Application of diffuse optical back reflection spectroscopy for determining articular cartilage thickness in a clinical setting.

PURPOSE: Develop a spectroscopic method to assess cartilage thickness during the arthroscopic examination. METHODS: Currently, arthroscopy assesses cartilage damage visually; outcomes are based on the surgeon's subjective experience. Light reflection spectroscopy is a promising method for measuring cartilage thickness based on the absorption of light by the subchondral bone. In the presented study, in vivo diffuse optical back reflection spectroscopic measurements were acquired by gently placing an optical fibre probe on different locations of the articular cartilage of 50 patients during complete knee replacement surgery. The optical fibre probe consists of two optical fibers with a diameter of 1 mm to deliver the light and detect back-reflected light from the cartilage. Centre to centre distance between the source and the detector fibers was 2.4 mm. Actual thicknesses of the articular cartilage samples were measured under microscopy using histopathological staining. RESULTS: Using half of the samples in the patient data, a linear regression model was formed to estimate cartilage thicknesses from the spectroscopic measurements. The regression model was then used to predict the cartilage thickness in the second half of the data. The cartilage thickness was predicted with a mean error of 8.7% if the actual thickness was less than 2.5 mm (R2 = 0.97). CONCLUSION: The outer diameter of the optical fibre probe was 3 mm, which can fit into the arthroscopy channel and can be used to measure the cartilage thickness in real-time during the arthroscopic examination of the articular cartilage.

The detection of cervical neoplasia via optical imaging: a pilot clinical study.

PURPOSE: The present study aims to develop a new high-resolution imaging system for the early diagnosis of cervical neoplasia based on increased vessel density of the cervical tissue. METHODS: An optical device was developed to obtain high contrast and resolution images of vascular structures of the cervix in the present study. The device utilizes a telecentric lens to capture cervix images under light illumination with a wavelength of 550 nm emitted from LEDs. Images were obtained using the telecentric lens with or without acetic acid application to the cervix. Image processing algorithms were used to contrast and extract the skeleton of the vascular structures on the cervix. In the evaluation of the vascular density, the cervical images were divided into 12 o'clock positions, and the fractal dimension of the vascularity was calculated for each dial area between the o'clock positions. The region with the largest fractal dimension was accepted as the region with the highest probability of lesion. The range of vessel sizes was split into small classes of "bins" for each dial area with the highest fractal dimension. To validate the system's success in differentiating between normal and HSIL lesions, forty five patients who underwent colposcopy and biopsy were included in a pilot study. RESULTS: The system correctly classified four HSIL cases out of five and failed to detect one HSIL case, achieving an accuracy rate of 97.8% with an 80% sensitivity and 100% specificity. CONCLUSION: The developed high-resolution optical imaging system may potentially be used in detecting cervical neoplasia just before the biopsy and reduce the number of false-positive cases.

Prediction of the extent of germ cell loss utilising a noninvasive spectroscopy method in rat testicular damage model.

The aim of this study is to investigate the efficiency of elastic light single-scattering spectroscopy system, a noninvasive method, to acquire spectra during testicular biopsy from normal and damaged seminiferous tubules with various degrees of germ cell loss. Adult control rats and doxorubicin-injected rats to achieve seminiferous germ cell loss (for 10 days [10D], 20 days [D20], 30 days [D30], 40 days [D40], and 50 days [D50]) were used. Spectroscopic measurements were acquired utilising a single-fibre optical probe, and histopathology of the biopsied testicular tissue samples were compared. Time-dependent testicular damage comprising various degrees of seminiferous tubule degeneration after doxorubicin-administration was observed. In D30, D40 and D50 groups, where significant germ cell loss was identified, elastic light single-scattering spectroscopy system signals were well correlated with disturbed spermatogenesis where significant differences in spectral signals were obtained. Our findings indicate that the elastic light single-scattering spectroscopy system has the potential to enable instant imaging of spermatogenesis in rats and could also be useful in humans for clinical applications, such as to increase sperm recovery success during micro-TESE for men with nonobstructive azoospermia.

