Similar Radiation Dose Research Articles

Analysis of the fecal metagenome in pelvic radiation survivors with or without chronic gastrointestinal toxicity.

e24041 Background: Whole pelvis radiation therapy (WPRT) is often used as a definitive or adjuvant treatment in patients with genitourinary, gynecologic, and gastrointestinal (GI) malignancies. Irradiation of nearby bowel can cause acute and chronic GI symptoms, which can affect patients’ quality of life. Radiation therapy has been shown to alter the microbial flora and may select for pathogenic species, which may enhance toxicity. Characteristics of the fecal metagenome in patients with or without chronic GI toxicity is unknown. Severity of GI symptoms can vary between patients who receive a similar radiation dose to normal bowel; therefore, there is a critical need to evaluate the interaction of RT and microbial species in the development of toxicity. Methods: An institutional database was used to identify survivors that completed WPRT for prostate, gynecologic, and anal cancer within the last 5 years. Patients were excluded if they had evidence of recurrent disease requiring additional therapy. Eligible patients were asked to participate via telephone. Consenting patients provided a stool sample and completed a customized PRO-CTCAE form (scale 1-5) assessing chronic GI symptoms. Comprehensive shotgun metagenomics were performed on stool. Stool was sequenced using an Illumina NextSeq500. The fecal metagenome in patients with or without chronic GI symptoms were compared. Patients were dichotomized by PRO-CTCAE diarrhea score (0-1 [mild] vs ≥2 [moderate-severe]). Raw reads were processed with Kneaddata for trimming, Kracken2 for taxonomic profiling, and Bracken for abundance estimation for bacterial, fungal and viral genomes using sequences from the National Center for Bioinformatics to determine quantitative genus and species differences. For microbial diversity assessments, estimated inverse Simpson and Shannon indices were performed. Results: Fecal metagenome and PRO-CTCAE results were available for 13 survivors. Thirty percent (n = 4) of patients reported moderate to severe diarrhea. The mean age was 66 years, 38% were male, 46% received concurrent or adjuvant chemotherapy, and the mean time from completion of WPRT to stool analysis was 34 months (range 14-62 months). Conventional radiation bowel constraints were met for each patient. Several species were enriched in patients with mild GI toxicity. Notably, Akkermansia muciniphilia had the largest differential enrichment in patients with without chronic GI toxicity. Conclusions: In this cohort of patients, A. muciniphilia, a mucin-degrading bacteria that modulates the gut barrier integrity and mucin layer thickness, was enriched in patients with no to mild diarrhea compared to patients with moderate to severe diarrhea. A. muciniphilia supplementation has been shown to decrease systemic inflammation in Western diet-fed mice. Evaluation of A. muciniphilia as a radioprotective gut bacterium warrants further evaluation.

Coronary CT angiography a new promising tool in Heart transplanted patients: from clinical and economical benefits to coronary inflammation detection

Abstract Background Heart transplanted patients are usually monitored with invasive diagnostic techniques for detecting cardiac allograft vasculopathy (CAV). However coronary CT angiography (CCTA) is a new promising tool in the initial stages of CAV bringing clinical and economical benefits. Purpose 1) assess the non-inferiority of CCTA in comparison to coronary angiography (CA), in terms of radiation and contrast dose, costs, hospitalization hours, complications and diagnostic accuracy; 2) analyse the different role of immunological and non-immunological risk factors predicting CAV in patients undergoing CCTA; 3) Investigate the rule of coronary inflammation through the pericoronary-fat-attenuation-index (pFAI) at CCTA in the progression of CAV. Methods 179 heart transplanted patients were retrospectively analysed: 78 performed a CCTA and 101 performed a CA between March 2021 and May 2022. Results CCTA and CA showed similar radiation doses (8.47 [1.46-30] versus 8.15 [1.38-87.34]; p=0.796) and rate of complications (0 (0%) vs 3 (3%); p=0,258). CCTA in comparison with CA required less hours of hospitalization (0.5 hours versus 23.7 12.31 hours; p<0.001), lower costs (120 euros versus 2800 euros; p<0.001) and less contrast agent (60.4 8.7 ml versus 95.68 47.6ml; p<0.001). Diagnostic accuracy was similar between CCTA and CA (95% vs 100%; p=0,169). Among the non immunological risk factors for CAV, only smoking showed a statistically significance in predicting CAV (p=0.015). Among immunological risk factors, TNF was the only independent predictor in the progression of CAV (HR 8.23; IC 95% 1.47-45.81; p=0.019). There were no statistically correlation between pFAI at CCTA either as a continuous variable or as a categorical variable (>-70.1HU) and the progression of CAV (p=NS). Conclusions CCTA is similar to CA in terms of radiation dose and rate of complications and is superior in terms of hospitalization hours, costs and contrast agent injected. Diagnostic accurancy was equivalent between CCTA and CA. TNF was the only independent predictor in the progression of CAV. Pericoronary inflammation assessed by pFAI at CCTA was not associated with the progression of CAV.

