomatic FAs, staged repair is recommended.

Simultaneous time-of-flight MR angiography and quantitative susceptibility mapping with key time-of-flight features.

A technique for combined time-of-flight (TOF) MR angiography (MRA) and quantitative susceptibility mapping (QSM) was developed with key features of standard three-dimensional (3D) TOF acquisitions, including multiple overlapping thin slab acquisition (MOTSA), ramped RF excitation, and venous saturation. The developed triple-echo 3D TOF-QSM sequence enabled TOF-MRA, susceptibility-weighted imaging (SWI), QSM, and R2* mapping. The effects of ramped RF, resolution, flip angle, venous saturation, and MOTSA were studied on QSM. Six volunteers were scanned at 3 T with the developed sequence, conventional TOF-MRA, and conventional SWI. Quantitative comparison of susceptibility values on QSM and normalized arterial and venous vessel-to-background contrasts on TOF and SWI were performed. The ramped RF excitation created an inherent phase variation in the raw phase. A generic correction factor was computed to remove the phase variation to obtain QSM without artifacts from the TOF-QSM sequence. No statistically significant difference was observed between the developed and standard QSM sequence for susceptibility values. However, maintaining standard TOF features led to compromises in signal-to-noise ratio for QSM and SWI, arising from the use of MOTSA rather than one large 3D slab, higher TOF spatial resolution, increased TOF background suppression due to larger flip angles, and reduced venous signal from venous saturation. In terms of vessel contrast, veins showed higher normalized contrast on SWI derived from TOF-QSM than the standard SWI sequence. While fast flowing arteries had reduced contrast compared with standard TOF-MRA, no statistical difference was observed for slow flowing arteries. Arterial contrast differences largely arise from the longer TR used in TOF-QSM over standard TOF-MRA to accommodate additional later echoes for SWI. In conclusion, although the sequence has a longer TR and slightly lower arterial contrast, provided an adequate correction is made for ramped RF excitation effects on phase, QSM may be performed from a multiecho sequence that includes all key TOF features, thus enabling simultaneous TOF-MRA, SWI, QSM, and R2* map computation.

Automated hyperspectral imaging for non-invasive characterization of human eye vasculature: A potential tool for ocular vascular evaluation.

The vascular supply to the human eye plays a vital role in maintaining ocular health, making its non-invasive evaluation essential for diagnosing and managing various ocular disorders. This paper presents a novel approach utilizing hyperspectral imaging (HSI) to non-invasively characterize human eye vasculature. The proposed system aims to specifically identify the blood atrium and veins of the human eye at 470 nm and 750 nm, respectively, using quantitative phase analysis and k-means clustering. The study involved capturing diffused reflection spectra and hyperspectral images of the human eye at different wavelengths to reveal distinctive vascular features. The results of ten volunteers demonstrate promising capabilities in automated differentiation of atrium and veins, as well as the potential for mapping varicose veins in the lower limb. This non-invasive and non-contact imaging technique shows great promise in facilitating accurate and detailed evaluation of ocular blood flow, providing valuable information for clinical diagnosis and treatment in ophthalmology and vascular medicine fields.

Adrenal Vein Sampling: Tips and Tricks.

Adrenal vein sampling (AVS) is the standard method for distinguishing unilateral from bilateral sources of autonomous aldosterone production in patients with primary aldosteronism. This procedure has been performed at limited specialized centers due to its technical complexity. With recent advances in imaging technology and knowledge of adrenal vein anatomy in parallel with the development of adjunctive techniques, AVS has become easier to perform, even at nonspecialized centers. Although rare, anatomic variants of the adrenal veins can cause sampling failure or misinterpretation of the sampling results. The inferior accessory hepatic vein and the inferior emissary vein are useful anatomic landmarks for right adrenal vein cannulation, which is the most difficult and crucial step in AVS. Meticulous assessment of adrenal vein anatomy on multidetector CT images and the use of a catheter suitable for the anatomy are crucial for adrenal vein cannulation. Adjunctive techniques such as intraprocedural cortisol assay, cone-beam CT, and coaxial guidewire-catheter techniques are useful tools to confirm right adrenal vein cannulation or to troubleshoot difficult blood sampling. Interventional radiologists should be involved in interpreting the sampling results because technical factors may affect the results. In rare instances, bilateral adrenal suppression, in which aldosterone-to-cortisol ratios of both adrenal glands are lower than that of the inferior vena cava, can be encountered. Repeat sampling may be necessary in this situation. Collaboration with endocrinology and laboratory medicine services is of great importance to optimize the quality of the samples and for smooth and successful operation. ©RSNA, 2024 Test Your Knowledge questions for this article are available in the supplemental material.

