Mean Blood Perfusion Research Articles

Clinical Observation of Subepidermal Vascular Network Flaps in Keloid Patients.

There are many different keloid treatment modalities. One surgical technique is to keep the "shell" of the keloid to cover the defect. We named this "shell" keloid subepidermal vascular network flap (KSVNF), and we outlined the characteristics of this flap by observing 35 flaps in keloid patients. A total of 35 KSVNFs were designed in 15 patients during 2020-2021. All patients underwent the operation and adjuvant radiotherapy as well as hyperbaric oxygen therapy. All flap lengths and widths were recorded, and the blood perfusion of the flaps was measured on the first day postoperation and the day of stitch removal. Flap survival and the quality of flaps were evaluated on the day of stitch removal. All harvested data were analyzed using the R (version 4.0.1) package. The mean blood perfusion on the first day postoperation (pod1) and the day of stitch removal was 120.4013 and 168.6900, respectively (p = 0.02249); 2 flaps had partial necrosis (5.714%). Receiver operating characteristic (ROC) curve analysis showed that when the length/width ratio was less than 1.05, the quality of the flap was good (AUC = 0.724), which suggests that the effective safe length/width ratio was 1.05. KSVNF is an applicable method for covering the remaining wound after keloid mass removal with sufficient blood perfusion and adequate skin quality. We recommend that the length/width ratio of the flap design not exceed 1. This journal requires that authors assign a level of evidence to each submission to which Evidence-Based Medicine rankings are applicable. This excludes Review Articles, Book Reviews, and manuscripts that concern Basic Science, Animal Studies, Cadaver Studies, and Experimental Studies. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Laser speckle contrast analysis is a reliable measure of digital blood perfusion in Black Africans with systemic sclerosis.

Laser speckle contrast analysis (LASCA) is evolving as a promising non-invasive tool to assess cutaneous microvascular function in systemic sclerosis (SSc). Reliability studies have mainly focused on Caucasian populations. To determine for the first time the inter-rater reliability of fingertip blood perfusion (BP) using LASCA in Black South African patients with SSc. Consecutive Black adult patients with SSc were evaluated for peripheral BP using LASCA. Mean BP in defined regions of interest for dorsal fingertips and volar fingertips were measured in two subgroups of 20 SSc patients, each by three independent operators. Two operators were experienced in the use of the LASCA instrument and one was newly trained. Standardised protocols for conditions were followed for all measurements. Inter-rater reliability was tested using the intraclass correlation coefficient (ICC). The majority (87.5%) of the 40 patients included were females and 67.5% had diffuse cutaneous SSc. The mean age (standard deviation) was 48.5 (9.9) years and the median disease duration (interquartile range) was 8.5 (4, 13) years. There was good to excellent agreement, inter-rater ICC (dorsal fingertip range: 0.86-0.97 and volar fingertip range: 0.85-0.96), in both subgroups irrespective of operator skill. LASCA is a credible instrument in patients of Black ethnicity with SSc, and across operator experience.

On the suitability of laser-Doppler flowmetry for capturing microvascular blood flow dynamics from darkly pigmented skin

Objective: To assess the performance of laser Doppler flowmetry (LDF) in measuring blood perfusion from darkly-pigmented skin, i.e. skin with high melanin concentration. LDF provides for the noninvasive monitoring of microvascular blood flow dynamics. It has been used extensively on light-skinned subjects, i.e. on skin with low melanin concentration, in both the healthy and pathological states. Because the optical properties of human skin might affect the reliability of optically-based diagnostic equipment, the effectiveness of LDF needs to be checked and evaluated on dark skin, too, if this method is to be useful in global healthcare. Approach: Thirteen dark-skinned subjects and ten light-skinned subjects were included in the study. Microvascular blood flow dynamics was measured on both the right and left ankles using LDF with a laser diode of wavelength 780 nm. The characteristics of time-varying blood flow oscillations were investigated by wavelet analysis, nonlinear mode decomposition and wavelet phase coherence. An electrocardiogram (ECG), skin temperature, and respiratory effort were measured simultaneously with the LDF for each subject. Main results: No significant differences were observed between the groups in the mean blood perfusion (p > 0.1), or wavelet power (p > 0.6). The instantaneous heart rate (IHR), extracted from the LDF at each of the recording sites, and from the ECG, did not differ significantly between the groups (p > 0.8). Nor did the wavelet power of the IHR differ (p > 0.8) between the groups. The only significant difference found between the groups lay in left/right ankle blood flow coherence near the cardiac frequency, attributable to known ethnic physiological differences. Significance: These results indicate that high melanin concentrations in skin exert no significant influence on the ability of LDF to monitor microvascular blood flow dynamics when using a laser diode of wavelength 780 nm. Hence LDF can help in the diagnosis and exploration of the pathogenesis of diseases such as diabetes, hypertension, or malaria in darkly pigmented patients across sub-Saharan Africa.

