TEMPy: a toolkit for the modeling of weighted tissue equivalent material in diagnostic imaging.

Objective.Accurate simulation of human tissues is imperative for advancements in diagnostic imaging, particularly in the fields of dosimetry and image quality evaluation. Developing Tissue Equivalent Materials (TEMs) with radiological characteristics akin to those of human tissues is essential for ensuring the reliability and relevance of imaging studies. This study presents the development of a mathematical model and a new toolkit (TEMPy) for obtaining the best composition of materials that mimic the radiological characteristics of human tissues. The model and the toolkit are described, along with an example showcasing its application to obtain desired TEMs.Approach.The methodology consisted of fitting volume fractions of the components of TEM in order to determine its linear attenuation coefficient as close as possible to the linear attenuation coefficient of the reference material. The fitting procedure adopted a modified Least Square Method including a weight function. This function reflects the contribution of the x-ray spectra in the suitable energy range of interest. TEMPy can also be used to estimate the effective atomic number and electron density of the resulting TEM.Main results.TEMPy was used to obtain the chemical composition of materials equivalent to water and soft tissue, in the energy range used in x-ray imaging (10 -150 keV) and for breast tissue using the energy range (5-40 keV). The maximum relative difference between the linear attenuation coefficients of the developed and reference materials was ±5% in the considered energy ranges.Significance.TEMPy facilitates the formulation of TEMs with radiological properties closely mimicking those of real tissues, aiding in the preparation of physical anthropomorphic or geometric phantoms for various applications. The toolkit is freely available to interested readers.

A custom-made integrated system for thermoluminescence and radioluminescence spectroscopy.

Thermoluminescence (TL) and Radioluminescence (RL) are widely used in dosimetry applications. We present a custom-built integrated system, designated LUMI22, for measuring TL, TL spectroscopy, RL, and RL as a function of temperature. LUMI22 includes a heating system based on Kanthal® A1 alloy (FeCrAl), a microcontroller to regulate the temperature ramps (e.g. 1-5 °C/s). To irradiate samples an X-ray tube (Moxtek 50 kV, 50 µA) is powered, controlled, and monitored by an FTC-200 standard controller. The dose rate at the sample position is 0.43 Gy/min. Light collection includes a Photomultiplier Tube (PMT, Hamamatsu H10493-012:HA, 185-850 nm). Additionally, a miniature fiber optic spectrometer (Ocean Optics, QE65000, range 200-1100 nm) coupled with a 1000 µm diameter fiber optic (QP1000- 2-UV-VIS) was employed for TL and RL spectroscopy measurements. To assess the functionality of the system, it was used to measure TL and RL from Al2O3:C,Mg, Al2O3:C and TLD-100 phosphors which have been previously well investigated. The measured TL and RL data were well compared to the published ones, confirming the functionality of the system.

Low-level laser in the treatment of patients with hypothyroidism induced by chronic autoimmune thyroiditis: a randomized, placebo-controlled clinical trial.

Chronic autoimmune thyroiditis (CAT) is the most common cause of acquired hypothyroidism, which requires lifelong levothyroxine replacement therapy. Currently, no effective therapy is available for CAT. Thus, the objective of this study was to evaluate the efficacy of low-level laser therapy (LLLT) in patients with CAT-induced hypothyroidism by testing thyroid function, thyroid peroxidase antibodies (TPOAb), thyroglobulin antibodies (TgAb), and ultrasonographic echogenicity. A randomized, placebo-controlled trial with a 9-month follow-up was conducted from 2006 to 2009. Forty-three patients with a history of levothyroxine therapy for CAT-induced hypothyroidism were randomly assigned to receive either 10 sessions of LLLT (830 nm, output power of 50 mW, and fluence of 707 J/cm(2); L group, n=23) or 10 sessions of a placebo treatment (P group, n=20). The levothyroxine was suspended 30 days after the LLLT or placebo procedures. Thyroid function was estimated by the levothyroxine dose required to achieve normal concentrations of T3, T4, free-T4 (fT4), and thyrotropin after 9 months of postlevothyroxine withdrawal. Autoimmunity was assessed by measuring the TPOAb and TgAb levels. A quantitative computerized echogenicity analysis was performed pre- and 30 days postintervention. The results showed a significant difference in the mean levothyroxine dose required to treat the hypothyroidism between the L group (38.59 ± 20.22 µg/day) and the P group (106.88 ± 22.90 µg/day, P<0.001). Lower TPOAb (P=0.043) and greater echogenicity (P<0.001) were also noted in the L group. No TgAb difference was observed. These findings suggest that LLLT was effective at improving thyroid function, promoting reduced TPOAb-mediated autoimmunity and increasing thyroid echogenicity in patients with CAT hypothyroidism.

