PubMed Health⌕ Search

Biomedical subjects

Shai Friedland

Publications and source records attributed to Shai Friedland.

17 recordsLinked to original sources
PubMed2006

Diagnosis of chronic mesenteric ischemia by visible light spectroscopy during endoscopy.

BACKGROUND: Chronic mesenteric ischemia can be difficult to diagnose by means of currently available clinical techniques. We developed a novel endoscopic device for objective measurement of GI mucosal ischemia. OBJECTIVE: Our purpose was to evaluate the performance of the device in patients with chronic mesenteric ischemia. DESIGN: A fiberoptic catheter-based visible light spectroscopy oximeter (T-Stat 303 Microvascular Oximeter, Spectros, Portola Valley, Calif) was used to evaluate 30 healthy control subjects and 3 patients with chronic mesenteric ischemia before and after successful percutaneous stenting. SETTING: Veterans Affairs Palo Alto Health Care System hospital. RESULTS: Normal mucosal (capillary) hemoglobin oxygen saturation was 60% to 73% in the duodenum and jejunum. In the 3 patients with chronic mesenteric ischemia, ischemic areas in the duodenum or proximal jejunum were found with mucosal saturations of 16% to 30%. After successful angioplasty and stent placement of the celiac, superior mesenteric, or inferior mesenteric arteries, the mucosal saturation in these areas increased to 51% to 60%. CONCLUSIONS: This preliminary study suggests that chronic mesenteric ischemia is detectable during endoscopy by use of visible light spectroscopy and that successful endovascular treatment results in near normalization of mucosal oxygen saturation.

Aged↗
PubMed2006

Colonoscopy with polypectomy in anticoagulated patients.

BACKGROUND: According to current practice guidelines for performance of colonoscopy in patients requiring long-term anticoagulation, polypectomy is considered a high-risk procedure for which anticoagulation must temporarily be discontinued. However, these guidelines are based on expert opinion, and the bleeding risk after polypectomy in anticoagulated patients is not known. OBJECTIVE: Measure the risk of postpolypectomy bleeding in patients who undergo colonoscopic polypectomy while anticoagulated. DESIGN: Retrospective review of patients who underwent polypectomy without discontinuation of anticoagulation. SETTING: Veterans Administration Palo Alto Health Care System. PATIENTS: Forty-one polypectomies were performed in 21 patients. All patients had been receiving long-term anticoagulation with warfarin; the average international normalized ratio was 2.3 (range 1.4-4.9; normal 0.9-1.2). To prevent supratherapeutic anticoagulation, warfarin was withheld for 36 hours before the procedure while the patients were on a liquid diet. The average polyp size was 5 mm (range 3-10 mm). INTERVENTIONS: All patients underwent polypectomy followed immediately by prophylactic application of one or two clips to prevent bleeding. MAIN OUTCOME MEASUREMENTS: Rate of postpolypectomy bleeding. RESULTS: There were no episodes of postpolypectomy bleeding. The 95% CI for the risk of bleeding was 0% to 8.6% when analyzed per polypectomy and 0% to 15% when analyzed per patient. LIMITATIONS: Small single-center retrospective study. CONCLUSIONS: Our experience suggests that small polyps can be removed with a very low risk of bleeding when clips are applied immediately after polypectomy. If these results can be confirmed in a larger multicenter study, our protocol may become an alternative to withholding anticoagulation in patients at high risk of thrombosis.

Anticoagulants↗
PubMed2005

18-Fluorodeoxyglucose positron emission tomography has limited sensitivity for colonic adenoma and early stage colon cancer.

BACKGROUND: 18-Fluorodeoxyglucose positron emission tomography (PET) is used clinically to detect recurrent colon cancer after surgical resection, but the sensitivity of PET for premalignant colon lesions and early stage colon cancer is not well defined. METHODS: In a prospective study, 45 patients with a total of 58 colonic neoplasms, including premalignant polyps, premalignant, flat lesions, and early stage cancers, were evaluated by PET. RESULTS: The sensitivity of PET for cancer was 62% (8/13). PET detected 100% (7/7) of cancers 2 cm or larger but only 17% (1/6) of cancers smaller than 2 cm. PET detected 23% (3/13) of flat, premalignant lesions; 70% (7/10) of protruded, premalignant lesions 3 cm or larger; 38% (3/8) of protruded, premalignant lesions between 2 and 2.9 cm; and 14% (2/14) of protruded, premalignant lesions between 1 and 1.9 cm. There was no false-positive PET reading. CONCLUSIONS: PET has limited sensitivity for flat, premalignant lesions; protruded, premalignant lesions smaller than 3 cm; and colon cancers smaller than 2 cm.

