First standardized assessment of perforators and perforasomes of the occipital artery - An anatomical study.

BACKGROUND: Flaps have become an integral part of plastic and reconstructive surgery. The robust blood supply of such flaps is a prerequisite to reduce flap failure. Despite the reported versatility of the occipital flap, comprehensive anatomical studies on its perforators and perforasomes are lacking. Hence, we examined the perforators originating from the occipital artery and their associated perforasomes, aiming to fill this knowledge gap for reconstructive surgery techniques. METHODS: 39 of 40 occipital arteries of 20 fresh anatomical head specimens were dissected. Perforators with a least an outer diameter of 0.50 mm were identified and injected with dye to color their respective perforasomes. Location and size of the colored skin areas were determined as well as the location of their perforators were documented and analyzed. RESULTS: In total, 183 perforators were found and described. The mean diameter of these vessels was 0.88 ± 0.27 mm (0.5-2.1 mm). The mean area of the perforasomes was 1288.26 ± 662.51 mm2 (144.60-3890.60 mm2). They were localized over the whole nuchal and occipital area. Lastly, perforator diameters were significantly associated with the size of their resulting perforasomes. CONCLUSION: This study is the first comprehensive overview of perforators and associated perforasomes of the occipital artery on a respectable amount of specimen. The arterial supply of big portions of the occipital and nuchal area is provided solely by the perforators of the occipital artery. For flap surgery, perforator diameter is a crucial detail to be considered in the decision-making process.

ARTERIAL DIAMETER VARIATIONS AS A NEW INDEX FOR STROKE VOLUME ASSESSMENT: AN EXPERIMENTAL STUDY ON A CONTROLLED HEMORRHAGIC SHOCK MODEL IN PIGLETS.

ABSTRACT: Background: The assessment of cardiac output (CO) is a major challenge during shock. The criterion standard for CO evaluation is transpulmonary thermodilution, which is an invasive technique. Speckle tracking is an automatized method of analyzing tissue motion using echography. This tool can be used to monitor pulsed arterial diameter variations with low interobserver variability. An experimental model of controlled hemorrhagic shock allows for multiple CO variations. The main aim of this study is to show the correlation between the femoral arterial diameter variations (fADVs) and the stroke volume (SV) measured by thermodilution during hemorrhagic shock management and the resuscitation of anesthetized piglets. The secondary objective is to explore the respective correlations between SV and subaortic time-velocity index, abdominal aorta ADV, carotid ADV, and subclavian ADV. Methods : Piglets were bled until mean arterial pressure reached 40 mm Hg. Controlled hemorrhage was maintained for 30 minutes before randomizing the piglets to three resuscitation groups-the fluid-filling group (reanimated with saline solution only), NEph group (norepinephrine + saline solution), and Eph group (epinephrin + saline solution). Speckle tracking, echocardiographic, and hemodynamic measures were performed at different stages of the protocol. Results : Thirteen piglets were recruited and included for statistical analysis. Of all the piglets, 164 fADV measures were attempted and 160 were successful (98%). The correlation coefficient between fADV and SV was 0.71 (95% confidence interval [CI], 0.62 to 0.78; P < 0.01). The correlation coefficient between SV and abdominal aorta ADV, subclavian ADV, and carotid ADV was 0.30 (95% CI, 0.13 to 0.46; P < 0.01), 0.56 (95% CI, 0.45 to 0.66, P < 0.01), and 0.15 (95% CI, -0.01 to 0.30, P = 0.06), respectively. Conclusions : In this hemorrhagic shock model using piglets, fADV was strongly correlated with SV.

Assessment of haemorrhoidal artery network using Doppler-guided haemorrhoidal artery ligation for haemorrhoids and pathogenesis implications.

