Dual Vascular Supply Research Articles

Assessment of Papillary Muscle Infarction with Dark-Blood Delayed Enhancement Cardiac MRI in Canines and Humans.

Background The relationship between papillary muscle infarction (papMI) and the culprit coronary lesion has not been fully investigated. Delayed enhancement cardiac MRI may detect papMI, yet its accuracy is unknown. Flow-independent dark-blood delayed enhancement (FIDDLE) cardiac MRI has been shown to improve the detection of myocardial infarction adjacent to blood pool. Purpose To assess the diagnostic performance of delayed enhancement and FIDDLE cardiac MRI for the detection of papMI, and to investigate the prevalence of papMI and its relationship to the location of the culprit coronary lesion. Materials and Methods A prospective canine study was used to determine the accuracy of conventional delayed enhancement imaging and FIDDLE imaging for detection of papMI, with pathology-based findings as the reference standard. Participants with first-time myocardial infarction with a clear culprit lesion at coronary angiography were prospectively enrolled at a single hospital from 2015 to 2018 and compared against control participants with low Framingham risk scores. In canines, diagnostic accuracy was calculated for delayed enhancement and FIDDLE imaging. Results In canines (n = 27), FIDDLE imaging was more sensitive (100% [23 of 23] vs 57% [13 of 23], P < .001) and accurate (100% [54 of 54] vs 80% [43 of 54], P = .01) than delayed enhancement imaging for detection of papMI. In 43 participants with myocardial infarction (mean age, 56 years ± 16 [SD]; 28 men), the infarct-related artery was the left anterior descending coronary artery (LAD), left circumflex coronary artery (LCX), and right coronary artery in 47% (20 of 43), 26% (11 of 43), and 28% (12 of 43), respectively. The prevalence of anterior papMI was lower than posterior papMI (37% [16 of 43 participants] vs 44% [19 of 43 participants]) despite more LAD culprit lesions. Culprits leading to papMI were restricted to a smaller "at-risk" portion of the coronary tree for anterior papMI (subtended first diagonal branch of the LAD or first marginal branch of the LCX) compared with posterior (subtended posterior descending artery or third obtuse marginal branch of the LCX). Culprits within these at-risk portions were predictive of papMI at a similar rate (anterior, 83% [15 of 18 participants] vs posterior, 86% [18 of 21 participants]). Conclusion Flow-independent dark-blood delayed enhancement cardiac MRI, unlike conventional delayed enhancement cardiac MRI, was highly accurate in the detection of papillary muscle infarction (papMI). Anterior papMI was less prevalent than posterior papMI, most likely due to culprit lesions being restricted to a smaller portion of the coronary tree rather than because of redundant, dual vascular supply. © RSNA, 2022 Online supplemental material is available for this article. See also the editorial by Kawel-Boehm and Bremerich in this issue.

Evaluation of the dual vascular supply patterns in ground-glass nodules with a dynamic volume computed tomography.

BACKGROUNDIn recent years, the detection rate of ground-glass nodules (GGNs) has been improved dramatically due to the popularization of low-dose computed tomography (CT) screening with high-resolution CT technique. This presents challenges for the characterization and management of the GGNs, which depends on a thorough investigation and sufficient diagnostic knowledge of the GGNs. In most diagnostic studies of the GGNs, morphological manifestations are used to differentiate benignancy and malignancy. In contrast, few studies are dedicated to the assessment of the hemodynamics, i.e., perfusion parameters of the GGNs. AIMTo assess the dual vascular supply patterns of GGNs on different histopathology and opacities.METHODSForty-seven GGNs from 47 patients were prospectively included and underwent the dynamic volume CT. Histopathologic diagnoses were obtained within two weeks after the CT examination. Blood flow from the bronchial artery [bronchial flow (BF)] and pulmonary artery [pulmonary flow (PF)] as well as the perfusion index (PI) = [PF/(PF + BF)] were obtained using first-pass dual-input CT perfusion analysis and compared respectively between different histopathology and lesion types (pure or mixed GGNs) and correlated with the attenuation values of the lesions using one-way ANOVA, student’s t test and Pearson correlation analysis.RESULTSOf the 47 GGNs (mean diameter, 8.17 mm; range, 5.3-12.7 mm), 30 (64%) were carcinoma, 6 (13%) were atypical adenomatous hyperplasia and 11 (23%) were organizing pneumonia. All perfusion parameters (BF, PF and PI) demonstrated no significant difference among the three conditions (all P > 0.05). The PFs were higher than the BFs in all the three conditions (all P < 0.001). Of the 30 GGN carcinomas, 14 showed mixed GGNs and 16 pure GGNs with a higher PI in the latter (P < 0.01). Of the 17 benign GGNs, 4 showed mixed GGNs and 13 pure GGNs with no significant difference of the PI between the GGN types (P = 0.21). A negative correlation (r = -0.76, P < 0.001) was demonstrated between the CT attenuation values and the PIs in the 30 GGN carcinomas. CONCLUSIONThe GGNs are perfused dominantly by the PF regardless of its histopathology while the weight of the BF in the GGN carcinomas increases gradually during the progress of its opacification.

