Trends of occupational exposure to ionizing radiation in Central China for the period 2000-2021

A retrospective analysis of occupational exposure to ionizing radiation from medical uses and industrial uses in the three provinces of Central China from 2000 to 2021 was conducted. The average annual effective dose in medical uses and industrial uses decreased from 2.042 mSv and 2.334 mSv in 2000-2002 to 0.476 mSv and 0.371 mSv in 2021 respectively; the fraction of monitored workers receiving annual dose not exceeding 1 mSv increased from 60.78% and 74.45% in 2000-2002 to 94.20% and 96.85% in 2021 respectively, while receiving annual doses exceeding 20 mSv declined from 1.35% and 1.91% in 2000-2002 to 0.18% and 0.03% in 2021 respectively. The average annual effective dose and NR20 in the period 2000-2021 were relatively high in professional public health institutions (0.955 mSv and 0.004) and hospitals (0.815 mSv and 0.004). In 2021, the average annual effective dose to monitored workers in different occupational categories in medical uses in the three provinces of Central China were in the range of 0.199-0.692 mSv, with interventional radiology received the highest dose and NR20 (0.692 mSv and 0.005); the average annual effective dose ranged from 0.161 to 0.493 mSv in industrial uses, with industrial radiography received the highest dose and NR20 (0.493 mSv and 0.001). Occupational exposure in medical uses and industrial uses declined obviously in Central China, and the groups receiving higher doses are the radiation workers working in hospitals and professional public health institutions, or engaged in interventional radiology, nuclear medicine and industrial radiography, warranting more effective radiation protection measures.

Intraoperative Radiation Exposure During Midfoot Charcot Reconstruction

While radiation exposure in foot and ankle surgery varies by procedure, attempts to minimize this hazard remain imperative to protect patients and surgeons. Hindfoot deformity correction employs significant radiation through intraoperative fluoroscopy, however, a paucity of data exists concerning Charcot reconstruction. This investigation describes and compares radiation exposure across varying Charcot pathology and fixation constructs. A retrospective chart review of patients undergoing midfoot Charcot reconstruction under large C-arm assistance from 2016-2022 was conducted. Demographics, pathology-specific, and intervention-specific variables were recorded and compared among midfoot reconstructions. The threshold for statistical significance was set at p ≤ .05. Among 40 patients, the average midfoot radiation exposure and fluoroscopy times were 9.5 ± 5.39 mGy and 256.64 ± 130.67 seconds, respectively. There existed no statistically significant difference in radiation exposure (p = .32) or fluoroscopy times (p = .71) among the different midfoot constructs. There existed a statistically significant relationship between radiation exposure with weight (p = .01) body mass index (p = .03) and number of stages (p = .04). Similarly, a relationship existed between fluoroscopy time with weight (p = .02), body mass index (p = .03), and number of beams/screws (p = .003). Due to the complexity of Charcot reconstruction coupled with multiple robust types of fixation, surgeons must remain cognizant of fluoroscopy usage. Moreover, providers who routinely perform Charcot reconstruction should wear personal protective equipment to protect against radiation.

Radiation exposure of patients during endourological procedures

PURPOSE

Considering the existing gaps in the literature regarding patient radiation dose (RD) and its associated risks, a systematic review of the literature on RD was conducted, focusing on percutaneous nephrolithotomy (PCNL), extracorporeal shock wave lithotripsy (SWL), and ureteroscopy (URS).

METHODS

Two authors conducted a literature search on PubMed, Web of Science, and Google Scholar to identify studies on RD during endourological procedures. Two thousand two hundred sixty-six articles were screened. Sixty-five publications met the inclusion criteria using the PRISMA standards.

RESULTS

RD was generally highest for PCNL, reaching levels up to 33 mSv, 28,700 mGycm2, and 430.8 mGy. This was followed by SWL, with RD reaching up to 7.32 mSv, 13,082 mGycm2, and 142 mGy. URS demonstrated lower RD, reaching up to 6.07 mSv, 8920 mGycm2, and 46.99 mGy. Surgeon experience and case load were inversely associated with RD. Strategies such as optimizing fluoroscopy settings, implementing ultrasound (US), and following the ALARA (As Low As Reasonably Achievable) principle minimized RD.

CONCLUSIONS

This is the first systematic review analyzing RD, which was generally highest during PCNL, followed by SWL and URS. There is no specific RD limit for these procedures. Implementation of strategies such as optimizing fluoroscopy settings, utilizing US, and adhering to the ALARA principle proved effective in reducing RD. However, further research is needed to explore the factors influencing RD, assess their impact on patient outcomes, and establish procedure-specific reference levels for RD.

Intravenous immunoglobulin protects the integrity of the intestinal epithelial barrier and inhibits ferroptosis induced by radiation exposure by activating the mTOR pathway

Radiation exposure often leads to serious health problems in humans. The intestinal epithelium is sensitive to radiation damage, and radiation causes destruction of the intestinal epithelial barrier, which leads to radiation enteritis (RE), the loss of fluids, and the translocation of intestinal bacteria and toxins; radiation can even threaten survival. In this study, we aimed to explore the influence of IVIg on the integrity of the intestinal epithelial barrier after RE. Using a RE mouse model, we investigated the protective effects of intravenous immunoglobulin (IVIg) on the epithelial junctions of RE mice and validated these findings with intestinal organoids cultured in vitro. In addition, transmission electron microscopy (TEM), western blotting (WB) and immunostaining were used to further investigate changes in intestinal epithelial ferroptosis and related signaling pathways. When RE occurs, the intestinal epithelial barrier is severely damaged. IVIg treatment significantly ameliorated this damage to epithelial tight junctions both in vivo and in vitro. Notably, IVIg alleviated RE by inhibiting intestinal epithelial ferroptosis in RE mice. Mechanistically, IVIg promoted activation of the mTOR pathway and inhibited ferroptosis in the intestinal epithelium of mice. Rapamycin, which is a potent inhibitor of the mTOR protein, significantly abolished the protective effect of IVIg against radiation-induced damage to intestinal epithelial tight junctions. Overall, IVIg can prevent RE-induced damage to the intestinal epithelial barrier and inhibit ferroptosis by activating the mTOR pathway; this study provides a new treatment strategy for patients with RE caused by radiotherapy or accidental nuclear exposure.

A NEXT generation ANMCO initiative

BACKGROUND

Gender-related discrepancies in personal and professional life have been reported among radio-exposed workers. We assessed this topic among cardiac catheterization workers in Italy, with a focus on gender and working position.

METHODS

Radio-exposed workers affiliated with the Italian Association of Hospital Cardiologists were invited to answer an online survey, which included 41 questions formatted as multiple choice.

RESULTS

Overall, 237 workers responded. The proportion of males was significantly higher than that of females in the population aged >50 years. A greater portion of females than males perceived female-gender discrimination regarding career advancement (77.2% vs 30.9%, p < 0.001) and work compensation (49.1% vs. 17.1%, p < 0.001). There was no difference in perceived gender- discrimination in terms of career advancement opportunities between physician and non-physicians. A larger portion of females than males experienced workplace discrimination (51.8% of females vs. 8.1% of males, p < 0.0001). Non-physician responders made up 38.8% of all respondents and reported a lower yearly radiation exposure than physicians. Non-physicians were more aware of the laws regulating lab access during pregnancy than physicians (93.5% vs. 48.3%, p < 0.0001). A greater percentage of female nurses than physicians communicate without hesitation the pregnancy status to their employers (45.6% vs 20%, p < 0.001).

CONCLUSIONS

Gender-based career disparities were perceived among physicians and non-physician staff of cardiology interventional laboratories. Strategies should be implemented to ensure gender equality in career opportunities and to increase knowledge of radioprotection and the laws regulating access to laboratories during pregnancy.

Lung ultrasound and procalcitonin, improving antibiotic management and avoiding radiation exposure in pediatric critical patients with bacterial pneumonia: a randomized clinical trial

BACKGROUND

Pneumonia is a major public health problem with an impact on morbidity and mortality. Its management still represents a challenge. The aim was to determine whether a new diagnostic algorithm combining lung ultrasound (LUS) and procalcitonin (PCT) improved pneumonia management regarding antibiotic use, radiation exposure, and associated costs, in critically ill pediatric patients with suspected bacterial pneumonia (BP).

METHODS

Randomized, blinded, comparative effectiveness clinical trial. Children < 18y with suspected BP admitted to the PICU from September 2017 to December 2019, were included. PCT was determined at admission. Patients were randomized into the experimental group (EG) and control group (CG) if LUS or chest X-ray (CXR) were done as the first image test, respectively. Patients were classified: 1.LUS/CXR not suggestive of BP and PCT < 1 ng/mL, no antibiotics were recommended; 2.LUS/CXR suggestive of BP, regardless of the PCT value, antibiotics were recommended; 3.LUS/CXR not suggestive of BP and PCT > 1 ng/mL, antibiotics were recommended.

RESULTS

194 children were enrolled, 113 (58.2%) females, median age of 134 (IQR 39-554) days. 96 randomized into EG and 98 into CG. 1. In 75/194 patients the image test was not suggestive of BP with PCT < 1 ng/ml; 29/52 in the EG and 11/23 in the CG did not receive antibiotics. 2. In 101 patients, the image was suggestive of BP; 34/34 in the EG and 57/67 in the CG received antibiotics. Statistically significant differences between groups were observed when PCT resulted < 1 ng/ml (p = 0.01). 3. In 18 patients the image test was not suggestive of BP but PCT resulted > 1 ng/ml, all of them received antibiotics. A total of 0.035 mSv radiation/patient was eluded. A reduction of 77% CXR/patient was observed. LUS did not significantly increase costs.

