COVID-19 and cancer risk arising from ionizing radiation exposure through CT scans: a cross-sectional study.

BACKGROUND: The surge in the utilization of CT scans for COVID-19 diagnosis and monitoring during the pandemic is undeniable. This increase has brought to the forefront concerns about the potential long-term health consequences, especially radiation-induced cancer risk. This study aimed to quantify the potential cancer risk associated with CT scans performed for COVID-19 detection. METHODS: In this cross-sectional study data from a total of 561 patients, who were referred to the radiology center at Imam Hossein Hospital in Shahroud, was collected. CT scan reports were categorized into three groups based on the radiologist's interpretation. The BEIR VII model was employed to estimate the risk of radiation-induced cancer. RESULTS: Among the 561 patients, 299 (53.3%) were males and the average age of the patients was 49.61 ± 18.73 years. Of the CT scans, 408 (72.7%) were reported as normal. The average age of patients with normal, abnormal, and potentially abnormal CT scans was 47.57 ± 19.06, 54.80 ± 16.70, and 58.14 ± 16.60 years, respectively (p-value < 0.001). The average effective dose was 1.89 ± 0.21 mSv, with 1.76 ± 0.11 mSv for males and 2.05 ± 0.29 mSv for females (p-value < 0.001). The average risk of lung cancer was 3.84 ± 1.19 and 9.73 ± 3.27 cases per 100,000 patients for males and females, respectively. The average LAR for all cancer types was 10.30 ± 6.03 cases per 100,000 patients. CONCLUSIONS: This study highlights the critical issue of increased CT scan usage for COVID-19 diagnosis and the potential long-term consequences, especially the risk of cancer incidence. Healthcare policies should be prepared to address this potential rise in cancer incidence and the utilization of CT scans should be restricted to cases where laboratory tests are not readily available or when clinical symptoms are severe.

Computationally Efficient System Matrix Calculation Techniques in Computed Tomography Iterative Reconstruction.

BACKGROUND: Relative to classical methods in computed tomography, iterative reconstruction techniques enable significantly improved image qualities and/or lowered patient doses. However, the computational speed is a major concern for these iterative techniques. In the present study, we present a method for fast system matrix calculation based on the line integral model (LIM) to speed up the computations without compromising the image quality. In addition, we develop a hybrid line-area integral model (AIM) that highlights the advantages of both LIM and AIMs. METHODS: The contributing detectors for a given pixel and a given projection view, and the length of corresponding intersection lines with pixels, are calculated using our proposed algorithm. For the hybrid method, the respective narrow-angle fan beam was modeled by multiple equally spaced lines. The computed system matrix was evaluated in the context of reconstruction using the simultaneous algebraic reconstruction technique (SART) as well as maximum likelihood expectation maximization (MLEM). RESULTS: The proposed LIM offers a considerable reduction in calculation times compared to the standard Siddon algorithm: 2.9 times faster. Differences in root mean square error and peak signal-to-noise ratio were not significant between the proposed LIM and the Siddon algorithm for both SART and MLEM reconstruction methods (P > 0.05). Meanwhile, the proposed hybrid method resulted in significantly improved image qualities relative to LIM and the Siddon algorithm (P < 0.05), though computations were 4.9 times more intensive than the proposed LIM. CONCLUSION: We have proposed two fast algorithms to calculate the system matrix. The first is based on LIM and was faster than the Siddon algorithm, with matched image quality, whereas the second method is a hybrid LIM-AIM that achieves significantly improved images though with its computational requirements.

Evaluation of the photon dose calculation accuracy in radiation therapy of malignant pleural mesothelioma.

BACKGROUND: Photon dose distribution of malignant pleural mesothelioma (MPM) in matched photon-electron technique is influenced by media inhomogeneity, lateral electronic disequilibrium at interfaces and narrow field. These may influence the dose calculation accuracy, calculated by treatment planning systems (TPS). This study aimed to evaluate the dose calculation accuracy of TiGRT TPS in radiation therapy of MPM. MATERIALS AND METHODS: 18 MV photon beams of ONCOR Siemens linear accelerator was simulated using EGSnrc Monte Carlo (MC) code. Data of four patients were used to compare TPS and MC results in different regions included: Open and in-field, under shied and out of field regions. RESULTS: Compared to MC results, the TPS overestimated the pleura dose coverage (90% of prescribed dose) about 3-12 mm, and also it overestimated the dose in under the shielded regions of lung (4-74%). While the TPS underestimated the dose profile width about 1-16 mm in low dose region (<50% prescribed dose) as well as the out of field region dose (4-100%). CONCLUSIONS: Results showed that TPS underestimated the dose in out of field and overestimated the dose in under the shielded regions. Unlike MC measurements, TPS calculation showed adequate pleural dose coverage. Based on the results, MC calculation can be used in matched photon-electron beam radiation therapy of MPM to modify the TPS photon dose calculations in the presence of heterogeneity, interfaces, and shield in MPM radiotherapy.