Hippocampal vascularization patterns exert local and distant effects on brain structure but not vascular pathology in old age.

The hippocampus within the medial temporal lobe is highly vulnerable to age-related pathology such as vascular disease. We examined hippocampal vascularization patterns by harnessing the ultra-high resolution of 7 Tesla magnetic resonance angiography. Dual-supply hemispheres with a contribution of the anterior choroidal artery to hippocampal blood supply were distinguished from single-supply ones with a sole dependence on the posterior cerebral artery. A recent study indicated that a dual vascular supply is related to preserved cognition and structural hippocampal integrity in old age and vascular disease. Here, we examined the regional specificity of these structural benefits at the level of medial temporal lobe sub-regions and hemispheres. In a cross-sectional study with an older cohort of 17 patients with cerebral small vessel disease (70.7 9.0 years, 35.5% female) and 27 controls (71.1 8.2 years, 44.4% female), we demonstrate that differences in grey matter volumes related to the hippocampal vascularization pattern were specifically observed in the anterior hippocampus and entorhinal cortex. These regions were especially bigger in dual-supply hemispheres, but also seemed to benefit from a contralateral dual supply. We further show that total grey matter volumes were greater in people with at least one dual-supply hemisphere, indicating that the hippocampal vascularization pattern has more far-reaching structural implications beyond the medial temporal lobe. A mediation analysis identified total grey matter as a mediator of differences in global cognition. However, our analyses on multiple neuroimaging markers for cerebral small vessel disease did not reveal any evidence that an augmented hippocampal vascularization conveys resistance nor resilience against vascular pathology. We propose that an augmented hippocampal vascularization might contribute to maintaining structural integrity in the brain and preserving cognition despite age-related degeneration. As such, the binary hippocampal vascularization pattern could have major implications for brain structure and function in ageing and dementia independent of vascular pathology, while presenting a simple framework with potential applicability to the clinical setting.

CT and MR perfusion techniques to assess diffuse liver disease.

Perfusion imaging allows for the quantitative extraction of physiological perfusion parameters of the liver microcirculation at levels far below the spatial the resolution of CT and MR imaging. Because of its peculiar structure and architecture, perfusion imaging is more challenging in the liver than in other organs. Indeed, the liver is a mobile organ and significantly deforms with respiratory motion. Moreover, it has a dual vascular supply and the sinusoidal capillaries are fenestrated in the normal liver. Using extracellular contrast agents, perfusion imaging has shown its ability to discriminate patients with various stages of liver fibrosis. The recent introduction of hepatobiliary contrast agents enables quantification of both the liver perfusion and the hepatocyte transport function using advanced perfusion models. The purpose of this review article is to describe the characteristics of liver perfusion imaging to assess chronic liver disease, with a special focus on CT and MR imaging.

Optimizing Reconstruction with Periorbital Transplantation: Clinical Indications and Anatomic Considerations.

