Effects of cryogen spray cooling and high radiant exposures on selective vascular injury during laser irradiation of human skin

BACKGROUND: Increasing radiant exposure offers a means to increase treatment efficacy during laser-mediated treatment of vascular lesions, such as port-wine stains; however, excessive radiant exposure decreases selective vascular injury due to increased heat generation within the epidermis and collateral damage to perivascular collagen. OBJECTIVE: To determine if cryogen spray cooling could be used to maintain selective vascular injury (ie, prevent epidermal and perivascular collagen damage) when using high radiant exposures (16-30 J/cm2). DESIGN: Observational study. SETTING: Academic hospital and research laboratory. PATIENTS: Twenty women with normal abdominal skin (skin phototypes I-VI). INTERVENTIONS: Skin was irradiated with a pulsed dye laser (wavelength = 585 nm; pulse duration = 1.5 milliseconds; 5-mm-diameter spot) using various radiant exposures (8-30 J/cm2) without and with cryogen spray cooling (50- to 300-millisecond cryogen spurts). MAIN OUTCOME MEASURE: Hematoxylin-eosin-stained histologic sections from each irradiated site were examined for the degree of epidermal damage, maximum depth of red blood cell coagulation, and percentage of vessels containing perivascular collagen coagulation. RESULTS: Long cryogen spurt durations (>200 milliseconds) protected the epidermis in light-skinned individuals (skin phototypes I-IV) at the highest radiant exposure (30 J/cm2); however, epidermal protection could not be achieved in dark-skinned individuals (skin phototypes V-VI) even at the lowest radiant exposure (8 J/cm2). The red blood cell coagulation depth increased with increasing radiant exposure (to >2.5 mm for skin phototypes I-IV and to approximately 1.2 mm for skin phototypes V-VI). In addition, long cryogen spurt durations (>200 milliseconds) prevented perivascular collagen coagulation in all skin types. CONCLUSIONS: Cryogen spurt durations much longer than those currently used in therapy (>200 milliseconds) may be clinically useful for protecting the epidermis and perivascular tissues when using high radiant exposures during cutaneous laser therapies. Additional studies are necessary to prove clinical safety of these protocols.     

Risk factors for suicide in epilepsy: a case control study

PURPOSE: Suicide is considered to be one of the most important causes of death contributing to the increased mortality of persons with epilepsy. We investigated the association between the risk of suicide in persons with epilepsy and clinical factors that might increase or have been suggested to increase the risk of suicide. METHODS: A case-control study was nested within a cohort of 6,880 patients registered in the Stockholm County In-Patient Register with a diagnosis of epilepsy. The study population was followed up through the National Cause of Death Register. Twenty-six cases of suicide, 23 cases of suspected but not proven suicide, and 171 controls, living epilepsy patients, were selected from the cohort. Clinical data were collected through medical record review. RESULTS: There was a ninefold increase in risk of suicide with mental illness and a 10-fold increase in relative risk (RR) with the use of antipsychotic drugs. The estimated RR of suicide was 16.0 [95% confidence interval (CI), 4.4-58.3] for onset of epilepsy at younger than 18 years, compared with onset after 29 years. The risk of suicide seemed to increase with high seizure frequency and antiepileptic drug (AED) polytherapy, although the estimates were imprecise and the associations not statistically significant. Insufficient data on seizure frequency and changes in AED dosage due to incomplete case records were associated with high RRs. We found no association between risk of suicide and any particular AED, with type of epilepsy, or localization or lateralization of epileptogenic focus on EEG [RR = 0.3 (95% CI, 0.1-1.7)]. CONCLUSIONS: The profile of the epilepsy patient who commits suicide that emerges from our study is a patient with early onset (particularly onset during adolescence) but not necessarily severe epilepsy, psychiatric illness, and perhaps inadequate neurologic follow-up. Previous reports of an association with temporal lobe epilepsy could not be confirmed.     

