Injection Of Fluorescein Dye Research Articles

Tongue-on-a-Chip: Parallel Recording of Sweet and Bitter Receptor Responses to Sequential Injections of Pure and Mixed Sweeteners.

A microfluidic tongue-on-a-chip platform has been evaluated relative to the known sensory properties of various sweeteners. Analogous metrics of typical sensory features reported by human panels such as sweet taste thresholds, onset, and lingering, as well as bitter off-flavor and blocking interactions were deduced from the taste receptor activation curves and then compared. To this end, a flow cell containing a receptor cell array bearing the sweet and six bitter taste receptors was transiently exposed to pure and mixed sweetener samples. The sample concentration gradient across time was separately characterized by the injection of fluorescein dye. Subsequently, cellular calcium responses to different doses of advantame, aspartame, saccharine, and sucrose were overlaid with the concentration gradient. Parameters describing the response kinetics compared to the gradient were quantified. Advantame at 15 μM recorded a significantly faster sweetness onset of 5 ± 2 s and a longer lingering time of 39 s relative to sucrose at 100 mM with an onset of 13 ± 2 s and a lingering time of 6 s. Saccharine was shown to activate the bitter receptors TAS2R8, TAS2R31, and TAS2R43, confirming its known off-flavor, whereas addition of cyclamate reduced or blocked this saccharine bitter response. The potential of using this tongue-on-a-chip to bridge the gap with in vitro assays and taste panels is discussed.

No dye, no glory: FFA and ICGA in uveitis

Uveitis is a potentially sight‐threatening condition characterized by inflammation of the uvea. Accurate diagnosis of uveitis is crucial for appropriate management and preservation of vision. The diagnosis of uveitis can be challenging due to the overlapping clinical features with other ocular diseases. In this context, imaging techniques such as fluorescein angiography (FA) and indocyanine green angiography (ICGA) have become indispensable tools in the differential diagnosis of uveitis.FA is a widely used imaging modality in the diagnosis and management of uveitis. It involves the intravenous injection of fluorescein dye, which highlights the blood vessels of the retina and choroid. FA can reveal the presence of leakage, staining, and non‐perfusion areas in the retinal and choroidal vasculature, which are indicative of the inflammatory process in uveitis. Moreover, FA can detect complications such as occlusive vasculitis or choroidal neovascularization. FA can also be used to monitor the response to treatment and detect complications of uveitis such as cystoid macular oedema.ICGA is another imaging modality that complements FA in the diagnosis of uveitis. ICGA involves the intravenous injection of indocyanine green dye, which better highlights the choroidal vasculature. ICGA can identify areas of choroidal hypoperfusion, which are often seen in posterior uveitis such as Vogt‐Koyanagi‐Harada disease or Birdshot retinochoroiditis. ICGA can also delineate areas of choroidal neovascularization. Furthermore, ICGA can help differentiate between active and inactive uveitis, which is crucial in determining the appropriate course of treatment.In addition to their diagnostic value, FA and ICGA can provide valuable information on the pathogenesis of uveitis. FA and ICGA can reveal the presence of subclinical inflammation in asymptomatic patients, which can guide the early initiation of treatment and prevent irreversible damage to the retina and choroid. Additionally, FA and ICGA can identify the location and extent of inflammation in uveitis, which can help in the selection of appropriate treatment modalities such as corticosteroids, immunomodulators and biologic agents.In conclusion, FA and ICGA are invaluable tools in the differential diagnosis and management of uveitis. These imaging modalities can provide vital information on the presence, location and extent of inflammation in uveitis, which can guide the selection of appropriate treatment modalities and prevent irreversible visual loss.

Emergency cricothyrotomy during the COVID-19 pandemic: how to suppress aerosolization.

BackgroundCricothyrotomy is associated with significant aerosolization that increases the potential risk of infection among healthcare providers. It is important to identify simple yet effective methods to suppress aerosolization and improve the safety of healthcare providers.Methods5 ear, nose and throat and general surgeons used a locally developed hybrid cricothyrotomy simulator with a porcine trachea to test three draping methods to suppress aerosolization during the procedure: an X-ray cassette drape, dry operating room (OR) towels and wet OR towels. The three methods were judged based on three categories: effectiveness of suppression, availability in all healthcare systems and ease of handling.ResultsAll five surgeons performed the procedure independently using each of the three suppression methods. The wet OR towel drape was found to be an effective method to suppress aerosolization, and it did not hinder the surgeons from performing the procedure accurately. This finding was confirmed by using an atomized fluorescein dye injection into the porcine trachea, representing aerosolized material while performing the procedure.ConclusionsWe present a novel intervention using wet towels to suppress aerosolization during cricothyrotomy. Wet towels are cheap and readily available within any healthcare setting regardless of the financial resources available.