BACKGROUND: Some authors, either with anatomical studies or Doppler laser flowmetric investigations have shown the blood flow to the posterior midline of the anus to be potentially deficient. This relative local ischaemia might explain pathogenesis of anal fissure, which is often located posteriorly. The aim of this study was to record the exact position of the distal branches of the superior rectal artery during Doppler-guided haemorrhoidal artery ligation-rectoanal repair (HAL-RAR) procedures with special reference to posterior distribution of the arteries. METHODS: All consecutive patients with symptomatic haemorrhoids who were treated with the HAL-RAR procedure between February 2008 and February 2014 in a single institution were included in the study. Number and position of Doppler-guided ligations were prospectively collected. Pearson's chi-squared test was used to compare artery locations. RESULTS: A total of 150 patients (75 women) with symptomatic haemorrhoids were included in the study. Median age was 53 years (range 23-83). A median of 10 ligations were placed per patient (range 3-18). A significantly lower number of cumulative arterial ligations was recorded in the posterior position (88 ligations overall, P = 0.025). CONCLUSIONS: The number of distal branches of the superior rectal artery that have been localized by the Doppler-guided HAL-RAR technique is lower at the posterior midline than in the other segments of the lower rectum. This is another evidence of the vascular deficiency at the posterior pole of the anal canal that might explain the pathogenesis of the anal fissure.

Assessment of turbulent flow effects on the vessel wall using four-dimensional flow MRI.

PURPOSE: To explore the use of MR-estimated turbulence quantities for the assessment of turbulent flow effects on the vessel wall. METHODS: Numerical velocity data for two patient-derived models was obtained using computational fluid dynamics (CFD) for two physiological flow rates. The four-dimensional (4D) Flow MRI measurements were simulated at three different spatial resolutions and used to investigate the estimation of turbulent wall shear stress (tWSS) using the intravoxel standard deviation (IVSD) of velocity and turbulent kinetic energy (TKE) estimated near the vessel wall. RESULTS: Accurate estimation of tWSS using the IVSD is limited by the spatial resolution achievable with 4D Flow MRI. TKE, estimated near the wall, has a strong linear relationship to the tWSS (mean R2 = 0.84). Near-wall TKE estimates from MR simulations have good agreement to CFD-derived ground truth (mean R2 = 0.90). Maps of near-wall TKE have strong visual correspondence to tWSS. CONCLUSION: Near-wall estimation of TKE permits assessment of relative maps of tWSS, but direct estimation of tWSS is challenging due to limitations in spatial resolution. Assessment of tWSS and near-wall TKE may open new avenues for analysis of different pathologies. Magn Reson Med 77:2310-2319, 2017. © 2016 International Society for Magnetic Resonance in Medicine.

A radiological and pathological assessment of ileocolic pedicle length as a predictor of lymph node retrieval following right hemicolectomy for caecal cancer.

BACKGROUND: In colon cancer, the number of harvested lymph nodes is critical for pathological staging. It has been proposed that the more central the mesenteric vascular ligation, the greater the nodal yield. The aim of the current study was to determine the association of radiological and pathological ileocolic pedicle length on nodal harvest following right hemicolectomy for caecal cancer. METHODS: A series of 50 patients undergoing right hemicolectomy for adenocarcinoma underwent specimen evaluation. Preoperative computed tomography images were reconstructed and analysed to determine the direct (vessel origin to caecum) ileocolic pedicle length. RESULTS: The median pathological distance from the tumour to the high vascular tie was 80 mm, and median nodal yield was 16.5 nodes. Radiological pedicle length did not correlate with the pathological distance from the tumour to the high vascular tie or nodal yield; however, the pathological pedicle length did correlate with the total nodal yield (r (2): 0.343, p = 0.015). The median pathologically determined length of colon resected (r (2): 0.153, p = 0.289), ileum resected (r (2): 0.087, p = 0.568) and total specimen length resected (r (2): 0.182, p = 0.205) did not correlate with the total nodal yield. An ileal specimen length ≤25 mm [hazard ratio (HR) 14.8, 95 % confidence interval (CI) 1.1-194.5, p = 0.040] and a well-differentiated tumour (HR 10.5, 95 % CI 1.1-95.9, p = 0.037) increased the likelihood of retrieving <12 lymph nodes. CONCLUSIONS: Based on these data, pathologic pedicle length is a determining factor in lymph node retrieval. Preoperative radiological calculation of pedicle length does not help predict the number of lymph nodes retrieved.