Superficial Venous Disease-An Updated Review.

BACKGROUND: This review article provides an updated review of a relatively common pathology with various manifestations. Superficial venous diseases (SVDs) are a broad spectrum of venous vascular disease that predominantly affects the body's lower extremities. The most serious manifestation of this disease includes varicose veins, chronic venous insufficiency, stasis dermatitis, venous ulcers, superficial venous thrombosis, reticular veins, and spider telangiectasias. METHODS: The anatomy, pathophysiology, and risk factors of SVD were discussed during this review. The risk factors for developing SVD were related to race, age, sex, lifestyle, and certain genetic conditions as well as comorbid deep vein thrombosis. Various classification systems were listed, focusing on the most common one-the revised Clinical-Etiology-Anatomy-Pathophysiology classification. The clinical features including history and physical examination findings elicited in SVD were outlined. RESULTS: Imaging modalities utilized in SVD were highlighted. Duplex ultrasound is the first line in evaluating SVD but magnetic resonance imaging and computed tomography venography, plethysmography, and conventional venography are feasible options in the event of an ambiguous venous duplex ultrasound study. Treatment options highlighted in this review ranged from conservative treatment with compression stockings, which could be primary or adjunctive to pharmacologic topical and systemic agents such as azelaic acid, diuretics, plant extracts, medical foods, nonsteroidal anti-inflammatory drugs, anticoagulants and skin substitutes for different stages of SVD. Interventional treatment modalities include thermal ablative techniques like radiofrequency ablationss, endovenous laser ablation, endovenous steam ablation, and endovenous microwave ablation as well as nonthermal strategies such as the Varithena (polidocanol microfoam) sclerotherapy, VenaSeal (cyanoacrylate) ablation, and Endovenous mechanochemical ablation. Surgical treatments are also available and include debridement, vein ligation, stripping, and skin grafting. CONCLUSIONS: SVDs are prevalent and have varied manifestations predominantly in the lower extremities. Several studies highlight the growing clinical and financial burden of these diseases. This review provides an update on the pathophysiology, classification, clinical features, and imaging findings as well as the conservative, pharmacological, and interventional treatment options indicated for different SVD pathologies. It aims to expedite the timely deployment of therapies geared toward reducing the significant morbidity associated with SVD especially varicose veins, venous ulcers, and venous insufficiency, to improve the quality of life of these patients and prevent complications.

Rejoining Veins for Forced Maturation of Small-Caliber Arteriovenous Fistula.

BACKGROUND: To evaluate the efficacy of rejoining mainstream and accessory veins for forced maturation of autogenous arteriovenous fistula (AVF). METHODS: Twenty-three patients who underwent forced maturation through vein rejoining between January 2018 and September 2022 were included. In cases where AVF maturation failure due to the presence of accessory veins, rejoining was primarily considered when distinguishing the main branch becomes challenging. This difficulty typically occurs when the sizes of the 2 vessels are nearly equal and the combined diameters of these veins exceed 6 mm. RESULTS: The mean age and follow-up duration were 57.39 ± 16.22 years and 965.65 ± 573.42 days, respectively. Rejoining of both arterial and venous cannulation sites was performed in 11 patients (47.8%), and rejoining of only the venous cannulation site or only the arterial cannulation site was performed in 11 patients (47.8%) and 1 patient (4.3%), respectively. The mean vein size was 0.35 ± 0.06 cm before rejoining and 0.69 ± 0.07 cm after surgery, indicating a significant increase in size (P < 0.01), whereas the flow did not change significantly following rejoining surgery. Maturation and cannulation success was 100%. The 1-year primary patency rate after surgery was 82.0%. During the follow-up period, 34.8% of the patients required additional percutaneous transluminal angioplasty to maintain patency, and 2 patients (11.8%) had stenosis in the rejoined section. CONCLUSIONS: Rejoining surgery is an effective method for achieving AVF maturation in patients with accessory veins when identification of the mainstream vein is difficult, and this method may be considered when achieving maturation by sacrificing 1 vein is expected to be challenging.