CONCLUSIONS

Combination of LUS and PCT showed no risk of mistreating BP, avoided radiation and did not increase costs. The algorithm could be a reliable tool for improving pneumonia management.

CLINICAL TRIAL REGISTRATION

NCT04217980.

Radiation levels outside a patient undergoing177Lu-PSMA radioligand therapy

Understanding the spatial distribution of radiation levels outside of a patient undergoing177Lu radioligand therapy is not only helpful for conducting correct tests for patient release, but also useful for estimation of its potential exposure to healthcare workers, caregivers, family members, and the general public. In this study, by mimicking the177Lu-labeled prostate-specific membrane antigen radioligand therapy for prostate cancers in an adult male, the spatial distribution of radiation levels outside of the phantom was simulated based on the Monte Carlo software of Particle and Heavy Ion Transport System, and verified by a series of measurements. Moreover, the normalized dose rates were further formulized on the three transverse planes representing the heights of pelvis, abdomen and chest. The results showed that the distributions of radiation levels were quite complex. Multi-directional and multi-height measurements are needed to ensure the external dose rate to meet the release criteria. In general, the radiation level was higher at the horizontal plane where the source was located, and the levels in front and behind of the body were higher than those of the left and right sides at the same height. The ratio of simulated dose rates to measured ones ranged from 0.82 to 1.19 within 1 m away from the body surface in all directions. Based on the established functions, the relative root mean square deviation between the calculated and simulated values were 0.21, 0.25 and 0.23 within a radius of 1 m on the pelvis, abdomen and chest transverse planes, respectively. It is expected that the results of this study would be helpful for guiding the test of extracorporeal radiation to determine the patient's release, and of benefit to estimate the radiation exposure to others.

Large variation in radiation dose for routine abdomen CT: reasons for excess and easy tips for reduction

OBJECTIVE

To characterize the use and impact of radiation dose reduction techniques in actual practice for routine abdomen CT.

METHODS

We retrospectively analyzed consecutive routine abdomen CT scans in adults from a large dose registry, contributed by 95 hospitals and imaging facilities. Grouping exams into deciles by, first, patient size, and second, size-adjusted dose length product (DLP), we summarized dose and technical parameters and estimated which parameters contributed most to between-protocols dose variation. Lastly, we modeled the total population dose if all protocols with mean size-adjusted DLP above 433 or 645 mGy-cm were reduced to these thresholds.

RESULTS

A total of 748,846 CTs were performed using 1033 unique protocols. When sorted by patient size, patients with larger abdominal diameters had increased dose and effective mAs (milliampere seconds), even after adjusting for patient size. When sorted by size-adjusted dose, patients in the highest versus the lowest decile in size-adjusted DLP received 6.4 times the average dose (1680 vs 265 mGy-cm) even though diameter was no different (312 vs 309 mm). Effective mAs was 2.1-fold higher, unadjusted CTDIvol 2.9-fold, and phase 2.5-fold for patients in the highest versus lowest size-adjusted DLP decile. There was virtually no change in kV (kilovolt). Automatic exposure control was widely used to modulate mAs, whereas kV modulation was rare. Phase was the strongest driver of between-protocols variation. Broad adoption of optimized protocols could result in total population dose reductions of 18.6-40%.

CONCLUSION

There are large variations in radiation doses for routine abdomen CT unrelated to patient size. Modification of kV and single-phase scanning could result in substantial dose reduction.

CLINICAL RELEVANCE

Radiation dose-optimization techniques for routine abdomen CT are routinely under-utilized leading to higher doses than needed. Greater modification of technical parameters and number of phases could result in substantial reduction in radiation exposure to patients.

KEY POINTS

• Based on an analysis of 748,846 routine abdomen CT scans in adults, radiation doses varied tremendously across patients of the same size and optimization techniques were routinely under-utilized. • The difference in observed dose was due to variation in technical parameters and phase count. Automatic exposure control was commonly used to modify effective mAs, whereas kV was rarely adjusted for patient size. Routine abdomen CT should be performed using a single phase, yet multi-phase was common. • kV modulation by patient size and restriction to a single phase for routine abdomen indications could result in substantial reduction in radiation doses using well-established dose optimization approaches.

Advanced Interventional Treatments in Retinoblastoma Management: A Comprehensive Review

Retinoblastoma is the most common eye malignancy in children that if left untreated can invade intraocular structures, metastasize, and rarely lead to death. Traditionally treated with systemic chemotherapy, Intra-arterial chemotherapy is gaining popularity as it allows for the direct administration of chemotherapy through the ophthalmic artery, thus reducing systemic side effects. Intra-arterial chemotherapy procedures have evolved, with refinements to reduce risks and radiation exposure. Intra-arterial chemotherapy boasts an impressive technical success rate and one year ocular survival even amongst advanced cases. This review offers a thorough examination of the technique, indications, contraindications, outcomes, and alternative options for Intra-arterial chemotherapy.

Photon-counting CT-angiography in pre-TAVR aortic annulus assessment: effects of retrospective vs. prospective ECG-synchronization on prosthesis valve selection

To compare the diagnostic value of ultrahigh-resolution CT-angiography (UHR-CTA) compared with high-pitch spiral CTA (HPS-CTA) using a first-generation, dual-source photon-counting CT (PCD-CT) scanner for preprocedural planning of transcatheter aortic valve replacement (TAVR). Clinically referred patients with severe aortic valve stenosis underwent both, retrospective ECG-gated cardiac UHR-CTA (collimation: 120 × 0.2 mm) and prospective ECG-triggered aortoiliac HPS-CTA (collimation: 144 × 0.4 mm, full spectral capabilities) for TAVR planning from August 2022 to March 2023. Radiation dose was extracted from the CT reports, and the effective dose was calculated. Two radiologists analyzed UHR-CTA and HPS-CTA datasets, assessing the image quality of the aortic annulus, with regard to the lumen visibility and margin delineation using a 4-point visual-grading scale (ranges: 4 = "excellent" to 1 = "poor"). Aortic annulus area (AAA) measurements were taken for valve prosthesis sizing, with retrospective UHR-CTA serving as reference standard. A total of 64 patients were included (mean age, 81 years ± 7 SD; 28 women) in this retrospective study. HPS-CTA showed a lower radiation dose, 4.1 mSv vs. 12.6 mSv (p < 0.001). UHR-CTA demonstrated higher image quality to HPS-CTA (median score, 4 [IQR, 3-4] vs. 3 [IQR, 2-3]; p < 0.001). Quantitative assessments of AAA from both CTA datasets were strongly positively correlated (mean 477.4 ± 91.1 mm2 on UHR-CTA and mean 476.5 ± 90.4 mm2 on HPS-CTA, Pearson r2 = 0.857, p < 0.001) with a mean error of 22.3 ± 24.6 mm2 and resulted in identical valve prosthesis sizing in the majority of patients (91%). Patients with lower image quality on HPS-CTA (score value 1 or 2, n = 28) were more likely to receive different sizing recommendations (82%). Both UHR-CTA and HPS-CTA acquisitions using photon-counting CT technology provided reliable aortic annular assessments for TAVR planning. While UHR-CTA offers superior image quality, HPS-CTA is associated with lower radiation exposure. However, severely impaired image quality on HPS-CTA may impact on prosthesis sizing, suggesting that immediate post-scan image evaluations may require complementary UHR-CTA scanning.

DSG-GAN:A dual-stage-generator-based GAN for cross-modality synthesis from PET to CT

PET/CT devices typically use CT images for PET attenuation correction, leading to additional radiation exposure. Alternatively, in a standalone PET imaging system, attenuation and scatter correction cannot be performed due to the absence of CT images. Therefore, it is necessary to explore methods for generating pseudo-CT images from PET images. However, traditional PET-to-CT synthesis models encounter conflicts in multi-objective optimization, leading to disparities between synthetic and real images in overall structure and texture. To address this issue, we propose a staged image generation model. Firstly, we construct a dual-stage generator, which synthesizes the overall structure and texture details of images by decomposing optimization objectives and employing multiple loss functions constraints. Additionally, in each generator, we employ improved deep perceptual skip connections, which utilize cross-layer information interaction and deep perceptual selection to effectively and selectively leverage multi-level deep information and avoid interference from redundant information. Finally, we construct a context-aware local discriminator, which integrates context information and extracts local features to generate fine local details of images and reasonably maintain the overall coherence of the images. Experimental results demonstrate that our approach outperforms other methods, with SSIM, PSNR, and FID metrics reaching 0.8993, 29.6108, and 29.7489, respectively, achieving the state-of-the-art. Furthermore, we conduct visual experiments on the synthesized pseudo-CT images in terms of image structure and texture. The results indicate that the pseudo-CT images synthesized in this study are more similar to real CT images, providing accurate structure information for clinical disease analysis and lesion localization.

Exposure frequency and radiation dose from CT examinations in Huaian

This study quantified the exposure frequency and established the local diagnostic reference levels (DRLs) for the most common computed tomography (CT) examinations. A combined method census and sampling survey was used to quantify both frequency and radiation dose of CT examinations. Data were acquired through Picture Archiving and Communication System (PACS) or Radiology Information System (RIS). The annual frequency of CT examinations was 239.8 per 1000 inhabitants. The P75 of volume CT dose index (CTDIvol) to adult patients from CT scanning for head, chest, abdomen and lumbar spine examinations were 63.0, 12.4, 20.0 and 24.0 mGy, respectively. The P75 of dose-length product were 858.6, 416.0, 620.7 and 559.2 mGy·cm, respectively. This dose audit of CT practice can act as a starting point for establishing Huaian local DRLs and could be a reference for dose optimisation in China. This study compared DRLs in different countries and analysed some reasons for the rapid growth of CT examination frequency in Huaian.