Novel treatment immediately after myelomeningocele repair applying low-level laser therapy in newborns: a pilot study.

BACKGROUND/AIMS: The use of low-level laser therapy (LLLT) in neurosurgery is still hardly disseminated and there are situations in which the effects of this therapeutic tool would be extremely relevant in this medical field. The aim of the present study is to analyze the effect of LLLT on tissue repair after the corrective surgical incision in neonates with myelomeningocele, in an attempt to diminish the incidence of postoperative dehiscences following surgical repair performed immediately after birth. MATERIALS AND METHODS: Prospective pilot study with 13 patients submitted to surgery at birth who received adjuvant treatment with LLLT (group A). A diode laser CW, λ = 685 nm, p = 21 mW, was applied punctually along the surgical incision, with 0.19 J delivered per point, accounting for a total of 4-10 J delivered energy per patient, according to the surgical wound area and then compared with the results obtained in 23 patients who underwent surgery without laser therapy (group B). RESULTS: This pilot study disclosed a significant decline in dehiscences of the surgical wounds in neonates who were submitted to LLLT (7.69 vs. 17.39%). CONCLUSION: This new adjuvant therapeutic modality with LLLT aided the healing of surgical wounds, preventing morbidities, as well as shortening the period of hospital stay, which implies a reduction of costs for patients and for the institution.

OSL dosimetric properties and efficiency of Brazilian natural calcium fluoride pellets.

Calcium fluoride (CaF2), in both natural and synthetic forms, has been exhaustively studied and explored as thermoluminescent (TL) detector. However its sensitivity to ambient light points to the applicability of CaF2 as OSL (Optically Stimulated Luminescence) detector, increasing the research about its luminescent properties. Although some properties to employ CaF2 detectors with OSL technique have been already demonstrated, there is a lack of some essential information as the OSL response to different types and energy of ionizing radiation. In order to extend the use of Brazilian natural CaF2 with OSL technique, we evaluated the efficiency and dosimetric properties of cold pressed CaF2:NaCl pellets. The CaF2 detectors presented good reproducibility and negligible fading of the signal over one month after irradiation. The dose response using OSL, TL and residual TL showed linear behavior for different radiation beams (protons, photons and alpha and beta particles), being equivalent to the results obtained with BeO and MTS (LiF) detectors through OSL and TL technique respectively. Moreover, differences were observed in OSL efficiency according the beam type and energy; CaF2 detectors presented a higher OSL and TL sensitivities to protons, photons and beta particles than to alpha particles. The energy response to photons obtained using OSL and residual TL intensities present an over response at lower photon energy similar to TL energy response. In addition, differences in the OSL curve shapes were observed according to radiation type and energy, pointing to the possibility of applying this material in mixed radiation fields and to estimate average LET (Linear Energy Transfer).

OSL and TL techniques combined in a beryllium oxide detector to evaluate simultaneously accumulated and single doses.

Optically stimulated luminescence (OSL) and thermoluminescence (TL) are similar techniques widely used in radiation dosimetry. The main difference between these techniques is the stimulus to induce luminescence emission: TL technique uses thermal stimulation, whereas OSL uses optical stimulation. One of the main intrinsic characteristics of the OSL technique is the possibility of reading several times the dosimetric materials with a negligible loss of signal. In the case of BeO, recent studies have shown that TL stimulation up to 250°C does not affect its OSL signal. Taking the advantages of dosimetric characteristics of BeO combined with both techniques, in this study, we demonstrated the possibility of measuring accumulated and single doses in the same BeO-based detector in order to use it to improve individual monitoring of radiation workers exposed to X-ray or gamma-ray fields. Single doses were measured using TL technique by heating the detector up to 250°C, whereas accumulated doses were estimated using OSL technique in the same detector in a relatively short time of optical stimulation. The detectors were exposed to two energies: 28keV X-rays and 1.25MeV Co-60 gamma rays. The doses estimated by OSL and TL of BeO (Thermalox 995) were compared with those obtained with LiF (TLD-100) and recorded with a calibrated ionization chamber. The results indicate that combined OSL and TL signals of BeO detectors can provide additional information of accumulated dose, with additional exploration of the advantages of both techniques, such as speed in readouts with OSL, and double-check the doses using TL and OSL intensities from BeO.

