Monitoring silver diamine fluoride application with optical coherence tomography.

The objective of this study was to investigate the use of optical coherence tomography (OCT) for monitoring changes in the structure of caries lesions overtime after treatment with silver diamine fluoride (SDF). Artificial caries lesions were formed on dentin bovine blocks. Each block was partitioned into 5 windows: one lesion was covered by nail varnish as control (LC), one sound window was covered with nail varnish (SC), one sound window was exposed to SDF (SCT), one lesion received 2 applications of SDF (L2), while the other lesion received one application of SDF (L1). Each window was scanned using OCT before SDF application, and every week subsequently, for 12 weeks after initial SDF treatment. Parameters such as mean intensity and the width of the peak of increased reflectivity located at the sample surface and the intensity at a depth of 180-µm were monitored. High-resolution microscopy was also used to for the analysis of selected samples. Changes in the parameters measured showed significant changes on dentin lesions after SDF application. OCT resolved structural changes after SDF application as well as changes overtime. High resolution microscopy images confirm penetration of SDF into the samples. Such changes can potentially be monitored to determine if and when re-application of SDF is needed.

Thermal Imaging of Root Caries In Vivo.

Improved methods are needed to assess the structure and activity of lesions on root surfaces in order to improve clinical decision making. Conventional visual and tactile methods for assessing lesion activity are not reliable, and the clinician is often unable to evaluate if the lesion is progressing or has remineralized. An important marker of an arrested lesion is a highly mineralized surface zone that forms when mineral is deposited in the outer layer of the lesion. In vitro studies have shown that a mineralized surface zone influences the kinetics of water evaporation and the surface temperature while drying. Temperature changes can be monitored by measuring the thermal emission with thermal imaging. Studies have also shown that the depth and severity of demineralization and the thickness of the highly mineralized transparent surface zone on arrested lesions can be measured nondestructively with optical coherence tomography (OCT). Thermal imaging at 8-µm to 13-µm wavelengths was completed on 30 test subjects with a suspected active root caries lesion by monitoring thermal emission from the tooth surfaces during 30 s of air drying. Lesions were also evaluated using cross-polarization OCT (CP-OCT) during lesion dehydration to identify transparent surface zones indicative of arrested lesions and determine if shrinkage occurred during drying. The overall thermal emission recorded during drying was significantly different (P < 0.001) when comparing sound tooth surfaces, lesion areas identified as arrested, and lesion areas identified as active, demonstrating that thermal imaging is a promising approach for the clinical assessment of lesion activity on root surfaces. Ten of the lesions in this study had distinct areas with transparent surface zones that were visible in CP-OCT images. Shrinkage was detected with CP-OCT during drying for 12 lesions. This study confirms that these novel approaches for assessing lesion activity on root surfaces can be implemented in vivo.

[Tyramine and tryptamine as ligands for medical and biotechnological affinity sorbents].

A novel technique for preparation affinity sorbent based on tyramine and tryptamine was proposed. It was shown that tryptamine-Sepharose and tyramine-Sepharose effectively bind IgG, IgA, lipoprotein (a) (Lp(a)) and low density lipoproteins (LDL) from blood plasma. The sorption capacity is 4-9 mg of IgG, 2-4 mg IgA, 3-5:mg of Lp(a) and 5-7 mg of LDL per mL of gel. It was found that new sorbents can bind Lp(a) and IgG as themselves or in a complex of Lp(a) with IgG. The existence of this complex may indicate the presence of anti-Lp(a) autoantibodies in the blood of some patients. The advantages of new sorbents are easiness of its synthesis and stability during use and storage. In practice they can be applied for medical and biotechnological purposes where it is necessary to bind Lp(a), LDL, IgG, IgA.

[Affine Haemosorbents Based on Aromatic Peptides for Binding of the Immunoglobulin G].

Affinity haemoadsorbents based on WY, WTY, WNY ligands and polysaccharide matrix were developed for the human immunoglobulin G binding. The characteristics of new sorbents such as the binding of total IgG and binding of IgG subclasses were compared. It was found that all new sorbents well extract the IgG from the blood plasma. It was evidenced that WNY-based sorbent is more effective for binding of IgG subclass 3. The determination of physic-chemical characteristics of IgG binding revealed that desorption constants for IgG are 10 ± 3, 28 ± 4 and 13 ± 3 µM for WY, WTY, WNY based sorbents respectively. Maximum sorption capacities for IgG are 43 ± 2, 45 ± 3 and 46 ± 3 mg IgG per ml of sorbent for WY, WTY, WNY based sorbents respectively. Also it was shown that the new sorbents are compatible with blood and are suitable for the medical purposes.