Management of Spontaneous CSF Rhinorrhea: An Institutional Experience.

Introduction Cerebrospinal fluid (CSF) rhinorrhea is the leakage of CSF through nasal cavity, due to abnormal communication between the arachnoid membrane and nasal mucosa. Middle-age (fourth to fifth decade) group, female gender, and obesity (body mass index > 40) are the most commonly reported risk-factors for this rare entity. In this study, we present our single center experience of spontaneous CSF rhinorrhea discussing important clinicoradiological aspects in preoperative evaluation and nuances in the endoscopic repair technique. Material and Methods A retrospective study conducted for 43 spontaneous CSF rhinorrhea patients admitted between Jan 2011 to Jan 2018 at our tertiary care center. All patients underwent endoscopic repair of the defect depending upon their site of leak. Results Mean age in our study was 36.7 ± 12.3 years (range: 9-62 years). Average BMI in males was found lower (28.7) as compared with females (32). Most common site of CSF leak was cribriform plate ( n = 32, 74.4%) and Planum was found to be the least common site ( n = 1, 2.3%) of CSF leak. Intraoperatively, 23 (53.5%) patients showed high-flow leak. Intrathecal injection of fluorescein dye was used to identify the site of CSF leakage in 15 cases (34.8%). The overall success rate of primary endoscopic repair in our study was 95.3%. Conclusion Spontaneous CSF rhinorrhea occurs secondary to elevated intracranial pressure, with a predilection for obese females in fourth to fifth decade. Individualized tailored surgical approach depending upon the site, size, and flow-variety of the defect forms the cornerstone of management.

Fluorescein as a diagnostic marker of bladder ruptures: an experimental study on rabbit model

Abstract Introduction: The aim of this study was to investigate fluorescein use in the diagnosis of bladder ruptures in rabbits as an experimental model. Material and Methods: The study was conducted on male New Zealand rabbits divided into a retrograde fluorescein group (n = 8) and an intravenous (IV) fluorescein group (n = 8). Following general anaesthesia, 10 mL of 10% fluorescein dye (sodium fluoresceine powder) was administered via ureterorenoscope to the bladder of the first group, and 0.5 mL of 10% fluorescein was administered intravenously to the second group. Then, the bladder was viewed through the cystoscope by urethral aspect. After experimental bladder perforation, groups were comparatively evaluated by paracentesis and laparotomy. Results: Following IV injection of fluorescein dye, the bladder veins were stained green within 10 s and then fluorescein mixed with urine flowed into bladder lumen. The green fluid flow was observed in the abdominal cavity after the perforation of the bladder in both groups. Conclusion: Fluorescein can be used as a marker in diagnosis of bladder ruptures. If there is no bleeding or intestinal content in the abdominal cavity, although a smoky yellow-green image is observed, bladder rupture can be suspected.

Injection-depth-locking axial motion guided handheld micro-injector using CP-SSOCT.

This paper presents a handheld micro-injector system using common-path swept source optical coherence tomography (CP-SSOCT) as a distal sensor with highly accurate injection-depth-locking. To achieve real-time, highly precise, and intuitive freehand control, the system used graphics processing unit (GPU) to process the oversampled OCT signal with high throughput and a smart customized motion monitoring control algorithm. A performance evaluation was conducted with 60-insertions and fluorescein dye injection tests to show how accurately the system can guide the needle and lock to the target depth. The evaluation tests show our system can guide the injection needle into the desired depth with 4.12 um average deviation error while injecting 50 nl of fluorescein dye.