Radiological Assessment of the Anatomy of Frontal Recess Cells and the Anterior Ethmoidal Artery.

It is necessary for the surgeon to be familiar with frontal recess anatomy during an endoscopic approach to the frontal sinuses. The aim of this study was to evaluate the prevalence of frontal recess cells in Japanese adults as well as the association between the frontal recess and the location of the anterior ethmoidal artery (AEA). The frontal recess cells and the AEAs were retrospectively evaluated in CT scans of the nasal and paranasal sinuses for 89 patients. The prevalence of agger nasi cells was 90.7%. The frequency of frontal cell types 1, 2, 3 and 4 was 28.8, 0.6, 2.6 and 0%, respectively. Suprabullar cells (SBCs) and frontal bullar cells (FBCs) were identified in 78/96 sides (81.3%) and 24/96 sides (24%), respectively. The prevalence of the medial group of frontal recess cells (interfrontal sinus septal cells) was 12.4%. In 42/61 sides (68.9%), the AEAs were located within the posterior margin of the SBCs or the FBCs. Therefore, SBCs, FBCs and the vertical portion of the middle turbinate are reliable landmarks for the identification of AEAs.

Assessment of the Endoscopic Endonasal Transclival Approach for Surgical Clipping of Anterior Pontine Anterior-Inferior Cerebellar Artery Aneurysms.

OBJECTIVE: Aneurysms of the anterior pontine segment of the anterior-inferior cerebellar artery (AICA) are uncommon. Their treatment is challenging because critical neurovascular structures are adjacent to it and the available surgical corridors are narrow and deep. Although endoscopic endonasal approaches are accepted for treating midline skull base lesions, their role in the treatment vascular lesions remains undefined. The present study is aimed to assess the anatomic feasibility of the endoscopic endonasal transclival (EET) approach for treating anterior pontine AICA aneurysms and compare it with the subtemporal anterior transpetrosal (SAT) approach. METHODS: Twelve cadaveric specimens were prepared for surgical simulation. The AICAs were exposed using both EET and SAT approaches. Surgical window area and the length of the exposed artery were measured. The distance from the origin of the artery to the clip applied for proximal control was measured. The number of AICA perforators exposed and the anatomic features of each AICA were recorded. RESULTS: The EET approach provided a wider surgical window area compared with the SAT (P < 0.001). More AICA perforators were visualized using the EET approach (P < 0.05). To obtain proximal control of the AICA, an aneurysm clip could be applied closer to the origin of AICA using EET (0.2 ± 0.42 mm) compared with SAT (6.26 ± 3.4 mm) (P < 0.001). CONCLUSION: Clipping anterior pontine AICA aneurysms using the EET approach is feasible. Compared with SAT, the EET approach provides advantages in surgical window area, ensuring proximal control before aneurysm dissection, visualization of perforating branches, and better proximal control.

Comprehensive multi-modality assessment of regional and global arterial structure and function in adults born preterm.

Preterm birth is associated with higher blood pressure, which could be because preterm birth alters early aortic elastin and collagen development to cause increased arterial stiffness. We measured central and conduit artery size and multiple indices of arterial stiffness to define the extent and severity of macrovascular changes in individuals born preterm. A total of 102 young adults born preterm and 102 controls who were born after an uncomplicated pregnancy underwent cardiovascular magnetic resonance on a Siemens 1.5 T scanner to measure the aortic cross-sectional area in multiple locations. Ultrasound imaging with a Philips CX50 and linear array probe was used to measure carotid and brachial artery diameters. Carotid-femoral pulse wave velocity and the augmentation index were measured by SphygmoCor, brachial-femoral pulse wave velocity by Vicorder and aortic pulse wave velocity by cardiovascular magnetic resonance. The cardio-ankle vascular index (CAVI) was used as a measurement of global stiffness, and ultrasound was used to assess peripheral vessel distensibility. Adults born preterm had 20% smaller thoracic and abdominal aortic lumens (2.19 ± 0.44 vs. 2.69 ± 0.60 cm(2), P<0.001; 1.25 ± 0.36 vs. 1.94 ± 0.45 cm(2), P<0.001, respectively) but similar carotid and brachial diameters to adults born at term. Pulse wave velocity was increased (5.82 ± 0.80 vs. 5.47 ± 0.59 m s(-1), P<0.01, 9.06 ± 1.25 vs. 8.33 ± 1.28 m s(-1), P=0.01, 5.23 ± 1.19 vs. 4.75 ± 0.91 m s(-1), P<0.01) and carotid distensibility was decreased (4.75 ± 1.31 vs. 5.60 ± 1.48 mm Hg(-1)10(3), P<0.001) in this group compared with the group born at term. However, the global and peripheral arterial stiffness measured by CAVI and brachial ultrasound did not differ (5.95 ± 0.72 vs. 5.98 ± 0.60, P=0.80 and 1.07 ± 0.48 vs. 1.19 ± 0.54 mm Hg(-1)10(3), P=0.12, respectively). Adults who are born preterm have significant differences in their aortic structure from adults born at term, but they have relatively small differences in central arterial stiffness that may be partially explained by blood pressure variations.