Visceral hypersensitivity in female but not in male serotonin transporter knockout rats.

BACKGROUND: Visceral hypersensitivity occurs in irritable bowel syndrome (IBS), particularly in women. Serotonin signaling, including reduced serotonin transporter (SERT) expression, may be disrupted in IBS patients. We studied SERT gene knockout (KO) rats to determine if they exhibited sex-related alterations in visceral sensitivity. METHODS: We measured serotonin in the colonic mucosa using HPLC and amperometric microelectrode techniques. Visceral sensitivity was assessed using the electromyographic visceromotor response (VMR) in response to colorectal balloon distention (CRD). We studied the electrophysiologic properties of colon projecting sensory neurons in vitro using whole-cell recordings. KEY RESULTS: Mucosal serotonin levels were not different among male and female WT and SERT KO rats. Serotonin oxidation currents in vitro were larger (P < 0.05) in tissues from male and female SERT KO compared with WT rats. Oxidation currents in male and female WT, but not SERT KO, rats were increased (P < 0.05) by the SERT inhibitor fluoxetine (1 µmol L(-1) ). The VMR to CRD was increased in female but not in male SERT KO rats (P < 0.05); this response varied with the estrous cycle. Colon projecting sensory neurons from female SERT KO rats fired more action potentials compared with neurons from female WT rats. There were no differences in action potential firing in neurons from male WT and SERT KO rats. CONCLUSIONS & INFERENCES: Increased colonic extracellular serotonin in female SERT KO rats is associated with visceral hypersensitivity and hyperexcitability of colon projecting sensory neurons. The SERT KO rat is a model for studying interactions between serotonin, sex and visceral sensation.

SU-E-T-603: Influence of PTV Delineation at Air Cavity Interface on Tomotherapy Plan Quality.

PURPOSE: To determine if different ways in PTV delineation at an air cavity interface yield differences in overall plan quality and treatment efficiency Methods: Three different PTVs were used for treating a patient whose CTV surrounded a large air cavity created by a resected hard palate. The CTV lined the surface of the air cavity while PTV1 included the entire air cavity, PTV2 extended 4mm from the surface of the cavity into air, and PTV3 was reduced 4mm within the surface of the cavity. Tomotherapy plans were generated for all three PTVs. During each planning, all constraints to target and normal structures were kept constant along with the number of optimizations. Same planning process was repeated on a head and neck digital phantom with mock target, normal structures and cavity. RESULTS: Three treatment planning approaches showed no significantly different target coverage in terms of minimum or maximum dose to their respective PTVs. All plans attained 95% coverage of the CTV and PTV by 100% of the prescription. The conformity index (CI) of the plans delivered to PTV1, PTV2, and PTV3 were 1.09, 1.11, and 1.18, respectively. The skin, optic nerves, brainstem and spinal cord all received similar maximum dose to their respective volumes for each plan within 1Gy. The monitor units required for each treatment plan were all within 6% of one another with PTV1 having the highest. For head and neck phantom, the CIs of three plans were 1.05, 1.21, and 1.18, respectively. The coverage of the phantom CTV and sparing of normal structures were nearly equivalent. The total treatment times were identical. CONCLUSIONS: Tomotherapy planning is able to deliver dose to a head and neck PTV containing a large air cavity without compromising target coverage, sparing of normal tissues, or delivery time.

SU-E-T-412: Can Cyberknife SBRT Be an Alternative to Brachytherapy for Cervical Cancer Treatment?