Impact of Interfractional Bladder and Trigone Displacement and Deformation on Radiation Exposure and Subsequent Acute Genitourinary Toxicity: A Post Hoc Analysis of Patients Treated with Magnetic Resonance Imaging-Guided Prostate Stereotactic Body Radiation Therapy in a Phase 3 Randomized Trial

PURPOSE

Emerging data suggest that trigone dosimetry may be more associated with poststereotactic body radiation therapy (SBRT) urinary toxicity than whole bladder dosimetry. We quantify the dosimetric effect of interfractional displacement and deformation of the whole bladder and trigone during prostate SBRT using on-board, pretreatment 0.35T magnetic resonance images (MRI).

METHODS AND MATERIALS

Seventy-seven patients treated with MRI-guided prostate SBRT (40 Gy/5 fractions) on the MRI arm of a phase 3 single-center randomized trial were included. Bladder and trigone structures were contoured on images obtained from a 0.35T simulation MRI and 5 on-board pretreatment MRIs. Dice similarity coefficient (DSC) scores and changes in volume between simulation and daily treatments were calculated. Dosimetric parameters including Dmax, D0.03 cc, Dmean, V40 Gy, V39 Gy, V38 Gy, and V20 Gy for the bladder and trigone for the simulation and daily treatments were collected. Both physician-scored (Common Terminology Criteria for Adverse Events, version 4.03 scale) as well as patient-reported (International Prostate Symptom Scores and the Expanded Prostate Cancer Index Composite-26 scores) acute genitourinary (GU) toxicity outcomes were collected and analyzed.

RESULTS

The average treatment bladder volume was about 30% smaller than the simulation bladder volume; however, the trigone volume remained fairly consistent despite being positively correlated with total bladder volume. Overall, the trigone accounted for <2% of the bladder volume. Median DSC for the bladder was 0.79, whereas the median DSC of the trigone was only 0.33. No statistically significant associations between our selected bladder and trigonal dosimetric parameters and grade ≥2 GU toxicity were identified, although numerically, patients with GU toxicity (grade ≥2) had higher intermediate doses to the bladder (V20 Gy and Dmean) and larger volumes exposed to higher doses in the trigone (V40 Gy, V39 Gy, and V38 Gy).

CONCLUSIONS

The trigone exhibits little volume change, but considerable interfractional displacement/deformation. As a result, the relative volume of the trigone receiving high doses during prostate SBRT varies substantially between fractions, which could influence GU toxicity and may not be predicted by radiation planning dosimetry.

Environmental radiation exposure at Chornobyl has not systematically affected the genomes or chemical mutagen tolerance phenotypes of local worms

The 1986 disaster at the Chornobyl Nuclear Power Plant transformed the surrounding region into the most radioactive landscape known on the planet. Whether or not this sudden environmental shift selected for species, or even individuals within a species, that are naturally more resistant to mutagen exposure remains an open question. In this study, we collected, cultured, and cryopreserved 298 wild nematode isolates from areas varying in radioactivity within the Chornobyl Exclusion Zone. We sequenced and assembled genomes de novo for 20 Oscheius tipulae strains, analyzed their genomes for evidence of recent mutation acquisition in the field, and observed no evidence of an association between mutation and radioactivity at the sites of collection. Multigenerational exposure of each of these strains to several chemical mutagens in the lab revealed that strains vary heritably in tolerance to each mutagen, but mutagen tolerance cannot be predicted based on the radiation levels at collection sites, and Chornobyl isolates were not systematically more resistant than strains from undisturbed habitats. In sum, the absence of mutational signatures does not reflect unique capacity for tolerating DNA damage.

Progression of Notch signaling regulation of B cells under radiation exposure

With the continuous development of nuclear technology, the radiation exposure caused by radiation therapy is a serious health hazard. It is of great significance to further develop effective radiation countermeasures. B cells easily succumb to irradiation exposure along with immunosuppressive response. The approach to ameliorate radiation-induced B cell damage is rarely studied, implying that the underlying mechanisms of B cell damage after exposure are eager to be revealed. Recent studies suggest that Notch signaling plays an important role in B cell-mediated immune response. Notch signaling is a critical regulator for B cells to maintain immune function. Although accumulating studies reported that Notch signaling contributes to the functionality of hematopoietic stem cells and T cells, its role in B cells is scarcely appreciated. Presently, we discussed the regulation of Notch signaling on B cells under radiation exposure to provide a scientific basis to prevent radiation-induced B cell damage.

Regenerating murine CD8+ lung tissue resident memory T cells after targeted radiation exposure

Radiation exposure occurs during medical procedures, nuclear accidents, or spaceflight, making effective medical countermeasures a public health priority. Naïve T cells are highly sensitive to radiation-induced depletion, although their numbers recover with time. Circulating memory CD8+ T cells are also depleted by radiation; however, their numbers do not recover. Critically, the impact of radiation exposure on tissue-resident memory T cells (TRM) remains unknown. Here, we found that sublethal thorax-targeted radiation resulted in the rapid and prolonged numerical decline of influenza A virus (IAV)-specific lung TRM in mice, but no decline in antigen-matched circulating memory T cells. Prolonged loss of lung TRM was associated with decreased heterosubtypic immunity. Importantly, boosting with IAV-epitope expressing pathogens that replicate in the lungs or peripheral tissues or with a peripherally administered mRNA vaccine regenerated lung TRM that was derived largely from circulating memory CD8+ T cells. Designing effective vaccination strategies to regenerate TRM will be important in combating the immunological effects of radiation exposure.

Digital registration versus cone-beam computed tomography for evaluating implant position: a prospective cohort study

BACKGROUND

Postoperative cone-beam computed tomography (CBCT) examination is considered a reliable method for clinicians to assess the positions of implants. Nevertheless, CBCT has drawbacks involving radiation exposure and high costs. Moreover, the image quality can be affected by artifacts. Recently, some literature has mentioned a digital registration method (DRM) as an alternative to CBCT for evaluating implant positions. The aim of this clinical study was to verify the accuracy of the DRM compared to CBCT scans in postoperative implant positioning.

MATERIALS AND METHODS

A total of 36 patients who received anterior maxillary implants were included in this clinical study, involving a total of 48 implants. The study included 24 patients in the single implant group and 12 patients in the dual implant group. The postoperative three-dimensional (3D) positions of implants were obtained using both CBCT and DRM. The DRM included three main steps. Firstly, the postoperative 3D data of the dentition and intraoral scan body (ISB) was obtained through the intraoral scan (IOS). Secondly, a virtual model named registration unit which comprised an implant replica and a matching ISB was created with the help of a lab scanner and reverse engineering software. Thirdly, by superimposing the registration unit and IOS data, the postoperative position of the implant was determined. The accuracy of DRM was evaluated by calculating the Root Mean Square (RMS) values after superimposing the implant positions obtained from DRM with those from postoperative CBCT. The accuracy of DRM was compared between the single implant group and the dual implant group using independent sample t-tests. The superimposition deviations of CBCT and IOS were also evaluated.

RESULTS

The overall mean RMS was 0.29 ± 0.05 mm. The mean RMS was 0.30 ± 0.03 mm in the single implant group and 0.29 ± 0.06 mm in the dual implant group, with no significant difference (p = 0.27). The overall registration accuracy of the IOS and CBCT data ranged from 0.14 ± 0.05 mm to 0.21 ± 0.08 mm.

CONCLUSION

In comparison with the 3D implant positions obtained by CBCT, the implant positions located by the DRM showed clinically acceptable deviation ranges. This method can be used in single and dual implant treatments to assess the implant positions.

PAE planning: Radiation exposure and image quality of CT and CBCT

PURPOSE

To determine accurate organ doses, effective doses, and image quality of computed tomography (CT) compared with cone beam CT (CBCT) for correct identification of prostatic arteries.

METHOD

A dual-energy CT scanner and a flat-panel angiography system were used. Dose measurements (gallbladder (g), intestine (i), bladder (b), prostate (p), testes (t), active bone marrow of pelvis (bmp) and femura (bmf)) were performed using an anthropomorphic phantom with 65 thermoluminescent dosimeters in the pelvis and abdomen region. For the calculation of the contrast-to-noise ratio (CNR) of the pelvic arteries, a patient whose weight and height were almost identical to those of the phantom was selected for each examination type.

RESULTS

The effective dose of CT was 2.7 mSv and that of CBCT was 21.8 mSv. Phantom organ doses were lower for CT than for CBCT in all organs except the testes (g: 1.2 mGy vs. 3.3 mGy, i: 5.8 mGy vs. 23.9 mGy, b: 6.9 mGy vs. 19.4 mGy, p: 6.4 mGy vs. 13.2 mGy, t: 4.7 mGy vs. 2.4 mGy, bmp: 5.1 mGy vs. 18.2 mGy, bmf: 3.3 mGy vs. 6.6 mGy). For human pelvic arteries, the CNR of CT was better than that of CBCT, with the exception of one prostate artery that showed stenosis on CT. Evaluation by experienced radiologists also confirmed the better detectability of prostate arteries on CT examination.

CONCLUSIONS

In our study preprocedural CT had lower organ doses and better image quality comparedd with CBCT and should be considered for the correct identification of prostatic arteries.

Radiation exposure in navigated techniques for AIS: is there a difference between pre-operative CT and intraoperative CT?

PURPOSE

Utilization of navigation improves pedicle screw accuracy in adolescent idiopathic scoliosis (AIS). Our center switched from intraoperative CT (ICT) to an optical navigation system that utilizes pre-operative CT (PCT). We aim to evaluate the radiation dose and operative time for low-dose ICT compared to standard and low-dose PCT used for optical navigation in AIS patients undergoing posterior spinal fusion.