Noninvasive assessment of oral lesions using elastic light single-scattering spectroscopy: a pilot study.

PURPOSE: In the present study, we investigated the potential application of elastic light single-scattering spectroscopy (ELSSS) as a noninvasive, adjunctive tool to differentiate between malignant and benign oral lesions in vivo. METHODS: ELSSS spectra were acquired from 52 oral lesions of 47 patients prior to surgical biopsy using a single optical fiber probe. The sign of the spectral slope was used as a diagnostic parameter and was compared to the histopathology findings to obtain sensitivity and specificity of the ELSSS system in differentiating between benign and malignant tissues. RESULTS: The sign of the spectral slope was positive for the benign tissues and negative for the malignant tissues. Nine malignant lesions and one high-grade dysplasia were correctly classified as cancerous. Six out of the ten low-grade dysplasia were correctly classified as cancerous, and four of them were misclassified as benign. Thirty benign lesions were correctly classified as benign, and two were misclassified as malignant. Our results indicate that the sign of the spectral slope enables the differentiation between malignant and benign oral lesions with a sensitivity of 80% and specificity of 94%. CONCLUSIONS: ELSSS has the potential to be developed as an adjunctive screening tool in the noninvasive evaluation of oral lesions in vivo. This new diagnostic system may reduce the number of unnecessary biopsies.

Low-cost home-use light-emitting-diode phototherapy as an alternative to conventional methods.

BACKGROUND: The aim of our study was to evaluate whether a portable, light-weight, light-emitting-diode phototherapy unit designed for home use is as effective as conventional blue-light fluorescent phototherapy (CFP) for treating hyperbilirubinemia in neonates. METHODS: A total of 50 patients were recruited sequentially for treatment using CFP (n = 25) and the home-type phototherapy unit (n = 25). RESULTS: The average rate of decrease in bilirubin levels was 0.17 ± 0.02 and 0.20 ± 0.01 mg/dL/hours at the end of 24 hours in the groups receiving phototherapy by CFP and home-type phototherapy units, respectively. There was no statistically significant difference in the rate of the decrease in bilirubin levels between the groups (p = 0.104). CONCLUSIONS: It has been shown that the home-type phototherapy unit is as effective as CFP units in the treatment of neonatal hyperbilirubinemia and has the potential to become a standard of care for treatment of jaundiced neonates.

Investigating viability of intestine using spectroscopy: a pilot study.

BACKGROUND: The differentiation of "viable" from "nonviable" bowel remains a challenge in the treatment of acute mesenteric ischemia. In this study, diffuse reflectance spectroscopy (DRS) was used to investigate the viability of bowel tissue after ischemia and reperfusion in an animal model in vivo and in real time. METHODS: A total of 25 females Sprague-Dawley rats were divided into five groups based on different bowel ischemia times. In each study group for four of them, the superior mesenteric artery was occluded using a vascular clamp for a different period (i.e., 30, 45, 60, and 90 min; n = 5 for each group). Intestinal reperfusion was accomplished by releasing the clamps after the given occlusion period for each group. Spectra were acquired by gently touching the optical fiber probe to the bowel tissue before the induce ischemia, at the end of the induced ischemia, and after the reperfusion. The data acquired before the ischemia were used as a control group. Without occluding the superior mesenteric artery, the spectra were acquired on the bowel with the same time intervals of the experiments were used as a sham group (n = 5). Subsequently, the same bowel segments were sent for histopathologic examination. RESULTS: Based on the correlation between the spectra acquired from the bowel segments and the results from the histopathologic investigation, DRS is able to differentiate the histopathologic grading that appears when the Chiu/Park score ≥5 (i.e., high-level ischemic injury) than Chiu/Park score <5. Eight out of nine low-level ischemic injury tissue samples were correctly defined using the spectroscopic classification system. All eleven high-level ischemic injury tissues that were histopathologically assigned grade 5 and above were correctly defined using the spectroscopic classification system in the ischemia-reperfusion groups. CONCLUSIONS: DRS could potentially be used intraoperatively for the assessment of bowel viability in real time. These preliminary findings suggest that DRS has the potential to reduce unnecessary resection of viable tissue or insufficient resection of nonviable tissues may reduce the mortality and morbidity rates of intestinal ischemia-reperfusion as acute mesenteric ischemia.

