Effect of optical clearing agents on optical coherence tomography images of cervical epithelium

Lasers in Medical Science - Optical coherence tomography (OCT) can be used as an adjunct to colposcopy in order to detect precancerous and cancerous cervical lesions. Optical clearing agents (OCAs)...     

Airtraq optical laryngoscope

BACKGROUND: We described an early experience of Airtraq laryngoscope in 20 patients receiving general anesthesia. METHODS: In all, 2 staff anesthesiologists, 3 anesthesia residents and 10 non-anesthesia residents performed endotracheal intubation with 14 polyvinyl chloride tubes with inside diameter of 7-8 mm, 5 double lumen 37-F tubes and 1 preformed nasotracheal tube. RESULTS: Every endotracheal intubation was achieved at the first trial, and the mean time to secure the airway was 46 +/- 18 seconds. CONCLUSIONS: Airtraq laryngoscope is a useful novel device for tracheal intubation.     

Technique of optical internal urethrotomy

Reviewed are 56 cases of children suffering from urinary calculous disease between 1970 and 1977; 27 were female and 29 male. The age distribution was from one month to fourteen years. I n 34 per cent of the children urodynamic disorders were responsible for stone -formation, 23 per cent had identifiable metabolic disorders, and in 43 per cent the cause of stone formation was unknown. Urinary infection was present in 60 per cent of the patients. Forty-five of the 56 children (80 per cent) had to undergo surgery. After surgery 78 per cent remained stone free, while 16 per cent had recurrent stones, only half requiring a second operation. In cases of active stone disease, especially in the group with underlying metabolic disorders, specific therapeutic measures have been applied and the patients regularly investigated afterward.     

Long-term results of optical urethrotomy

In a 7-year period 137 men with urethral stricture underwent optical urethrotomy. Over 91% were relieved of their stricture symptoms and required no further treatment, including 41 patients in whom the follow-up period exceeded 4 years. The surgical technique is outlined. Strictures with the best prospect of cure were short and single. Optical urethrotomy is confirmed as the treatment of choice in strictures of the male urethra.     

Effect of optical clearing agents on the in vivo optical properties of squamous epithelial tissue

BACKGROUND AND OBJECTIVES: Optical clearing agents (OCAs) have previously been shown to increase depth penetration within turbid tissue ex vivo. This paper quantifies tissue optical properties of the hamster cheek pouch model in order to provide a means to assess the effect of OCAs quantitatively in vivo. STUDY DESIGN/MATERIALS AND METHODS: Diffuse reflectance spectra were obtained from both cheeks of 12 hamsters before and after immersion in dimethyl sulfoxide (DMSO), glycerol or a phosphate buffer saline (PBS) control for 20 minutes. A Monte Carlo model was then utilized to derive the wavelength dependent reduced scattering and absorption coefficients. RESULTS: DMSO caused a statistically significant decrease in the absorption and reduced scattering coefficients derived by the model. Glycerol caused a statistically significant increase in the wavelength dependent absorption coefficient, but no statistically significant changes in the reduced scattering coefficient. CONCLUSIONS: DMSO and glycerol act upon tissues differently as reflected by the tissue optical properties, implying that not all OCAs are equally effective in optically clearing tissues.     

Cold knife optical urethrotomy

Cold knife optical urethrotomy with the Sachse urethrotome was used in 44 patients with urethral strictures. Appraisal if the results, after a mean follow-up of fourteen months, showed 77.3 per cent success rate regarding urine flow rates and 81.8 per cent regarding subjective response of the patient.     

Nonlinear optical microscopy of articular cartilage

OBJECTIVE: To assess the ability of nonlinear optical microscopy (NLOM) to image ex vivo healthy and degenerative bovine articular cartilage. METHOD: Fresh bovine femoral-tibial joints were obtained from an abattoir. Articular cartilage specimens were harvested from the tibial plateau. Normal and degenerative specimens were imaged by NLOM and subsequently fixed and processed for histological examination. RESULTS: NLOM provided high resolution images of articular cartilage at varying depths with high sensitivity to tissue morphology and high specificity to tissue components without fixing, sectioning or staining. Spectroscopic segmentation of nonlinear optical signals isolated the collagen matrix from the chondron (chondrocyte and non-collagen pericellular matrix). Images from the superficial zone were consistent with the presence of a matrix composed of both elastin-like and collagen fibers distributed in a depth-dependent morphological arrangement, whereas only collagen was demonstrated in the middle and deep zones. Alterations of collagen matrix associated with advanced degenerative joint disease (fibrocartilage) were observed with NLOM. Individual chondrocytes were imaged and demonstrated intracellular fluorescence consistent with the presence of products of intracellular biochemical processes. CONCLUSION: Thin images of living articular cartilage using NLOM may be obtained with (sub-)cellular resolution at varying depths without fixing, sectioning or staining. Extracellular matrical collagen and chondron may be imaged separately in native tissue using spectrally distinct, endogenous, nonlinear optical signals. NLOM was sensitive to macromolecular composition and pathologic changes in articular cartilage matrix. Advances in instrumentation may lead to the application of NLOM to study articular cartilage in vivo.     