Prevalence, Clinical and Imaging Characteristics of Superior Ophthalmic Vein Periphlebitis in Thyroid Eye Disease.

PURPOSE: To determine the prevalence, clinical features, and radiographic findings of superior ophthalmic vein periphlebitis (SOVP) in thyroid eye disease (TED). METHODS: Patients with a clinical diagnosis of thyroid eye disease and contrast-enhanced imaging were included. Imaging was reviewed for the presence of SOVP, and patients with SOVP were compared to those without. A random eye was determined to be the affected eye in patients without SOVP. RESULTS: A total of 212 patients met the inclusion criteria. Unilateral SOVP was identified in 4.7% of cases. There was no significant difference in age ( p = 0.22), gender ( p = 0.09), or disease duration ( p = 0.14) between patients with and without SOVP. There was a significant ( p < 0.05) difference in stage classification and clinical activity core between the groups. The affected eye in patients with SOVP had significantly ( p < 0.05) greater margin reflex distance 1, degree of relative proptosis, horizontal motility restriction, and vertical motility restriction than in patients without SOVP. There was no significant difference in horizontal strabismus ( p = 1.0), vertical strabismus ( p = 0.87), or relative intraocular pressure ( p = 0.77). On imaging, the maximal diameter of the SR and IR were found to be significantly ( p < 0.05) larger in the affected eye of patients with periphlebitis; however, there was no difference in measured diameter of the medial rectus and ( p = 0.30) or lateral rectus ( p = 0.78). CONCLUSIONS: SOVP is an under-reported imaging finding of thyroid eye disease. It is associated with significantly greater margin reflex distance 1, relative proptosis, and motility restriction on exam as well as larger superior rectus and inferior rectus diameter on imaging. These patients tend to present in the active stage of disease with greater clinical activity score.

Anatomical features of a crossing vein connecting left and right internal mammary veins: A preliminary study with computerized tomography or magnetic resonance imaging.

BACKGROUND: In breast reconstruction with free flaps, retrograde venous anastomosis into the internal mammary vein (IMV) is often unavoidable. Utility of a crossing vein between the right and left IMV, one of the anatomical foundations which make retrograde flow possible, has been reported but only with a few detailed features. This study evaluated the presence, actual location, and diameter of the crossing veins using preoperative imaging such as contrast-enhanced computed tomography (CECT), or contrast-enhanced magnetic resonance imaging (CEMRI). Moreover, this is a preliminary non-invasive study to clarify these processes on a larger scale. METHODS: We included 29 cases of unilateral breast reconstruction performed between July 2018 and September 2023 at our institution using unipedicled or bipedicled free deep inferior epigastric artery perforator (DIEP) flaps with retrograde venous anastomosis to only one IMV at the level of anastomosis. No congestion or necrosis was observed. In the final 24 cases with sufficient imaging coverage of preoperative contrast-enhanced images (15 CECT and 9 CEMRI), the crossing veins of IMVs were detected and the number, localization, and diameter were measured. RESULTS: In 20 cases of 24 images, the crossing veins between IMVs were completely identified (83%). In 18 of the cases, only one crossing vein was established immediately ventral to the xiphoid process, averaging 19.3 ± 7.18 mm caudal to the fibrous junction between the sternal body and xiphoid process. The average diameter of the veins was 1.57 ± 0.42 mm. In two other cases, the second crossing vein originated on the dorsal surface of the sternum, but it was a very thin vein of about 0.4 mm. Three images indicated incomplete identification of the crossing vein at the xiphoid process, and in one case, no crossing vein was observed between bilateral IMVs. CONCLUSION: The contrast-enhanced imaging study revealed an anatomic feature that the crossing veins (about 1.5 mm in diameter) connecting the right and left IMVs are located just ventral to the xiphoid process. Furthermore, the crossing veins can be identified on contrast-enhanced images, and refinement of this method is expected to lead to future non-invasive anatomical investigations in an even larger number of cases.

Finger Vein Identification Based on Large Kernel Convolution and Attention Mechanism.