Abstract 13323: Impact of an Institutional Process Change Adopting End-Systolic Coronary CTA Acquisition on Patient Throughput and Image Quality

Introduction: Prospective ECG-triggered end-systolic coronary computed tomographic angiography (CCTA) acquisition is less prone to motion artifacts with arrhythmias and high heart rates, and with increasing utilization, has the potential to improve scan and CT laboratory efficiency by reducing the need for IV/oral beta-blockers (BB) prior to the scan. Methods: We implemented an institutional process change in CCTA performance effective January 2023, transitioning from prospective ECG-triggered mid-diastolic acquisitions supervised by a physician at the scanner to an algorithmic approach with prospective end-systolic acquisition (200-400 ms after R peak) without BB administration, all on 3 rd -generation 192 slice dual-source scanners. We reviewed 100 consecutive CCTAs done pre- and post-process change in Jan 2022 and Jan 2023. Two experienced CCTA readers assessed segmental image quality by consensus using an 18-segment SCCT model on a 5-point Likert scale (1=non-interpretable; 2=poor; 3=satisfactory; 4=good; 5=excellent). Results: Post-process change, median overall patient appointment [94 (78 - 127) min vs. 69 (53 - 86) min; P < 0.001] and scan times [12 (10 - 16) min vs. 7 (6 - 9) min; P <.001] were significantly lower, and patient throughput doubled [2 (2 - 3)/day vs. 4 (3 - 6)/day; P =.024]. Median segmental image quality score decreased from excellent to good [5 (4 - 5) vs. 4 (4 - 5); P <.001], with a decrease in signal-noise ratio [23.5 (18 - 28.8) vs. 11.8 (8.7 - 14.7); P <.001], and no significant difference in poor or non-interpretable segments in the end-systolic cohort. More scans were repeated with end-systolic scans (10% vs. 18%), with no significant change in radiation dose (Table 1). Conclusion: Utilizing prospective ECG-triggered end-systolic acquisition avoided the use of BB, significantly reduced scan times, doubled patient throughput, at similar radiation doses, and maintained diagnostic performance with only a mild compromise in image quality.

Ultra-high-resolution photon-counting detector computed tomography of the lungs: Phantom and clinical assessment of radiation dose and image quality

PurposePhoton-counting-detector computed tomography (PCD-CT) offers enhanced noise reduction, spatial resolution, and image quality in comparison to energy-integrated-detectors CT (EID-CT). These hypothesized improvements were compared using PCD-CT ultra-high (UHR) and standard-resolution (SR) scan-modes. MethodsPhantom scans were obtained with both EID-CT and PCD-CT (UHR, SR) on an adult body-phantom. Radiation dose was measured and noise levels were compared at a minimum achievable slice thickness of 0.5 mm for EID-CT, 0.2 mm for PCD-CT-UHR and 0.4 mm for PCD-CT-SR. Signal-to-noise ratios (SNR) and contrast-to-noise ratios (CNR) were calculated for five tissue densities. Additionally, data from 25 patients who had PCD-CT of chest were reconstructed at 1 mm and 0.2 mm (UHR) slice-thickness and compared quantitatively (SNR) and qualitatively (noise, quality, sharpness, bone details). ResultsPhantom PCD-CT-UHR and PCD-CT-SR scans had similar measured radiation dose (16.0mGy vs 15.8 mGy). Phantom PCD-CT-SR (0.4 mm) had lower noise level in comparison to EID-CT (0.5 mm) (9.0HU vs 9.6HU). PCD-CT-UHR (0.2 mm) had slightly higher noise level (11.1HU). Phantom PCD-CT-SR (0.4 mm) had higher SNR in comparison to EID-CT (0.5 mm) while achieving higher resolution (Bone 115 vs 96, Acrylic 14 vs 14, Polyethylene 11 vs 10). SNR was slightly lower across all densities for PCD-CT UHR (0.2 mm). Interestingly, CNR was highest in the 0.2 mm PCD-CT group; PCD-CT CNR was 2.45 and 2.88 times the CNR for 0.5 mm EID-CT for acrylic and poly densities. Clinical comparison of SNR showed predictably higher SNR for 1 mm (30.3 ± 10.7 vs 14.2 ± 7, p = 0.02). Median subjective ratings were higher for 0.2 mm UHR vs 1 mm PCD-CT for nodule contour (4.6 ± 0.3 vs 3.6 ± 0.1, p = 0.02), bone detail (5 ± 0 vs 4 ± 0.1, p = 0.001), image quality (5 ± 0.1 vs 4.6 ± 0.4, p = 0.001), and sharpness (5 ± 0.1 vs 4 ± 0.2). ConclusionBoth UHR and SR PCD-CT result in similar radiation dose levels. PCD-CT can achieve higher resolution with lower noise level in comparison to EID-CT.