Complex periorbital subunit reconstruction is challenging because the goals of effective reconstruction vary from one individual to another. The purpose of this article is to explore the indications and anatomic feasibility of periorbital transplantation by reviewing our institutional repository of facial injury. Institutional review board approval was obtained at the R Adams Cowley Shock Trauma Center for a retrospective chart review conducted on patients with periorbital defects. Patient history, facial defects, visual acuity, and periorbital function were critically reviewed to identify indications for periorbital or total face (incorporating the periorbital subunit) vascularized composite allotransplantation. Cadaveric allograft harvest was then designed and performed for specific patient defects to determine anatomic feasibility. Disease conditions not captured by our patient population warranting consideration were reviewed. A total of 7 facial or periorbital transplant candidates representing 6 different etiologies were selected as suitable indications for periorbital transplantation. Etiologies included trauma, burn, animal attack, and tumor, whereas proposed transplants included isolated periorbital and total face transplants. Allograft recovery was successfully completed in 4 periorbital subunits and 1 full face. Dual vascular supply was achieved in 5 of 6 periorbital subunits (superficial temporal and facial vessels). Transplantation of isolated periorbital structures or full face transplantation including periorbital structures is technically feasible. The goal of periorbital transplantation is to re-establish protective mechanisms of the eye, to prevent deterioration of visual acuity, and to optimize aesthetic outcomes. Criteria necessary for candidate selection and allograft design are identified by periorbital defect, periorbital function, ophthalmologic evaluation, and defect etiology.

Angiographic Evidence of a Purely Pial Bihemispheric Intracranial Hemangiopericytoma

Background. Classification of hemangiopericytoma (HPC) has evolved to a mesenchymal, nonmeningothelial grade two or three neoplasm according to the World Health Organization; however its blood supply has always been defined by dual origin, pial and dural contribution. Case Description. We present the case of a patient with an intracranial HPC with only pial vascular supply. Angiography confirmed the lack of dural supply to this bihemispheric intracranial mass. Subsequent histologic examination confirmed the diagnosis of hemangiopericytoma. Angiographic evidence here is atypical of the natural history of hemangiopericytomas with dual vascular supply and was critical in the decision-making towards surgical resection without tumor embolization. Conclusion. Data presented suggests the lack of dural vascular supply alone does not rule out the diagnosis of hemangiopericytoma.

Abdominal Pain Following Drug-Eluting Bead Transarterial Chemoembolisation

Acute ischemic cholecystitis following DEB TACE. Drug-eluting bead transarterial chemoembolisation (DEB TACE) is a therapeutic option in the management of hepatocellular carcinoma that reduces vascular supply to the tumour and delivers intra-arterial chemotherapy coated beads directly to the lesion. Unlike, hepatic tissue, the gallbladder does not have a dual vascular supply and thus with selective hepatic artery chemoembolisation there is a risk of inducing gallbladder ischemia and acute cholecystitis. The incidence of this complication is reported to be between 0.3 and 10%.1Wagnetz U. Jaskolka J. Yang P. Jhaveri K.S. Acute ischemic cholecystitis after transarterial chemoembolization of hepatocellular carcinoma: incidence and clinical outcome.J Comput Assist Tomogr. 2010 May-Jun; 34: 348-353Crossref PubMed Scopus (40) Google Scholar It is more common with right lobar chemoembolisation, likely related to inadvertent embolization of the cystic artery, which normally originates from the right hepatic artery. This form of cholecystitis often improves with conservative management although cases requiring urgent cholecystectomy have been reported.2Karaman B. Battal B. Ören N.C. Üstünsöz B. Yağci G. Acute ischemic cholecystitis after transarterial chemoembolization with drug-eluting beads.Clin Imaging. 2012 Nov-Dec; 36: 861-864Abstract Full Text Full Text PDF PubMed Scopus (4) Google Scholar The new findings of gallbladder wall thickening on ultrasound (Figure 1) suggests cholecystitis and the discontinuous enhancement of the gallbladder wall seen on CT (Figure 2) are consistent with regions of gallbladder wall necrosis secondary to DEB TACE induced ischemia. Our patient was managed with five days of intravenous piperacillin and tazobactam (4.5 g three times daily) and then switched to oral antibiotics for one week. At one month follow-up he had made a complete recovery and was asymptomatic.Figure 2CT scan showing discontinuous enhancement of gallbladder wall.View Large Image Figure ViewerDownload (PPT) While a number of differential diagnosis need to be considered in a patient with abdominal pain after transarterial chemoembolization, including post-embolization syndrome and, less commonly, hepatic abscess formation, one must consider cholecystitis especially for right sided hepatic tumors. All authors have none to declare.

Can we justify not doing liver perfusion imaging in 2013?