Effects of radiofrequency radiation in the presence of gold nanoparticles for the treatment of renal cell carcinoma.

Introduction: The most common type of kidney cancer is renal cell carcinoma (RCC), which accounts for more than 80% of all kidney cancers. Objectives: The aim of this study was to evaluate the effects of radiofrequency (RF) radiation in the presence of gold nanoparticles (GNPs) for the treatment of RCC. Materials and Methods: Human embryonic kidney (HEK) cancer cells were divided into 6 groups. Various tests were performed on HEK cells in the presence of RF and GNPs. In order to investigate the radiation effects on the cells' survival, MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-iphenyltetrazolium bromide] assay was performed at different days during and post-irradiation period. The repeated measure analysis of variance (ANOVA) method was used for statistical analysis of the cells' survival using SPSS version 16.0. A significant level of 0.05 was considered to the tests. Results: Using the ANOVA test, a significant decrease in cell's survival was seen in the RF exposed group 3 compared to the control group (P=0.035). While, differences were not significant between RF exposed group 2 and the control group (P>0.05). A significant decrease in cell's survival in the RF exposed groups 5 (P=0.025) and 6 (P=0.018) at the presence of GNP compared to the control group was seen. Conclusion: Results of this study showed that, this method can be efficiently used for RCC treatment as an alternative to nephrectomy. More follow up in vivo studies on mammalians are needed to investigate the potential of the presented method for clinical applications.

ELISA reader does not interfere by mobile phone radiofrequency radiation.

BACKGROUND: The increasing number of mobile phones can physically cause electromagnetic interference (EMI) in medical environments; can also cause errors in immunoassays in laboratories. The ELISA readers are widely used as a useful diagnostic tool for Enzymun colorimetric assay in medicine. The aim of this study was to investigate whether the ELISA reader could be interfered by the exposure to the 900 MHz cell phones in the laboratory. MATERIALS AND METHODS: Human serum samples were collected from 14 healthy donors (9 women and 5 men) and each sample was divided into four aliquots and was placed into four batches for the in-vitro quantitative determination of human chorionic gonadotropin (hCG). During colorimetric reading of the first, second, and third batches, the ELISA reader (Stat Fax 2100, Awareness Technology, Inc., USA) was exposed to 0.5, 1.0, and 2.0 W exposure of 900 MHz radiation, respectively. For the forth batch (control group), no radiation was applied. All experiments were performed comparing ELISA read out results of the I, II, and III batches with the control batch, using the Wilcoxon test with criterion level of P = 0.050. RESULTS: The final scores in the exposed batches I, II, and III were not statistically significant relative to the control batch (P > 0.05). The results showed that 900 MHz radiation exposure did not alter the ELISA measured levels of hCG hormone in I (P = 0.219), II (P = 0.909), and III (P = 0.056) batches compared to the control batch. CONCLUSION: This study showed that ELISA reader does not interfere by mobile phone RF radiation at a closed contact (less than 5 cm distance). However, we recommend that medical institutions discuss these issues in the context of their specific use of technologies and frame a policy that is clear and straightforward to guide staff, patients, and visitors.

The efficacy of combination of ondansetron and aprepitant on preventing the radiotherapy-induced nausea and vomiting.