Supportive Use of Adipose-Derived Stem Cells in Cell-Assisted Lipotransfer for Localized Scleroderma

The authors aimed to analyze factors related to lipotransfer for localized scleroderma, and to explore the feasibility of cell-assisted lipotransfer for localized scleroderma treatment. Abdominal fat samples were taken from six scleroderma patients without corticosteroid therapy, five scleroderma patients with corticosteroid therapy, and 10 normal liposuction patients. Their quantity, morphology, and proliferation ability were measured. Blood flow was measured by laser speckle contrast imaging in localized scleroderma lesions and normal contralateral regions for eight localized scleroderma patients. Bleomycin-induced skin fibrosis nude mice were also used to investigate differences between lipotransfer and cell-assisted lipotransfer. Fat weight was measured, and expression of transforming growth factor (TGF)-β1 and type III collagen in the injected skin was determined by immunohistochemistry. The number of stem cells from scleroderma patients with corticosteroid treatment was significantly reduced. Mean blood perfusion in localized scleroderma lesions was not significantly different than in the contralateral normal regions. In normal nude mice, there were no significant changes in TGF-β1 and type III collagen between the control, lipotransfer, and cell-assisted lipotransfer groups, whereas in bleomycin-induced skin fibrosis nude mice, lipotransfer and cell-assisted lipotransfer reduced TGF-β1 and type III collagen expression. For scleroderma patients, fewer adipose-derived stem cells, because of a history of corticosteroid therapy and a local inflammatory microenvironment, are more important factors, whereas blood supply showed no significant change. Therefore, cell-assisted lipotransfer not only improves the survival rate of transplanted fat but also improves skin texture in bleomycin-induced skin fibrosis nude mice.

The effect of calf neuromuscular electrical stimulation and intermittent pneumatic compression on thigh microcirculation

ObjectiveThis study compares the effectiveness of a neuromuscular electrical stimulation (NMES) device and an intermittent pneumatic compression (IPC) device on enhancing microcirculatory blood flow in the thigh of healthy individuals, when stimulation is carried out peripherally at the calf. Materials and methodsBlood microcirculation of ten healthy individuals was recorded using laser speckle contrast imaging (LSCI) technique. A region of interest (ROI) was marked on each participant thigh. The mean flux within the ROI was calculated at four states: rest, NMES device with visible muscle actuation (VMA), NMES device with no visible muscle actuation (NVMA) and IPC device. ResultsBoth NMES and IPC devices increased blood flow in the thigh when stimulation was carried out peripherally at the calf. The NMES device increased mean blood perfusion from baseline by 399.8% at the VMA state and 150.6% at the NVMA state, IPC device increased the mean blood perfusion by 117.3% from baseline. ConclusionThe NMES device at VMA state increased microcirculation by more than a factor of 3 in contrast to the IPC device. Even at the NVMA state, the NMES device increased blood flow by 23% more than the IPC device. Given the association between increased microcirculation and reduced oedema, NMES may be a more effective modality than IPC at reducing oedema, therefore further research is needed to explore this.

Abstract 12626: Co-Injection of Induced Pluripotent Stem Cell-Derived Endothelial Cells With Shear Thinning Hydrogel Enhances Survival and Angiogenesis in a Murine Model of Peripheral Arterial Disease