FV (finger vein) identification is a biometric identification technology that extracts the features of FV images for identity authentication. To address the limitations of CNN-based FV identification, particularly the challenge of small receptive fields and difficulty in capturing long-range dependencies, an FV identification method named Let-Net (large kernel and attention mechanism network) was introduced, which combines local and global information. Firstly, Let-Net employs large kernels to capture a broader spectrum of spatial contextual information, utilizing deep convolution in conjunction with residual connections to curtail the volume of model parameters. Subsequently, an integrated attention mechanism is applied to augment information flow within the channel and spatial dimensions, effectively modeling global information for the extraction of crucial FV features. The experimental results on nine public datasets show that Let-Net has excellent identification performance, and the EER and accuracy rate on the FV_USM dataset can reach 0.04% and 99.77%. The parameter number and FLOPs of Let-Net are only 0.89M and 0.25G, which means that the time cost of training and reasoning of the model is low, and it is easier to deploy and integrate into various applications.

A Degraded Finger Vein Image Recovery and Enhancement Algorithm Based on Atmospheric Scattering Theory.

With the development of biometric identification technology, finger vein identification has received more and more widespread attention for its security, efficiency, and stability. However, because of the performance of the current standard finger vein image acquisition device and the complex internal organization of the finger, the acquired images are often heavily degraded and have lost their texture characteristics. This makes the topology of the finger veins inconspicuous or even difficult to distinguish, greatly affecting the identification accuracy. Therefore, this paper proposes a finger vein image recovery and enhancement algorithm using atmospheric scattering theory. Firstly, to normalize the local over-bright and over-dark regions of finger vein images within a certain threshold, the Gamma transform method is improved in this paper to correct and measure the gray value of a given image. Then, we reconstruct the image based on atmospheric scattering theory and design a pixel mutation filter to segment the venous and non-venous contact zones. Finally, the degraded finger vein images are recovered and enhanced by global image gray value normalization. Experiments on SDUMLA-HMT and ZJ-UVM datasets show that our proposed method effectively achieves the recovery and enhancement of degraded finger vein images. The image restoration and enhancement algorithm proposed in this paper performs well in finger vein recognition using traditional methods, machine learning, and deep learning. The recognition accuracy of the processed image is improved by more than 10% compared to the original image.

Ultrasound diagnosis of Mondor's disease involving the superficial scrotal veins: Unveiling a rare mimicker of acute scrotal emergencies.

We describe a rare case of Mondor disease of the superficial scrotal veins, which can clinically mimic acute testicular pathologies such as testicular torsion or epididymo-orchitis, and highlight the value of grayscale/Doppler ultrasound examination in distinguishing these entities, which have different management implications.

Blood within the bone: orbital intraosseous venous malformation.

PURPOSE: Description of clinical features, radiological characteristics, and management strategies in primary orbital intraosseous venous malformation (OIVM) with pertinent literature review. METHODS: A retrospective analysis including clinical, radiologic, operative, and histopathological data of six cases of histopathologically proven OIVM was done. A comprehensive literature review was conducted using online databases and augmented with manual search to identify reported cases of OIVM. RESULTS: Study data showed five females and one male in young to middle-age group, with an average age of 30 years (range: 20-48 years). Proptosis was noted in five cases (83.33%), and the duration of symptoms ranged from 6 months to 10 years. Frontal and zygomatic bones were most frequently affected and expansile bony lesion was the most common CT scan finding. Three patients underwent pre-operative embolization of feeders followed by en bloc excision of mass and surgical reconstruction (50%); one patient was managed with partial excision (16.66%) while two were regularly followed-up after incision biopsy (33.33%). Histopathology revealed vascular spaces with endothelial lining, separated by bony trabeculae in all patients. Follow-up periods ranged from 6 to 48 months and no recurrence or progression were noted. CONCLUSIONS: OIVM is an exceptionally rare disorder with a gradually progressive benign course. Ophthalmologists need to be mindful of this entity during patient evaluation as it has propensity for large volume blood loss intra-operatively, owing to its vascular nature. Complete excision with reconstruction of resultant defect is the preferred treatment strategy and without known recurrence.

The athlete's vein: venous adaptations in the lower limbs of endurance athletes.