PURPOSE: To investigate the effectiveness of stereotactic body radiation therapy (SBRT) with Cyberknife for treatment of squamous cell carcinoma (SCCa) of cervix that are commonly treated with brachytherapy. METHODS: SCCa of cervix is routinely treated with external beam radiation therapy (EBRT) followed by brachytherapy. Common practice is to use high-dose- rate (HDR) brachytherapy, mainly with Ir-192; however, low-dose-rate (LDR) brachytherapy with Cs-137 is also used. Three of our patients with cervical SCCa who were chosen to have LDR brachytherapy (Cs-137 with tandem and ovoids) could not tolerate the prolonged treatment or applicator placement. All these patients previously received 45Gy (1.8Gy/fratction) from EBRT and well tolerated. Planned LDR treatment dose and time were for patient-1: 42.63Gy in 73.5hr, patient-2: 42.34Gy in 73hr, patient-3: 41.76Gy in 72hr. Delivered LDR dose and time were: 3.75Gy in 6.5hr, OGy in Ohr, and 17.3Gy in 19.8hr, for patient-1, -2 and -3, respectively. Two of the three patients tolerated LDR treatment partially; the second patient could not tolerate the applicator, which required immediate removal after placement. Treatments were completed with Cyberknife SBRT (CK-SBRT)doses of 25Gy, 15Gy and 25Gy for patient-1, -2 and -3, respectively; all had 5Gy/fraction and 3fractions/week. Prescriptions were at 80% isododelines; CTV coverages were 96.6%, 99.9% and 100% for patient-1, -2 and -3, respectively. RESULTS: Till their last follow-up in February 2012, all three patients were doing fine clinically without any evidence of disease; none of these patients had any complications that could be related to CK-SBRT. CONCLUSIONS: Appears that CK-SBRT can be a viable treatment alternative to brachytherapy. CK-SBRT may also be more appealing to patients and physicians for a variety of reasons such as out-patient procedure, shorter treatment time, no need for operating room, and no need for applicator insertion and tolerance. However, extensive clinical study is warranted in this regard.

High contrast near-infrared polarized reflectance images of demineralization on tooth buccal and occlusal surfaces at lambda = 1310-nm.

BACKGROUND AND OBJECTIVES: Sound enamel manifests peak transparency in the near-IR (NIR) at 1310-nm, therefore the near-IR is ideally suited for high contrast imaging of dental caries. The purpose of this study was to acquire images of early demineralized enamel on the buccal and occlusal surfaces of extracted human teeth using NIR reflectance imaging and compare the contrast of those images with the contrast of images taken using other methods. MATERIALS AND METHODS: Fifteen human molars were used in this in vitro study. Teeth were painted with a clear acid-resistant varnish, leaving two 2 mm x 2 mm windows on the buccal and occlusal surfaces of each tooth for demineralization. Artificial lesions were produced in the exposed windows after a 2-day exposure to a demineralizing solution at pH 4.5. Lesions were imaged using NIR transillumination, NIR and visible light reflectance, and fluorescence imaging methods. Crossed polarizers were used where appropriate to improve contrast. Polarization sensitive optical coherence tomography (PS-OCT) was also used to non-destructively assess the depth and severity of demineralization in each sample window. RESULTS: NIR reflectance imaging had the highest image contrast for both the buccal and occlusal groups and it was significantly higher contrast than visible light reflectance (P < 0.05). CONCLUSION: The results of the study suggest that NIR reflectance imaging is a promising new method for acquiring high contrast images of early demineralization on tooth surfaces.

Dentin caries zones: mineral, structure, and properties.

Caries Detector staining reveals 4 zones in dentin containing caries lesions, but characteristics of each zone are not well-defined. We therefore investigated the physical and microstructural properties of carious dentin in the 4 different zones to determine important differences revealed by Caries Detector staining. Six arrested dentin caries lesions and 2 normal controls were Caries-Detector-stained, each zone (pink, light pink, transparent, apparently normal) being analyzed by atomic force microscopy (AFM) imaging for microstructure, by AFM nano-indentation for mechanical properties, and by transverse digital microradiography (TMR) for mineral content. Microstructure changes, and nanomechanical properties and mineral content significantly decreased across zones. Hydrated elastic modulus and mineral content from normal dentin to pink Caries-Detector-stained dentin ranged from 19.5 [10.6-25.3] GPa to 1.6 [0.0-5.0] GPa and from 42.9 [39.8-44.6] vol% to 12.4 [9.1-14.2] vol%, respectively. Even the most demineralized pink zone contained considerable residual mineral.

Remineralization of enamel caries can decrease optical reflectivity.