Precision radiation oncology in head and neck cancer: beyond physical precision - a narrative review

Radiotherapy is an integral part of the management of head and neck cancers, both in radical and adjuvant settings. Traditionally, similar radiation dose and fractionation schedules have been used based on tumor stage with variable outcomes indicating “one size does not fit all”. In the era of precision medicine, though we have achieved physical precision with technological advancements, we have yet to attain biologic precision. In the current review, we have highlighted the different aspects of precision oncology such as hypoxia targeting, radiomics and radiogenomics, radiobiologic targeting, and big data. The review also discusses various potential therapeutic targets and approaches in head and neck cancer management that might help to increase radiosensitization, which in turn increase survival, and quality of life. This can be incorporated into the armamentarium of radiation oncology in all the phases of radiation planning, from diagnosis to treatment to the prognosis and management of long-term side effects. Biologic precision can be applied in the clinic to provide individualized, personalized treatment in the future.

Coronary CT angiography a new promising tool in Heart transplanted patients: from clinical and economical benefits to coronary inflammation detection

Abstract Funding Acknowledgements Type of funding sources: None. Background Heart transplanted patients are usually monitored with invasive diagnostic techniques for detecting cardiac allograft vasculopathy (CAV). However coronary CT angiography (CCTA) is a new promising tool in the initial stages of CAV bringing clinical and economical benefits. Purpose 1) assess the non-inferiority of CCTA in comparison to coronary angiography (CA), in terms of radiation and contrast dose, costs, hospitalization hours, complications and diagnostic accuracy; 2) analyse the different role of immunological and non-immunological risk factors predicting CAV in patients undergoing CCTA; 3) Investigate the rule of coronary inflammation through the pericoronary-fat-attenuation-index (pFAI) at CCTA in the progression of CAV. Methods 179 heart transplanted patients were retrospectively analysed: 78 performed a CCTA and 101 performed a CA between March 2021 and May 2022. Results CCTA and CA showed similar radiation doses (8.47 [1.46–30] versus 8.15 [1.38–87.34]; p = 0.796) and rate of complications (0 (0%) vs 3 (3%); p = 0,258). CCTA in comparison with CA required less hours of hospitalization (0.5 hours versus 23.7 12.31 hours; p<0.001), lower costs (120 euros versus 2800 euros; p<0.001) and less contrast agent (60.4 8.7 ml versus 95.68 47.6ml; p<0.001). Diagnostic accuracy was similar between CCTA and CA (95% vs 100%; p = 0,169). Among the non immunological risk factors for CAV, only smoking showed a statistically significance in predicting CAV (p = 0.015). Among immunological risk factors, TNF was the only independent predictor in the progression of CAV (HR 8.23; IC 95% 1.47–45.81; p = 0.019). There were no statistically correlation between pFAI at CCTA either as a continuous variable or as a categorical variable (>-70.1HU) and the progression of CAV (p = NS). Conclusions CCTA is similar to CA in terms of radiation dose and rate of complications and is superior in terms of hospitalization hours, costs and contrast agent injected. Diagnostic accurancy was equivalent between CCTA and CA. TNF was the only independent predictor in the progression of CAV. Pericoronary inflammation assessed by pFAI at CCTA was not associated with the progression of CAV.

Photon-counting versus Dual-Source CT of Congenital Heart Defects in Neonates and Infants: Initial Experience.

Background Photon-counting CT (PCCT) has been shown to improve cardiovascular CT imaging in adults. Data in neonates, infants, and young children under the age of 3 years are missing. Purpose To compare image quality and radiation dose of ultrahigh-pitch PCCT with that of ultrahigh-pitch dual-source CT (DSCT) in children suspected of having congenital heart defects. Materials and Methods This is a prospective analysis of existing clinical CT studies in children suspected of having congenital heart defects who underwent contrast-enhanced PCCT or DSCT in the heart and thoracic aorta between January 2019 and October 2022. CT dose index and dose-length product were used to calculate effective radiation dose. Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were calculated by standardized region-of-interest analysis. SNR and CNR dose ratios were calculated. Visual image quality was assessed by four independent readers on a five-point scale: 5, excellent or absent; 4, good or minimal; 3, moderate; 2, limited or substantial; and 1, poor or massive. Results Contrast-enhanced PCCT (n = 30) or DSCT (n = 84) was performed in 113 children (55 female and 58 male participants; median age, 66 days [IQR, 15-270]; median height, 56 cm [IQR, 52-67]; and median weight, 4.5 kg [IQR, 3.4-7.1]). A diagnostic image quality score of at least 3 was obtained in 29 of 30 (97%) with PCCT versus 65 of 84 (77%) with DSCT. Mean overall image quality ratings were higher for PCCT versus DSCT (4.17 vs 3.16, respectively; P < .001). SNR and CNR were higher for PCCT versus DSCT with SNR (46.3 ± 16.3 vs 29.9 ± 15.3, respectively; P = .007) and CNR (62.0 ± 50.3 vs 37.2 ± 20.8, respectively; P = .001). Mean effective radiation doses were similar for PCCT and DSCT (0.50 mSv vs 0.52 mSv; P = .47). Conclusion At a similar radiation dose, PCCT offers a higher SNR and CNR and thus better cardiovascular imaging quality than DSCT in children suspected of having cardiac heart defects. © RSNA, 2023.