A Simple Strategy in Avulsion Flap Injury: Prediction of Flap Viability Using Wood's Lamp Illumination and Resurfacing with a Full-thickness Skin Graft

BackgroundExtensive degloving injuries of the extremities usually result in necrosis of the flap, necessitating comprehensive skin grafting. Provided there is a sufficient tool to evaluate flap viability, full-thickness skin can be used from a nonviable avulsed flap. We used a Wood's lamp to determine the viability of avulsed flaps in the operation field after intravenous injection of fluorescein dye.MethodsWe experienced 13 cases during 16 months. Fifteen minutes after the intravenous injection of fluorescein dye, the avulsed skin flaps were examined and non-fluorescent areas were marked under Wood's lamp illumination. The marked area was defatted for full-thickness skin grafting. The fluorescent areas were sutured directly without tension. The non-fluorescent areas were covered by defatted skin. Several days later, there was soft tissue necrosis within the flap area. We measured necrotic area and revised the flap.ResultsAmong all the cases, necrotic area was 21.3% of the total avulsed area. However, if we exclude three cases, one of a carelessly managed patient and two cases of the flaps were inappropriately applied, good results were obtained, with a necrotic area of only 8.4%. Eight patients needed split-thickness skin grafts, and heel pad reconstruction was performed with free flap.ConclusionsA full-thickness skin graft from an avulsed flap is a good method for addressing aesthetic concerns without producing donor site morbidity. Fluorescein dye is a useful, simple, and cost-effective tool for evaluating flap viability. Avulsed flap injuries can be managed well with Wood's lamp illumination and a full-thickness skin graft.

Loss of N-Cadherin from the Endothelium Causes Stromal Edema and Epithelial Dysgenesis in the Mouse Cornea

We analyzed the role of N-cadherin in maintaining proper architecture and function of corneal endothelium. To achieve specific removal of N-cadherin from corneal endothelium, we bred mice carrying a floxed N-cadherin gene with those expressing the Cre-recombinase gene under the control of P0 promoter. The corneal structure was analyzed by immunostaining for cell junction proteins as well as by electron microscopy. The apoptotic status was assessed by TUNEL staining. The permeability of corneal endothelium was evaluated using fluorescein dye. Removal of endothelial N-cadherin led to the appearance of opacity in the adult corneas. All corneal layers exhibited histological defects: The apical junctional complex (AJC) in corneal endothelium was disorganized, losing the continuity in tight junctions. Collagen fibrils were rearranged in the stroma. The corneal epithelium showed decreased thickness and TUNEL staining revealed increased central areas of apoptosis. Fluorescein dye injection in the anterior chamber confirmed an increased permeability of the endothelial layer. Developmental analysis indicated that, although N-cadherin was lost during embryonic stages, the AJC was maintained normally until early postnatal stages, probably due to the presence of other cadherins at these developmental stages. The junctional defects in endothelial cells, however, became obvious by postnatal day 21 (P21), although stromal and epithelial phenotypes were clearly detectable only in the adult eyes. N-cadherin is essential for maintaining proper structure of corneal endothelial AJCs from late postnatal to adult stages. Its ablation leads to increased endothelial permeability and corneal edema in mature eyes.

Use of Fundus Autofluorescence in the Diagnosis and Management of Uveitis

International Ophthalmology Clinics: Fall 2012 - Volume 52 - Issue 4 - p 45-54 doi: 10.1097/IIO.0b013e3182662ee9

Immediate Break-Down of Blood Retinal Barrier by Infusion of Triolein Emulsion Observed by Fluorescein Angiography

The purpose of this study is to investigate immediate changes in the blood retinal barrier (BRB) after the infusion of triolein emulsion. Triolein emulsion was infused into the carotid artery of 12 cats to induce experimental fat embolism. The injection of fluorescein dye into the carotid artery followed immediately. Early retinal vascular flow was recorded by a fluorescein angiography (FA) video, and then a FA photograph was obtained up to 30 min after the injection. Leakage of the dye in the choroidal or retinal vessels was evaluated. In the early phase, multifocal non-perfuse areas were noted in all cats due to embolism by triolein emulsion, which was released by blood perfusion in the late phase. Perfusion defects persisted in the retina of five cats and in the choroid of four cats. Leakage of the dye through the retinal vessels was seen in five cats (42%) in the early phase and in nine cats (75%) in the late phase. In the choroid, leakage of the dye was seen in seven cats (58%) in the early phase and in all cats (100%) in the late phase. The inner and outer BRB was opened immediately after infusion of triolein emulsion into the carotid artery. Embolism by triolein emulsion was readily resolved due to the liquid nature of triolein.