Endurance exercise induces cardiovascular adaptations; the athletic phenotypes of the heart and arteries are well characterized, but few studies have investigated the effects of chronic exercise on the venous system. The aim of this study was to describe the anatomy and function of lower-limb deep and superficial veins in athletes compared with controls. Endurance-trained athletes and untrained controls (13 males, 7 females per group) were examined using ultrasound to measure vein diameter and flow, and air plethysmography to assess calf venous volume dynamics and muscle pump function at rest, during a single step, ambulation (10 steps) and after acute treadmill exercise (30 min ∼80% age-predicted heart rate maximum). Diameters of three of the seven deep veins assessed were larger in athletes (P ≤ 0.0167) and more medial calf perforators were detectable (5 vs. 3, P = 0.0039). Calf venous volume was 22% larger in athletes (P = 0.0057), and calf muscle pump ejection volume and ambulatory venous volume after 10 steps were both greater in athletes (20 and 46% respectively, P ≤ 0.0482). Following acute exercise, flow recovery profiles in deep and superficial veins draining the leg were not different between groups, despite athletes performing approximately four times more work. After exercise, venous volume and ejection volume were reduced by ∼20% in athletes with no change in controls (interaction, P ≤ 0.0372) and although ambulatory venous volume reduced, this remained greater in athletes. These findings highlight venous adaptations that compensate for the demands of regular endurance exercise, all of which are suited to enhance flow through the lower-limb venous system.NEW & NOTEWORTHY Although much literature exists describing adaptations to the heart and arteries in response to endurance exercise training, less is known about the effects on the venous system. Characteristics of "the athlete's vein" described here include deep and perforator vein remodeling, improved drainage, and greater calf venous volume at rest and on calf muscle pump activation. Following exercise, athletes demonstrated prompt flow recovery and appropriate volume reductions, and veins beneficially adapt to better tolerate the demands of regular physical activity.

Early clinical experience and comparison between percutaneous and surgical arteriovenous fistula.

BACKGROUND: Percutaneous arteriovenous fistula (pAVF) has been recently developed as an alternative to surgical AVF (sAVF). We report our experience with pAVF in comparison with a contemporaneous sAVF group. METHODS: Charts of all 51 patients with pAVF performed at our institution were analyzed retrospectively, in addition to 51 randomly selected contemporaneous patients with sAVF (2018-2022) with available follow-up. Outcomes of interest were (i) procedural success rate, (ii) number of maturation procedures required, (iii) fistula maturation rates, and (iv) rates of tunneled dialysis catheter (TDC) removal. For patients on hemodialysis (HD), sAVF and pAVF were considered mature when the AVF was used for HD. For patients not on HD, pAVF were considered mature if flow rates of ≥500 mL/min were documented in superficial venous outflow; for sAVF, documentation of maturity based on clinical criteria was required. RESULTS: Compared patients with sAVF, patients with pAVF were more likely to be male (78% vs 57%; P = .033) and less likely to have congestive heart failure (10% vs 43%; P < .001) and coronary artery disease (18% vs 43%; P = .009). Procedural success was achieved in 50 patients with pAVF (98%). Fistula angioplasties (60% vs 29%; P = .002) and ligation (24% vs 2%; P = .001) or embolization (22% vs 2%; P = .002) of competing outflow veins were more frequently performed on patients with pAVF. The surgical cohort had more planned transpositions (39% vs 6%; P < .001). When all maturation interventions were combined, pAVF required more maturation procedures, but this was not statistically significant (76% vs 53%; P = .692). When planned second-stage transpositions were excluded, pAVF had a statistically significant higher rate of maturation procedures (74% vs 24%; P < .001). Overall, 36 pAVF (72%) and 29 sAVF (57%) developed mature fistulas. This difference, however, was not statistically significant (P = .112). At the time of AVF creation, 26 patients with pAVF and 40 patients with sAVF were on HD, all through use of a TDC. Catheter removal was recorded in 15 patients with pAVF (58%) and 18 patients with sAVF (45%) (P = .314). The mean time until TDC removal in pAVF group was 146 ± 74 days, compared with 175 ± 99 in the sAVF group (P = .341). CONCLUSIONS: Compared with sAVF, rates of maturation after pAVF seem to be similar, but this result may be related to the higher intensity of maturation procedures and patient selection. An analysis of appropriately matched patients will assist in elucidating the possible role of pAVF vis-a-vis sAVF.

Pelvic pain and venous congestion revisited: examining relationship between chronic pelvic pain and uterine venous size and blood flow.