Introduction: Human induced pluripotent stem cell-derived endothelial cells (iPSC-ECs) are a promising cell source for enhancing blood perfusion for treatment of peripheral arterial disease (PAD). However, poor cell survival is a critical bottleneck to the efficacy of stem cell therapy. Hypothesis: We hypothesize that encapsulation of cells within an injectable shear-thinning hydrogel with controllable properties will prolong cell survival under ischemic conditions and maintain cellular phenotype, in comparison to cell injection in saline. Methods: The protein hydrogel is comprised of two complementary engineered proteins that self-assemble upon simple mixing. The hydrogel network incorporates a polyethylene glycol physical crosslinker that modulates hydrogel stiffness and degradation. Bioluminescent iPSC-ECs were encapsulated within the hydrogel with controllable stiffness ( G’ ~10-800 Pa) under conditions of hypoxia (1% O 2 ). The cells within hydrogel were then subjected to an in vitro model of injection and assayed for cell survival, proliferation, and endothelial phenotype for up to 14 days. To verify these results in an experimental model of PAD, 10 6 cells were injected in saline or in 400 Pa hydrogel into the ischemic limb of SCID mice for assessment of cell viability and blood flow recovery. Results: Acutely after injection in vitro , cell survival in saline was 65%, in comparison to 94% in hydrogels with stiffnesses of 10-800 Pa. Bioluminescence imaging demonstrated the highest cell proliferation in the hydrogel with 400 Pa stiffness after 14 days. In the 400 Pa hydrogel, iPSC-ECs maintained elongated morphology with robust expression of endothelial phenotypic marker, CD31. In the ischemic hindlimb, iPSC-EC retention was markedly increased when encapsulated in the 400 Pa hydrogel, compared to saline delivery. Concomitantly, mean blood perfusion recovery in the ischemic limb after 14 days was 0.68 when treated with cells in hydrogel, in contrast to 0.61 when cells were injected in saline. Conclusions: These findings demonstrate that stem cell encapsulation within the 400 Pa protein hydrogel improves cell viability and blood perfusion, which may have therapeutic benefit for treatment of PAD.

Laser speckle contrast imaging identifies ischemic areas on gastric tube reconstructions following esophagectomy.

Gastric tube reconstruction (GTR) is a high-risk surgical procedure with substantial perioperative morbidity. Compromised arterial blood supply and venous congestion are believed to be the main etiologic factors associated with early and late anastomotic complications. Identifying low blood perfusion areas may provide information on the risks of future anastomotic leakage and could be essential for improving surgical techniques. The aim of this study was to generate a method for gastric microvascular perfusion analysis using laser speckle contrast imaging (LSCI) and to test the hypothesis that LSCI is able to identify ischemic regions on GTRs.Patients requiring elective laparoscopy-assisted GTR participated in this single-center observational investigation. A method for intraoperative evaluation of blood perfusion and postoperative analysis was generated and validated for reproducibility. Laser speckle measurements were performed at 3 different time pointes, baseline (devascularized) stomach (T0), after GTR (T1), and GTR at 20° reverse Trendelenburg (T2).Blood perfusion analysis inter-rater reliability was high, with intraclass correlation coefficients for each time point approximating 1 (P < 0.0001). Baseline (T0) and GTR (T1) mean blood perfusion profiles were highest at the base of the stomach and then progressively declined towards significant ischemia at the most cranial point or anastomotic tip (P < 0.01). After GTR, a statistically significant improvement in mean blood perfusion was observed in the cranial gastric regions of interest (P < 0.05). A generalized significant decrease in mean blood perfusion was observed across all GTR regions of interest during 20° reverse Trendelenburg (P < 0.05).It was feasible to implement LSCI intraoperatively to produce blood perfusion assessments on intact and reconstructed whole stomachs. The analytical design presented in this study resulted in good reproducibility of gastric perfusion measurements between different investigators. LSCI provides spatial and temporal information on the location of adequate tissue perfusion and may thus be an important aid in optimizing surgical and anesthesiological procedures for strategically selecting anastomotic site in patients undergoing esophagectomy with GTR.