BACKGROUND: Depending on the site of irradiation, about 40-80% of patients undergoing radiotherapy (RT) will experience nausea and/or vomiting. The current study aimed to investigate the efficacy of ondansetronas as a single agent and with a combination to aprepitant on preventing RT-induced nausea and vomiting (RINV). MATERIALS AND METHODS: In a clinical randomized controlled trial (from September 2010 to September 2011), conducted in Radiation Oncology Department of Seyed-al-Shohada Hospital, Isfahan University of Medical Sciences, 40 abdominopelvic malignancies cancer patients were allocated into two aliquots using block randomization of size. Patients in the first group (group I) received ondansetron alone while those patients in the remaining group (group II) received ondansetron and aprepitant. Then, developing of RINV and its severity and benefit of adding aprepitant to ondansetron, in comparison with ondansetron as a single drug therapy were evaluated. RESULTS: The average age of the patients in group I was 61.15 ± 12.27 years while in group II it was 50.1 ± 13.27 years. No statistically significant gender differences were found between the two groups. In patients treated with ondansetron single drug therapy (group I), frequency and grade of RINV were significantly more than the group treated simultaneously by aprepitant and ondansetron (group II) (odds ratio [OR] = 21.2; P < 0.01). Compared with RT alone, the patients whom underwent RT along with chemotherapy showed lower probability of experiencing RINV (OR = 0.13; P < 0.05). CONCLUSION: The present study indicated a significant superiority of combination of ondansetron and aprepitant in management of RINV, in patients undergoing RT, compared to ondansetron as a single agent therapy. More accurate follow-up studies are needed for the evaluation of the efficacy of ondansetron with combination to aprepitant on preventing the RINV.

(99m)Tc-Phytate Lymphoscintigraphy for Detection of Sentinel Node: Preliminary Results of the First Year's Clinical Experience in Isfahan, Iran.

Sentinel lymph node is the first regional lymph node that drains the lymph from the primary tumor. It is potentially the first node to receive the seeding of lymph-borne metastatic cells. This study aimed to discuss lymphoscintigraphy procedural guidelines for detection of sentinel node using (99m)Tc-Phytate in Isfahan, Iran. Moreover, the preliminary results of the first year's clinical experience of lymphoscintigraphy in Isfahan, Iran are also presented. A total of 36 consecutive sentinel node procedures were performed following our protocol in March 2013 to March 2014. For all 36 patients, after intradermal injection of 0.5-1 mCi of (99m)Tc-Phytate, 5, 30 and 120 min with hands up lymphoscintigraphy was performed. All procedures were performed in a 1-day setting with (99m)Tc-Phytate injection in intradermal volume of about 0.1 cc. At 5, 30 and 120 min after injection, anterior and lateral images (4 min), were acquired using gamma-camera (energy 140 keV, window 15-20% and LEHR collimator). For all patients, at least one axillary sentinel lymph node was detected. For three patients, 2 SNs were seen. The images 5 min after injection showed at least one axillary sentinel node in 18 of 36 patients. However for the remaining patients, more delayed images (after 30 and 120 min) were needed. Although, no changes were seen in 120 min images compared to 30 min images. Considering the used protocol, from the evaluated data it can be concluded that lymphoscintigraphy after 30 min periareolar injection of about 0.5-1 mCi (99m)Tc-Phytate in an intradermal volume of about 0.1 cc yields an axillary sentinel node in all the patients. Imaging 120 min after injection is of no additional value and can be omitted.

Estimation of cell response in fractionation radiotherapy using different methods derived from linear quadratic model.

BACKGROUND: The aim of this study was to use various theoretical methods derived from the Linear Quadratic (LQ) model to calculate the effects of number of subfractions, time intervals between subfractions, dose per subfraction, and overall fraction time on the cells' survival. Comparison of the results with experimental outcomes of melanoma and breast adenocarcinoma cells was also performed. Finally, the best matched method with experimental outcomes is introduced as the most accurate method in predicting the cell response. MATERIALS AND METHODS: The most widely used theoretical methods in the literature, presented by Keall et al., Brenner, and Mu et al., were used to calculate the cells' survival following radiotherapy with different treatment schemes. The overall treatment times were ranged from 15 to 240 minutes. To investigate the effects of number of subfractions and dose per subfraction, the cells' survival after different treatment delivery scenarios were calculated through fixed overall treatment times of 30, 60 and 240 minutes. The experimental tests were done for dose of 4 Gy. The results were compared with those of the theoretical outcomes. RESULTS: The most affective parameter on the cells' survival was the overall treatment time. However, the number of subfractions per fractions was another effecting parameter in the theoretical models. This parameter showed no significant effect on the cells' survival in experimental schemes. The variations in number of subfractions per each fraction showed different results on the cells' survival, calculated by Keall et al. and Brenner methods (P<0.05). CONCLUSIONS: Mu et al. method can predict the cells' survival following fractionation radiotherapy more accurately than the other models. Using Mu et al. method, as an accurate and simple method to predict the cell response after fractionation radiotherapy, is suggested for clinical applications.