OBJECTIVE: To investigate the relationship between increased uterine venous plexus diameter and chronic pelvic pain in women attending a gynecology clinic. METHODS: This was a retrospective study of patients attending a tertiary university hospital in London, UK. Women presenting to the gynecology clinic undergoing transvaginal ultrasound examination were recruited into the study. The largest trunk of the uterine venous plexus was measured on each side. Blood flow within the uterine veins was categorized into continuous or interrupted flow and evaluated using color and spectral Doppler ultrasound during normal respiration and on Valsalva maneuver to demonstrate the presence of venous reflux. The largest uterine vein diameter and its blood flow were used for the analysis. The main variables of interest were chronic pelvic pain, uterine vein diameter and type of blood flow. RESULTS: We included 1500 women in the study, of whom 584 (38.9% (95% CI, 36.5-41.5%)) reported chronic pelvic pain. Dysmenorrhea was the most common type of pelvic pain. Age (P < 0.001), menopausal status (P = 0.02), varicose veins (P = 0.01), adenomyosis (P < 0.001) and endometriosis (P < 0.001) were found to be independently associated with the occurrence of pain on multiple logistic regression analysis. There was no difference in uterine vein diameter between women with and those without pain (P = 0.10). Neither uterine vein diameter (P = 0.47) nor type of blood flow (P = 0.07) was significantly associated with the occurrence of pelvic pain on multiple logistic regression. CONCLUSIONS: Our findings show that uterine vein diameter is not associated with pelvic pain. However, we found other important clinical and demographic factors that are associated with chronic pelvic pain. © 2022 International Society of Ultrasound in Obstetrics and Gynecology.

The Distensibility of the Human Vena Cava and Its Importance to In Vitro Studies of Venous Compression Syndromes: A Search for a Suitable Polymer for 3-Dimensional Printing.

BACKGROUND: Venous compression syndromes are clinical conditions in which the large veins are compressed by other anatomical structures. Laboratory simulations may help us better understand the hemodynamics in venous compressions by creating situations similar to those seen in vivo. The aim of this study is to produce a model of the caval bifurcation using a polymer with distensibility similar to the human vena cava. METHODS: Fragments of the inferior vena cava were collected from 13 deceased kidney donors (aged 15-37 years) and were tested for deformation (strain) when subjected to distension at 50 N/cm2. Strips of 5 different polymers-thermic polyurethane and Agilus30 with Vero Magenta (AV) (in 3 different hardnesses) and silicone-were subjected to the same biomechanical tests and compared with the vena cava. A model of the caval bifurcation was produced with 3-D printing. RESULTS: The deformation (strain) of the vena cava wall was 0.16 ± 0.9 when submitted to stress close to 50 N/cm2. Silicone showed a strain higher than the standard deviation of venous fragments. The strain of AV resin 95 Shore was lower than the standard deviation of the venous fragments. AV Resins 70 and 85 Shore showed strains within the standard deviation of the venous specimen, with 70 Shore being closest to the mean venous strain. Therefore, this material was selected for modeling the caval bifurcation. The computed tomography scan image generated a computer model of the caval bifurcation and was printed in 3 dimensions. In addition, the segments of 2 adjacent vertebrae were also printed to reference the compression site. CONCLUSIONS: The 3-D printing of large veins can produce models with anatomy and biomechanics similar to those of human veins and opens a field of investigation into the hemodynamics of venous compression syndromes. Polymers with Shore A70 appear to have biomechanical properties similar to those of the vena cava wall. The model obtained in this study can be used in several in vitro studies of May-Thurner Syndrome.

Discordant imaging: adrenal vein sampling in almost half of patients with primary aldosteronism and a unilateral adrenal adenoma.

BACKGROUND: Primary hyperaldosteronism (PHA) is an underdiagnosed cause of secondary hypertension, with an increased risk of cardiovascular and renal complications compared with those with essential hypertension alone. Distinguishing between unilateral and bilateral aldosterone secretion is important as management differs. Adrenal vein sampling (AVS) is the gold standard for determining lateralisation. Current international guidelines suggest AVS may be omitted in those aged <35 years with PHA and a unilateral adrenal adenoma on imaging. AIM: To characterise all patients referred for AVS at Waitemata District Health Board (WDHB), review the success rate of AVS and compare concordance of AVS with imaging. METHODS: All patients who underwent AVS in WDHB from January 2015 to September 2020 were retrospectively assessed. Clinical records, laboratory data and radiological findings were reviewed. RESULTS: Ninety-six patients underwent AVS, with four excluded as private records were unable to be obtained. Of the 92 patients included, age ranged from 22 to 79 years. AVS was successful on first attempt in 89 (96.7%) patients. AVS and imaging findings were concordant in 62.2% of patients. One (14.3%) of seven aged <35 years had discordant results, and 16 (47%) of 34 patients with a unilateral adenoma on imaging had discordant results to AVS. CONCLUSIONS: AVS at WDHB is successful on first attempt in most patients. AVS is essential in the management of PHA for those deemed to be surgical candidates, regardless of age.