The Occurrence Rate and Diameter of Arteries Traveling Near the Mandible and an Assessment of the Relative Hemorrhage Risk in Implant Surgery.

BACKGROUND: Bleeding in the floor of the mouth during implant surgery is attributed to arterial injuries in the sublingual space. PURPOSE: This study aimed to assess the relative hemorrhage risk during implant surgery. MATERIALS AND METHODS: We investigated the occurrence rate and diameter of submental and sublingual arteries with special reference to their relationship with the course patterns of these arteries using 26 human cadavers. RESULTS: Three types of arteries were distinguished: main duct (MD), mucoperiosteal branches (MB), and cortical branches (CB). The occurrence rate of MB and CB was significantly high at the central incisor region in the upper part of the mylohyoid muscle, whereas the diameter of the MB and CB was significantly smaller than the occurrence rate of MD at the incisor regions. The occurrence rate of MD in the submental artery was significantly higher at the lateral incisor, canine, and premolar regions in the lower parts, whereas the occurrence rate of MD was significantly lower at the second and third molars in the upper parts. CONCLUSION: The susceptibility of the submental artery to injury is suggested at the incisors, canine, premolars, and first molar regions during implant surgery.

Quantitative assessment of multiscale structural and functional alterations in asthmatic populations.

Relationships between structural and functional variables in asthmatic lungs at local and global (or lobar) levels remain to be discovered. This study aims to investigate local alterations of structural variables [bifurcation angle, circularity, airway wall thickness (WT), and hydraulic diameter (Dh)] in asthmatic subjects, and their correlations with other imaging and pulmonary function test-based global and lobar metrics, including lung shape, air-trapping, regional volume change, and more. Sixty-one healthy subjects, and 67 nonsevere and 67 severe asthmatic subjects were studied. The structural variables were derived from computed tomography images at total lung capacity (TLC). Air-trapping was measured at functional residual capacity, and regional volume change (derived from image registration) was measured between functional residual capacity and TLC. The tracheal diameter and WT predicted by 61 healthy subjects were used to normalize the Dh and WT. New normalization schemes allowed for the dissociation of luminal narrowing and wall thickening effects. In severe asthmatic subjects, the alteration of bifurcation angle was found to be correlated with a global lung shape at TLC, and circularity was significantly decreased in the right main bronchus. While normalized WT increased especially in the upper lobes of severe asthmatic subjects, normalized Dh decreased in the lower lobes. Among local structural variables, normalized Dh was the most representative variable, because it was significantly correlated with alterations of functional variables, including pulmonary function test's data. In conclusion, understanding multiscale phenomena may help to provide guidance in the search for potential imaging-based phenotypes for the development and outcomes assessment of therapeutic intervention.

Assessment of flow distribution in the mouse fetal circulation at late gestation by high-frequency Doppler ultrasound.

