A new finite element approach for near real‐time simulation of light propagation in locally advanced head and neck tumors

Background and Objectives

Several clinical studies suggest that interstitial photodynamic therapy (I‐PDT) may benefit patients with locally advanced head and neck cancer (LAHNC). For I‐PDT, the therapeutic light is delivered through optical fibers inserted into the target tumor. The complex anatomy of the head and neck requires careful planning of fiber insertions. Often the fibers' location and tumor optical properties may vary from the original plan therefore pretreatment planning needs near real‐time updating to account for any changes. The purpose of this work was to develop a finite element analysis (FEA) approach for near real‐time simulation of light propagation in LAHNC.

Methods

Our previously developed FEA for modeling light propagation in skin tissue was modified to simulate light propagation from interstitial optical fibers. The modified model was validated by comparing the calculations with measurements in a phantom mimicking tumor optical properties. We investigated the impact of mesh element size and growth rate on the computation time, and defined optimal settings for the FEA. We demonstrated how the optimized FEA can be used for simulating light propagation in two cases of LAHNC amenable to I‐PDT, as proof‐of‐concept.

Results

The modified FEA was in agreement with the measurements (P = 0.0271). The optimal maximum mesh size and growth rate were 0.005–0.02 m and 2–2.5 m/m, respectively. Using these settings the computation time for simulating light propagation in LAHNC was reduced from 25.9 to 3.7 minutes in one case, and 10.1 to 4 minutes in another case. There were minor differences (1.62%, 1.13%) between the radiant exposures calculated with either mesh in both cases.

Conclusions

Our FEA approach can be used to model light propagation from diffused optical fibers in complex heterogeneous geometries representing LAHNC. There is a range of maximum element size (MES) and maximum element growth rate (MEGR) that can be used to minimize the computation time of the FEA to 4 minutes. Lasers Surg. Med. 47:60–67, 2015. © 2015 The Authors. Lasers in Surgery and Medicine Published by Wiley Periodicals, Inc.     

Rapid,high‐fluence multi‐pass q‐switched laser treatment of tattoos with a transparent perfluorodecalin‐infused patch: A pilot study

Background and Objectives

Perfluorodecalin (PFD) has previously been shown to rapidly dissipate the opaque, white micro‐bubble layer formed after exposure of tattoos to Q‐switched lasers [1]. The current pilot study was conducted to qualitatively determine if the use of a transparent PFD‐infused silicone patch would result in more rapid clearance of tattoos than conventional through‐air techniques.

Materials and Methods

Black or dark blue tattoos were divided into two halves in a single‐site IRB‐approved study with 17 subjects with Fitzpatrick skin types I–III. One half of each tattoo served as its own control and was treated with one pass of a standard Q‐switched Alexandrite laser (755 nm). The other half of the tattoo was treated directly through a transparent perfluorodecalin (PFD) infused patch (ON Light Sciences, Dublin, CA). The rapid whitening reduction effect of the Patch routinely allowed three to four laser passes in a total of approximately 5 minutes. Both sides were treated at highest tolerated fluence, but the optical clearing, index‐matching, and epidermal protection properties of the PFD Patch allowed significantly higher fluence compared to the control side. Standard photographs were taken at baseline, immediately prior to treatment with the PFD Patch in place, and finally before and after each treatment session. Treatments were administered at 4‐ to 6‐week intervals.

Results

In a majority of subjects (11 of 17), tattoos treated through a transparent PFD‐infused patch showed more rapid tattoo clearance with higher patient and clinician satisfaction than conventional treatment. In no case did the control side fade faster than the PFD Patch side. No unanticipated adverse events were observed.

Conclusions

Rapid multi‐pass treatment of tattoos with highest tolerated fluence facilitated by a transparent PFD‐infused patch clears tattoos more rapidly than conventional methods. Lasers Surg. Med. 47:613–618, 2015. © 2015 The Authors. Lasers in Surgery and Medicine published by Wiley Periodicals, Inc.     