METHODS

A single-center matched-control cohort study of 38 patients was conducted. Nineteen patients underwent ICT navigation (O-arm) and were matched by sex, age, and weight to 19 patients who underwent PCT for use with an optical-guided navigation (7D, Seaspine). A total of 418 levels were instrumented and reviewed. PCT was either a standard dose (N = 7) or a low dose (N = 12). The mean volume CT dose index, dose-length product, overall effective dose (ED), ED per level instrumented, and operative time per level were compared.

RESULTS

ED per level instrumented was 0.061 ± 0.029 mSv in low-dose PCT and 0.14 ± 0.05 mSv in low-dose ICT (p < 0.0001). ED per level instrumented was significantly higher in standard PCT (1.46 ± 0.39 vs. 0.14 ± 0.03 mSv; p < 0.0001). Mean operative time per level was 31 ± 7 min for ICT and 33 ± 3 min for PCT (p = 0.628).

CONCLUSION

Low-dose PCT resulted in 0.70 mSv exposure per case and 31 min per level, standard-dose was 16.95 mSv, while ICT resulted in 1.34-1.62 mSv and a similar operative time. Use of a standard-dose PCT involves radiation exposure about 9 times higher than ICT and 23 times higher than low-dose PCT per level instrumented.

LEVEL OF EVIDENCE

Level III.

A quality care study

PURPOSES

The primary objective of this retrospective study was to assess whether the CT dose delivered to oncologic patients was different in a subspecialty radiology department, compared to a general radiology department. The secondary explorative objective was to assess whether the objective image quality of CT examinations was different in the two settings.

MATERIALS AND METHODS

Chest and abdomen CT scans performed for oncologic indications were selected from a general radiology department and a subspecialty radiology department. By using a radiation dose management platform, we extracted and compared CT dose index (CTDIvol) and dose length product (DLP) both for each phase and for the entire CT exams. For objective image quality evaluation, we calculated the signal-to-noise ratio (SNR) and the contrast-to-noise ratio (CNR) at the level of the liver and of the aorta. A P-value < 0.05 was considered significant.

RESULTS

A total of 7098 CT examinations were included. CTDIvol was evaluated in 12,804 phases; DLP in 10,713 phases and in 6714 examinations. The CTDIvol and DLP overall were significantly lower in the subspecialty radiology department compared to the general radiology department CTDI median (IQR) 5.19 (3.91-7.00) and 5.51 (4.17-7.72), DLP median and IQR of 490.0 (342.4-710.6) and 503.4 (359.9-728.8), p < 0.001 and p = 0.01, respectively. The objective image quality showed no significant difference in the general and subspecialty radiology departments, with median and IQR of 4.03 (2.82-5.51) and 3.84 (3.09-4.94) for SNRLiv (p = 0.58); 4.81 (2.70-7.62) and 4.34 (3.05-6.25) for SNRAo (p = 0.30); 0.83 (0.20-1.89) and 1.00 (0.35-1.57) for CNRLiv (p = 0.99); 2.23 (0.09-3.83) and 1.01 (0.15-2.84) for CNRAo (p = 0.24) with SNRLiv (p = 0.58), SNRAo (p = 0.30), CNRLiv (p = 0.99) and CNRAo (p = 0.24).

CONCLUSION

In a subspecialty radiology department, CT protocols are optimized compared to a general radiology department leading to lower doses to oncologic patients without significant objective image quality degradation.

Proteomic changes in the hippocampus of large mammals after total-body low dose radiation

There is a growing interest in low dose radiation (LDR) to counteract neurodegeneration. However, LDR effects on normal brain have not been completely explored yet. Recent analyses showed that LDR exposure to normal brain tissue causes expression level changes of different proteins including neurodegeneration-associated proteins. We assessed the proteomic changes occurring in radiated vs. sham normal swine brains. Due to its involvement in various neurodegenerative processes, including those associated with cognitive changes after high dose radiation exposure, we focused on the hippocampus first. We observed significant proteomic changes in the hippocampus of radiated vs. sham swine after LDR (1.79Gy). Mass spectrometry results showed 190 up-regulated and 120 down-regulated proteins after LDR. Western blotting analyses confirmed increased levels of TPM1, TPM4, PCP4 and NPY (all proteins decreased in various neurodegenerative processes, with NPY and PCP4 known to be neuroprotective) in radiated vs. sham swine. These data support the use of LDR as a potential beneficial tool to interfere with neurodegenerative processes and perhaps other brain-related disorders, including behavioral disorders.

Multicenter Quantification of Radiation Exposure and Associated Risks for Prostatic Artery Embolization in 1476 Patients

Background Prostatic artery embolization (PAE) is a safe, minimally invasive angiographic procedure that effectively treats benign prostatic hyperplasia; however, PAE-related patient radiation exposure and associated risks are not completely understood. Purpose To quantify radiation dose and assess radiation-related adverse events in patients who underwent PAE at multiple centers. Materials and Methods This retrospective study included patients undergoing PAE for any indication performed by experienced operators at 10 high-volume international centers from January 2014 to May 2021. Patient characteristics, procedural and radiation dose data, and radiation-related adverse events were collected. Procedural radiation effective doses were calculated by multiplying kerma-area product values by an established conversion factor for abdominopelvic fluoroscopy-guided procedures. Relationships between cumulative air kerma (CAK) or effective dose and patient body mass index (BMI), fluoroscopy time, or radiation field area were assessed with linear regression. Differences in radiation dose stemming from radiopaque prostheses or fluoroscopy unit type were assessed using two-sample t tests and Wilcoxon rank sum tests. Results A total of 1476 patients (mean age, 69.9 years ± 9.0 [SD]) were included, of whom 1345 (91.1%) and 131 (8.9%) underwent the procedure with fixed interventional or mobile fluoroscopy units, respectively. Median procedure effective dose was 17.8 mSv for fixed interventional units and 12.3 mSv for mobile units. CAK and effective dose both correlated positively with BMI (R2 = 0.15 and 0.17; P < .001) and fluoroscopy time (R2 = 0.16 and 0.08; P < .001). No radiation-related 90-day adverse events were reported. Patients with radiopaque implants versus those without implants had higher median CAK (1452 mGy [range, 900-2685 mGy] vs 1177 mGy [range, 700-1959 mGy], respectively; P = .01). Median effective dose was lower for mobile than for fixed interventional systems (12.3 mSv [range, 8.5-22.0 mSv] vs 20.4 mSv [range, 13.8-30.6 mSv], respectively; P < .001). Conclusion Patients who underwent PAE performed with fixed interventional or mobile fluoroscopy units were exposed to a median effective radiation dose of 17.8 mSv or 12.3 mSv, respectively. No radiation-related adverse events at 90 days were reported. © RSNA, 2024 See also the editorial by Mahesh in this issue.

Influence of resident involvement on fluoroscopy time and ionizing radiation exposure in fluoroscopy-guided spinal procedures

BACKGROUND

Fluoroscopic guidance has become the standard for a variety of medical procedures. Mastering these techniques requires practice, which may entail additional radiation for patients and providers. Despite their widespread use, the literature examining factors influencing radiation exposure in fluoroscopically guided pain procedures is scarce.

OBJECTIVE

To evaluate the influence of resident involvement on radiation exposure during fluoroscopy-guided spinal interventions.

DESIGN

Single-center, observational study.

SETTING

Outpatient physiatry clinic in a teaching hospital.

PATIENTS

All patients who received cervical or lumbar facet block(s) (FBs), transforaminal epidural steroid injection(s) (TFESIs) without digital subtraction, or a caudal epidural (CE) during the study period were included.

INTERVENTIONS

Resident involvement in the procedures: absent, observing, or participating.

MAIN OUTCOME MEASURES

Machine-indicated fluoroscopy time (seconds) and radiation dose (milligrays [mGy]).

RESULTS

Two hundred ninety six procedures were included: 188 FBs (58 cervical, 130 lumbar), 48 CEs, and 60 TFESIs. For lumbar FBs, fluoroscopy time and radiation dose increased significantly when residents performed them (meantime  = 24.5 s, confidence interval [CI] = 20.4-28.7; meandose  = 3.53 mGy, CI = 2.57-4.49) compared to when they observed (meantime  = 9.9 s, CI = 8.1-11.7; meandose  = 1.28 mGy, CI = 0.98-1.59) (mean difference: time = 14.63 s, CI = 9.31-19.94; dose = 2.25 mGy, CI = 1.17-3.33) and were absent during the procedure (meantime  = 12.9 s, CI = 11.1-14.6; meandose  = 1.65 mGy, CI = 1.40-1.89) (mean difference: time = 11.67 s, CI = 7.35-15.98; dose = 1.88 mGy, CI = 1.01-2.76). In the case of TFESIs, time, but not dose, increased significantly when residents observed (meantime  = 39.1 s, CI = 30.7-47.6; meandose  = 6.73 mGy, CI = 3.39-10.07) compared to when they were absent (meantime  = 27.1 s, CI = 22.4-31.8; meandose  = 4.41 mGy, CI = 3.06-5.76 (mean difference: time = 11.99 s, CI = 1.37-22.61; dose = 2.32 mGy, CI = -1.20-5.84). Finally, resident involvement did not significantly affect the outcomes for CEs (ptime  = .032, pdose  = .74) and cervical FBs (ptime  = .64, pdose  = .68).

CONCLUSION

Resident participation affected lumbar FBs the most, with an increase in both fluoroscopy time and radiation dose.