This study used high-frequency ultrasound to evaluate the flow distribution in the mouse fetal circulation at late gestation. We studied 12 fetuses (embryonic day 17.5) from 12 pregnant CD1 mice with 40 MHz ultrasound to assess the flow in 11 vessels based on Doppler measurements of blood velocity and M-mode measurements of diameter. Specifically, the intrahepatic umbilical vein (UVIH), ductus venosus (DV), foramen ovale (FO), ascending aorta (AA), main pulmonary artery (MPA), ductus arteriosus (DA), descending thoracic aorta (DTA), common carotid artery (CCA), inferior vena cava (IVC), and right and left superior vena cavae (RSVC, LSVC) were examined, and anatomically confirmed by micro-CT. The mouse fetal circulatory system was found to be similar to that of the humans in terms of the major circuit and three shunts, but characterized by bilateral superior vena cavae and a single umbilical artery. The combined cardiac output (CCO) was 1.22 ± 0.05 ml/min, with the left ventricle (flow in AA) contributing 47.8 ± 2.3% and the right ventricle (flow in MPA) 52.2 ± 2.3%. Relative to the CCO, the flow percentages were 13.6 ± 1.0% for the UVIH, 10.4 ± 1.1% for the DV, 35.6 ± 2.4% for the DA, 41.9 ± 2.6% for the DTA, 3.8 ± 0.3% for the CCA, 29.5 ± 2.2% for the IVC, 12.7 ± 1.0% for the RSVC, and 9.9 ± 0.9% for the LSVC. The calculated flow percentage was 16.6 ± 3.4% for the pulmonary circulation and 31.2 ± 5.3% for the FO. In conclusion, the flow in mouse fetal circulation can be comprehensively evaluated with ultrasound. The baseline data of the flow distribution in normal mouse fetus serve as the reference range for future studies.

Variation in arterial supply to the floor of the mouth and assessment of relative hemorrhage risk in implant surgery.

OBJECTIVES: Bleeding in the floor of the mouth during implant surgery is attributed to arterial injuries in the sublingual space: clinicians may injure the submental and sublingual arteries, which originate from the facial and lingual arteries, respectively. This study aimed to clarify the three-dimensional courses of submental and sublingual arteries and their topographic relation to the mandible. MATERIALS AND METHODS: During the gross anatomy course at the Faculty of Dentistry and Graduate School, Niigata University (2009-2011), we investigated the relationship between the courses of submental and sublingual arteries and their dividing patterns of the mylohyoid muscle, sublingual gland, and mandible using 27 human cadavers. RESULTS: The courses of submental and sublingual arteries were divided into four patterns: (1) the sublingual space was supplied by the sublingual artery (type I: 63%), (2) it was supplied by both the sublingual and submental arteries (type II: 5.6%), (3) it was supplied by the submental artery without the sublingual artery (type III: 29.6%), and (4) type III without the deep lingual artery originated from the lingual artery (type IV: 1.8%). In type II, III, and IV, the submental artery perforates the mylohyoid muscle or takes a roundabout route to travel near the surface of the mandible. The percentage occurrence of arteries traveling between the sublingual gland and mandible in type II, III, and IV (55%) is higher than that in type I (8.8%). CONCLUSION: Susceptibility of the submental artery in type II, III, and IV to injury during implant surgery is suggested.

Assessment of the accuracy of MRI wall shear stress estimation using numerical simulations.

PURPOSE: To investigate the accuracy of wall shear stress (WSS) estimation using MRI. Specifically, to investigate the impact of different parameters and if MRI WSS estimates are monotonically related to actual WSS. MATERIALS AND METHODS: The accuracy of WSS estimation using methods based on phase-contrast (PC) MRI velocity mapping, Fourier velocity encoding (FVE) and intravoxel velocity standard deviation mapping were studied using numerical simulations. The influence of spatial resolution, velocity encoding, wall segmentation, and voxel location were investigated over a range of WSS values. RESULTS: WSS estimates were found to be sensitive to parameter settings in general and spatial resolution in particular. All methods underestimated WSS, except for the FVE-based method, which instead was extremely sensitive to voxel position relative to the wall. Methods using PC-based WSS estimation with wall segmentation showed to be accurate for low WSS, but were sensitive to segmentation errors. CONCLUSION: Even in the absence of noise and for relatively simple velocity profiles, MRI WSS estimates cannot always be assumed to be linearly or even monotonically related to actual WSS. High WSS values cannot be resolved and the estimates depend on parameter setting. Nevertheless, distinguishing areas of low and moderate WSS may be feasible.