Intrathecal Preoperative Contrast Enhanced Computed Tomography (CT) and Intraoperative Fluorescein Dye for Cerebrospinal Fluid (CSF) Leaks

Objectives: To describe the utility of intrathecal contrast-enhanced computed tomography and intrathecal fluorescein dye injection for the preoperative localization and intraoperative control of CSF leaks. Study Design: Retrospective case series Methods: Preoperative assessment with intrathecal contrast-enhanced CT was used to predict the likely site of CSF leak. These sites were confirmed by the intraoperative identification of fluoresceincontaining CSF, and the skull base defect was repaired using established techniques. Results: In each patient, the site of CSF leakage corresponded to the region of primary concern on each of the contrast-enhanced CT scans. In one patient, fluorescein permitted the visualization of a small encephalocele protruding through the posterosuperior roof of the sphenoid sinus where an abnormality had been correspondingly identified on contrast-enhanced CT scan. Conclusions: Intrathecal fluorescein dye placement and intrathecal contrast-enhanced CT scans provide complementary information that may be used for the localization and control of CSF leaks.

Use of Intravenous Fluorescein to Localize Gastrointestinal Ischemia

Background: Small bowel and colonic ischemia is a difficult diagnosis to make. Patients who have a delay in the diagnosis have an increased morbidity and mortality. Purpose: To develop a canine model of bowel ischemia. To develop a method for the early diagnosis of small bowel and colonic ischemia, using endoscopy. Methods: A canine model was developed to simulate small bowel and colonic ischemia. The dogs underwent arteriography. The SMA (superior mesenteric artery) and/or IMA (inferior mesenteric artery) were localized. These arteries were injected with coils and gel foam in order to obstruct the circulation to the bowel. Two hours after blocking the arteries an intravenous injection of fluorescein dye (10 mg/Kg) was given to the dogs. Within 10 minutes of the fluorescein injection, the dogs were either endoscoped or sacrificed. Endoscopy was performed with 4 blue LEDs attached to the outside of the endoscope (each with a wavelength of 465 nm-470 nm, forward voltage of 3.5V, Luminous Intensity of 5000 mcd) to evaluate the mucosal surface. Laparotomy was performed after the dogs were sacrificed to evaluate the serosal surface. Results: During endoscopy, areas of perfused mucosa fluoresced green. Areas of nonperfused mucosa did not fluoresce and appeared blue. The abdominal cavity of the sacrificed dog was opened and blue LEDs were used to evaluate the serosal surface, areas of perfused bowel again fluoresced green while areas of nonperfused bowel did not fluoresce and appeared blue. There was a clear demarcation between perfused and nonperfused bowel based on fluorescent imaging on both the mucosal and serosal surfaces. Conclusion: Blue LEDs used endoscopically to evaluate the mucosal surfaces and used laproscopically or at open surgery to evaluate the serosal surfaces can detect areas of nonperfused bowel by the lack of green fluorescence after intravenous injection of fluorescein. Perfused bowel fluoresces green, which is easily detected by video endoscopy or laparoscopy. Nonperused bowel appears blue when exposed to blue LED light. This method can be used both endoscopically and laproscopically to evaluate for ischemic bowel.

In Vivo Imaging of Mammalian Cochlear Blood Flow Using Fluorescence Microendoscopy

We sought to develop techniques for visualizing cochlear blood flow in live mammalian subjects using fluorescence microendoscopy. Inner ear microcirculation appears to be intimately involved in cochlear function. Blood velocity measurements suggest that intense sounds can alter cochlear blood flow. Disruption of cochlear blood flow may be a significant cause of hearing impairment, including sudden sensorineural hearing loss. However, inability to image cochlear blood flow in a nondestructive manner has limited investigation of the role of inner ear microcirculation in hearing function. Present techniques for imaging cochlear microcirculation using intravital light microscopy involve extensive perturbations to cochlear structure, precluding application in human patients. The few previous endoscopy studies of the cochlea have suffered from optical resolution insufficient for visualizing cochlear microvasculature. Fluorescence microendoscopy is an emerging minimally invasive imaging modality that provides micron-scale resolution in tissues inaccessible to light microscopy. In this article, we describe the use of fluorescence microendoscopy in live guinea pigs to image capillary blood flow and movements of individual red blood cells within the basal turn of the cochlea. We anesthetized eight adult guinea pigs and accessed the inner ear through the mastoid bulla. After intravenous injection of fluorescein dye, we made a limited cochleostomy and introduced a compound doublet gradient refractive index endoscope probe 1 mm in diameter into the inner ear. We then imaged cochlear blood flow within individual vessels in an epifluorescence configuration using one-photon fluorescence microendoscopy. We observed single red blood cells passing through individual capillaries in several cochlear structures, including the round window membrane, spiral ligament, osseous spiral lamina, and basilar membrane. Blood flow velocities within inner ear capillaries varied widely, with observed speeds reaching up to approximately 500 microm/s. Fluorescence microendoscopy permits visualization of cochlear microcirculation with micron-scale optical resolution and determination of blood flow velocities through analysis of video sequences.