Determination of characteristics of degenerative joint disease using optical coherence tomography and polarization sensitive optical coherence tomography

BACKGROUND AND OBJECTIVES: Previous studies have demonstrated that optical coherence tomography (OCT) could be used to delineate alterations in the microstructure of cartilage, and have suggested that changes in the polarization state of light as detected by OCT could provide information on the birefringence properties of articular cartilage as influenced by disease. In this study we have used both OCT and polarization sensitive optical coherence tomography (PS-OCT) technologies to evaluate normal and abnormal bovine articular cartilage according to established structural, organizational, and birefringent characteristics of degenerative joint disease (DJD) in order to determine if this technology can be used to differentiate various stages of DJD as a minimally invasive imaging tool. MATERIALS AND METHODS: Fresh bovine femoral-tibial joints were obtained from an abattoir, and 45 cartilage specimens were harvested from 8 tibial plateaus. Whole ex vivo specimens of normal and degenerative articular cartilage were imaged by both OCT and PS-OCT, then fixed and processed for histological evaluation. OCT/PS-OCT images and corresponding histology sections of each specimen were scored according to a modified Mankin structural grading scale and compared. RESULTS: OCT and PS-OCT imaging allowed structural evaluation of intact articular cartilage along a 6 mm surface length to a depth of 2 mm with a transverse resolution of 12 microm and an axial resolution of 10 microm. The OCT and PS-OCT images demonstrated characteristic alterations in the structure of articular cartilage with a high correlation to histological evaluation (kappa = 0.776). The OCT images were able to demonstrate early to advanced structural changes of articular cartilage while the optical phase retardation images obtained by PS-OCT imaging were able to discriminate areas where disorganization of the cartilage matrix was present, however, these characteristics are much different than those reported where OCT images alone were used to characterize tissue birefringence. No evidence of differences in OCT or PS-OCT images were detected between specimens of similar structural characteristics where proteoglycan was judged present or absent by safranin-O Fast Green staining. CONCLUSIONS: The combined use of OCT and PS-OCT technologies to obtain images from a single system is able to demonstrate and discriminate between characteristics of very early stages of surface irregularities not previously reported for OCT imaging, to deep clefts and collagen matrix disorganization for tissue at depths of up to 2 mm with good correlation to histology. PS-OCT and accumulated optical phase retardation images of articular cartilage as constructed from alterations in Stokes vector parameters appear to give a valuable but different assessment of alterations in tissue birefringence and organization than have been reported for OCT images obtained with the use of polarized or non-polarized light sources. This is the first time that alterations in the polarization state of light reflected from within the tissue have been demonstrated to be consistent with changes observed in the orientation and organization of the collagen matrix in advanced stages of DJD. The degree of phase transformation of light reflected from within the tissue as determined by PS-OCT imaging does not appear to be altered by the presence or absence of proteoglycan.     

Noninvasive optical detection of bone mineral.

