***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: BACKGROUND The most severe diabetic foot ulcers are those related with critical ischemia , which is primarily diagnosed with non-invasive diagnostics . However , these diagnostics have several disadvantages . For example , they only provide global indications of the (macro)level of ischemia . A potential solution can be found in novel optical imaging techniques for local assessment of the microcirculation in diabetic foot ulcers . This review provides an overview of these imaging techniques ( Laser Doppler Perfusion Imaging , Laser Speckle Contrast Imaging , Photoacoustic Imaging and Hyperspectral Imaging ) and their applicability for the diagnostic assessment of microcirculation in diabetic foot ulcers . METHOD For each technique , the following parts are described : a ) their technical background ; b ) general clinical applications ; and , c ) its application for microcirculation assessment in diabetic foot ulcers . Parts a-b are based on a narrative review of the literature , part c on a systematic review that was performed in the data base Scopus , covering the period from January 1 , 2000 to November 31 , 2017 . RESULTS Each of these techniques has specific advantages and disadvantages for imaging microcirculation . Potential clinical use depends on measurement aims , and clinical relevance . However , none of the techniques has a strongly established clinical relevance yet : we found a limited number of publications describing clinical outcomes . Future research is needed to determine which technique is the most clinical ly relevant for the assessment of microcirculation in diabetic foot ulcers . CONCLUSION Although promising , the currently available novel optical techniques need to be further improved technically and prospect i ve trials are necessary to evaluate their clinical value AIMS Diagnosis of vascular involvement in diabetic foot ulceration ( DFU ) remains challenging . We conducted a proof of concept study to investigate the feasibility of microwave radiometry ( MWR ) thermometry for non-invasive differential diagnosis of critical limb ischemia ( CLI ) in subjects with DFU . METHODS This prospect i ve , multi-center , study included 80 participants , divided into four groups ( group N : normal control subjects ; group DN : participants with diabetes and verified neuropathic ulcers without vascular involvement ; group DC : participants with diabetes and CLI and group NDC : participants with CLI without diabetes ) . Vascular disease was confirmed with angiography . All patients underwent MWR  ( RTM-01-RES : University of Bolton , UK ) to record mean tissue temperatures at various pre-determined foot sites . Comparisons of temperature measurements between study groups were performed using one-way ANOVA and Dunn tests . ROC analysis was performed to determine sensitivity , specificity and cut-off value of MWR for CLI diagnosis . RESULTS Temperatures recorded in vicinity to the foot ulcers of participants with diabetes and CLI were similar to those with CLI without diabetes , but significantly lower than in subjects with neuropathic ulcers without vascular involvement and normal controls ( group DC:29.30 ° C±1.89 vs. group NDC:29.18 ° C±1.78vs . group N:33.01 ° C±0.45 vs. group DN:33.39 ° C±1.37;P<.0001 ) . According to ROC analysis , cut-off temperature value to diagnose CLI was < 31.8 ° C ( area under the curve : 0.984 ; 95 % CI : 0.965 - 1.005;P<.001 ) , with a sensitivity of 100.0 % ( 95%CI : 90.26 - 100.0 ) and specificity of 88.37 % ( 95 % CI : 74.92 - 96.11 ) . CONCLUSIONS Tissue temperatures in vicinity to ulcers were significantly lower in participants with CLI , with or without diabetes , compared to non-ischemic controls . MWR could be used for differential diagnosis of arterial ischemia in subjects with DFU OBJECTIVE Foot ulceration remains a major health problem for diabetic patients and has a major impact on the cost of diabetes treatment . We tested a hyperspectral imaging technology that quantifies cutaneous tissue hemoglobin oxygenation and generated anatomically relevant tissue oxygenation maps to assess the healing potential of diabetic foot ulcers ( DFUs ) . RESEARCH DESIGN AND METHODS A prospect i ve single-arm blinded study was completed in which 66 patients with type 1 and type 2 diabetes were enrolled and followed over a 24-week period . Clinical , medical , and diabetes histories were collected .  