Effects of low-level laser therapy on the serum TGF-ß1 concentrations in individuals with autoimmune thyroiditis.

OBJECTIVE: The objective of this study was to evaluate the serum concentration of transforming growth factor-ß1 (TGF-ß1) after low-level laser therapy (LLLT) in patients with hypothyroidism resulting from chronic autoimmune thyroiditis (CAT). BACKGROUND DATA: Certain data indicate that LLLT is effective in patients with hypothyroidism caused by CAT; however, the mechanisms of action of LLLT in thyroid tissue are unknown. Cytokines could play a role in the response to LLLT. METHODS: A randomized, placebo-controlled trial included 43 patients with a history of levothyroxine therapy for CAT-induced hypothyroidism. The patients were randomly assigned to receive either 10 sessions of LLLT (830 nm, 50 mW output power, and 707 J/cm(2) fluence; L group, n=23) or 10 sessions of a placebo treatment (P group, n=20) twice a week. Levothyroxine was maintained at the same dose during the entire study period. TGF-ß1 was measured both pre-intervention and 30 days post-intervention in both groups. The differences were calculated between the TGF-ß1 values observed 30 days post-intervention and the pre-intervention TGF-ß1 values for each group (intragroup). RESULTS: Comparing the differences in TGF-ß1 levels between the L group (874.9±541.7 pg/mL) and the P group (-128.4±832.8 pg/mL) revealed that there was a statistically significant increase in TGF-ß1 levels 30 days post-intervention in group L compared with the placebo group (p=0.0379). CONCLUSIONS: This finding suggested that the significant increase in serum TGF-ß1 levels in patients with CAT-induced hypothyroidism was associated with the thyroid LLLT procedure. Future studies of the effect of LLLT on TGF-ß1 gene expression in thyroid tissue are necessary to confirm these findings.

Assessment of the effects of low-level laser therapy on the thyroid vascularization of patients with autoimmune hypothyroidism by color Doppler ultrasound.

Background. Chronic autoimmune thyroiditis (CAT) frequently alters thyroid vascularization, likely as a result of the autoimmune process. Objective. To evaluate the effects of low-level laser therapy (LLLT) on the thyroid vascularization of patients with hypothyroidism induced by CAT using color Doppler ultrasound parameters. Methods. In this randomized clinical trial, 43 patients who underwent levothyroxine replacement for CAT-induced hypothyroidism were randomly assigned to receive either 10 sessions of LLLT (L group, n = 23) or 10 sessions of a placebo treatment (P group, n = 20). Color Doppler ultrasounds were performed before and 30 days after interventions. To verify the vascularity of the thyroid parenchyma, power Doppler was performed. The systolic peak velocity (SPV) and resistance index (RI) in the superior (STA) and inferior thyroid arteries (ITAs) were measured by pulsed Doppler. Results. The frequency of normal vascularization of the thyroid lobes observed in the postintervention power Doppler examination was significantly higher in the L than in the P group (P = 0.023). The pulsed Doppler examination revealed an increase in the SPV of the ITA in the L group compared with the P group (P = 0.016). No significant differences in the SPV of the STA and in the RI were found between the groups. Conclusion. These results suggest that LLLT can ameliorate thyroid parenchyma vascularization and increase the SPV of the ITA of patients with hypothyroidism caused by CAT.

Diagnostic reference levels for the most frequent radiological examinations carried out in Brazil.