Interpretation of flow cytometric measurement of lymphocytes after fluorescein angiography.

By use of flow cytometry (FCM), lymphocyte subsets were evaluated with fluorochrome-labeled monoclonal antibodies (MoAbs). Recent fluorescein angiography (FA) produces temporary elevation of serum background fluorescence at certain wavelengths of light, producing falsely decreased lymphocyte subset quantitations. The authors evaluated the duration of this effect on one subset of lymphocytes after FA. CD4 counts were determined by FCM before and 10 minutes, 1, 6, and 24 hours after injection of fluorescein dye in 12 patients. The MoAbs used were directly conjugated to fluorescein isothiocyanate (FITC) or phycoerythrin (PE). Using FITC-labeled MoAbs, falsely decreased CD4 counts occurred in all patients at 10 minutes and in all but one patient 1 hour after injection. Return to baseline levels occurred in 50% (95% confidence interval [CI], 0.21, 0.79) by 6 hours and in 75% (95% CI, 0.43, 0.95] by 24 hours. No such effect was observed using PE-labeled MoAbs. Falsely decreased CD4 values as determined by FCM were present immediately after FA in all 12 patients and persisted 24 hours in some patients when FITC-labeled MoAbs were used. CD4 evaluation should be delayed in patients who have undergone recent FA or the analysis should be performed with PE-labeled MoAbs.

A comparative study of betaxolol and dorzolamide effect on ocular circulation in normal-tension glaucoma patients

ObjectiveTo determine whether dosages of a selective β-blocking agent (betaxolol) and a topical carbonic anhydrase inhibitor (dorzolamide), sufficient to significantly lower intraocular pressure (IOP), have similar or disparate impact on the retinal and retrobulbar circulation. DesignCounterbalanced crossover, with open-label use of medications. ParticipantsNine persons with normal-tension glaucoma (NTG). InterventionAfter a 3-week drug washout, NTG patients were studied after 1 month of treatment with either dorzolamide or betaxolol, with determinations of IOP and retinal and retrobulbar hemodynamics. Main outcome measuresAt baseline and after treatment with each drug, retinal arteriovenous passage time was determined by scanning laser ophthalmoscopy after fluorescein dye injection, and flow velocities in the central retinal and ophthalmic arteries were measured with color Doppler ultrasonography imaging. ResultsBetaxolol and dorzolamide each lowered IOP significantly, with these changes apparent and maximal after 2 weeks (each P < 0.05). In contrast, dorzolamide (but not betaxolol) accelerated arteriovenous passage of fluorescein dye in the inferior temporal quadrant of the retina (P < 0.05). Neither drug affected arteriovenous passage in the superotemporal retina or any aspect of central retinal or ophthalmic artery flow velocity after either 2 or 4 weeks. ConclusionsAlthough both dorzolamide and betaxolol are effective ocular hypotensive agents and their topical instillation leaves retrobulbar hemodynamics unaltered, dorzolamide alone accelerates inferotemporal retinal dye transit.

A multimodal registration algorithm of eye fundus images using vessels detection and Hough transform.

Image registration is a real challenge because physicians handle many images. Temporal registration is necessary in order to follow the various steps of a disease, whereas multimodal registration allows us to improve the identification of some lesions or to compare pieces of information gathered from different sources. This paper presents an algorithm for temporal and/or multimodal registration of retinal images based on point correspondence. As an example, the algorithm has been applied to the registration of fluorescein images (obtained after a fluorescein dye injection) with green images (green filter of a color image). The vascular tree is first detected in each type of images and bifurcation points are labeled with surrounding vessel orientations. An angle-based invariant is then computed in order to give a probability for two points to match. Then a Bayesian Hough transform is used to sort the transformations with their respective likelihoods. A precise affine estimate is finally computed for most likely transformations. The best transformation is chosen for registration.