Adenoma↗
PubMed2005

Optical detection of tumors in vivo by visible light tissue oximetry.

Endoscopy is a standard procedure for identifying tumors in patients suspected of having gastrointestinal (G.I.) cancer. The early detection of G.I. neoplasms during endoscopy is currently made by a subjective visual inspection that relies to a high degree on the experience of the examiner. This process can be difficult and unreliable, as tumor lesions may be visually indistinguishable from benign inflammatory conditions and the surrounding mucosa. In this study, we evaluated the ability of local ischemia detection using visible light spectroscopy (VLS) to differentiate neoplastic from normal tissue based on capillary tissue oxygenation during endoscopy. Real-time data were collected (i) from human subjects (N = 34) monitored at various sites during endoscopy (enteric mucosa, malignant, and abnormal tissue such as polyps) and (ii) murine animal subjects with human tumor xenografts. Tissue oximetry in human subjects during endoscopy revealed a tissue oxygenation (StO2%, mean +/- SD) of 46 +/- 22% in tumors, which was significantly lower than for normal mucosal oxygenation (72 +/- 4%; P < or = 0.0001). No difference in tissue oxygenation was observed between normal and non-tumor abnormal tissues (P = N.S.). Similarly, VLS tissue oximetry for murine tumors revealed a mean local tumor oxygenation of 45% in LNCaP, 50% in M21, and 24% in SCCVII tumors, all significantly lower than normal muscle tissue (74%, P < 0.001). These results were further substantiated by positive controls, where a rapid real-time drop in tumor oxygenation was measured during local ischemia induced by clamping or epinephrine. We conclude that VLS tissue oximetry can distinguish neoplastic tissue from normal tissue with a high specificity (though a low sensitivity), potentially aiding the endoscopic detection of gastrointestinal tumors.

Adult↗
PubMed2004

Reflectance spectrophotometry for the assessment of mucosal perfusion in the gastrointestinal tract.

Reflectance spectrophotometry (RS) is an optical technology that has been used for nearly three decades in the measurement of tissue hemoglobin oxygen saturation in the gastrointestinal tract. The technology has evolved substantially throughout this period,and commercial devices are now available for use in clinical trials. Numerous studies have used RS to investigate the importance of mucosal perfusion in disorders such as ulcer disease, portal hypertension, and septic shock. More recently, the technique has been applied to measure changes in perfusion in response to infusion of vasoactive medications and maneuvers such as cardiopulmonary bypass. The results of current trials investigating the application of RS in critical care monitoring and vascular interventions will likely determine whether the technique will evolve from predominantly a research tool to a clinically useful device.

Gastric Mucosa↗
PubMed2004

Continuous, noninvasive, and localized microvascular tissue oximetry using visible light spectroscopy.

BACKGROUND: The authors evaluated the ability of visible light spectroscopy (VLS) oximetry to detect hypoxemia and ischemia in human and animal subjects. Unlike near-infrared spectroscopy or pulse oximetry (SpO2), VLS tissue oximetry uses shallow-penetrating visible light to measure microvascular hemoglobin oxygen saturation (StO2) in small, thin tissue volumes. METHODS: In pigs, StO2 was measured in muscle and enteric mucosa during normoxia, hypoxemia (SpO2 = 40-96%), and ischemia (occlusion, arrest). In patients, StO2 was measured in skin, muscle, and oral/enteric mucosa during normoxia, hypoxemia (SpO2 = 60-99%), and ischemia (occlusion, compression, ventricular fibrillation). RESULTS: In pigs, normoxic StO2 was 71 +/- 4% (mean +/- SD), without differences between sites, and decreased during hypoxemia (muscle, 11 +/- 6%; P < 0.001) and ischemia (colon, 31 +/- 11%; P < 0.001). In patients, mean normoxic StO2 ranged from 68 to 77% at different sites (733 measures, 111 subjects); for each noninvasive site except skin, variance between subjects was low (e.g., colon, 69% +/- 4%, 40 subjects; buccal, 77% +/- 3%, 21 subjects). During hypoxemia, StO2 correlated with SpO2 (animals, r2 = 0.98; humans, r2 = 0.87). During ischemia, StO2 initially decreased at -1.3 +/- 0.2%/s and decreased to zero in 3-9 min (r2 = 0.94). Ischemia was distinguished from normoxia and hypoxemia by a widened pulse/VLS saturation difference (Delta < 30% during normoxia or hypoxemia vs. Delta > 35% during ischemia). CONCLUSIONS: VLS oximetry provides a continuous, noninvasive, and localized measurement of the StO2, sensitive to hypoxemia, regional, and global ischemia. The reproducible and narrow StO2 normal range for oral/enteric mucosa supports use of this site as an accessible and reliable reference point for the VLS monitoring of systemic flow.