OBJECTIVES: A large-scale survey of doses to patients undergoing the most frequent radiological examinations was carried out in health services in São Paulo (347 radiological examinations per 1 000 inhabitants), the most populous Brazilian state. METHODS: A postal dosimetric kit with thermoluminescence dosimeters was used to evaluate the entrance surface dose (ESD) to patients. A stratified sampling technique applied to the national health database furnished important data on the distribution of equipment and the annual number of examinations. Chest, head (skull and sinus), and spine (cervical, thoracic, and lumbar) examinations were included in the trial. A total of 83 rooms and 868 patients were included, and 1 415 values of ESD were measured. RESULTS: The data show large coefficients of variation in tube charge, giving rise to large variations in ESD values. Also, a series of high ESD values associated with unnecessary localizing fluoroscopy were detected. Diagnostic reference levels were determined, based on the 75th percentile (third quartile) of the ESD distributions. For adult patients, the diagnostic reference levels achieved are very similar to those obtained in international surveys. However, the situation is different for pediatric patients: the ESD values found in this survey are twice as large as the international recommendations for chest radiographs of children. CONCLUSIONS: Despite the reduced number of ESD values and rooms for the pediatric patient group, it is recommended that practices in chest examinations be revised and that specific national reference doses and image quality be established after a broader survey is carried out.

Diagnostic reference levels for the most frequent radiological examinations carried out in Brazil / Niveles de referencia diagnósticos para los exámenes radiológicos más frecuentes realizados en Brasil

OBJECTIVES: A large-scale survey of doses to patients undergoing the most frequent radiological examinations was carried out in health services in São Paulo (347 radiological exami nations per 1 000 inhabitants), the most populous Brazilian state. METHODS: A postal dosimetric kit with thermoluminescence dosimeters was used to evalu ate the entrance surface dose (ESD) to patients. A stratified sampling technique applied to the national health database furnished important data on the distribution of equipment and the an nual number of examinations. Chest, head (skull and sinus), and spine (cervical, thoracic, and lumbar) examinations were included in the trial. A total of 83 rooms and 868 patients were in cluded, and 1 415 values of ESD were measured. RESULTS: The data show large coefficients of variation in tube charge, giving rise to large variations in ESD values. Also, a series of high ESD values associated with unnecessary lo calizing fluoroscopy were detected. Diagnostic reference levels were determined, based on the 75th percentile (third quartile) of the ESD distributions. For adult patients, the diagnostic ref erence levels achieved are very similar to those obtained in international surveys. However, the situation is different for pediatric patients: the ESD values found in this survey are twice as large as the international recommendations for chest radiographs of children. CONCLUSIONS: Despite the reduced number of ESD values and rooms for the pediatric pa tient group, it is recommended that practices in chest examinations be revised and that specific national reference doses and image quality be established after a broader survey is carried out.

OBJETIVOS: Estudio a gran escala de las dosis aplicadas a pacientes sometidos a los exámenes radiológicos más frecuentes realizados en los servicios de salud de São Paulo (347 exámenes radiológicos por 1 000 habitantes), el estado más poblado de Brasil. MÉTODOS: Se empleó un sistema dosimétrico postal con dosímetros termoluminiscentes para evaluar la dosis en la superficie de entrada (DSE) de los pacientes. Se realizó un muestreo estratificado de la base de datos nacional de salud que aportó información importante sobre la distribución del equipamiento y el número de pruebas realizadas anualmente. El estudio abarcó los exámenes de tórax, cabeza (cráneo y senos paranasales) y columna vertebral (cervical, dorsal y lumbar). Se incluyeron 83 instalaciones y 868 pacientes; se obtuvieron 1 415 mediciones de DSE. RESULTADOS: Los resultados mostraron grandes coeficientes de variación en la carga del tubo, lo que originó variaciones considerables en las DSE. Además, se detectaron valores elevados de DSE asociados con fluoroscopias de localización innecesarias. Los niveles de referencia diagnósticos se determinaron a partir del percentil 75 (tres cuartiles) de las distribuciones de las DSE. Para pacientes adultos, los niveles de referencia diagnósticos alcanzados fueron muy similares a los obtenidos en estudios internacionales. No obstante, la situación fue diferente en los pacientes pediátricos: los valores de DSE obtenidos en este estudio fueron dos veces mayores que los recomendados internacionalmente para radiografías de tórax en niños. CONCLUSIONES: A pesar del reducido número de valores de DSE e instalaciones en el grupo de pacientes pediátricos, se recomienda revisar la práctica de estudios radiológicos de tórax y establecer referencias nacionales específicas para las dosis y la calidad de las imágenes, después de realizar un estudio más amplio.