Liver perfusion imaging is a quantitative functional investigation. Liver perfusion imaging is complicated because of the liver's dual vascular supply, artefacts due to respiratory movements and the fenestrated sinusoidal capillaries which allow the contrast medium to diffuse out. Liver perfusion can be examined by ultrasound, CT or MRI: each technique has its limitations and specific features. The major indications in hepatology are oncology (detection, characterization and tumor response) and non-invasive investigation of patients with chronic liver disease. Work is needed to standardize acquisition and modeling methods to allow wider use of results and more widespread use of the technique.

Perfusion Evaluation of Lung Cancer

The aim of this study was to investigate the feasibility of separately evaluating bronchial (BAP) and pulmonary arterial perfusion (PAP) of lung cancers using dual-input perfusion computed tomography. Twenty-nine lesions from 28 patients [19 men and 9 women; age, 65.8±11.3 y (mean±SD); range, 39 to 85 y] were included in this study (1 patient had 2 tumors). From computed tomography data, quantitative maps of PAP and BAP were created using the dual-input maximum-slope method. Total blood perfusion (TBP) was defined as the sum of PAP and BAP, and the percentage of PAP to TBP was defined as %PAP. Correlation of these values with tumor size, location, and pathologic type was statistically analyzed. PAP ranged from 2.0 to 93.1 mL/min/100 mL (mean±SD, 26.8±26.4), BAP was 0 to 65.4 (25.1±19.12), TBP was 20.7 to 132.0 (52.0±29.0), and %PAP was 4% to 100% (48.8%±31.9%). PAP, TBP, and %PAP correlated negatively with tumor size (P<0.05). PAP and %PAP were higher in the peripheral zone than in the central zone (P<0.05). There was significant correlation between pathologic type and the respective perfusion parameters (P>0.05). We were successful in separating the dual vascular supply to assess dual-input perfusion of lung cancer. We found perfusion of lung cancers to depend on tumor size and location. Acknowledging and assessing the dual vascular supply in lung perfusion may have clinical implications in the management of lung cancer treatment.

Differentiation of malignant and benign pulmonary nodules with first-pass dual-input perfusion CT

To assess diagnostic performance of dual-input CT perfusion for distinguishing malignant from benign solitary pulmonary nodules (SPNs). Fifty-six consecutive subjects with SPNs underwent contrast-enhanced 320-row multidetector dynamic volume CT. The dual-input maximum slope CT perfusion analysis was employed to calculate the pulmonary flow (PF), bronchial flow (BF), and perfusion index [Formula: see text]. Differences in perfusion parameters between malignant and benign tumours were assessed with histopathological diagnosis as the gold standard. Diagnostic value of the perfusion parameters was calculated using the receiver-operating characteristic (ROC) curve analysis. Amongst 56 SPNs, statistically significant differences in all three perfusion parameters were revealed between malignant and benign tumours. The PI demonstrated the biggest difference between malignancy and benignancy: 0.30 ± 0.07 vs. 0.51 ± 0.13 , P < 0.001. The area under the PI ROC curve was 0.92, the largest of the three perfusion parameters, producing a sensitivity of 0.95, specificity of 0.83, positive likelihood ratio (+LR) of 5.59, and negative likelihood ratio (-LR) of 0.06 in identifying malignancy. The PI derived from the dual-input maximum slope CT perfusion analysis is a valuable biomarker for identifying malignancy in SPNs. PI may be potentially useful for lung cancer treatment planning and forecasting the therapeutic effect of radiotherapy treatment. • Modern CT equipment offers assessment of vascular parameters of solitary pulmonary nodules (SPNs) • Dual vascular supply was investigated to differentiate malignant from benign SPNs. • Different dual vascular supply patterns were found in malignant and benign SPNs. • The perfusion index is a useful biomarker for differentiate malignancy from benignancy.

Spontaneously Resolving Lower Polar ATN in a Transplant Kidney With Dual Vascular Supply Demonstrated on 99mTc EC Renography

We report the presence of a differential acute tubular necrosis pattern on renography in a renal transplant recipient who had received a donor kidney with dual renal arterial supply. The proximal accessory renal artery was supplying the lower pole which had been demonstrated on CT angiography. This possibility should be kept in mind while reporting renography with tubular agents like 99mTc EC in transplant patients. Follow-up renography effectively demonstrated spontaneous resolution of the differential retention pattern and acute tubular necrosis. This case reiterates the usefulness of retention of tubular tracers like 99mTc EC for detection of tubular necrosis.