Evaluation of Peripheral Vascular Impairment in the Fingers of Baseball Players

PURPOSE: Digital vessel trauma from repetitive impact on the fingers and hand is a concern for baseball players (BPs). Laser-Doppler blood perfusion imaging (LDPI) is a technique that employs two-dimensional horizontal scanning of the blood flow in a specific tissue, without the necessity for surface contact. The LDPI method may have the benefit of detecting vasospastic abnormalities and occlusion of the digital arteries, which generally appears as an inhomogeneous reaction to the cold. This study used LDPI to investigate whether the changes in finger skin blood flow that occurred in response to a cold water immersion test depended on the position of BPs. METHODS: The study included 57 male university BPs, aged 20 ± 1 years, who play at 3 different positions. From this study subject group, there were: 18 pitchers, 23 infielders (InF), and 16 outfielders (OtF). A cold provocation test was carried out by immersing a subject’s catching hand into cold water (10°C) for 10 min. Repeated image scanning of skin blood flow on the palm was performed every 2 min before, during, and after cold water immersion, by using LDPI. The mean blood perfusion values in the index finger area were calculated on each color-coded image. A numerical perfusion reading was also obtained for each measurement site in terms of the voltage (V). From the perfusion reading and the mean blood pressure, we calculated the cutaneous vascular conductance (CVC). The finger skin temperature was recorded by using an electrode thermistor attached to the skin on the dorsal side of the index finger. RESULTS: CVC values of the InF were significantly lower compared with those of the OtF at pre-immersion (2.4 ± 0.6 V/mmHg vs. 3.3 ± 1.0 V/mmHg, p < 0.01) and at early post-immersion (1.2 ± 0.4 V/mmHg vs. 1.5 ± 0.5 V/mmHg, p < 0.05). However, the index finger skin temperature did not significantly differ among the different player positions at any measurement point. CONCLUSIONS: These findings suggest that the changes in finger skin blood flow that occurred in response to cold water immersion, as measured by using LDPI, were dependent on the position of the BP. Repetitive trauma caused by the impact of a baseball also leads to peripheral vascular impairment in the index finger on the gloved hand of InF. Therefore, this method can be used for the assessment of peripheral circulatory function in BPs.

Use of laser speckle contrast imaging to reveal changes in temperature and blood perfusion in the skin of healthy subjects after administration of heated moxa sticks and Daiwenjiu ointment

ObjectiveTo investigate the influence of heated moxa sticks (“moxibustion”) and Daiwenjiu ointment (DO) on changes in temperature and blood perfusion volume on the skin of the backs of healthy subjects. MethodsDO was spread on the left side of the body, and the right side of the body was treated with a heated moxa stick. Images denoting blood perfusion and body temperature were collected 7-8 cm lateral to the spinous process of the sixth thoracic vertebra using laser speckle contrast imaging (LSCI). Data obtained from eight-frame images were analyzed and used to calculate the mean blood perfusion volume. Simultaneously, blood-perfusion images were collected from the body surface and used to compare the change in blood flow on the body surface and the actual position of imaging. ResultsAfter moxibustion, a rapid increase in blood perfusion volume and body temperature was noted in the local skin surface. The maximum blood perfusion volume and body temperature was noted at 20 min (P<0.05). At 80-110 min after the spreading of DO, a gradual increase was noted in blood perfusion volume (P<0.05) and body temperature (P<0.05) compared with the baseline level. The maximum blood perfusion volume was at 110 min. ConclusionsUsing LSCI, these data revealed a rapid and sharp increase in blood perfusion volume and body temperature after treatment with moxibustion, but the respective changes seen in the DO group were gradual and moderate.

Comparison of Acupuncture Effect on Blood Perfusion between Needling Nonacupoint on Meridian and Needling Nonacupoint off Meridian

To verify the ancient theory of rather missing the acupoint than missing the meridian, acupuncture at nonacupoint on meridian and acupuncture at nonacupoint off meridian were performed, respectively. The blood perfusion (BP) on the calf around bladder meridian area was measured with a laser Doppler perfusion imager before, during, and after acupuncture. The whole scanning field was divided into seven subareas, and mean BP on each area was calculated. The ratio of mean BP between a subarea and a reference subarea was gotten, and then the change rate was calculated as ratio change rate (RCR). The results showed that RCR on bladder meridian area and around Chengshan (BL57) during or after acupuncture at nonacupoint on meridian was significantly higher than that at nonacupoint off meridian, which supports the ancient theory. Such differences may be attributable to some factors that can facilitate the signals transmission and produce a better acupuncture effect, such as richer nerve terminals, blood vessels, and mast cells which can produce stronger signals on the acupoints and the low hydraulic resistance channel along meridians which plays a role of signal transmitting channel to get a better effect of acupuncture.

Contributions of dorsal root reflex and axonal reflex to formalin-induced inflammation

The dorsal root reflex (DRR) and the axonal reflex (AR) are antidromic activities in primary afferents and are involved in neurogenic inflammation. DRRs and/or ARs lead to release of neuropeptides calcitonin gene-related peptide (CGRP) and substance P (SP). CGRP causes blood vessels to dilate leading to an increase in blood perfusion, whereas SP causes plasma extravasation, leading to edema. Both DRR and AR can be evoked by noxious stimuli. The goal of this study was to determine the role of DRR and AR in neurogenic inflammation by examining the blood perfusion (BP) change in hindpaws in response to formalin injection (an acute inflammatory agent). Laser Doppler images were collected simultaneously in both hindpaws in anesthetized rats to determine the level of BP. Local lidocaine was applied to the left sciatic nerve to block both orthodromic signals and antidromic DRRs without affecting ARs. All rats then received a subcutaneous formalin injection to the left hindpaw. Our results showed that (1) the mean BP of the left paw increased significantly following formalin injection, with or without lidocaine; (2) application of lidocaine in the left sciatic nerve alone significantly increased BP ipsilaterally; (3) formalin injection following lidocaine application significantly increased BP more than the group without lidocaine; and (4) there was delayed significant BP increase in the right (contralateral) hindpaw following formalin injection with or without lidocaine. It is concluded that ARs play a more important role than DRRs in formalin-induced neurogenic inflammation.