Sonographic assessment of arterial frequency and distribution within the brachial plexus: a comparison with the cadaveric record.

We investigated the number and distribution of arteries within the brachial plexus territory using a portable ultrasound device, and compared these findings with known cadaveric data. We recruited 200 volunteers and carried out 400 brachial plexus examinations in a prospective observational study design. We identified arteries within the brachial plexus in more than 90% of subjects. Most of these were located in the upper and middle zones of the plexus and therefore lie within the possible path of a block needle. These findings correlate well with previous cadaveric studies, suggesting that arteries within the brachial plexus territory can be reliably identified with a portable ultrasound device. The presence of these vessels may impact upon the safety and efficacy of brachial plexus blockade. Routine pre-procedural sonographic assessment may offer improved safety and efficacy. You can respond to this article at http://www.anaesthesiacorrespondence.com.

Assessment of the effect of haematocrit-dependent arterial input functions on the accuracy of pharmacokinetic parameters in dynamic contrast-enhanced MRI.

The detection and prognosis of prostate cancer in its early stages are critically important. It is therefore essential to improve the existing dynamic contrast-enhanced MRI (DCE MRI) techniques commonly used for the assessment of the tumour vascular environment. The goal of this study was to describe a method for the estimation of the arterial input function (AIF) in DCE MRI by measuring R(2) * values in the femoral artery of patients with early-stage prostate cancer. The calculation of contrast agent concentrations was based on calibration curves determined in whole blood samples for a range of normal haematocrit (HCT) values (HCT = 0.35-0.525). Individual AIFs corrected for HCT were compared with individual AIFs calibrated with a mean whole blood [R(2)*-Gd-DTPA-BMA] [Gd-DTPA-BMA, gadolinium diethylenetriaminepentaacetate-bis(methylamide) (gadodiamide)] curve at an assumed HCT = 0.44, as well as a population AIF at an assumed HCT = 0.45. The area under the curve of the first-pass bolus ranged between 0.6 min mM at HCT = 0.53 and 1.3 min mM at HCT = 0.39. Significant differences in magnitude at peak contrast agent concentrations (HCT = 0.36, [Gd-DTPA-BMA](max) = 9 ± 0.4 mM; HCT = 0.46, [Gd-DTPA-BMA](max) = 4.0 ± 0.2 mM) were found. Using model-based simulations, the accuracy of the kinetic parameters estimated using individual AIFs corrected for HCT demonstrated that, for the use of individual calibration curves with HCT values differing by more than 10%, K(trans) and k(ep) values were largely underestimated (up to 60% difference for K(trans)). Moreover, blood volume estimates were severely underestimated. Estimates of kinetic parameters in early-stage prostate cancer patients demonstrated that the efflux rate constant (k(ep)) was influenced significantly by the definition of AIF. Regardless of whether an individually calibrated AIF or a population AIF (average of all individually calibrated AIFs) was used, pixel-by-pixel mapping of k(ep) and v(b) in the prostate gland appeared to be more sensitive than with the usual biexponential approach.

Quantitative assessment of the vascularity of the proximal part of the humerus.