Modern Prospection for Hepatic Arterial Infusion Chemotherapy in Malignancies with Liver Metastases

Malignancy with liver metastasis plays an important role in daily oncology practice, especially for primary cancers of the gastrointestinal tract and hepatopancreatobiliary system. On account of the dual vascular supply system and the fact that most metastatic liver tumors are supplied by the hepatic artery, hepatic artery infusion chemotherapy (HAIC) is an appealing method for the treatment of liver metastases. Herein, we summarize recent study results reported in the literature regarding the use of HAIC for metastatic liver tumors, with special focus on colorectal cancer.

Radiological Anatomy of Prostatic Arteries

One of the most challenging aspects of prostatic arterial embolization for patients with lower urinary tract symptoms and prostate enlargement or benign prostatic hyperplasia is identifying the prostatic arteries (PAs). With preprocedural computed tomography angiography it is possible to plan treatment and exclude patients when arterial anatomy is not suited, or when extensive atherosclerotic changes may affect technical success. There is an excellent correlation between the computed tomography angiography and digital subtraction angiography findings, enabling correct depiction of the male pelvic arterial anatomy (internal iliac branching patterns, relevant variants as accessory pudendal arteries, and PA anatomy). The prostate has a dual vascular arterial supply: a cranial or vesico-PA (named anterior-lateral prostatic pedicle) and a caudal PA (named posterior-lateral prostatic pedicle). These 2 prostatic pedicles may arise from the same artery in patients with only 1 PA (found in 60% of pelvic sides), or may arise independently in patients with 2 independent PAs (found in 40% of pelvic sides). The anterior-lateral prostatic pedicle vascularizes most of the central gland and benign prostatic hyperplasia nodules, frequently arises from the superior vesical artery in patients with 2 independent PAs, and is the preferred artery to embolize. The posterior-lateral prostatic pedicle has an inferior or distal origin, vascularizes most of the peripheral and caudal gland, and may have a close relationship with rectal or anal branches. In up to 60% of cases considerable anastomoses may be seen between the prostatic branches and surrounding arteries that should be taken into account when planning embolization. PAs lack pathognomonic digital subtraction angiography features; thus correct anatomical identification of the male pelvic and PAs is necessary to avoid untargeted ischemia to the bladder, rectum, anus, or corpus cavernosum.

Perforator plus flaps: Optimizing results while preserving function and esthesis

Background:The tenuous blood supply of traditional flaps for wound cover combined with collateral damage by sacrifice of functional muscle, truncal vessels, or nerves has been the bane of reconstructive procedures. The concept of perforator plus flaps employs dual vascular supply to flaps. By safeguarding perforators along with supply from its base, robust flaps can be raised in diverse situations. This is achieved while limiting collateral damage and preserving nerves, vessels, and functioning muscle with better function and aesthesis.Materials and Methods:The perforator plus concept was applied in seven different clinical situations. Functional muscle and fasciocutaneous flaps were employed in five and adipofascial flaps in two cases, primarily involving lower extremity defects and back. Adipofascial perforator plus flaps were employed to provide cover for tibial fracture in one patients and chronic venous ulcer in another.Results:All flaps survived without any loss and provided long-term stable cover, both over soft tissue and bone. Functional preservation was achieved in all cases where muscle flaps were employed with no clinical evidence of loss of power. There was no sensory loss or significant oedema in or distal to the flap in both cases where neurovascular continuity was preserved during flap elevation. Fracture union and consolidation were satisfactory. One patient had minimal graft loss over fascia which required application of stored grafts with subsequent take. No patient required re-operation.Conclusions:Perforator plus concept is holistic and applicable to most flap types in varied situations. It permits the exercise of many locoregional flap options while limiting collateral functional damage. Aesthetic considerations are also addressed while raising adipofascial flaps because of no appreciable donor defects. With quick operating times and low failure risk, these flaps can be a better substitute to traditional flaps and at times even free tissue transfers.