Assessment of dosimetric approaches in evaluating radiation exposure for interventional cardiologists in Sri Lanka

Interventional cardiologists face significant radiation exposure during interventional cardiology procedures. Therefore, this study focuses on assessing radiation exposure among interventional cardiologists during their procedures. Specifically, it aims to determine the effectiveness of both single and double dosimeter methods in estimating annual occupational radiation doses. This research holds pioneering significance as it represents the very first study undertaken in Sri Lanka. Thirteen interventional cardiologists performed 486 interventional cardiology procedures over three months in three different healthcare institutes. Active Hp(10) dosimeters were placed to measure radiation exposure. Effective doses were calculated using single and double dosimetric algorithms. Annual occupational doses were assessed on an operator basis. Statistical analyses were conducted to assess algorithmic differences and dose variations using the Kruskal-Wallis test and linear regression. The highest annual occupational dose for each dosimetric algorithm received as 2.00 ± 0.24 mSv, 2.29 ± 0.48 mSv, 3.35 ± 0.71 mSv, and 2.64 ± 0.42 mSv, respectively, and remained below the recommended safety limit of 20 mSv/year. The Kruskal-Wallis test revealed no significant differences in the effective doses among double dosimetric algorithms, as well as between single and double dosimetric algorithms (p > 0.05). Linear regression showed strong correlations among various algorithms, demonstrating consistency. The findings of this study hold significant effects on interventional cardiology practice in Sri Lanka, enhancing radiation safety and monitoring.

Improved survival for dose-intensive chemotherapy in primary mediastinal B-cell lymphoma: a systematic review and meta-analysis of 4,068 patients

Primary mediastinal B-cell lymphoma (PMBCL) is a distinct clinicopathologic entity. Currently, there is a paucity of randomized prospective data to inform on optimal front-line chemoimmunotherapy (CIT) and use of consolidative mediastinal radiation (RT). To assess if distinct CIT approaches are associated with disparate survival outcomes, we performed a systematic review and meta-analysis comparing dose-intensive (DI-CIT) versus standard CIT for the front-line treatment of PMBCL. Standard approach (S-CIT) was defined as R-CHOP-21/CHOP-21, with or without RT. DI-CIT were defined as regimens with increased frequency, dose, and/or number of systemic agents. We reviewed data on 4,068 patients (2,517 DI-CIT; 1,551 S-CIT) with a new diagnosis of PMBCL. Overall survival for DI-CIT patients was 88% (95% CI: 85-90) compared to 80% for the S-CIT cohort (95% CI: 74-85). Meta-regression revealed an 8% overall survival (OS) benefit for the DI-CIT group (P<0.01). Survival benefit was maintained when analyzing rituximab only regimens; OS was 91% (95% CI: 89-93) for the rituximab-DI-CIT arm compared to 86% (95% CI: 82-89) for the R-CHOP-21 arm (P=0.03). Importantly, 55% (95% CI: 43-65) of the S-CIT group received RT compared to 22% (95% CI: 15-31) of DI-CIT patients (meta-regression P<0.01). To our knowledge, this is the largest meta-analysis reporting efficacy outcomes for the front-line treatment of PMBCL. DI-CIT demonstrates a survival benefit, with significantly less radiation exposure, curtailing long-term toxicities associated with radiotherapy. As we await results of randomized prospective trials, our study supports the use of dose-intensive chemoimmunotherapy for the treatment of PMBCL.

Imperfect match between radiation exposure times required for conidial viability loss and infective capacity reduction attenuate UV-B impact on Beauveria bassiana

BACKGROUND

UV-B radiation represents a significant challenge for the widespread use of entomopathogenic fungi in pest management. This study focused on research of the asynchronous response between virulence and conidial viability against Ceratitis capitata adults using specific statistical models. Moreover, it was also investigated whether the observed differences in susceptibility to UV-B radiation in in vitro assays among three selected isolates of Beauveria bassiana were reflected in the above-mentioned asynchrony.

RESULTS

While the irradiation of the three isolates of B. bassiana was associated with a significant loss of conidial viability, their virulence was not significantly affected compared to nonirradiated treatments when exposed to 1200 mW m-2 for 6 h before or after the inoculation of C. capitata. In fact, the irradiation time needed to reduce the mortality to 50% compared to the controls was 34.69 h for EABb 10/225-Fil, 16.36 h for EABb 09/20-Fil, and 24.59 h for EABb 09/28-Fil. Meanwhile, the irradiation time necessary to reduce conidial viability to 50% was 9.89 h for EABb 10/225-Fil, 8.74 h for EABb 09/20-Fil, and 4.71 h for EABb 09/28-Fil.

CONCLUSION

These results highlight the importance of modeling the response of entomopathogenic fungi virulence and conidial susceptibility when exposed to UV-B radiation for the selection of environmentally competent isolates, regardless of the results obtained in previous in vitro assays on conidial germination. This strategic approach is critical in overcoming the challenges posed by UV-B radiation and holds the key to realizing the full potential of entomopathogenic fungi in pest management. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Do Flat Panel Detector C-Arms Decrease Radiation Exposure Compared to Conventional Image Intensifiers?

OBJECTIVE

To compare the radiation dose and image quality between flat panel detector (FPD) and traditional image intensifier (II) C-arms at their lowest radiation settings.

METHODS

In a ureteroscopy simulation using a cadaver model, the radiation exposure was compared between FPD and II at 4 pulses-per-second (pps) using both low dose and automatic exposure control (AEC) settings. Additionally, the lowest dose settings for each machine were compared (4 pps with low dose in the FPD and 1 pps with low dose in the II). Five trials of 5 minutes were conducted for each setting. Four new optically stimulated luminescent dosimeters were used in each trial to record radiation exposure. Ten blinded urologists completed a survey rating image quality for each setting.

RESULTS

When comparing the FPD and II at their lowest possible settings, the FPD produced significantly more radiation (P <.05). Using both machines at 4 pps in low dose mode resulted in no significant difference between C-arms (P >.05). Conversely, operating the C-arms at 4 pps and AEC resulted in significantly higher radiation exposure from the FPD compared to the II (P <.05). There was no significant difference in image quality at each setting.

CONCLUSION

FPDs produce significantly more radiation at the lowest settings compared to IIs. Surgeons should employ IIs when reducing radiation exposure as low as possible is imperative, such as when operating on pediatric and pregnant patients.

Radiation exposure to the orthopedic surgeon-a dosimetric comparison of two mini C-arm fluoroscopy models: a pilot study

OBJECTIVE

Perform a cadaveric experimental pilot study to measure and compare potential radiation exposure to an orthopedic surgeon from 2 different-generation mini C-arm models during a simulated orthopedic surgery.

SAMPLE

16 radiation dosimeters.

METHODS

Mock surgery setups were constructed with a canine cadaver thoracic limb and 2 different-generation mini C-arm models. Four radiation dosimeters were placed near the mini C-arm to mimic common locations of radiation exposure during image acquisition. One mini C-arm was placed in auto technique mode, and 100 static images were acquired. The dosimeters were replaced, and a 5-minute-long dynamic image was acquired. The same protocols were repeated for the second mini C-arm. The dosimetry badges were then submitted for radiation exposure quantification.

RESULTS

All but 1 dosimeter had radiation exposure levels below the detectable limits of the dosimeter. The dosimeter closest to the primary x-ray beam of 1 mini C-arm during dynamic image acquisition had a reading of 1 mrem.

CLINICAL RELEVANCE

Intraoperative radiation exposure from the mini C-arm is low, specifically to areas not protected by lead and in close proximity to the primary x-ray beam. That being said, surgeons should always practice the principles of ALARA (ie, as low as reasonably achievable) to minimize radiation exposure in the workplace.

Radiation exposure lymphocyte damage assessed by γ-H2AX level using flow cytometry

DNA double-strand breaks (DSBs) are considered the most relevant lesions to the DNA damage of ionizing radiation (IR), and γ-H2AX foci in peripheral blood lymphocytes are regarded as an adequate marker for DSB quantitative studies. This study aimed to investigate IR-induced DNA damage in mice through γ-H2AX fluorescence analyses by flow cytometry (FCM). The levels of γ-H2AX in CD4/CD8/B220-positive lymphocytes were quantified by FCM through mean fluorescence intensity (MFI) values. Peripheral venous blood samples were collected for evaluation, and all the control groups were restrained from irradiation. For external irradiation experiments, the dose-dependency of MFI values and temporal alternations were assessed both in vitro and in vivo. External radiation exposure damage was positively correlated with the absorbed radiation dose, and the lymphocyte recovered from damage within 3 days. I-131 sodium iodide solution (74 MBq) was injected into the mice intraperitoneally for internal irradiation experiments. Gamma counting and γH2AX foci analyses were performed at 1 h and 24 h by the group. The blood-to-blood S values (Sblood←blood) were applied for the blood-absorbed dose estimation. Internal low-dose-irradiation-induced damage was proved to recover within 24 h. The FCM method was found to be an effective way of quantitatively assessing IR-induced DNA damage.

Synthetic interpolated DSA for radiation exposure reduction via gamma variate contrast flow modeling: a retrospective cohort study

BACKGROUND

Digital subtraction angiography (DSA) yields high cumulative radiation dosages (RD) delivered to patients. We present a temporal interpolation of low frame rate angiograms as a method to reduce cumulative RDs.

METHODS

Patients undergoing interventional evaluation and treatment of cerebrovascular vasospasm following subarachnoid hemorrhage were retrospectively identified. DSAs containing pre- and post-intervention runs capturing the full arterial, capillary, and venous phases with at least 16 frames each were selected. Frame rate reduction (FRR) of the original DSAs was performed to 50%, 66%, and 75% of the original frame rate. Missing frames were regenerated by sampling a gamma variate model (GVM) fit to the contrast response curves to the reduced data. A formal reader study was performed to assess the diagnostic accuracy of the "synthetic" studies (sDSA) compared to the original DSA.