The remineralization of enamel caries can lead to distinct optical changes within a lesion. We hypothesized that the restoration of mineral volume would result in a measurable decrease in the depth-resolved reflectivity of polarized light from the lesion. To test this hypothesis, we measured optical changes in artificial caries undergoing remineralization as a function of depth, using Polarization-sensitive Optical Coherence Tomography (PS-OCT). Lesions were imaged non-destructively before and after exposure to a remineralization regimen. After imaging, microradiographs of histological thin sections indicated that the significant reflectivity reduction measured by PS-OCT accurately represented the increase in mineral content within a larger repaired surface zone. Mineral volume changes arising from remineralization can be measured on the basis of the optical reflectivity of the lesion.

Imaging artificial caries on the occlusal surfaces with polarization-sensitive optical coherence tomography.

Polarization-sensitive optical coherence tomography (PS-OCT) is a nondestructive imaging system that can utilize near-infrared (IR) light to produce depth-resolved images of dental enamel and has the potential to monitor early enamel occlusal caries. The objective of this study was to investigate the relationship between the magnitude of backscattered light and depolarization recorded by PS-OCT with changes in the enamel mineral volume in an artificial caries model. Artificial lesions were created on a selected region on the occlusal surfaces of sound posterior teeth (n=10) using a well-characterized 14-day pH cycling model. An all-fiber-based PS-OCT system operating at 1,310 nm was used to collect serial images at day 0 and day 14 prior to tooth sectioning. The quantitative mineral content profile and relative mineral loss, DeltaZ (%volxmicrom), of the carious enamel samples were obtained from transverse sections using high-resolution digital microradiography (DM). Line profiles of PS-OCT and DM images were used to evaluate the artificial caries severity and depth. The integrated reflectivity of the perpendicular-axis PS-OCT image, quantifying lesion severity, was correlated to the DeltaZ of the caries lesions. There was also a strong correlation between the lesion depth calculated from both imaging modalities. PS-OCT can image and quantify artificial occlusal caries by measuring the increase in backscattering and depolarization of near-IR light. This optical method has promising applications for in vivo detection and monitoring of early enamel occlusal caries.

Influence of laser irradiation on the constant composition kinetics of enamel dissolution.

The influence of 9.6 microm CO2 laser irradiation on enamel dissolution kinetics was investigated using a constant composition method designed for rate measurements of enamel dissolution as a function of depth, on a micrometer scale. In contrast to lower irradiation intensities (< or =1.0 J cm(-2)), which consistently showed reduced dissolution rates, higher fluences (energy per surface area) resulted in initially increased dissolution rates, which rapidly decreased, after dissolution times corresponding to removal of a few micrometers, to rates similar to those acquired using lower fluences. It was also demonstrated that surface damage during laser irradiation could be limited to the first 1-2 microm by lowering the number of pulses per spot during the irradiation procedure. The constant composition method can be used to measure detailed kinetics of inhibition of acid dissolution of dental enamel that has been treated by low fluence 9.6-microm CO2 laser irradiation.

Thrombelastographic changes in OPCAB surgical patients.

The purpose of this study was to determine whether thrombelastography could detect hypercoagulability in the off-pump coronary artery bypass (OPCAB) patient. Seventeen OPCAB and six cardiopulmonary bypass (CPB) patients were studied pre- and postprocedure, as well as on each of the first three postoperative days (POD). In the OPCAB patients, there was a small reduction in the postprocedure coagulation index (CI). This was followed by an increase in the CI on each of the next three POD, reaching a level exceeding the mean preprocedure CI by 2.32 units, indicative of a state of relative hypercoagulability. The mean CI for the CPB patients decreased significantly in the postprocedure sample. Over the next 72 h, the CI increased to a level that nearly equaled the preprocedure 'baseline'. We concluded that our study identified a state of relative hypercoagulability in the OPCAB patient 72 h after surgery. The mechanism of this hypercoagulation, as well as the clinical significance of this finding, is yet to be determined.

Effect of CO2 laser on pulpal temperature and surface morphology: an in vitro study.