Analysis of particle deposition in the turbinate and olfactory regions using a human nasal computational fluid dynamics model.

The human nasal passages effectively filter particles from inhaled air. This prevents harmful pollutants from reaching susceptible pulmonary airways, but may leave the nasal mucosa vulnerable to potentially injurious effects from inhaled toxicants. This filtering property may also be strategically used for aerosolized nasal drug delivery. The nasal route has recently been considered as a means of delivering systemically acting drugs due to the large absorptive surface area available in close proximity to the nostrils. In this study, a computational fluid dynamics (CFD) model of nasal airflow was used with a particle transport and deposition code to predict localized deposition of inhaled particles in human nasal passages. The model geometry was formed from MRI scan tracings of the nasal passages of a healthy adult male. Spherical particles ranging in size from 5 to 50 microm were released from the nostrils. Particle trajectories and deposition sites were calculated in the presence of steady-state inspiratory airflow at volumetric flow rates of 7.5, 15, and 30 L/min. The nasal valve, turbinates, and olfactory region were defined in the CFD model so that particles depositing in these regions could be identified and correlated with their release positions on the nostril surfaces. When plotted against impaction parameter, deposition efficiencies in these regions exhibited maximum values of 53%, 20%, and 3%, respectively. Analysis of preferential deposition patterns and nostril release positions under natural breathing scenarios can be used to determine optimal particle size and flow rate combinations to selectively target drug particles to specific regions of the nose.     

Temporal effects of cell adhesion on mechanical characteristics of the single chondrocyte.

Cell adhesion to material surfaces is a fundamental phenomenon in tissue response to implanted devices, and an important consideration in tissue engineering. For example, elucidation of phenomena associated with adhesion of chondrocytes to biomaterials is critical in addressing the difficult problem of articular cartilage regeneration. The first objective of this study was to measure the mechanical adhesiveness characteristics of individual rabbit articular chondrocytes as a function of seeding time to provide further understanding of the cell adhesion process. The second objective was to quantify the force required to separate the plasma membrane from the underlying cytoskeleton as a function of seeding time. After culturing chondrocytes on glass coverslips for 1, 2, 4, 6 h, two biomechanical tests were performed on single chondrocytes: (i) mechanical adhesiveness measurement by the cytodetacher; and (ii) plasma membrane tether formation force measurement by optical tweezers. Cell mechanical adhesiveness increased from 231+/-149 Pa at 1 h to 1085+/-211 Pa at 6 h. The cell contact area with the substrata increased from 161+/-52 microm(2) at 1 h to 369+/-105 microm(2) at 6 h. The tether formation force increased from 232+/-23 pN at 1 h to 591+/-17 pN at 6 h. Moreover, fluorescence staining by rhodamine-phalloidin demonstrated the process of actin spreading within the cytoskeleton from 0.5 to 6 h and allowed for measurement of cell height which was found to decrease from 12.3+/-2.9 microm at 0.5 h to 6.2+/-0.9 microm at 6 h.     

Autofluorescence characterization for the early diagnosis of neoplastic changes in DMBA/TPA-induced mouse skin carcinogenesis