Transcutaneous oxygen tension was measured at the ankles .  Superficial tissue oxyhemoglobin ( oxy ) and deoxyhemoglobin ( deoxy ) were measured with hyperspectral imaging from intact tissue bordering the ulcer . A healing index derived from oxy and deoxy values was used to assess the potential for healing . RESULTS Fifty-four patients with 73 ulcers completed the study ; at 24 weeks , 54 ulcers healed while 19 ulcers did not heal . When using the healing index to predict healing , the sensitivity was 80 % ( 43 of 54 ) , the specificity was 74 % ( 14 of 19 ) , and the positive predictive value was 90 % ( 43 of 48 ) . The sensitivity , specificity , and positive predictive values increased to 86 , 88 , and 96 % , respectively , when removing three false-positive osteomyelitis cases and four false-negative cases due to measurements on a callus . The results indicate that cutaneous tissue oxygenation correlates with wound healing in diabetic patients . CONCLUSIONS Hyperspectral imaging of tissue oxy and deoxy may predict the healing of DFUs with high sensitivity and specificity based on information obtained from a single visit BACKGROUND Hyperspectral imaging technology is a novel method of using transcutaneous measurement of oxyhemoglobin ( HT-Oxy ) and deoxyhemoglobin ( HT-Deoxy ) concentrations to create a two-dimensional , color-coded " oxygen map . " The aims of this study were to compare the use of a hyperspectral imaging device with the transcutaneous oxygen measurement ( TCOM ) , ankle-brachial index ( ABI ) , and severity of peripheral vascular disease ( PVD ) and to assess their correlations . METHODS This prospect i ve study recruited 294 participants divided into three distinct groups composed of healthy volunteers and patients with PVD . Patients underwent measurements of lower limbs at a st and ardized point over the head of the first metatarsal on the plantar aspect using the hyperspectral imaging device , generating four outputs including HT-Oxy , HT-Deoxy , oxygen saturation ( HT-Sat ) , and skin temperature , and the TCOM system , generating transcutaneous partial pressure of oxygen ( TcpO2 ) and carbon dioxide ( TcpCO2 ) . Demographic data , severity of PVD , ABI , and other pertinent information were obtained from both the participants and medical records . RESULTS Interoperator reliability ranged from 86 % to 94 % across the four hyperspectral imaging device outputs , whereas intraoperator reliability ranged from 92 % to 94 % . The HT-Oxy , HT-Sat , TcpCO2 , and ABI of the diseased limb correlated significantly with the severity of PVD . HT-Sat significantly correlated with TcpO2 ( R = 0.19 ) , TcpCO2 ( R = -0.26 ) , ABI ( R = 0.42 ) , and skin temperature ( R = 0.56 ) . HT-Deoxy also correlated with TcpCO2 ( R = 0.27 ) . CONCLUSIONS This study demonstrates the reliability of hyperspectral imaging in comparison to TCOM , ABI , skin temperature , and severity of PVD in a series of patients . Its correlation to other established modalities and low interoperator and intraoperator variability could enable this modality to be a useful screening tool in PVD Background The early diagnosis of atherosclerotic disease is essential for developing preventive strategies in population s at high risk and acting when the disease is still asymptomatic . A low ankle-arm index is a good marker of vascular events and may be diminished without presenting symptomatology ( silent peripheral arterial disease ) . The aim of the study is to know the prevalence and associated risk factors of peripheral arterial disease in the general population . Methods We performed a cross-sectional , multicentre , population -based study in 3786 individuals > 49 years , r and omly selected in 28 primary care centres in Barcelona ( Spain ) . Peripheral arterial disease was evaluated using the  ankle-arm index . Values < 0.9 were considered as peripheral arterial disease . Results The