Animals↗
PubMed2003

Measurement of mucosal capillary hemoglobin oxygen saturation in the colon by reflectance spectrophotometry.

BACKGROUND: Advances in optical and computer technology have enabled the development of a device that uses white-light reflectance spectrophotometry to measure capillary hemoglobin saturation in intestinal mucosa during colonoscopy. METHODS: Studies were performed with the colon oximeter in anesthetized animals and patients undergoing colonoscopy. RESULTS: Mean (SD) mucosal hemoglobin saturation in the normal colon was 72% (3.5%). In an animal model, ischemia induced by arterial ligation and hypoxemia via hypoxic ventilation each resulted in a decrease of over 40% in the mucosal saturation. In patients with colon polyps, ischemia induced by epinephrine injection, stalk ligation with a loop, or clipping of the polyp stalk each resulted in a decrease of over 40% in the mucosal saturation (p < 0.02). In contrast, saline solution injection did not decrease the mucosal saturation. CONCLUSIONS: A novel device for measuring capillary hemoglobin saturation in intestinal mucosa during colonoscopy is capable of providing reproducible measurements in normal patients and clearly detects dramatic decreases in saturation with ischemic and hypoxic insults.

Aged↗
PubMedDate not supplied

Design of a visible-light spectroscopy clinical tissue oximeter.

We develop a clinical visible-light spectroscopy (VLS) tissue oximeter. Unlike currently approved near-infrared spectroscopy (NIRS) or pulse oximetry (SpO2%), VLS relies on locally absorbed, shallow-penetrating visible light (475 to 625 nm) for the monitoring of microvascular hemoglobin oxygen saturation (StO2%), allowing incorporation into therapeutic catheters and probes. A range of probes is developed, including noncontact wands, invasive catheters, and penetrating needles with injection ports. Data are collected from: 1. probes, standards, and reference solutions to optimize each component; 2. ex vivo hemoglobin solutions analyzed for StO2% and pO2 during deoxygenation; and 3. human subject skin and mucosal tissue surfaces. Results show that differential VLS allows extraction of features and minimization of scattering effects, in vitro VLS oximetry reproduces the expected sigmoid hemoglobin binding curve, and in vivo VLS spectroscopy of human tissue allows for real-time monitoring (e.g., gastrointestinal mucosal saturation 69+/-4%, n=804; gastrointestinal tumor saturation 45+/-23%, n=14; and p<0.0001), with reproducible values and small standard deviations (SDs) in normal tissues. FDA approved VLS systems began shipping earlier this year. We conclude that VLS is suitable for the real-time collection of spectroscopic and oximetric data from human tissues, and that a VLS oximeter has application to the monitoring of localized subsurface hemoglobin oxygen saturation in the microvascular tissue spaces of human subjects.

Algorithms↗
PubMedDate not supplied

Dual-axes confocal reflectance microscope for distinguishing colonic neoplasia.

A dual-axes confocal reflectance microscope has been developed that utilizes a narrowband laser at 1310 nm to achieve high axial resolution, image contrast, field of view, and tissue penetration for distinguishing among normal, hyperplastic, and dysplastic colonic mucosa ex vivo. Light is collected off-axis using a low numerical aperture objective to obtain vertical image sections, with 4- to 5-microm resolution, at tissue depths up to 610 microm. Post-objective scanning enables a large field of view (610 x 640 microm), and balanced-heterodyne detection provides sensitivity to collect vertical sections at one frame per second. System optics are optimized to effectively reject out-of-focus scattered light without use of a low-coherence gate. This design is scalable to millimeter dimensions, and the results demonstrate the potential for a miniature instrument to detect precancerous tissues, and hence to perform in vivo histopathology.

Anatomy, Cross-Sectional↗