RESULTS

Thirty-eight studies met inclusion criteria (average RD 1,361.9 mGy). Seven were excluded for differing views, magnifications, or motion. GVMs fit to 50%, 66%, and 75% FRR studies demonstrated average voxel errors of 2.0 ± 2.5% (mean ± standard deviation), 6.5 ± 1.5%, and 27 ± 2%, respectively for anteroposterior projections, 2.0 ± 2.2%, 15.0 ± 3.1%, and 14.8 ± 13.0% for lateral projections, respectively. Reconstructions took 0.51 s/study. Reader studies demonstrated an average rating of 12.8 (95% CI 12.3-13.3) for 75% FRR, 12.7 (12.2-13.2) for 66% FRR and 12.0 (11.5-12.5) for 50% FRR using Subjective Image Grading Scale. Kendall's coefficient of concordance resulted in W = 0.506.

CONCLUSION

FRR by 75% combined with GVM reconstruction does not compromise diagnostic quality for the assessment of cerebral vasculature.

RELEVANCE STATEMENT

Using this novel algorithm, it is possible to reduce the frame rate of DSA by as much as 75%, with a proportional reduction in radiation exposure, without degrading imaging quality.

KEY POINTS

• DSA delivers some of the highest doses of radiation to patients. • Frame rate reduction (FRR) was combined with bolus tracking to interpolate intermediate frames. • This technique provided a 75% FRR with preservation of diagnostic utility as graded by a formal reader study for cerebral angiography performed for the evaluation of cerebral vasospasm. • This approach can be applied to other types of angiography studies.

High variability in short and long-term recovery kinetic of blood cell count and blood chemistry in a partial body irradiation mouse model

PURPOSE

In the aftermath of a nuclear disaster or accident, survivors will suffer from radiation-induced normal tissue damage. Recovery after radiation exposure is dictated by several factors, one of which is degree of shielding at time of exposure. This study aims to characterize the short and late term changes in kinetics and magnitude of pancytopenia and blood chemistry in a model of heterogeneous radiation exposure, or partial body irradiation (PBI), compared to whole body irradiation (WBI).

MATERIALS AND METHODS

Male C57BL/6 mice, 8-10 weeks of age, were WBI at 6 different doses (6, 6.1. 6.15, 6.2, 6.5, and 7.5 Gy) to establish the LD50. To determine the effect of shielding on blood cell counts and chemistry, animals were either WBI at 6 Gy (LD2230) or 6 Gy PBI with one leg shielding (LD030). Complete blood counts and chemistry were measured at 1, 5-, 10-, 20-, 30- and 120-days post-irradiation.

RESULTS AND CONCLUSIONS

Irradiated animals had significant depletion of white blood cells, red blood cells and platelets up to 10 days post-irradiation. Separation between PBI and WBI were observed at 10- and 20-days post-irradiation at which point PBI animals showed sign of recovery while overall cell count remains depleted in WBI animals up to 30 days post-irradiation. In addition, significant changes were found in parameters indicative of hematopoietic injury including hemoglobin count, hematocrit count and white blood cell population. Significant changes were observed in kidney function with changes to blood urea nitrogen and calcium concentration at 5-days post-irradiation. At 10-days post-irradiation. liver function changes differentiated WBI from PBI animals. Long-term, irradiated animal's chemistry values and many blood counts were not significantly different from Sham. In conclusion, partial shielding ensured complete survival and demonstrated a different recovery kinetics of blood and chemistry parameters after irradiation compared to survivors of whole body irradiation and no single hemopoietic parameter was able to consistently differentiate irradiated from Sham animals. This seems to indicate that there is no single robust hemopoietic parameter to differentiate those exposed from those who were not due to the inherent variability in individual responses. Furthermore, there were no significant long-term effects on these blood parameters between survivors of WBI and PBI except that shielding accelerated recovery.

Significant variation in computed tomography imaging of pregnant trauma patients: a retrospective multicenter study

PURPOSE

Following motor vehicle collisions (MVCs), patients often undergo extensive computed tomography (CT) imaging. However, pregnant trauma patients (PTPs) represent a unique population where the risk of fetal radiation may supersede the benefits of liberal CT imaging. This study sought to evaluate imaging practices for PTPs, hypothesizing variability in CT imaging among trauma centers. If demonstrated, this might suggest the need to develop specific guidelines to standardize practice.

METHODS

A multicenter retrospective study (2016-2021) was performed at 12 Level-I/II trauma centers. Adult (≥18 years old) PTPs involved in MVCs were included, with no patients excluded. The primary outcome was the frequency of CT. Chi-square tests were used to compare categorical variables, and ANOVA was used to compare the means of normally distributed continuous variables.

RESULTS

A total of 729 PTPs sustained MVCs (73% at high speed of ≥ 25 miles per hour). Most patients were mildly injured but a small variation of injury severity score (range 1.1-4.6, p < 0.001) among centers was observed. There was a variation of imaging rates for CT head (range 11.8-62.5%, p < 0.001), cervical spine (11.8-75%, p < 0.001), chest (4.4-50.2%, p < 0.001), and abdomen/pelvis (0-57.3%, p < 0.001). In high-speed MVCs, there was variation for CT head (12.5-64.3%, p < 0.001), cervical spine (16.7-75%, p < 0.001), chest (5.9-83.3%, p < 0.001), and abdomen/pelvis (0-60%, p < 0.001). There was no difference in mortality (0-2.9%, p =0.19).

CONCLUSION

Significant variability of CT imaging in PTPs after MVCs was demonstrated across 12 trauma centers, supporting the need for standardization of CT imaging for PTPs to reduce unnecessary radiation exposure while ensuring optimal injury identification is achieved.

Radiation oncology department policy development for patients who may become pregnant

In the context of radiation oncology, radiation exposure from radiation therapy simulation, image guidance, and radiation therapy procedures can have severe adverse biological effects on a developing embryo or fetus. Patients who may be pregnant are screened for the possibility of pregnancy to prevent unnecessary or excessive exposure of radiation in utero. Some radiation therapy patients for whom a pregnancy test is indicated may elect to decline the test. In addition, some patients who are found upon screening to be pregnant may decide, with their attending radiation oncologist, to continue with treatment. A radiation oncology department policy was developed to provide guidelines regarding screening and consent. The policy was designed to prevent unnecessary exposure to patients who may be pregnant, and to limit dose to the embryo or fetus in patients for whom treatment is medically indicated. The policy is presented as an example for physicists intending to develop or revise their own practice's policy regarding patients who may become pregnant.

A standardised communication tool reduces radiation exposure associated with intraoperative fluoroscopy

BACKGROUND

The widespread use of intraoperative fluoroscopy in orthopaedic procedures has revolutionised surgical practice. However, there are risks associated with using ionising radiation. Efforts to reduce radiation exposure include low-dose imaging protocols and lead protective equipment. Current communication during fluoroscopic procedures can be inefficient and lead to excessive radiation exposure for patients and staff.

AIMS

This study aims to implement a communication tool with standardised commands to reduce radiation exposure in an Irish orthopaedic department.

METHODS

Radiation exposure was evaluated using dose-area product (DAP) measured in uGy/m2. A control group was recorded before implementing the communication tool. Training sessions were conducted and posters of the standardised commands were displayed. Feedback was collected from surgeons and radiographers via surveys. Statistical analysis was performed to compare pre- and post-intervention groups.

RESULTS

A total of 673 surgical cases were included over 6 months. The post-intervention group showed a mean reduction in radiation exposure from 59.8 to 36.4 uGy/m2 (p < 0.011). Subset analyses revealed reduced radiation exposure for ORIF of the distal radius, ankle, humerus, and phalanges. Surgeons and radiographers recognised the need for improved communication and expressed willingness to learn the new tool.

CONCLUSIONS

Implementation of a standardised communication tool effectively reduced patient and staff radiation exposure. It was also believed to have a positive effect on theatre staff morale. Incorporating a universal language tool into training programmes could be beneficial. Surgeons and radiographers provided several suggestions to improve the effectiveness and implementation of this tool into other units.

Clinical image quality assessment and mean glandular dose for full field digital mammography

This study aims to assess the image quality (IQ) of 12 mammographic units and to identify units with potential optimisation needs. Data for 350 mammography examinations meeting inclusion criteria were collected retrospectively from April 2021 to April 2022. They were categorised based on the medical reports into 10 normal cases, 10 cases displaying calcifications and 10 cases presenting lesions. Two radiologists assessed the IQ of 1400 mammograms, evaluating system performance per Boitaet al's study and positioning performance following European guidelines. To measure agreement between the two radiologists, the Cohen's Kappa coefficient (κ) was computed, quantifying the excess of agreement beyond chance. The visual grading analysis score (VGAS) was computed to compare system and positioning performance assessments across different categories and facilities. Median average glandular dose (AGD) values for cranio caudal and medio lateral oblique views were calculated for each category and facility and compared to the national diagnostic reference levels. The health facilities were categorised by considering both IQ VGAS and AGD levels. Inter-rater agreement between radiologists ranged from poor (κ< 0.20) to moderate (0.41 <κ< 0.60), likely influenced by inherent biases and distinct IQ expectations. 50% of the facilities were classified as needing corrective actions for their system performance as they had IQ or high AGD that could increase recall rate and radiation risk and 50% of the health facilities exhibited insufficient positioning performance that could mask tumour masses and microcalcifications. The study's findings emphasise the importance of implementing quality assurance programs to ensure optimal IQ for accurate diagnoses while adhering to radiation exposure guidelines. Additionally, comprehensive training for technologists is essential to address positioning challenges. These initiatives collectively aim to enhance the overall quality of breast imaging services, contributing to improved patient care.