prevalence ( 95 % confidence interval ) of peripheral arterial disease was 7.6 % ( 6.7 - 8.4 ) , ( males 10.2 % ( 9.2 - 11.2 ) , females 5.3 % ( 4.6 - 6.0 ) ; p < 0.001).Multivariate analysis showed the following risk factors : male sex [ odds ratio ( OR ) 1.62 ; 95 % confidence interval 1.01 - 2.59 ] ; age OR 2.00 per 10 years ( 1.64 - 2.44 ) ; inability to perform physical activity [ OR 1.77 ( 1.17 - 2.68 ) for mild limitation to OR 7.08 ( 2.61 - 19.16 ) for breathless performing any activity ] ; smoking [ OR 2.19 ( 1.34 - 3.58 ) for former smokers and OR 3.83 ( 2.23 - 6.58 ) for current smokers ] ; hypertension OR 1.85 ( 1.29 - 2.65 ) ; diabetes OR 2.01 ( 1.42 - 2.83 ) ; previous cardiovascular disease OR 2.19 ( 1.52 - 3.15 ) ; hypercholesterolemia OR 1.55 ( 1.11 - 2.18 ) ; hypertriglyceridemia OR 1.55 ( 1.10 - 2.19 ) . Body mass index ≥25 Kg/m2 OR 0.57 ( 0.38 - 0.87 ) and walking > 7 hours/week OR 0.67 ( 0.49 - 0.94 ) were found as protector factors . Conclusions The prevalence of peripheral arterial disease is low , higher in males and increases with age in both sexes . In addition to previously described risk factors we found a protector effect in physical exercise and overweight OBJECTIVE To vali date micro-lightguide spectrophotometry ( O2C ) in patients with lower limb ischemia and to compare results with those obtained from toe blood pressure . METHODS We prospect ively examined 59 patients , 24 of whom complained of claudication , 31 had critical ischemia , and four were asymptomatic . Diabetes was present in 19 ( 32 % ) patients .  Saturation ( SO(2 ) ) and flow measured with O2C  were determined with the limb in the horizontal position followed by a 55-cm elevation . Toe pressures  were determined in the horizontal position only . In addition , 13 patients were examined before and , on average , 3 days after revascularization . RESULTS Median SO(2 ) was 62 % ( 25%-75 % percentile : 37%-75 % ) with the limb in the horizontal position and 16 % ( 3%-41 % ) with the limb elevated . Comparing the individual toe pressures with SO(2 ) values measured in the horizontal position and elevated position revealed a significant correlation ( r(s ) = 0.40 ; P < .01 and r(s ) = 0.56 ; P < .01 , respectively ) . A low SO(2 ) ( ie , < 40 % in the horizontal position and < 20 % in the elevated position ) was highly predictive of a toe pressure of 40 mm Hg or less . In the horizontal position , the positive predictive value was 100 % , whereas the negative predictive value was 47 % . The similar figures in the elevated position were a positive predictive value of 97 % and a negative predictive value of 68 % . Postoperatively , SO(2 ) increased significantly from 27 % ( P25%-75 % : 11%-75 % ) to 79 % ( 68%-87 % ) in the horizontal position ( P = .008 ) and from 14 % ( P25%-75 % : 2%-39 % ) to 55 % ( 30%-73 % ) in the elevated position ( P = .011 ) , respectively . Looking at the individual 13 cases in which revascularization was performed , three patients had a partial reconstruction ( ie , superficial femoral artery occlusion distal to a central reconstruction or reconstruction to a popliteal blind segment ) . These patients had significantly lower postoperative SO(2 ) as well as toe pressure compared with the 10 patients with unobstructed flow to the foot . CONCLUSIONS O2C was easy to use , fast , and painless . The most useful finding was the high predictive value of a low saturation and the rise in O2C values after successful revascularization OBJECTIVE Vascular optical tomographic imaging ( VOTI ) is a novel imaging modality that is capable of detecting hemoglobin concentrations in tissue . VOTI is non-invasive , non-ionizing and does not require contrast injection . This technology was applied to the diagnosis of peripheral arterial disease ( PAD ) within lower extremities of diabetic patients with calcified arter 
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Expert opinion : So far , transcutaneous oxygen measurements are most often used to measure tissue oxygenation in PAD patients , but evidence seems too low to define this technique as a gold st and ard , and implementing this technique for home monitoring is difficult .