Evaluation of Executive Functions With Functional Near-Infrared Spectroscopy in Euthymic Bipolar and Borderline Personality Disorders.

Introduction: Bipolar disorder (BD) and borderline personality disorder (BPD) are often indistinguishable, given both the key features of impulsivity and emotional dysregulation. This indicates widespread comorbidity and potential misdiagnosis in both groups. Therefore, this study aimed to differentiate BD and BPD by using alterations of brain hemodynamics under the influence of executive tests. Methods: Twenty patients with the euthymic phase of BD and 20 patients with BPD, and 20 healthy control subjects were included in this study. The prefrontal cortex (PFC) hemodynamic responses were evaluated using functional near-infrared spectroscopy (fNIRS) during the Stroop Test and Wisconsin Card Sorting Test (WCST). Results: Left dorsolateral prefrontal cortex (DLPFC) activation was significantly decreased in BPD during both tests. On the other hand, the BD group showed medial PFC hypoactivation during both tests, and this finding is distinct from BPD (p<0.05). Conclusion: Our results indicate that brain hemodynamics during the executive test can highlight differences between BP and BPD. While medial PFC hypoactivation was more prominent in the BP group, DLPFC hypoactivation was more pronounced in the BPD group.

Diagnosis of Testicular Torsion and Differentiation From Other Pathologies Using Near-Infrared Spectroscopy.

OBJECTIVE: To develop a near-infrared (NIR) spectroscopy device to diagnose testicular torsion with high sensitivity and specificity. Specifically, we aim to investigate the differentiation between testicular torsion from other pathologies such as orchidoepididymitis, varicocele, and hydrocele. METHODS: Two LEDs with wavelengths of 660 nm and 940 nm were used as light sources in the device. Each wavelength was sent to the testicle successively, and a photodiode detected back-reflected diffuse light. The ratio of the light intensities of 660 nm and 940 nm was used as a diagnostic parameter. A multi-center clinical trial was performed in 5 different hospitals. RESULTS: In total, 62 patients in urology clinics with acute testicular pain have been recruited for the study. The developed NIR spectroscopy correctly defined all 8 testicular torsion cases. Besides, 3 orchidoepididymitis, 1 varicocele, and 3 hydrocele cases were correctly distinguished from testicular torsion. Only 1 hydrocele case was misdiagnosed as torsion. The range of the ratio was between 0.14 and 1.16 overall measurements. The ratio varied between 0.14 and 0.3 for the testicle with torsion. The ratio was between 0.49 and 1.16 for the normal testicle and testicle with other pathologies mentioned above. CONCLUSION: We have chosen the threshold ratio of 0.4 to differentiate between the normal and torsion testis and diagnosed all the torsion cases among all normal and other pathologies. The developed optical device to diagnose testicular torsion is inexpensive, user-friendly, and works based on objective criteria with high sensitivity and specificity in real time.

Diagnosis and demarcation of skin malignancy using elastic light single-scattering spectroscopy: a pilot study.