A Finger Vein Liveness Detection System Based on Multi-Scale Spatial-Temporal Map and Light-ViT Model.

Prosthetic attack is a problem that must be prevented in current finger vein recognition applications. To solve this problem, a finger vein liveness detection system was established in this study. The system begins by capturing short-term static finger vein videos using uniform near-infrared lighting. Subsequently, it employs Gabor filters without a direct-current (DC) component for vein area segmentation. The vein area is then divided into blocks to compute a multi-scale spatial-temporal map (MSTmap), which facilitates the extraction of coarse liveness features. Finally, these features are trained for refinement and used to predict liveness detection results with the proposed Light Vision Transformer (Light-ViT) model, which is equipped with an enhanced Light-ViT backbone, meticulously designed by interleaving multiple MN blocks and Light-ViT blocks, ensuring improved performance in the task. This architecture effectively balances the learning of local image features, controls network parameter complexity, and substantially improves the accuracy of liveness detection. The accuracy of the Light-ViT model was verified to be 99.63% on a self-made living/prosthetic finger vein video dataset. This proposed system can also be directly applied to the finger vein recognition terminal after the model is made lightweight.

Fast and Accurate ROI Extraction for Non-Contact Dorsal Hand Vein Detection in Complex Backgrounds Based on Improved U-Net.

In response to the difficulty of traditional image processing methods to quickly and accurately extract regions of interest from non-contact dorsal hand vein images in complex backgrounds, this study proposes a model based on an improved U-Net for dorsal hand keypoint detection. The residual module was added to the downsampling path of the U-Net network to solve the model degradation problem and improve the feature information extraction ability of the network; the Jensen-Shannon (JS) divergence loss function was used to supervise the final feature map distribution so that the output feature map tended to Gaussian distribution and improved the feature map multi-peak problem; and Soft-argmax is used to calculate the keypoint coordinates of the final feature map to realize end-to-end training. The experimental results showed that the accuracy of the improved U-Net network model reached 98.6%, which was 1% better than the original U-Net network model; the improved U-Net network model file was only 1.16 M, which achieved a higher accuracy than the original U-Net network model with significantly reduced model parameters. Therefore, the improved U-Net model in this study can realize dorsal hand keypoint detection (for region of interest extraction) for non-contact dorsal hand vein images and is suitable for practical deployment in low-resource platforms such as edge-embedded systems.

Automatic segmentation of peripheral arteries and veins in ferumoxytol-enhanced MR angiography.

PURPOSE: To automate the segmentation of the peripheral arteries and veins in the lower extremities based on ferumoxytol-enhanced MR angiography (FE-MRA). METHODS: Our automated pipeline has 2 sequential stages. In the first stage, we used a 3D U-Net with local attention gates, which was trained based on a combination of the Focal Tversky loss with region mutual loss under a deep supervision mechanism to segment the vasculature from the high-resolution FE-MRA datasets. In the second stage, we used time-resolved images to separate the arteries from the veins. Because the ultimate segmentation quality of the arteries and veins relies on the performance of the first stage, we thoroughly evaluated the different aspects of the segmentation network and compared its performance in blood vessel segmentation with currently accepted state-of-the-art networks, including Volumetric-Net, DeepVesselNet-FCN, and Uception. RESULTS: We achieved a competitive F1 = 0.8087 and recall = 0.8410 for blood vessel segmentation compared with F1 = (0.7604, 0.7573, 0.7651) and recall = (0.7791, 0.7570, 0.7774) obtained with Volumetric-Net, DeepVesselNet-FCN, and Uception. For the artery and vein separation stage, we achieved F1 = (0.8274/0.7863) in the calf region, which is the most challenging region in peripheral arteries and veins segmentation. CONCLUSION: Our pipeline is capable of fully automatic vessel segmentation based on FE-MRA without need for human interaction in <4 min. This method improves upon manual segmentation by radiologists, which routinely takes several hours.