BACKGROUND AND OBJECTIVE: Squamous cell carcinoma (SCC), the second most common skin cancer, usually remains confined to the epidermis for some time but eventually penetrates the underlying tissues, if left untreated. The non-invasive early detection of the SCC is important for appropriate therapeutic strategies. In this study, we aim to characterize the tissue transformation in DMBA/TPA induced mouse skin tumor model using autofluorescence excitation emission matrix (EEM) in conjunction with a multivariate statistical method for early detection of the neoplastic changes. STUDY DESIGN/MATERIALS AND METHODS: The fluorescence EEM from experimental group (n = 40; DMBA/TPA application), control group (n = 6; acetone application), and the blank group (n = 6; no application of DMBA/TPA or acetone) were measured every week using a spectrofluorometer coupled with a fiber optic bundle. The EEM was recorded at excitation wavelengths from 280 to 460 nm at 10 nm intervals and the fluorescence emission was scanned from 300 to 750 nm. The fluorescence emission characteristics corresponding to different fluorophores were extracted from the EEM and the spectral data were used in a multiple/linear discriminant statistical algorithm. RESULTS: The changes in the fluorescence emission intensity were observed as early as the 1st week of tumor initiation by DMBA. Morphological changes as well as differences in the gross appearance of the skin surface were observed during the entire tumor initiation and promotion period of 15 weeks. The statistical analysis was performed for each excitation wavelength in the EEM and better classification accuracy was obtained for 280 and 410 nm excitations, corresponding to tryptophan and endogenous porphyrins, respectively. The statistical analysis of the combination wavelengths resulted in 11.6% increase in the overall classification accuracy when compared to the highest classification accuracy obtained with single wavelength analysis. CONCLUSION: The intensity ratio mapping using the combination of emission intensities of key fluorophores such as tryptophan, collagen, NADH, and endogenous porphyrins from the measured EEM in conjunction with a simple multivariate statistical analysis can be used as a potential tool for the discrimination of early neoplastic changes with improved classification accuracy. Tryptophan and endogenous porphyrins may be used as biomarkers for the discrimination of early neoplastic changes when single wavelength excitations are used.     

Comparison of 585 and 595 nm laser-induced vascular response of normal in vivo human skin

BACKGROUND AND OBJECTIVES: Two wavelengths, 585 and 595 nm, are currently common options for treating vascular malformations such as port-wine stains (PWS). Controversy exists as to which wavelength induces greater photothermal damage to the blood vessels and subsequent resolution of the malformations. STUDY DESIGN/MATERIALS AND METHODS: We irradiated normal, human skin in vivo at 585 and 595 nm wavelengths using fluences of 10-30 J/cm(2) with a 1.5 millisecond laser pulse. The level of purpura, total vascular damage, maximum coagulation depth (MCD), and perivascular damage were quantified by gross observation and histological analysis. RESULTS: Results demonstrated that 585 nm light caused greater purpura, vascular damage, maximum coagulation depth, and perivascular damage than 595 nm. Purpura showed a positive correlation with total vascular damage to a certain extent beyond which the total vascular damage did not change. For equivalent purpura, 585 and 595 nm produced no statistically significant difference in vascular damage. The difference in the laser-induced vascular damage between 585 and 595 nm, although statistically significant, was no more than 50%. CONCLUSIONS: The bathochromic (red) shift and formation of met-hemoglobin, which reduces the 585 nm light absorption and increases that of 595 nm compared to native oxy-hemoglobin, play a considerable role in creating more parity in vascular damage between the two wavelengths than would be expected based on their respective "native" absorption coefficients alone.     

Laser-induced thermal injury to dermal blood vessels: analysis of wavelength (585 nm vs. 595 nm), cryogen spray cooling, and wound healing effects