FRFP binds to mineral at osteoblastic, osteoclastic, and quiescent surfaces, with accumulation likely modulated by vascular delivery. In vivo visualization and quantification of binding can be accomplished noninvasively in animal models through optical tomographic imaging. INTRODUCTION: The development of near-infrared optical markers as reporters of bone metabolism will be useful for early diagnosis of disease. Bisphosphonates bind differentially to osteoblastic and osteoclastic surfaces depending on choice of side-chain and dose, and fluorescently tagged bisphosphonates provide a convenient way to visualize these sites. This study examines the ability of a fluorescently labeled pamidronate imaging probe to bind to regions of bone formation and resorption in vivo. MATERIALS AND METHODS: In vitro binding of a far-red fluorescent pamidronate (FRFP) to mineral was assessed using intact and demineralized dentine slices. In vivo, FRFP binding was studied in three models: developing neonatal mouse, bone healing after injury, and metastasis-induced osteolysis and fracture. 3D fluorescence molecular tomographic (FMT) imaging was used to visualize signal deep within the body. RESULTS: FRFP binding to bone depends on the quantity of mineral present and can be liberated from the bone during decalcification. In vivo, FRFP binds to surfaces of actively forming bone, as assessed by alkaline phosphatase staining, surfaces undergoing active resorption, as noted by scalloped bone border and presence of osteoclasts, and to quiescent surfaces not involved in formation or resorption. Binding is likely modulated by vascular delivery of the imaging agent to the exposed mineral surface and total quantity of surface exposed. FMT imaging is capable of visualizing regions of bone formation because of a large volume of labeled surface, but like radiolabeled bone scans, cannot discriminate pure osteolysis caused by metastasis. CONCLUSIONS: FRFP may function as a local biomarker of bisphosphonate deposition to assess interplay between drug and cellular environment or may be combined with other imaging agents or fluorescent cells for the noninvasive assessment of local bone metabolism in vivo.     

Inhibition of LDH-X by gossypol optical isomers

Racemic gossypol is an effective male antifertility agent in several mammalian species. However, (+)-gossypol is not an effective male antifertility agent in the rat or the hamster. Previous studies have demonstrated the ability of racemic gossypol to inhibit the testis-specific LDH-X enzyme derived from various mammalian species and have suggested LDH-X as the potential site of gossypol antifertility action. In the present study, the effects of racemic gossypol and the (+) and (-) optical isomers of gossypol on LDH-X derived from rat and hamster testicular cytosol are compared to determine if there is any correlation between the in vitro inhibition of the LDH-X enzyme and in vivo antifertility effects. Both optical isomers of gossypol as well as racemic gossypol inhibit rat and hamster testicular cytosolic LDH-X activity. Inhibition of hamster testicular cytosolic LDH-X activity by (-)-gossypol was less than by either racemic gossypol or (+)-gossypol. Based on the previous reports of racemic gossypol inhibition of LDH-X, therefore, it cannot be simply concluded that LDH-X is the specific site of antifertility action of gossypol since, in the present study, (+)-gossypol, which is not an effective male antifertility agent, also inhibited rat and hamster testicular cytosolic LDH-X.     

Assessment of tissue pathology using optical polarimetry

Lasers in Medical Science - Optical polarimetry have been extensively used for the non-invasive assessment of biological tissues. However, the knowledge regarding differences in polarimetric...     

Studying erythrocyte deformation by optical methods

Erythrocyte deformation is an important factor of the microcirculation in physiological and pathophysiological conditions. MATERIAL AND METHOD: Deformability was evaluated through the elongation index (IE) using two instruments based on optical methods: LORCA and RHEODYN-SSD. RESULTS: The elongation index (IE) was compared for normal red blood cell (RBC) and heated RBC at 49 degrees C for 9, 30, 60 minutes duration. Erythrocyte deformability was measured for RBC treated with diamide (two concentrations), too. The results show that the increase of the diamide concentration induces the increase of the rigidity and a decreased deformability through the decreased IE. The elongation index was found decreasing as long as the time of heating is bigger, the RBC becoming more rigid.     

A novel ultrasmall composite optical fiberscope

Background  

Accurately aiming laser energy at a target from a two-dimensional endoscopic view is difficult during endoscopic laser surgery, particularly when the endoscope and the laser fiber are misaligned. We developed a composite optical fiberscope (COF) that can simultaneously visualize a target area and perform laser irradiation. The identical orientation of the endoscope and the laser fiber allows intuitive aiming at a target, even from a two-dimensional endoscopic view.     

Respective value of direct vision or optical lumboscopy

The lumbar retroperitoneal space can be explored with 2 endoscopic procedures: direct lumboscopy with the Hald-type retroperitoneoscope and optical lumboscopy with a laparoscope inserted into the retroperitoneal space after CO2 insufflation. The latter procedure was tried without success due to the insufficient opening of the lumbar retroperitoneal space by the retropneumascos. On the contrary, direct lumboscopy was performed 44 times and yielded encouraging results as histological interpretation was possible for 40 samples (sensitivity 90%). This preliminary experiment seems to demonstrate the superiority of direct lumboscopy over optical lumboscopy, although the latter procedure theoretically has the advantage of a greater field of view.