Response to: Comparison of laser Doppler imaging, fingertip lacticemy test, and nailfold capillaroscopy for assessment of digital microcirculation in systemic sclerosis

We read with interest the article by Correa and colleagues [1] in a recent issue of Arthritis Research & Therapy: 'Comparison of laser Doppler imaging, fingertip lacticemy test, and nailfold capillaroscopy for assessment of digital microcirculation in systemic sclerosis'. Using the laser Doppler imaging (LDI) technique, the authors found lower digital blood flow in systemic sclerosis (SSc) patients when compared with healthy controls. However, the authors did not discover any correlation between the functional (LDI) and morphological microvascular abnormalities, evaluated by nailfold capillaroscopy (NFC), suggesting that these techniques are complementary tools for the evaluation of independent microangiopathy aspects in SSc patients. The conclusions of the article may be controversial since these findings are in contrast with those of other recent reports that were not reported and considered in the authors' investigation. In particular, some recent studies described a correlation between fingertip blood perfusion (FBP), evaluated separately by LDI and laser Doppler flowmetry (LDF) techniques, and the extent of nailfold microvascular damage, as evaluated by nailfold videocapillaroscopy (NVC) [2-4]. The paper from Cutolo and colleagues [2] demonstrated a significantly lower FBP in SSc patients (P < 0.05) com-pared with controls, and this FBP was found to be partially reversible (increasing) after heating of the LDF probe at 36°C (P < 0.001), even if the slope of variation was significantly lower in SSc patients compared with controls (P < 0.05). Interestingly, SSc patients showing the 'late' NVC pattern of microangiopathy showed an FBP that was significantly lower than that of patients with the 'active' or 'early' NVC patterns (P < 0.05) [2,5]. In addition, a negative correlation between the FBP degree and the NVC rating (score) of the microvascular damage was observed (P < 0.05) [2,6,7]. Similar results were found by Rosato and colleagues [3], who described significantly lower mean blood perfusion in the hand/fingers of SSc patients characterized by the 'late' NVC pattern of microangiopathy when compared with patients showing the 'early' or 'active' NVC patterns. The authors concluded that the LDI and capillaroscopic images fully matched the definition of the various stages of the microvascular digital damage in SSc [3]. In the third study, again, SSc patients characterized by the 'active' or 'late' NVC patterns showed a red blood cell velocity that was more decreased (65.5% and 66.2% reduction, respectively) than that of patients sharing the 'early' pattern of microangiopathy [4]. This reduced red blood cell velocity was significantly associated with selected NVC morphological parameters, including capillary ramification and capillary loss that characterize the advanced microvascular damage (P < 0.01) [4]. In recent years, the morphological features identifying the SSc microvascular damage progression have been recognized. Consequently, microvascular lesions detected by NVC in patients with SSc have been classified according to the three different NVC patterns mentioned above (namely, 'early', 'active', and 'late'), which are clearly distinguishable from the 'normal' nailfold capillaroscopic pattern [5,8]. The 'early' pattern is characterized by the presence of a small number of giant capillaries and capillary micro-hemorrhages, no evident loss of capillaries, and relatively well-preserved capillary distribution. If the vascular disease progresses, an 'active' SSc pattern becomes evident: giant capillaries and capillary microhemorrhages increase and there is moderate loss of capillary, whereas ramified capillaries are absent or mildly branched and the capillary architecture is mildly disorganized. Finally, the 'late' SSc pattern becomes manifest in the more advanced stage of the vascular disease. This latter pattern is characterized by the absence of giant capillaries and microhemorrhages but shares severe loss of capillaries and the development of extensive avascular areas, together with ramified and bushy capillaries (indicative of neoangiogenesis) [5,8]. As a matter of fact, the different nailfold microvascular abnormalities are not all present at the same time but are expressed in a dynamic manner during the progression of the SSc microangiopathy [9]. For these reasons, when searching in SSc patients for a possible link between digital blood flow and nailfold capillary abnormalities without considering the dynamic evolution of these morphological markers, a lack of correlation may be expected. Obviously, further studies are needed to better understand whether the morphological nailfold capillary abnormalities are the cause or the effect (or both) of digital blood hypoperfusion in patients with SSc.