BACKGROUND: Elastic light single-scattering spectroscopy (ELSSS) is a noninvasive and real-time technique that has been used to differentiate tumors from surrounding nontumor tissue in animal models and humans. OBJECTIVE: To investigate potential application of ELSSS as an adjunctive tool for noninvasive, in vivo, real-time differentiation of malignant and benign skin lesions and to detect positive surgical margins of excised biopsy samples. METHODS: In vivo spectroscopic measurements were performed on 28 lesions in 23 patients. The distribution of the lesions was as follows: nine basal cell carcinoma (BCC), four melanoma, two squamous cell carcinoma (SCC), and 13 benign lesions. Intraoperative margin assessments were performed on the 28 biopsy samples using ELSSS. RESULTS: The sign of the spectral slopes was positive for benign and negative for malignant tissues. It was used as a discrimination parameter between malignant and benign lesions with a sensitivity and specificity of 87% and 85%, respectively. Sensitivity and specificity of the system in detecting positive surgical margins on 14 excised biopsy samples were 80% and 90%, respectively. CONCLUSION: ELSSS has the potential for use as an adjunctive tool to reduce the number of negative biopsies and to detect positive surgical margins in real time.

Investigating spectroscopic measurement of sublingual veins and tissue to estimate central venous oxygen saturation.

BACKGROUND: Venous oxygen saturation reflects venous oxygenation status and can be used to assess treatment and prognosis in critically ill patients. A novel method that can measure central venous oxygen saturation (ScvO2) non-invasively may be beneficial and has the potential to change the management routine of critically ill patients. OBJECTIVE: The study aims to evaluate the potential of sublingual venous oxygen saturation (SsvO2) to be used in the estimation of ScvO2. METHODS: We have developed two different approaches to calculate SsvO2. In the first one, near-infrared spectroscopy (NIRS) measurements were performed directly on the sublingual veins. In the second approach, NIRS spectra were acquired from the sublingual tissue apart from the sublingual veins, and arterial oxygen saturation was measured using a pulse oximeter on the fingertip. RESULTS: Twenty-six healthy subjects were included in the study. In the first and second approaches, average SsvO2 values were 75.0% ± 1.8 and 75.8% ± 2.1, respectively. The results of the two different approaches were close to each other and similar to ScvO2 of healthy persons (> 70%). CONCLUSION: Oxygen saturation of sublingual veins has the potential to be used in intensive care units, non-invasively and in real-time, to estimate ScvO2.

Early detection onset of flap failure using near infrared spectroscopy.

BACKGROUND: Near-infrared spectroscopy (NIRS) is widely used to assess flap perfusions by measuring tissue oxygen saturation (StO2). However, the StO2 level for the onset of perfusion failure is still a controversial issue. AIM: This study proposes a new threshold of StO2 level for detecting the onset of perfusion failure as early as possible to increase flap salvage rates. METHODS: Twenty patients undergoing flap surgery were included in this study - 13 flaps were implemented to cover defects that occurred due to trauma and 7 flaps to hide imperfections that occurred after cancer treatment. Thirteen flaps were in the lower extremity, six in the mandible, and one in the breast. NIRS was used to measure StO2 in 240 flap regions of the 20 patients to determine flap viability using descriptive statistics. RESULTS: The mean StO2 values from healthy flap and control regions were obtained as 81.6% ± 0.36 and 82% ± 0.18, respectively. The lowest StO2 value of 77.2% was defined as the onset of a vascular complication at a probability of 99.74% by subtracting three times the standard deviation from the mean StO2 of healthy flaps. Vascular complications were observed from 21 regions in the four flaps with StO2 values lower than 77.2%, but only one was lost. CONCLUSION: The threshold value for the onset of perfusion failure was a 5% decrease from the expected value, much lower than previously described thresholds that may facilitate the detection of perfusion failure in the early stage and increase salvage rates in flap revisions.

Rapid thermal inactivation of aerosolized SARS-CoV-2.