Effect of highly purified capsaicin on articular cartilage and rotator cuff tendon healing: An in vivo rabbit study

Highly purified capsaicin has emerged as a promising injectable compound capable of providing sustained pain relief following a single localized treatment during orthopedic surgical procedures. To further assess its reliability for clinical use, the potential effect of highly purified capsaicin on articular cartilage metabolism as well as tendon structure and function warrants clarification. In the current study, rabbits received unilateral supraspinatus transection and repair with a single 1 ml injection of capsaicin (R + C), PEG‐only placebo (R + P), or saline (R + S) into the glenohumeral joint (GHJ). An additional group received 1 ml capsaicin onto an intact rotator cuff (I + C). At 18 weeks post‐op, cartilage proteoglycan (PG) synthesis and content as well as cell viability were similar (p > 0.05) across treatment groups. Biomechanical testing revealed no differences (p > 0.05) among tendon repair treatment groups. Similarly, histologic features of both cartilage and repaired tendons showed minimal differences across groups. Hence, in this rabbit model, a single injection of highly purified capsaicin into the GHJ does not induce a deleterious response with regard to cartilage matrix metabolism and cell viability, or rotator cuff healing. These data provide further evidence supporting the use of injectable, highly purified capsaicin as a safe alternative for management of postoperative pain following GHJ surgery. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 33:1854–1860, 2015.     

The Impact of Infidelity on Combat‐Exposed Service Members

This study examined relationships between combat‐exposed Operation Enduring Freedom/Operation Iraqi Freedom veterans’ experiences related to infidelity during deployment (i.e., indicating that a partner was unfaithful or reporting concern about potential infidelity) and postdeployment mental health, as well as the role of subsequent stress exposure and social support in these associations. The sample consisted of 571 individuals (338 men). There were 128 participants (22.2%) who indicated that their partners were unfaithful during their most recent deployment. Of the remaining 443 participants, 168 (37.8%) indicated that they were concerned that their partners might have been unfaithful. Individuals who indicated that their partners were unfaithful exhibited higher levels of posttraumatic stress symptomatology (β = .08; f²= .18) and depression symptom severity (β = .09; f² = .14), compared to individuals who did not indicate that their partners were unfaithful. For both men and women, reported infidelity was associated with mental health indirectly via postdeployment life stressors, whereas infidelity concerns were indirectly associated with mental health via postdeployment life stressors for men only. Findings suggested that infidelity can have a significant impact on combat‐exposed veterans’ mental health and highlight the need for additional research on this understudied topic within the military population.     

Traumatic Brain Injury and Suicidal Ideation Among U.S. Operation Enduring Freedom and Operation Iraqi Freedom Veterans

Traumatic brain injury (TBI) is associated with suicidal behavior among veterans, and gender differences in the strength of associations may exist. Almost all research has been limited to Veterans Health Administration (VHA) patients, and it is unclear if findings generalize to veterans who do not use VHA services. We examined gender‐ and VHA‐user‐specific associations between TBI related to deployment and postdeployment suicidal ideation in a U.S. national sample of 1,041 female and 880 male Operation Enduring Freedom (OEF) and Operation Iraqi Freedom (OIF) veterans. Path analysis was used to estimate TBI and suicidal ideation association, and examine PTSD and depression symptomatology in these associations. TBI was associated with suicidal ideation among male VHA users, OR = 3.64, 95% CI [2.21, 6.01]; and male and female nonusers, OR = 2.24, 95% CI [1.14, 4.44] and OR = 2.65, 95% CI [1.26, 5.58], respectively, in unadjusted analyses. This association was explained by depression symptoms among male and female nonusers. Among male VHA users an association between TBI and suicidal ideation remained when accounting for depression symptoms, OR = 2.50, 95% CI [1.33, 4.71]. Our findings offered evidence of an association between TBI and suicidal ideation among male OEF/OIF VHA users.     

Homelessness‐Related Traumatic Events and PTSD Among Women Experiencing Episodes of Homelessness in Three U.S. Cities

In this article, we report the prevalence of traumatic events (TEs), lifetime and 12‐month posttraumatic stress disorder (PTSD) among 148 women experiencing homelessness in 3 midsized cities in the United States (Omaha, NE, Pittsburgh, PA, and Portland, OR). The women ranged in age from 19 to 54 years with an average age of 38.89 years (SD = 10.18). The sample was 42.6% White/European American. We investigated the mediation of distal TEs (i.e., childhood maltreatment) by more proximal TEs associated with being homeless (i.e., homelessness‐related stressors) for meeting diagnostic criteria for 12‐month PTSD. Results indicated that 42.6% of the women met criteria for lifetime PTSD and 39.7% met criteria for past‐year PTSD. The number of TEs reported ranged from 0 to 16 in order of prevalence with a median of 6 TEs. The correlations between childhood maltreatment and 12‐month PTSD ranged from .16 to .20 and the correlations between homelessness‐related stressors and 12‐month PTSD ranged from .21 to .30. The mediation analysis was consistent with the association between childhood maltreatment and past‐year PTSD being fully mediated by homelessness‐related trauma.