Comparison of the Usefulness of Brain Perfusion SPECT and MIBG Myocardial Scintigraphy for the Diagnosis of Dementia with Lewy Bodies

Background: Supportive features in the diagnostic criteria for dementia with Lewy bodies (DLB) include occipital hypoperfusion and decreased cardiac uptake of ¹²³I-metaiodobenzylguanidine (MIBG). In this study, we performed both brain perfusion single photon emission computed tomography (SPECT) and MIBG myocardial scintigraphy in the same subjects and evaluated their sensitivity to detect the characteristic features of DLB. Methods: Twenty-five patients with probable DLB (76.8 ± 5.1 years old, 10 male) underwent ^99mTc-ethylcysteinate dimer brain perfusion SPECT and ¹²³I-MIBG myocardial scintigraphy. The results of SPECT were analyzed using a qualitative analysis program, easy Z score imaging system (eZIS), and an automated quantitative analysis program, 3DSRT. Results: Qualitative analysis using eZIS demonstrated occipital hypoperfusion in 17 subjects (68%). The quantified mean blood perfusion in the occipital segment on the 3DSRT template was 40.7 ± 5.03 ml/100 g/min (right) and 40.5 ± 5.38 ml/100 g/min (left), and in 19 DLB patients these values were below the normal limit. Twenty-four of 25 subjects (96%) had decreased cardiac MIBG uptake in the delayed image. Conclusion: MIBG myocardial scintigraphy was superior to brain perfusion SPECT in detecting a characteristic feature of DLB. Our results suggest that combining SPECT and MIBG scintigraphy could increase the accuracy of clinical diagnosis of DLB.

Laser Doppler Imaging of Skin Blood Flow for Assessing Peripheral Vascular Impairment in Hand-Arm Vibration Syndrome

The objective of this study was to evaluate the usefulness of laser Doppler imaging (LDPI) of the skin blood flow for assessing peripheral vascular impairment in the hand-arm vibration syndrome (HAVS). The subjects were 46 male patients with HAVS, aged 50 to 69 yr, and 31 healthy male volunteers of similar age as controls. A cold provocation test was carried out by immersing a subject's hand on his more severely affected side into cold water at a temperature of 10 degrees C for 10 min. Repeated image scanning of skin blood flow of the index, middle, and ring fingers was performed every 2 min before, during, and after the cold water immersion using a PMI-II laser Doppler perfusion imager. The mean blood perfusion values in the distal phalanx area of the fingers were calculated on each image. The patients suffering from vibration-induced white finger (VWF, n=20) demonstrated significantly lower skin blood perfusion at each interval of the test as compared with those without VWF (n=26) and the controls (p<0.01, ANOVA). The blood perfusions in the HAVS patients were associated with the severity of the symptoms as classified by the Stockholm Workshop scale for vascular staging. When a subject was considered to be positive if any of the tested fingers showing a decreased blood perfusion and/or a delayed recovery pattern, the sensitivity was 80.0%, and the specificity was 84.6% and 93.5% for patients without VWF and the controls, respectively. These results suggest that the LDPI technique could provide detailed and accurate information that may help detect the existence of impaired vascular regulation to cold exposure in the fingers of workers exposed to hand-transmitted vibration.

Blood flow in proximal femur of the dog determined by the local 133Xe injection method.

A new approach for measuring blood flow in bone is presented. It consists of the local injection of 133Xe into the proximal femur of adult beagles and the external measurement of isotope washout curves. The curves were analyzed using a two-compartment exponential model. The half-times for the tracer washout from the fast and slow compartment were 3.34 +/- 0.48 min and 33.6 +/- 11.7 min (mean +/- 1 S.D.) respectively. Blood flow was calculated using a measured blood to bone partition coefficient of 1.55 ml/g. The mean blood perfusion in proximal femur of the dog was 10.8 +/- 4.3 ml/100 g/min (mean +/- 1 S.D.). This value agrees well with most estimates of bone circulation. Due to rapid disappearance of 133Xe the method is easy to repeat and is thus suitable for physiological studies of local blood flow in bones.