BACKGROUND: The current consensus in the literature is that the anterolateral branch of the anterior humeral circumflex artery provides the main blood supply to the humeral head. While the artery is disrupted in association with 80% of proximal humeral fractures, resultant osteonecrosis is infrequent. This inconsistency suggests a greater role for the posterior humeral circumflex artery than has been previously described. We hypothesized that the posterior humeral circumflex artery provides a greater percentage of perfusion to the humeral head than the anterior humeral circumflex artery does. METHODS: In twenty-four fresh-frozen cadaver shoulders (twelve matched pairs), we cannulated the axillary artery proximal to the thoracoacromial branch and ligated the brachial artery in the forearm. In each pair, one shoulder served as a control with intact vasculature and, in the contralateral shoulder, either the anterior humeral circumflex artery or the posterior humeral circumflex artery was ligated. Gadolinium was injected through the cannulated axillary arteries, and magnetic resonance imaging was performed. After imaging, a urethane polymer was injected, and specimens were dissected. For volumetric analysis, the gadolinium uptake on the magnetic resonance imaging was quantified in each quadrant of the humeral head with use of a custom automated program. The gadolinium uptake was compared between the control and ligated sides and between the ligated anterior humeral circumflex artery and ligated posterior humeral circumflex artery groups. RESULTS: The posterior humeral circumflex artery provided 64% of the blood supply to the humeral head overall, whereas the anterior humeral circumflex artery supplied 36%. The posterior humeral circumflex artery also provided significantly more of the blood supply in three of the four quadrants of the humeral head. CONCLUSIONS: The finding that the posterior humeral circumflex artery provides 64% of the blood supply to the humeral head provides a possible explanation for the relatively low rates of osteonecrosis seen in association with displaced fractures of the proximal part of the humerus. In addition, protecting the posterior humeral circumflex artery during the surgical approach and fracture fixation may minimize loss of the blood supply to the humeral head.

Histological assessment of selected blood vessels of the phocid seals (northern elephant and harbour seals).

Phocid seals exhibit vascular adaptations that allow them to undertake prolonged deep dives. These vascular adaptations are either unique to phocids, or are modified vascular equivalents to those present in terrestrial mammals. One such adaptation, the aortic bulb, is a spherical enlargement of the ascending aorta specific to phocid seals. Its histological make-up consists of a reinforced tunica media with circular and longitudinal layers of elastic fibres. This reinforcement enables multi-axial deformation of the aortic bulb, thus complementing its function as a prominent elastic reservoir or 'windkessel'. A second adaptation, the hepatic sinus, is an asymmetrical dilation of the abdominal portion of the caudal vena cava and accompanying hepatic veins. The hepatic sinus is comprised of a relatively thin tunica media, with a scant smooth muscle component. The bulk of the sinus wall is comprised of tunica adventitia. A third vascular adaptation distinctive to the phocids is the pericardial venous plexus, composed of convoluted veins circumnavigating the perimeter of the heart. Microscopically, these veins have a thick tunica media and also contain valves. Smaller arteries, venules and distinct capillary beds are observed interspersed in-between these veins. It can be hypothesized, that in seals, certain vascular embryonic development may be arrested at an earlier embryonic stage, resulting in these unusual vascular formations. These modifications play a vital role in blood pressure regulation and distribution of oxygenated blood during prolonged deep diving. The purpose of this work was to elucidate the histological aspects of these unique vascular modifications and relate them to specific function.

Assessment of the blood supply to the lingual surface of the mandible for reduction of bleeding during implant surgery.

OBJECTIVES: The aim of this study was to assess the frequency of the foramina and their canals on the lingual surface of the mandible using computed tomography (CT), which was carried out for dental implant planning. MATERIAL AND METHODS: First, the visibility of the lingual canals of the CT image was verified by dissecting five cadavers. CT images of 200 patients, who had decided on implant treatment, were used in this study. The visibility of the foramina and their canals on the lingual surface of the mandible were assessed. RESULTS: The foramina were divided into two groups by the positions of the mandible, the medial lingual foramen and the lateral lingual foramen. At least one foramen was found in all patients. In the medial group, a higher level of mental spine was seen in 190 patients, the same level of mental spine was observed in 99 patients and a lower level of mental spine was observed in 114 patients. The lateral lingual foramina were found in 160/200 patients and 88/200 patients presented bilaterally. CT can predict the position and the size of the foramina and their canals on the lingual surface of the mandible. All the patients had more than one foramen in the middle of the lingual surface of the mandible on the CT image. CONCLUSION: The frequency of the lingual foramina in the medial region was 100% and that in the lateral region was 80%. It would also be useful to emphasize the significant variation in the precise location of these lingual foramina, and that these can only be visualized presurgically with volumetric imaging modalities, such as CT or Cone beam 3D systems.