Combined microlightguide spectrophotometry and microendoscopy for measurement of oxygen saturation in peripheral nerves

Microlightguide measurements of the spectral composition of backscattered light may be used to determine local tissue oxygen saturation and monitor tissue perfusion using intravenous injection of fluorescein dye as a contrast agent. We have used a combination of microlightguide spectrophotometry and microendoscopy to measure intravascular oxygen saturation (%) and monitor blood flow in the sciatic nerve of 12 healthy male Sprague-Dawley rats. The microlightguide and endoscope combination is a relatively new measurement technique. The aims of this study were to determine whether microlightguide spectrophotometry and microendoscopy could be used to measure and blood flow in peripheral nerves and to compare the measurements made using the flexible lightguide with the endoscope-lightguide combination. We found no significant difference between the two types of measurement over similar regions of the nerve, mean % values 77.1% (95% CI = 75.4-78.8) and 78.8% (95% CI = 77.5-80.1) respectively. During a period of hypoxia there was a similar fall in both arterial and nerve oxygen saturation. Following injection of fluorescein, the rate of increase in nerve fluorescence was used as a measure of perfusion. The combination of microlightguide spectrophotometry and microendoscopy allows the exact site of measurement to be directly visualized. The minimally invasive nature of this technique may allow its application to the study of peripheral nerves in human subjects in conditions such as diabetic neuropathy where vascular factors are thought to have an important role in aetiology. Keywords: lightguide, oxygen saturation, spectrophotometry, peripheral nerve

Rash, fever, and chills after intravenous fluorescein angiography

PURPOSE: To report a previously unreported complication associated with intravenous injection of fluorescein dye. METHOD: Case report. A 75-year-old man developed a unique complication after intravenous injection of fluorescein dye for angiography. RESULTS: Two hours after receiving an intravenous injection of fluorescein for angiography, the patient developed a fever, rash, and chills. Admission to a hospital and careful systemic evaluation determined that this reaction was a noninfectious allergic response to intravenous fluorescein dye injection. CONCLUSION: A delayed allergic response to intravenous fluorescein dye injection can occur.

Infarct Size Reduction by Ischemic Preconditioning Is a Monophasic, Short-Lived Phenomenon in Anesthetized Pigs.

BACKGROUND: Controversy exists concerning the duration of infarct size reduction with ischemic preconditioning in different species. In the present study, we (a) evaluated the time course of protection with preconditioning and (b) sought to determine whether late protection (the "second window") after 24 hours is manifest in the open-chest pig model. METHODS AND RESULTS: Six groups of pentobarbital-anesthetized pigs underwent 1 hour of left anterior descending coronary artery occlusion and 2 hours of reperfusion. Group 1 served as control, and pigs in group 2 received two 10-minute episodes of preconditioning ischemia followed by 30 minutes of reperfusion before the sustained 1-hour occlusion. In groups 3-6, the period of intervening reperfusion between the preconditioning stimulus and the index ischemia was extended to 60, 90, and 300 minutes and 24 hours, respectively. The area at risk was determined by fluorescein dye injection, and infarct size was measured by incubation in p-nitrobluetetrazolium and expressed as percent of the risk area. Infarct size in preconditioned pigs (group 2) was significantly reduced compared with controls (25.6 +/- 3.9% v 71.3 +/- 5.9%, P <.001). Extension of the intervening reperfusion to 60, 90, and 300 minutes and 24 hours resulted in infarct sizes of 64.5 +/- 5.5%, 67.2 +/- 8%, 62.6 +/- 6.1%, and 75.3 +/- 7%, respectively (P = NS v control). CONCLUSIONS: The infarct size-limiting effects of ischemic preconditioning last less than 1 hour in the pig model. Moreover, in contrast to other species, a late protection at 24 hours after the preconditioning stimulus was not detected. These results indicate that precondition-induced reduction of infarct size is monophasic in anesthetized pigs.

Perfusion imaging of skin island flap blood flow by a scanning laser-Doppler technique

Conventional laser-Doppler perfusion measurements can only obtain information from a single site. Since superficial blood flow is heterogeneous, this is a serious limitation, particularly in studies of methods to improve skin flap survival. A scanning laser-Doppler instrument has been developed which provides both an image and quantitative information about perfusion of the superficial tissue. We have evaluated this instrument in a circumflex iliac artery island flap model in the pig. The validity of the model was demonstrated by fluorescein dye injection and histology. Elevation of flaps was found to increase proximal flap blood flow but to decrease it in the distal portion. In flaps subjected to arterial ischaemia (9 h) and reperfusion we found an early increase in proximal flow, which gradually extended distally over the first 40 to 60 min. 16 h later, flow had declined, compatible with reperfusion damage to the vasculature. We suggest that perfusion imaging may be a valuable technique for investigating the mechanisms and extent of