Dosimetry model for photobiomodulation based on anthropometric and hemodynamic variables in patients with orofacial pain post-Covid-19: Study protocol for randomized clinical trial
Authors: Schuler Silvana Simões Velloso , Campos Mayra Costanti Vilela , Lacerda Ana Julia , Mazzoni Adriana Cátia , Silva Tamiris , Silva Francine Cristina da , Martins Manoela Domingues , Fernandes Kristianne Porta Santos , Fonseca Elsa Susana , Mesquita-Ferrari Raquel Agnelli , Horliana Anna Carolina Ratto Tempestini , Bussadori Sandra Kalil , Motta Lara Jansiski 
Published: October 2024

Introduction
Orofacial pain and tension headache are symptoms that affect a large portion of the population, compromising productivity, social ability, and functional development. The treatment for reducing painful sensation should be chosen carefully, as pharmacological treatment may bring side effects and overload the organism of patients in pain. Low-level laser therapy has been used with local and systemic [vascular] applications for pain control. However, there is still uncertainty in the literature about the ideal dosimetric parameters for photobiomodulation treatment according to patient characteristics.

Methods
The objective of this project is to validate a dosimetry model based on the relationship between the effects of photobiomodulation with anthropometric and hemodynamic variables, both in local application and systemic application in patients with symptoms of orofacial pain and tension headache. For this purpose, 180 participants with orofacial pain post-covid eligible participants will be randomly assigned to Group 1—Local Photobiomodulation, Group 2—Vascular Photobiomodulation, Group 3—Placebo Local Photobiomodulation, or Group 4—Placebo Vascular Photobiomodulation [Therapy EC–DMC device, São Carlos, Brazil,– 660 nm, 100mW] using stratified block randomization. Before the application, sociodemographic information such as age, skin phototype [classified by the Fitzpatrick scale], weight, height, body mass index [BMI], oxygen saturation [SaO2], blood pressure [BP], heart rate [HR], and thickness of skin, fat, and facial muscles will be collected. During the application, we will collect local temperature, SaO2, BP, and HR. Before and after laser application, blood levels of lactate and hemoglobin, BP, and HR will be measured in the first and last session. In addition to demographic, anthropometric, and hemodynamic variables, the penetrated energy will be quantified using a power meter, and information from orofacial pain and headache symptom questionnaires will be analyzed. The Monte Carlo simulation technique will be used to systematically study the relationship between the light penetration profile into the target tissues and the most relevant variables, namely BMI, tissue layer thicknesses, and skin phototype. Light transmittance, measured in vivo and simulated, will be compared to validate a personalized dosimetry model.

Discussion
The results of this study contribute to validating a Monte Carlo Simulation model to calculate the appropriate dosimetry for photobiomodulation therapies in the control of patients with Post-Covid-19 orofacial pain.

Trial registration
Trial registration number: NCT06065969.