OBJECTIVES: The objective of this study was to evaluate the potential effects on underlying dental hard tissues of a high pulse rate carbon dioxide (CO2) laser that was designed for soft tissue surgery. METHODS: Eighteen extracted human teeth were sectioned longitudinally, cleaned, and varnished, leaving nine exposed windows on each: six on the coronal surface (enamel) and three on the root surface (cementum, dentin). The CO2 irradiation conditions used were: wave length 10.6 microm; 1.2-2.6J/cm(2) fluence per pulse; repetition rate 120-1000Hz; 100-200ms pulse duration; and cumulative fluences ranging from 14 to 2200J/cm(2). Each window was irradiated with a 0.3mm beam diameter at one of nine power settings for 0.1, 0.5, or 1.0s. The pulp chamber temperature was measured with a microthermocouple. The irradiated teeth were evaluated by Polarized Light Microscopy (PLM) and Scanning Electron Microscopy (SEM). RESULTS: The pulp chamber temperature rise ranged from 0.5 to 19 degrees C depending on the location of the window and distance to pulp chamber. SEM revealed crystal fusion in both enamel and dentin at all cumulative fluences. At cumulative fluences of 40J/cm(2), 200 pulses/second and higher, measurable tissue loss was observed with PLM both in dentin and enamel. CONCLUSIONS: These results indicate there are threshold conditions above which pulsed CO2 laser light used for soft tissue surgery may cause detrimental changes to underlying oral hard tissue and to the pulp.

Residual heat deposition in dental enamel during IR laser ablation at 2.79, 2.94, 9.6, and 10.6 microm.

BACKGROUND AND OBJECTIVE: The principal factor limiting the rate of laser ablation of dental hard tissue is the risk of excessive heat accumulation in the tooth. Excessive heat deposition or accumulation may result in unacceptable damage to the pulp. The objective of this study was to measure the residual heat deposition during the laser ablation of dental enamel at those IR laser wavelengths well suited for the removal of dental caries. Optimal laser ablation systems minimize the residual heat deposition in the tooth by efficiently transferring the deposited laser energy to kinetic and internal energy of ejected tissue components. STUDY DESIGN/MATERIALS AND METHODS: The residual heat deposition in dental enamel was measured at laser wavelengths of 2.79, 2.94, 9.6, and 10.6 microm and pulse widths of 150 nsec -150 microsec using bovine block "calorimeters." Water droplets were applied to the surface before ablation with 150 microsec Er:YAG laser pulses to determine the influence of an optically thick water layer on reducing heat deposition. RESULTS: The residual heat was at a minimum for fluences well above the ablation threshold where measured values ranged from 25-70% depending on pulse duration and wavelength for the systems investigated. The lowest values of the residual heat were measured for short (< 20 micros) CO(2) laser pulses at 9.6 microm and for Q-switched erbium laser pulses at 2.79 and 2.94 microm. Droplets of water applied to the surface before ablation significantly reduced the residual heat deposition during ablation with 150 microsec Er:YAG laser pulses. CONCLUSIONS: Residual heat deposition can be markedly reduced by using CO(2) laser pulses of less than 20 microsec duration and shorter Q-switched Er:YAG and Er:YSGG laser pulses for enamel ablation.

Dental hard tissue modification and removal using sealed transverse excited atmospheric-pressure lasers operating at lambda=9.6 and 10.6 microm.

Pulsed CO(2) lasers have been shown to be effective for both removal and modification of dental hard tissue for the treatment of dental caries. In this study, sealed transverse excited atmospheric pressure (TEA) laser systems optimally tuned to the highly absorbed 9.6 microm wavelength were investigated for application on dental hard tissue. Conventional TEA lasers produce an initial high energy spike at the beginning of the laser pulse of submicrosecond duration followed by a long tail of about 1-4 micros. The pulse duration is well matched to the 1-2 micros thermal relaxation time of the deposited laser energy at 9.6 microm and effectively heats the enamel to the temperatures required for surface modification at absorbed fluences of less than 0.5 J/cm(2). Thus, the heat deposition in the tooth and the corresponding risk of pulpal necrosis from excessive heat accumulation is minimized. At higher fluences, the high peak power of the laser pulse rapidly initiates a plasma that markedly reduces the ablation rate and efficiency, severely limiting applicability for hard tissue ablation. By lengthening the laser pulse to reduce the energy distributed in the initial high energy spike, the plasma threshold can be raised sufficiently to increase the ablation rate by an order of magnitude. This results in a practical and efficient CO(2) laser system for caries ablation and surface modification.