Vertebral body integrity: a review of various anatomical factors involved in the lumbar region

The body of the vertebra can be affected in the majority of the conditions involving the lumbar spine. Multiple references, both books and periodicals, have been reviewed, and the anatomical factors responsible for the vertebral body integrity in the lumbar spine have been included under the following important areas, namely, morphology, development, genetics, microscopic examination using histology, structural architecture, blood supply, neuromuscular control, and biomechanics. The anatomy provides a three-dimensional frame work to support the interaction between the physiological and pathological alterations. The body of the vertebra can be affected in a majority of acute or chronic conditions involving the lumbar spine. The etiology of these conditions is multifactorial, which has been dealt with in previous studies sporadically. This study aims to review and incorporate the important anatomical factors which can influence the integrity of vertebral bodies in the lumbar region and manifest as low back pain. Multiple references, both books and periodicals, have been reviewed for the literature. Electronic databases, including Medline and PubMed, were used to collect the latest information. They were finally arranged in an anatomical framework for the article. An attempt has been made to cover these relevant issues in an integrated way in the article and have been structured into introduction, morphology, development, genetics, microscopic examination using histology, structural architecture, blood supply, neuromuscular control, biomechanics, and conclusion. The aforementioned anatomical aspects, some of which have received less attention in the literature, may be helpful to clinicians for restoring the mobility, stability, and load bearing capacity of the lumbar spine as well as planning better management strategies, especially for the chronic low back pain. In our article all the anatomical factors affecting the integrity of vertebral body, including the morphology, development, genetics, growth and ossification, blood supply, specifically in the lumbar region, have been described, which were not covered earlier. The limitations of this review is its wide dimensions; hence, there are fair scopes of missing many relevant facts, as all of them cannot be compiled in a single article. We have attempted to confine our views to different anatomical domains only, this is our second limitation. Additional studies are required to incorporate and discuss the uncovered relevant scientific details. The integrity of the body of the lumbar vertebra is multifactorial (Fig. 8). The vast spectrum of the anatomical domain influencing it has been summarized. The evolution of erect posture is a landmark in the morphology of human beings and the lumbar lordosis, which has also contributed to the gross design of the vertebral body, is one of the most important adaptations for axial loading and bipedal movements. The role of metamerism in the evolution of vertebrate morphology is repeated in the development of spine. The body of the vertebra is intersegmental in origin, which results in dual vascular and nerve supply, both from superior and inferior aspects of the body of the lumbar vertebrae. The vertebral body ossifies from three primary centers, one for centrum, which will form the major portion of body, and the other two for neural arches. The cartilaginous growth plate is mainly responsible for the longitudinal vertebral growth. Regional differentiation of the vertebral column, and the definite pattern of the structure of the different vertebra, is regulated by a large number of genetic factors, including the Hox genes. The vertebral body design therefore provides the requirements for optimal load transfer by maximal strength with minimal weight. Bone mineral density (BMD), bone quality, microarchitecture, and material properties are the important factors that contribute to bone strength. BMD is highly heritable; bone mineral distribution and architecture are also shown to be under strong genetic influence. All the aforementioned factors finally integrate to ensure mainly the mobility, stability, and load bearing capacity of the lumbar spine.

The Superior EpigastricRECTUS ABDOMINIS Muscle Perforator Flap

The concept of the muscle perforator flap has been proven valid repeatedly, now including the territories of almost all known musculocutaneous flap donor sites. It is well known that the rectus abdominis muscle has a dual vascular supply from 2 dominant source vessels. Yet only the deep inferior epigastric vessels have been used for a relatively long time to supply the well-known DIEP muscle perforator flap. Logically, as previously predicted in this journal, a muscle perforator flap utilizing the cephalic pedicle to the rectus abdominis muscle should also be possible. This prophecy has now become a reality in this first report where a superior epigastric(RECTUS ABDOMINIS) muscle perforator flap was used successfully as a local flap to close a chest defect.

Chemoembolization in the management of liver tumors.