Radiation exposure in augmented fluoroscopic bronchoscopy procedures: a comprehensive analysis for patients and physicians

Cancer is a major health challenge and causes millions of deaths worldwide each year, and the incidence of lung cancer has increased. Augmented fluoroscopic bronchoscopy (AFB) procedures, which combine bronchoscopy and fluoroscopy, are crucial for diagnosing and treating lung cancer. However, fluoroscopy exposes patients and physicians to radiation, and therefore, the procedure requires careful monitoring. The National Council on Radiation Protection and Measurement and the International Commission on Radiological Protection have emphasised the importance of monitoring patient doses and ensuring occupational radiation safety. The present study evaluated radiation doses during AFB procedures, focusing on patient skin doses, the effective dose, and the personal dose equivalent to the eye lens for physicians. Skin doses were measured using thermoluminescent dosimeters. Peak skin doses were observed on the sides of the patients' arms, particularly on the side closest to the x-ray tube. Differences in the procedures and experience of physicians between the two hospitals involved in this study were investigated. AFB procedures were conducted more efficiently at Hospital A than at Hospital B, resulting in lower effective doses. Cone-beam computed tomography (CT) contributes significantly to patient effective doses because it has higher radiographic parameters. Despite their higher radiographic parameters, AFB procedures resulted in smaller skin doses than did image-guided interventional and CT fluoroscopy procedures. The effective doses differed between the two hospitals of this study due to workflow differences, with cone-beam CT playing a dominant role. No significant differences in left and right eyeHp(3) values were observed between the hospitals. For both hospitals, theHp(3) values were below the recommended limits, indicating that radiation monitoring may not be required for AFB procedures. This study provides insights into radiation exposure during AFB procedures, concerning radiation dosimetry, and safety for patients and physicians.

Genetic profiling of rat gliomas and cardiac schwannomas from life-time radiofrequency radiation exposure study using a targeted next-generation sequencing gene panel

The cancer hazard associated with lifetime exposure to radiofrequency radiation (RFR) was examined in Sprague Dawley (SD) rats at the Ramazzini Institute (RI), Italy. There were increased incidences of gliomas and cardiac schwannomas. The translational relevance of these rare rat tumors for human disease is poorly understood. We examined the genetic alterations in RFR-derived rat tumors through molecular characterization of important cancer genes relevant for human gliomagenesis. A targeted next-generation sequencing (NGS) panel was designed for rats based on the top 23 orthologous human glioma-related genes. Single-nucleotide variants (SNVs) and small insertion and deletions (indels) were characterized in the rat gliomas and cardiac schwannomas. Translational relevance of these genetic alterations in rat tumors to human disease was determined through comparison with the Catalogue of Somatic Mutations in Cancer (COSMIC) database. These data suggest that rat gliomas resulting from life-time exposure to RFR histologically resemble low grade human gliomas but surprisingly no mutations were detected in rat gliomas that had homology to the human IDH1 p.R132 or IDH2 p.R172 suggesting that rat gliomas are primarily wild-type for IDH hotspot mutations implicated in human gliomas. The rat gliomas appear to share some genetic alterations with IDH1 wildtype human gliomas and rat cardiac schwannomas also harbor mutations in some of the queried cancer genes. These data demonstrate that targeted NGS panels based on tumor specific orthologous human cancer driver genes are an important tool to examine the translational relevance of rodent tumors resulting from chronic/life-time rodent bioassays.

Transcriptional Inflammatory Signature in Healthy Donors and Different Radiotherapy Cancer Patients

Cancer and ionizing radiation exposure are associated with inflammation. To identify a set of radiation-specific signatures of inflammation-associated genes in the blood of partially exposed radiotherapy patients, differential expression of 249 inflammatory genes was analyzed in blood samples from cancer patients and healthy individuals. The gene expression analysis on a cohort of 63 cancer patients (endometrial, head and neck, and prostate cancer) before and during radiotherapy (24 h, 48 h, ~1 week, ~4-8 weeks, and 1 month after the last fraction) identified 31 genes and 15 up- and 16 down-regulated genes. Transcription variability under normal conditions was determined using blood drawn on three separate occasions from four healthy donors. No difference in inflammatory expression between healthy donors and cancer patients could be detected prior to radiotherapy. Remarkably, repeated sampling of healthy donors revealed an individual endogenous inflammatory signature. Next, the potential confounding effect of concomitant inflammation was studied in the blood of seven healthy donors taken before and 24 h after a flu vaccine or ex vivo LPS (lipopolysaccharide) treatment; flu vaccination was not detected at the transcriptional level and LPS did not have any effect on the radiation-induced signature identified. Finally, we identified a radiation-specific signature of 31 genes in the blood of radiotherapy patients that were common for all cancers, regardless of the immune status of patients. Confirmation via MQRT-PCR was obtained for BCL6, MYD88, MYC, IL7, CCR4 and CCR7. This study offers the foundation for future research on biomarkers of radiation exposure, radiation sensitivity, and radiation toxicity for personalized radiotherapy treatment.

Muller's genetic load/species extinction hypothesis

The genetic load hypothesis of Hermann Muller raised the profound question of possible species extinction, even for humans, following a prolonged accumulation of recessive genes due to ionizing radiation exposure within the population. Two major mouse radiation research teams in the United States provided the most extensive tests of Muller's hypothesis. One group continued its study for more than two decades, over 82 consecutive generations, approximating 2500 human years. Even though Muller had stressed for decades his fear of species-threatening effects, no significant effects were observed for related factors such as reproductive fitness and longevity. Yet, the paper presenting the data of the 82-generation negative study has only been cited five times in 45 years. Altogether numerous laboratories worldwide collected vast amounts of data on mice, rats, and swine in an unsuccessful attempt to see if there was convincing evidence to support the genetic load theory and claims that species might deteriorate or be rendered extinct. This paper re-examines Muller's genetic load hypothesis with a new evaluation of how that hypothesis was tested and the significance of the findings, with most of those studies being completed before the BEIR I Committee Report in 1972. That committee briefly discussed the available evidence, mostly ignoring those results as they proceeded to make hereditary risk estimates both for (1) the first generation after a radiation exposure and (2) for the time, in the distant future, when a hypothetical genetic equilibrium would be reached. Their estimates assumed accumulation of harmful mutations and a linear no-threshold dose response extending all of the way down to a single ionization. More recent data on induction by ionizing radiation of dominant mutations that affect the skeletons of mice provide further robust supporting evidence that the generationally cumulative and LNT-based assumptions underpinning Muller's genetic load hypothesis are not correct.

A Review of Numerical Models of Radiation Injury and Repair Considering Subcellular Targets and the Extracellular Microenvironment

Astronauts in space are subject to continuous exposure to ionizing radiation. There is concern about the acute and late-occurring adverse health effects that astronauts could incur following a protracted exposure to the space radiation environment. Therefore, it is vital to consider the current tools and models used to describe and study the organic consequences of ionizing radiation exposure. It is equally important to see where these models could be improved. Historically, radiobiological models focused on how radiation damages nuclear deoxyribonucleic acid (DNA) and the role DNA repair mechanisms play in resulting biological effects, building on the hypotheses of Crowther and Lea from the 1940s and 1960s, and they neglected other subcellular targets outside of nuclear DNA. The development of these models and the current state of knowledge about radiation effects impacting astronauts in orbit, as well as how the radiation environment and cellular microenvironment are incorporated into these radiobiological models, aid our understanding of the influence space travel may have on astronaut health. It is vital to consider the current tools and models used to describe the organic consequences of ionizing radiation exposure and identify where they can be further improved.

Susceptibility to radiation adverse effects in veterans with Gulf War illness and healthy civilians

We evaluated whether veterans with Gulf War illness (VGWI) report greater ionizing radiation adverse effects (RadAEs) than controls; whether radiation-sensitivity is tied to reported chemical-sensitivity; and whether environmental exposures are apparent risk factors for reported RadAEs (rRadAEs). 81 participants (41 VGWI, 40 controls) rated exposure to, and rRadAEs from, four radiation types. The relations of RadAE-propensity (defined as the ratio of rRadAEs to summed radiation exposures) to Gulf War illness (GWI) presence and severity, and to reported chemical-sensitivity were assessed. Ordinal logistic regression evaluated exposure prediction of RadAE-propensity in the full sample, in VGWI, and stratified by age and chemical-sensitivity. RadAE-propensity was increased in VGWI (vs. controls) and related to GWI severity (p < 0.01) and chemical-sensitivity (p < 0.01). Past carbon monoxide (CO) exposure emerged as a strong, robust predictor of RadAE-propensity on univariable and multivariable analyses (p < 0.001 on multivariable assessment, without and with adjustment for VGWI case status), retaining significance in age-stratified and chemical-sensitivity-stratified replication analyses. Thus, RadAE-propensity, a newly-described GWI-feature, relates to chemical-sensitivity, and is predicted by CO exposure-both features reported for nonionizing radiation sensitivity, consistent with shared mitochondrial/oxidative toxicity across radiation frequencies. Greater RadAE vulnerability fits an emerging picture of heightened drug/chemical susceptibility in VGWI.

Gel Rolls Increase Percutaneous Nephrolithotomy Radiation Exposure

Introduction: Despite increasing interest in reducing radiation doses during endoscopic stone surgery, there is conflicting evidence as to whether percutaneous nephrolithotomy (PCNL) positioning (prone or supine) impacts radiation. We observed clinically that a patient placed prone on gel rolls had higher than expected radiation with intraoperative CT imaging and that gel rolls were visible on the coaxial imaging. We hypothesized that gel rolls directly increase radiation doses. Methods: Anthropomorphic experiments to simulate PCNL positions were performed using a robotic multiplanar fluoroscopy system (Artis Zeego Care+Clear, Siemens) and a 5-second coaxial imaging protocol (5s BODY). A fluoroscopy phantom was placed in various positions, including prone on a gel roll; prone on blankets of equal thickness; prone and supine directly on the table; and modified supine (MS) positions using a thin gel roll or rolled blanket. Impacts of C-arm direction and use of a 1 L saline bag were also evaluated. Measured dose area product (DAP) was compared for the groups. Results: Measured DAP was found to increase by 146 μGy*m2 (287%) when prone on gel rolls compared with only 62.29 (23%) when placed on blankets of equal thickness, although the model likely both overstates the relative impact and understates the absolute impact that would be seen clinically. Measured DAP between experimental groups also varied considerably despite fluoroscopy time being held constant. Conclusions: Our experiments support our hypothesis that gel rolls directly increase radiation dose, which has not been previously reported, using an anthropomorphic model. Surgeons should consider radiolucent materials for positioning to limit radiation exposure to patients and the surgical team.