BACKGROUND AND OBJECTIVES: Successful laser treatment of cutaneous hyper-vascular lesions requires appropriate laser irradiation parameters for selective photothermolysis of ectatic dermal blood vessels as well as appropriate cooling parameters for epidermal protection based on an individual patient basis. Using the rabbit ear as an in vivo model for dermal vasculature, we investigated the influences of laser wavelength (585 nm vs. 595 nm) and cryogen spray cooling with various spurt durations on the laser-induced thermal injury to dermal blood vessels. Wound healing response was also evaluated in 2 hours and 4 days. STUDY DESIGN/MATERIALS AND METHODS: Flashlamp-pumped pulsed dye laser ScleroPlus (operated at the wavelength of 585 or 595 nm) was used for the comparison between the influences of two wavelengths (585 nm vs. 595 nm). R134-a cryogen spurts with the durations from 50 to 300 milliseconds were sprayed onto the sites to be irradiated and terminated 20 milliseconds before the onset of the laser pulses. In vivo rabbit ear was used as the model for cutaneous hyper-vascular lesions. Totally 10 New Zealand Albino white rabbits were experimented and in each rabbit ear six to seven sites were irradiated. Five animals were sacrificed 2 hours after the irradiation, and the remaining five sacrificed 4 days after the irradiation. Thermal injury to the blood vessel was assessed by hematoxylin and eosin stained histological sections and confirmed by an apoptosis assay. RESULTS: When the radiant exposures were above 10 J/cm2, 595 nm wavelength induced equivalent or more severe thermal injury to dermal blood vessels than 585 nm. Cryogen spray cooling with the spurt durations above 100 milliseconds resulted in increased depth of the most superficial thermal injury to dermal blood vessels than without cooling, indicating that superficial blood vessels were non-specifically cooled by the cryogen spurts applied at these parameters. Laser-induced thermal injury was significantly healed in the rabbit ear vasculature at 4 days post irradiation. CONCLUSIONS: Given sufficient radiant exposure, 595 nm wavelength can induce equivalent or more severe vascular injury compared with 585 nm. Cryogen spray cooling with the spurt durations above 100 ms may impair the photocoagulation of superficial blood vessels. Irreversible thermal injury to blood vessel can be achieved only when the basement membrane of blood vessel wall is irreversibly damaged.     

Epidermal and vascular damage analysis of in vivo human skin in response to 595 nm pulsed laser irradiation

BACKGROUND AND OBJECTIVES: Laser irradiation is the current modality for treatment of cutaneous hypervascular malformations such as port wine stains and telangiectasia. Although cryogen spray cooling (CSC) is used to protect the epidermis from non-specific laser-induced thermal damage in moderately-pigmented skin types, individuals with high melanin content are still at risk for epidermal damage using the current laser irradiation and CSC parameters. The objective of this study was to investigate the influence of the spray Weber number (1,100 or 5,100) on epidermal protection and examine vascular coagulation in response to pulsed dye laser irradiation. STUDY DESIGN/MATERIALS AND METHODS: Normal, in vivo human skin from eight subjects of Fitzpatrick skin types I-V were precooled with either low or high Weber number cryogen sprays and subsequently irradiated with a pulsed dye laser at 595 nm. Analysis of gross purpura, morphological vascular damage, and apoptosis of the vascular walls were performed. RESULTS: Results demonstrated a high Weber number spray of 5,100 decreased the level of epidermal damage in darker and moderate pigmented individuals compared to a Weber number spray of 1,100. This study also established a positive correlation between gross purpura and the level of vessel wall apoptosis. CONCLUSIONS: This study has demonstrated that CSC with a high Weber number spray can decrease nonspecific thermal damage to the epidermis in response to laser irradiation in vivo. We have also established a positive correlation between gross purpura and the level of vessel wall apoptosis. Lasers Surg. Med. (c) 2005 Wiley-Liss, Inc.     

Para-aortic lymph node radiation in advanced cervical cancer

From 1970 until December, 1977, 36 patients with advanced carcinoma of the uterine cervix and with iliac or para-aortic nodes interpreted as un-equivocally positive on lymphangiography have received radiation therapy (4500–5000 rad) to the para-aortic area at the Department of Therapeutic Radiology at Tufts-New England Medical Center Hospital. Of 29 patients who received para-aortic area irradiation as part of their initial treatment, local control was achieved in 18 patients (62%). Of these, 11 patients are currently alive with no evidence of disease (NED); two died without evidence of tumor. The remaining 16 patients died of their tumor (11 with locally uncontrolled tumor and five with distant metastasis). Of seven patients in whom the para-aortic area was treated because of retroperitoneal nodal recurrence, only two are alive without disease and the rest succumbed to their tumor. Overall, four patients developed major complications requiring surgical intervention. Detailed results and our current pre-treatment evaluation policy including lymphangiography, percutaneous needle biopsy and selective extra-peritoneal lymph node biopsy will be discussed.