Airborne transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is one of the leading mechanisms of spread, especially in confined environments. The study aims to assess the thermal inactivation of SARS-CoV-2 at high temperatures in the time scale of seconds. An electric heater with a coiled resistance wire is located perpendicularly to the airflow direction inside an air tunnel. The airflow rate through the tunnel was 0.6 m3/h (10 L/ min). SARS-CoV-2 were suspended in Dulbecco's modified Eagle's medium (DMEM) with 10 % fetal bovine serum (FBS), aerosolized by a nebulizer at a rate of 0.2 L/min and introduced to the airflow inside the heater with the use of a compressor and an aspirator. In the control experiment, with the heater off, SARS-CoV-2 passed through the system. In the virus inactivation test experiments, the heater's outlet air temperature was set to 150 ± 5 °C and 220 ± 5 °C, and the air traveling through the tunnel was exposed to heat for 1.44 s. An inline gelatine filter harvested SARS-CoV-2 that passed through the system. The viral titer obtained from the gelatine filter in the control experiment was about 5.5 log10 TCID50. The virus's loss in viability in test experiments at 150 °C and 220 °C were 99.900 % and 99.999 %, respectively. The results indicate that high-temperature thermal inactivation substantially reduces the concentration of SARS-CoV-2 in the air within seconds.

Differentiation of melanoma from non-cancerous tissue in an animal model using elastic light single-scattering spectroscopy.

Cutaneous melanoma is the most serious form of skin cancer and is curable only if it is detected early. The most effective treatment for the melanoma is surgical excision of the lesion. Traditionally, wide margins of excision have been used for effective treatment, but are not always desirable due to increased risk of infection and esthetic reasons. Besides, safe surgical margins of the lesion are not always correlated well with the size of the lesions. We have previously developed a system using elastic light single-scattering spectroscopy to differentiate cancerous tissue from non-cancerous tissue and tested it in vitro. The goal of this study was, therefore, to determine the effectiveness of this system ex vivo by using a mouse model of melanoma. First, a melanoma cell line; B16F10 were injected subcutaneously at right mid flank region of C57BL6 mice (n=5) and allowed to develop for two weeks. Tumors were dissected and spectra were taken on tumor tissue and on normal looking skin tissue that was 10 mm distant from the incision. Since these tumors become markedly necrotic in the middle, spectra of necrotic area was also taken. Slopes of the spectra were positive taken on non-cancerous skin tissues that were later verified by histological examination. On the other hand, it gave negative slopes on melanomas. Increased sizes of the nuclei correlated with the negative slope while smaller nuclei found in non-cancerous tissue gave positive slope. Spectrum taken from necrotic area differed from both cancerous and non-cancerous tissue such that it gave a U-shaped spectrum. These results demonstrate that elastic light single-scattering spectroscopy system can differentiate cancerous tissue from non-cancerous and has potential to be used intraoperatively to determine the surgical margins.

Intraoperative assessment of laryngeal malignancy using elastic light single-scattering spectroscopy: A pilot study.

OBJECTIVES/HYPOTHESIS: The elastic light single-scattering spectroscopy (ELSSS) system is a new tool for the real-time diagnosis of cancerous lesions. In the current study, we have employed ELSSS to investigate its ability in differentiation between normal and cancerous larynx tissues ex vivo. STUDY DESIGN: Basic science study in assessment of laryngeal malignancy using spectroscopy. METHODS: ELSSS spectra of the larynx tissue were acquired using a single-fiber optical probe. Ex vivo spectroscopic measurements were acquired on 95 laryngeal lesions of 40 patients. Average slopes of the spectra in the wavelength range of 450 to 750 nm were calculated. The signs of the spectral slopes were positive for benign and negative for cancerous larynx tissues. Histopathology results were used as a gold standard to define sensitivity and specificity. RESULTS: The ELSSS system correctly defined 38 out of 41 malignant tissues as cancerous; three of them were misclassified as benign. All benign tissues were correctly classified. Moderate, severely dysplastic, and malignant tissues were correctly classified as cancerous. The system could not classify mild dysplastic tissues either benign or cancerous, whereas nearly half of them were classified as benign and the other half as malignant. The signs of the spectral slopes were used as a discrimination parameter between benign and cancerous (moderate, severely dysplastic, and malignant) lesions with a sensitivity and specificity of 94% and 100%, respectively. CONCLUSIONS: The ELSSS system has the potential to be used as an adjunctive tool in the diagnosis of cancerous laryngeal tissues in real time and noninvasively. This new diagnostic technique may reduce the number of negative biopsies. LEVEL OF EVIDENCE: NA Laryngoscope, 127:611-615, 2017.