Underestimation of Occupational Radiation Exposure During Endovascular Abdominal Aortic Aneurysm Repair

ABSTRACT

During interventional procedures of endovascular abdominal aortic aneurysm repair (EVAR), the dosimeter was conventionally placed on chest facing toward the surgical table, instead of the main source of scatter radiation. Purpose of this study is to evaluate the underestimation of occupational radiation exposure. Phantom experiments were performed in a hybrid operating room equipped with an interventional angiography system. Electric personal dosimeters were placed at the level of eyes, chest, abdomen, and gonad of three positions, representing the principal operator (PO), assistant operator (AO), and sterile nurse (SN). Personal dose equivalent was measured with two different orientations of radiation detection, facing the table and facing the phantom, respectively. In addition to fluoroscopy, the dose produced by digital subtraction angiography was also measured to estimate the radiation exposure of routine EVAR. In this study, staff doses of 26 EVAR cases were also collected in our hospital to correlate the estimated dose. Our results show that the facing-phantom dose normalized by dose area product of patient is significantly higher than the facing-table dose when the latter is regularly seen in clinical practice. This underestimation could be even worse at a more distant position (e.g., AO and SN) as the incident angle of scatter radiation is larger. Besides, the estimated dose is highly correlated with the on-site measured dose (R 2 ~ 0.8) at chest and gonad of the PO.

Naive CD4 T Cells Highly Expressing the Inflammatory Chemokine Receptor CXCR3 Increase with Age and Radiation Exposure in Atomic Bomb Survivors

The numbers of naive T cells that react to novel pathogens not yet encountered by an immune system, decrease during aging, mainly due to age-associated involution of the thymus. CD45RA+ naive CD4 T cells consist of heterogeneous populations, including highly CXCR3-expressing cells that appear during the homeostatic proliferation of naive T cells and exhibit enhanced type-1 inflammatory phenotypes. Based on previous evidence of radiation-associated reductions in thymic function and peripheral blood naive CD4 T cells, we hypothesized that the homeostatic proliferation of naive CD4 T cells compensates for deficits in peripheral T-cell populations after radiation injury, which may increase the proportion of CXCR3high cells in naive CD4 T cells and enhance inflammation. The statistical models employed in this study revealed positive associations between the number of CXCR3high naive CD4 T cells and age as well as radiation dose among 580 Hiroshima atomic bomb survivors. In addition, the CXCR3high cells in these survivors increased not only with the levels of homeostatic cytokines, IL6 and IL7, but also with those of inflammatory indicators, CXCL10 and CRP. These results suggest that thymic T-cell production deficiency due to radiation and aging results in enhanced homeostatic proliferation that drives the appearance of CXCR3high naive CD4 T cells poised for an inflammatory response. Molecular mechanisms and clinical relevance of increasing CXCR3high cells in naive CD4 T populations should be further investigated in the context of inflammatory disease development long after radiation exposure.

Refined scan protocol for the evaluation of pulmonary perfusion standardized image quality and reduced radiation dose in dynamic chest radiography

PURPOSE

Dynamic chest radiography (DCR) is a novel imaging technique used to noninvasively evaluate pulmonary perfusion. However, the standard DCR protocol, which is roughly adapted to the patient's body size, occasionally causes over- or underexposure, which could influence clinical evaluation. Therefore, we proposed a refined protocol by increasing the number of patient body mass index (BMI) categories from three to seven groups and verified its usefulness by comparing the image sensitivity indicators (S-values) and entrance surface doses (ESDs) of the conventional protocol with those of our refined protocol.

METHODS

This retrospective observational study included 388 datasets (standing position, 224; supine position, 164) for the conventional protocol (December 2019-April 2021) and 336 datasets (standing position, 233; supine position, 103) for the refined protocol (June-November 2021). The conventional protocol (BMI-3 protocol) divided the patients into three BMI groups (BMI < 17, 17≤BMI < 25, and BMI ≥ 25 kg/m2 ), whereas the refined protocol (BMI-7 protocol) divided the patients into seven BMI groups (BMI < 17, 17 ≤ BMI < 20, 20 ≤ BMI < 23, 23 ≤ BMI < 26, 26 ≤ BMI < 29, 29 ≤ BMI < 32, and BMI ≥ 32 kg/m2 ). The coefficients of variation (CVs) for the S-values and ESDs acquired using the two protocols were compared.

RESULTS

The CVs of the S-values in the BMI-7 protocol group were significantly lower than those in the BMI-3 protocol group for the standing (28.8% vs. 16.7%; p < 0.01) and supine (24.5% vs. 17.7%; p < 0.01) positions. The ESDs of patients scanned using the BMI-7 protocol were significantly lower than those scanned using the BMI-3 protocol in the standing (1.3 vs. 1.1 mGy; p < 0.01) and supine positions (2.5 vs. 1.6 mGy; p < 0.01), although the mean BMI of the two groups were similar.

CONCLUSION

We introduced the BMI-7 protocol and demonstrated its standardized image quality and reduced radiation exposure in patients undergoing DCR.

Safety and Accuracy of Robot-Assisted Cervical Screw Placement: A Systematic Review and Meta-Analysis

OBJECTIVE

The purpose of this study was to compare the accuracy and safety of robot-assisted (RA) cervical screw placement with conventional freehand (FH) technique.

METHODS

Computer-based searches were conducted on various databases including PubMed, Embase, Cochrane Library, Web of Science, the China Biology Medicine, the China National Knowledge Infrastructure, and Wanfang Database. Inclusion criteria were studies reporting the use of RA techniques for cervical screw placement and providing data on safety and accuracy outcomes. Primary outcome indicators focused on the accuracy of screw placement, while secondary outcome indicators included operative time, intraoperative blood loss, length of hospital stay, complication rate, and radiation dose. Data from eligible studies were extracted and synthesized using a forest plot analysis.

RESULTS

A total of 312 patients (1233 screws) from 6 studies were included, with 148 patients (47.4% with 567 screws) in the RA group. Perfect screw accuracy, as categorized by Gertzbein-Robbins grade A, was significantly superior with RA surgery compared to FH technique. RA screw implantation significantly reduced complication rates, intraoperative blood loss, length of hospitalization, and radiation dose compared to the conventional FH group. However, there was no statistically significant difference in surgery time between the RA and FH groups.

CONCLUSIONS

RA surgery significantly improves the accuracy of cervical screw insertion and offers potential advantages in terms of reduced complications and blood loss, shorter hospital stays, and decreased radiation exposure. However, the impact on operative time remains uncertain. Further high-quality studies, including large-scale randomized controlled trials, are needed to strengthen the evidence base.

Definition of a maximum threshold of direct solar radiation exposure for pedestrians of diverse walking abilities

Since pedestrians are impacted by solar radiation differently, urban designers must evaluate solar radiation exposure of pedestrian paths adopting an inclusive approach. This paper proposes a maximum threshold of direct solar radiation exposure for pedestrians based on activity, user profile and environmental conditions, defined as the difference between the energy consumption before feeling exhausted and the energy cost of walking. Two users of diverse walking abilities, a young adult and an elderly person with mobility impairment, were characterised by metabolic activity, walking speed and maximum energy capacity. Based on the theoretical framework, the energy budget of young adults to cope with thermal stress was set as three times higher than for the elderly. This framework was used to quantify the contribution of direct solar radiation to energy balance and then classify walkability during clear-sky summer hours; the term 'walkable' referred to environmental conditions allowing users to walk without feeling exhausted. The methodology was tested on an open area and an urban canyon in Milan; applicability by urban designers was key in developing a simplified way to evaluate shading needs. This approach could be applied to evaluate solar radiation exposure of pedestrian paths adopting diverse user experiences as an evaluation criterion.

Mathematical modeling the gene mechanism of colorectal cancer and the effect of radiation exposure

Cancer is the result of continuous accumulation of gene mutations in normal cells. The number of mutations is different in different types of cancer and even in different patients with the same type of cancer. Therefore, studying all possible numbers of gene mutations in malignant cells is of great value for the understanding of tumorigenesis and the treatment of cancer. To this end, we applied a stochastic mathematical model considering the clonal expansion of any premalignant cells with different mutations to analyze the number of gene mutations in colorectal cancer. The age-specific colorectal cancer incidence rates from the Surveillance, Epidemiology and End Results (SEER) registry in the United States and the Life Span Study (LSS) in Nagasaki and Hiroshima, Japan are chosen to test the reasonableness of the model. Our fitting results indicate that the transformation from normal cells to malignant cells may undergo two to five driver mutations for colorectal cancer patients without radiation-exposed environment, two to four driver mutations for colorectal cancer patients with low level radiation-exposure, and two to three driver mutations for colorectal cancer patients with high level radiation-exposure. Furthermore, the net growth rate of the mutated cells with radiation-exposure was is higher than that of the mutated cells without radiation-exposure for the models with two to five driver mutations. These results suggest that radiation environment may affect the clonal expansion of cells and significantly affect the development of tumors.