The dual vascular supply of the liver affords a unique opportunity to explore intraarterial therapies for hepatic malignancies. Chemoembolization is a well-established technique combining intra-arterial chemotherapy with delivery of embolic agents in order to achieve an antitumor effect due to a high local concentration and prolonged dwell time of the drug, along with select ischemia. Many tumors, such as hepatocellular carcinoma, colorectal cancer, and neuroendocrine tumors, cause symptoms and death by local growth and destruction of the liver. While there are other methods capable of controlling small or isolated hepatic neoplasms, none are suitable for the majority of these patients. Chemoembolization can produce significant results in terms of tumor shrinkage in many of these patients, and there are studies to suggest a survival advantage in hepatocellular carcinoma. Toxicity, however, may be substantial, and patient selection is crucial in order to achieve the optimal benefit of this powerful technique for individual populations.

Anatomy of the Intervertebral Foramen

The intervertebral foramen serves as the doorway between the spinal canal and periphery. It lies between the pedicles of neighboring vertebrae at all levels in the spine. A number of categorization schemes have been attempted to describe the boundaries of the intervertebral foramen. No uniform agreement has been made on which classification best describes this area. Studies of the nerve root canals have clearly noted variations in the angle of take-off from the thecal sac, length of the nerve root, and placement of the dorsal root ganglion from different lumbar levels. The nerve root canal receives a dual blood supply from central and peripheral sources. The dorsal root ganglion also has a dual vascular supply that aids in preventing damage to this vital foraminal structure. The presence of ligamentous structures within the foramen has been demonstrated by a number of recent studies. These ligaments serve a protective and organizational role for the neurovascular structures of the foramen. A thorough knowledge of the intervertebral foramen will allow the understanding of the pathological and degenerative changes that cause compression or injury to these foraminal structures.

Vascular Supply to the Lumbar Spine: An Intimate Look at the Lumbosacral Nerve Roots

The vascular supply of the lumbar vertebral column is a diverse collection of arteries originating from both central and peripheral sites. Until recently, the majority of these studies have been dedicated to the blood supply of the spinal cord and vertebral bodies. More recent effort has been directed toward the identification of the vascular supply to the lumbar nerve roots. These studies have conclusively documented the presence of a dual blood supply to the nerve roots. In addition, this dual vascular supply has been discovered to have the capability for bi-directional flow. This unique property may allow for prevention of localized, compressive ischemic symptoms secondary to either herniated disc material or osteophytes. The nutrient contributions of the cerebrospinal fluid and venous supply to nerve roots have also been investigated. Early studies indicate that they may play a greater role than suspected. The presence of multiple sources of nutrient supply to the lumbar nerve roots enables them to be resistant to the potential compressive phenomenon that may occur in the lumbar spine.

Breath-hold perfusion and permeability mapping of hepatic malignancies using magnetic resonance imaging and a first-pass leakage profile model.

We have applied a novel pharmacokinetic model of the distribution of contrast media to dynamic contrast-enhanced MRI data from patients with hepatic neoplasms. The model uses data collected during the passage of a bolus of contrast medium and allows breath-hold image acquisition. The aims of the study were to investigate the feasibility of permeability mapping using the first pass technique and breath-hold acquisitions, and to examine the reproducibility of the technique and the effect of the liver's dual vascular supply on the assumptions of the model. Imaging was performed in 14 patients with hepatic neoplasms. Dynamic data clearly demonstrated differences in the timing and shape of the contrast medium concentration-time course curve in the systemic arterial and portal venous systems. Mapping of the arrival time (T(0)) of contrast medium allowed identification of tissue supplied by the hepatic arteries and portal vein. Hepatic tumours all showed typical hepatic arterial enhancement. Repeated measurements of endothelial permeability surface area product (k(fp)) and relative blood volume (rBV), performed in five patients, showed excellent reproducibility with variance ratios (V(r)) of 0.134 and 0.113, respectively. Measurement of enhancing tumour volume was also highly reproducible (V(r) = 0.096) and this was further improved by the use of T(0) maps to identify pixels supplied by the hepatic artery (V(r) = 0.026). Estimates of k(fp) and rBV in normal hepatic tissue supplied by the portal vein were highly inaccurate and these pixels were identified by use of the T(0) parameter and excluded from the analysis. In conclusion, dynamic MRI contrast enhancement combined with a pharmacokinetic model of the distribution of contrast media in the first pass allows us to produce highly reproducible parametric maps of k(fp) and rBV from hepatic tumours that are supplied by the hepatic arterial system using breath-hold acquisitions.