Diagnosis of pelvic lymph node metastasis in prostate cancer using single optical fiber probe.

Elastic light single-scattering spectroscopy system (ELSSS) is a biomedical tool which is used for detection of cancerous tissues ex-vivo. ELSSS spectra depend primarily on the size of scatterers in the tissue and are not directly related to changes in the absorption which are caused by variations of the biological macromolecules. In the present study, we aimed to detect metastasis in the pelvic lymph node by using combination of Principal Components Analysis (PCA) and Linear Discriminant Analysis (LDA). Single-scattering spectra in the 450-750nm wavelength regions were obtained from the total of 83 reactive lymph node and 12 metastatic lymph node samples from 10 prostatic cancer patients. The ELSSS spectral data were compared against the "gold standard" histopathology results. Data analyses were done via using PCA, followed by LDA. Receiver Operating Characteristic (ROC) curve analysis was employed for differentiating performance. The classification based on discriminant score provided sensitivity of 100% and specificity of 96.4%, in differentiating non-metastatic (reactive) from metastatic pelvic lymph nodes, with a Positive Predictive Value (PPV) of 0.8, a Negative Predictive Value (NPV) of 0.99 and the area under the ROC curve (AUC) of 0.99, respectively. In this study, it was shown that ELSSS system can accurately distinguish reactive and metastatic pelvic lymph nodes of prostate cancer with high PPV and NPV. It can be concluded that diagnostic accuracy of ELSSS system allows detecting metastatic tissues during operation.

Differentiating cancerous tissues from noncancerous tissues using single-fiber reflectance spectroscopy with different fiber diameters.

Elastic light-scattering spectra acquired with single-fiber optical probes with diameters of 100, 200, 400, 600, 800, 1000, 1200, and 1500 µm were used to differentiate cancerous from noncancerous prostate tissues. The spectra were acquired ex vivo on 24 excised prostate tissue samples collected from four patients. For each probe, the spectra and histopathology results were compared in order to investigate the correlation between the core diameters of the single-fiber optical probe and successful differentiation between cancerous and noncancerous prostate tissues. The spectra acquired using probes with a fiber core diameter of 400 µm or smaller successfully differentiated cancerous from noncancerous prostate tissues. Next, the spectra were acquired from monosized polystyrene microspheres with a diameter of 5.00±0.01 µm to investigate the correlation between the core diameters of the probes and the Mie oscillations on the spectra. Monte Carlo simulations of the light distribution of the tissue phantoms were run to interrogate whether the light detected by the probes with different fiber core diameters was in the ballistic or diffusive regime. If the single-fiber optical probes detect light in the ballistic regime, the spectra can be used to differentiate between cancerous and noncancerous tissues.

Detecting positive surgical margins using single optical fiber probe during radical prostatectomy: a pilot study.