Comparison of Er:YAG and 9.6-microm TE CO(2) lasers for ablation of skull tissue.

BACKGROUND AND OBJECTIVE: Craniotomy by using a drill and saw frequently results in fragmentation of the skull plate. Lasers have the potential to remove the skull plate intact, simplifying the reconstructive surgery. STUDY DESIGN/MATERIALS AND METHODS: Transverse-excited CO(2) lasers operating at the peak absorption wavelength of bone (lambda = 9.6 microm) and with pulse durations of 5-8 microsec, approximately the thermal relaxation time in hard tissue, produced high ablation rates and minimal peripheral thermal damage. Both thick (2 mm) and thin (250 microm) bovine skull samples were perforated and the ablation rates calculated. Results were compared with Q-switched and free-running Er:YAG lasers (lambda = 2.94 microm, tau(p) = 0.5 microsec and 300 microsec). RESULTS: The CO(2) laser produced ablation rates of up to 60 and 15 microm per pulse for thin and thick sections, respectively, and perforated thin and thick sections with fluences of less than 1 J/cm(2) and 6 J/cm(2), respectively. There was no discernible thermal damage and no need for water irrigation during ablation. Pulse durations > or =20 microsec resulted in significant tissue charring, which increased with the pulse duration. Although the free-running Er:YAG laser produced ablation rates of up to 100 microm per pulse, fluences of 10 J/cm(2) and 30 J/cm(2) were required to perforate thin and thick samples, respectively, and peripheral thermal damage measured 25-40 microm. CONCLUSIONS: In summary, the novel 5- to 8-microsec pulse length of the TE CO(2) laser is long enough to avoid a marked reduction in the ablation rate due to plasma formation and short enough to avoid peripheral thermal damage through thermal diffusion during the laser pulse. Furthermore, in vivo animal studies with the TE CO(2) laser are warranted for potential clinical application in craniotomy and craniofacial procedures.

CDI Blood Parameter Monitoring System 500--a new tool for the clinical perfusionist.

Sarns/3M Health Care has recently introduced the CDI 500 Blood Parameter Monitoring System. In addition to parameters previously available, this system now offers continuous monitoring of the patient's oxygen consumption (VO2/min) and potassium concentration ([K+]). The purpose of this study was: (1) to compare the [K+] from the CDI 500 with the [K+] derived from our hospital's laboratory; and (2) to compare the VO2/min from the CDI 500 with the results obtained utilizing the "gold-standard" Fick equation. The mean absolute difference in [K+] was 0.10 mEq/L with a mean percentage error of only 3.93%. The mean absolute difference in VO2/min was 18.78 ml O2/min, with a mean percentage error of 11.63%. We concluded that the [K+] correlated well and that 9.13% of the oxygen consumption percentage error was attributable to the exclusion of dissolved oxygen in the calculation used by the CDI 500, with the remaining 2.5% attributable to differences in technology. We recommended that future upgrades to the CDI 500 should include dissolved O2 when measuring oxygen consumption and consideration should be given to increasing the operating range for [K+].

Selective ablation of orthodontic composite by using sub-microsecond IR laser pulses with optical feedback.

BACKGROUND AND OBJECTIVE: Conventional methods of residual composite removal after debonding orthodontic brackets involve the use of abrasives that damage the underlying enamel. The objective of this study was to determine whether infrared pulsed lasers are suitable for the removal of composite through selective laser ablation. STUDY DESIGN/MATERIALS AND METHODS: Pulsed CO(2) and Er:YAG lasers were evaluated for their ability to selectively ablate orthodontic composites. Optical emission spectra of the luminous plasma produced during composite and enamel ablation were acquired to differentiate between enamel and composite ablation to minimize accidental removal of enamel. RESULTS: TEA CO(2) laser pulses at a wavelength of 10.6 microm were best suited for the selective ablation of composite. Spectral analysis of plume emission identified several calcium emission lines that can potentially be used to distinguish between enamel and composite ablation. CONCLUSION: TEA CO(2) lasers operating at 10.6 microm used in conjunction with optical feedback have the potential to selectively ablate residual dental composite and minimize inadvertent removal of enamel.