OBJECTIVE: To investigate for the potential of detection of positive surgical margins by the elastic light single-scattering spectroscopy (ELSSS) system with a single optical fiber probe during radical prostatectomy. MATERIALS AND METHODS: ELSSS spectra in the 450- to 750-nm wavelength regions were obtained from a total of 31 benign tissue samples and 14 malignant tissue samples from 18 patients. The ELSSS spectral data were assessed by comparing these against the "gold standard" histopathology results. Data were analyzed using principal component analysis , followed by linear discriminant analysis. Receiver operating characteristic curve analysis was used for differentiating performance. RESULTS: Classification based on the discriminant score provided a sensitivity of 86% and a specificity of 97%, in differentiating benign from malignant surgical margins of prostate tissues, with a positive predictive value of 0.92, a negative predictive value of 0.94, and the area under the receiver operating characteristic curve of 0.87. CONCLUSION: The ELSSS system can accurately distinguish between benign and malignant surgical margins of prostate tissues with a high positive predictive value and negative predictive value. It is a promising technique, and it may be a valuable new tool for determining positive surgical margins during radical prostatectomy.

Elastic light single-scattering spectroscopy for the detection of cervical precancerous ex vivo.

Potential application of elastic light single-scattering spectroscopy (ELSSS) for differentiating high-grade squamous intraepithelial lesions (HSIL) from non-HSIL tissues was investigated. An ELSSS system was used to acquire spectra from cervix tissues. A single-fiber optical probe with a diameter of 100 µm was used for both delivery and detection of white light to and from the cervix tissue. Spectroscopic measurements were acquired from 95 ex vivo biopsy samples of 60 pap smear positive patients and normal cervix tissue from 10 patients after hysterectomy were used as a negative control group. Spectroscopic results of 95 cervix biopsy were compared to the histopathology of the biopsy samples. Sensitivity and specificity of the ELSSS system in the differentiation of HSIL and non-HSIL tissues are 87.5% and 45.6%, respectively, for the pap smear and colposcopy positive biopsy samples. The ELSSS system has the potential for use in real-time diagnosis of HSIL tissues as an adjunct to Papanicolaou test (pap smear) and colposcopy.

Diagnosis of testicular torsion by measuring attenuation of dual wavelengths in transmission geometry across the testis: an experimental study in a rat model.

OBJECTIVE: To develop a noninvasive and real-time dual-wavelengths optic system to detect testicular torsion in an animal model. Diagnosis of testicular torsion is challenging in emergency conditions and frequently ends with surgical exploration. MATERIALS AND METHODS: In this study, 9 male 8-month-old Wistar albino rats weighing an average of 400 g were used. A transverse incision on the upper scrotum was done and the right testis was torsed with a 720° medial rotation. The other testis of each rat was used as the control or sham group. In the sham group, the testicle was moved out of the body but no torsion was applied before repositioning into the scrotum. Transmission of continuous-wave light through all testes at wavelengths of 660 nm and 940 nm were measured. RESULTS: The ratio of the average intensities of the transmitted light of both wavelengths--660 nm to 940 nm--was used as a parameter to diagnose testis torsion. The ratios were significantly different (P = .001) between the torsion group and control group. CONCLUSION: Our noninvasive technique measuring attenuation of dual wavelengths in transmission geometry across the testis has the ability to distinguish between the testis with and without torsion on the basis of a threshold value of the ratio.

Wavelength selection in measuring red blood cell aggregation based on light transmittance.

The reversible aggregation of red blood cells (RBC) is of current basic science and clinical interest. Using a flow channel and light transmittance (LT) through RBC suspensions, we have examined the effects of wavelength (500 to 900 nm) on the static and dynamic aspects of RBC aggregation for normal blood and suspensions with reduced or enhanced aggregation; the effects of oxygenation were also explored. Salient observations include: 1. significant effects of wavelength on aggregation parameters reflecting the extent of aggregation (i.e., number of RBC per aggregate); 2. no significant effects of wavelength on parameters reflecting the time course of RBC aggregation; 3. a prominent influence of hemoglobin oxygen saturation on both extent and time-course related aggregation parameters measured at wavelengths less than 700 nm, but only on the time-course at 800 nm; and 4. the power of parameters in detecting a given alteration of RBC aggregation is affected by wavelength, in general being greater at higher wavelengths. It is recommended that light sources with wavelengths around 800 nm be used in instruments for measuring RBC aggregation via LT.