P152 CORONARY CT ANGIOGRAPHY A NEW PROMISING TOOL IN HEART TRANSPLANTED PATIENTS: FROM CLINICAL AND ECONOMICAL BENEFITS TO CORONARY INFLAMMATION DETECTION

Abstract Background Heart transplanted patients are usually monitored with invasive diagnostic techniques for detecting cardiac allograft vasculopathy (CAV). However coronary CT angiography (CCTA) is a new promising tool in the initial stages of CAV bringing clinical and economical benefits. Purpose: 1) assess the non–inferiority of CCTA in comparison to coronary angiography (CA), in terms of radiation and contrast dose, costs, hospitalization hours, complications and diagnostic accuracy; 2) analyse the different role of immunological and non–immunological risk factors predicting CAV in patients undergoing CCTA; 3) Investigate the rule of coronary inflammation through the pericoronary–fat–attenuation–index (pFAI) at CCTA in the progression of CAV. Methods 179 heart transplanted patients were retrospectively analysed: 78 performed a CCTA and 101 performed a CA between March 2021 and May 2022. Results CCTA and CA showed similar radiation doses (8.47 [1.46–30] versus 8.15 [1.38–87.34]; p=0.796) and rate of complications (0 (0%) vs 3 (3%); p=0,258). CCTA in comparison with CA required less hours of hospitalization (0.5 hours versus 23.7 ± 12.31 hours; p&amp;lt;0.001), lower costs (120 euros versus 2800 euros; p&amp;lt;0.001) and less contrast agent (60.4 ± 8.7 ml versus 95.68 ± 47.6ml; p&amp;lt;0.001). Diagnostic accuracy was similar between CCTA and CA (95% vs 100%; p=0,169). Among the non immunological risk factors for CAV, only smoking showed a statistically significance in predicting CAV (p=0.015). Among immunological risk factors, TNF was the only independent predictor in the progression of CAV (HR 8.23; IC 95% 1.47–45.81; p=0.019). There were no statistically correlation between pFAI at CCTA either as a continuous variable or as a categorical variable (&amp;gt;–70.1HU) and the progression of CAV (p=NS). Conclusions CCTA is similar to CA in terms of radiation dose and rate of complications and is superior in terms of hospitalization hours, costs and contrast agent injected. Diagnostic accurancy was equivalent between CCTA and CA. TNF was the only independent predictor in the progression of CAV. Pericoronary inflammation assessed by pFAI at CCTA was not associated with the progression of CAV.

Dual Energy Computed Tomography and Effect on the Management of Uric Acid Renal Calculi

Attenuation differences from 2 x-ray sources allow differentiation and characterization of stone types with similar radiation dose compared to single-energy CT scan. The difference is shown in colours, allowing preoperative prediction and management of stones. We determined the effect of DECT-KUB on urological management of patients with uric acid stones since it was first introduced in our centre. 50 patients with uric acid stones were selected from 2 year groups, each with 25 patients and their urological managements were reviewed retrospectively. We concluded that DECT-KUB is an accurate way of determining the chemical characteristics of renal calculi and can alter patients’ management. It has gained wide acceptance among clinicians in our centre and is now widely used to plan urological management of patients with renal calculi. Based on urological management comparison of patients who presented in the year 2011 with uric acid stones and patients in the year 2020, we concluded that patients with uric acid stones based on DECT-KUB findings can start dissolution therapy instead of surgical extraction or lithotripsy prior to biochemical analysis results become available. Although utility of DECT-KUB is widely accepted among clinicians in our centre it may not be available worldwide and this is the limiting factor in its universal use.

Facial Nerve Schwannoma Treatment with Stereotactic Radiosurgery (SRS) versus Resection followed by SRS: Outcomes and a Management Protocol.

Background Stereotactic radiosurgery (SRS) and resection are treatment options for patients with facial nerve schwannomas without mass effect. Objective This article evaluates outcomes of patients treated with SRS versus resection + SRS. Method We retrospectively compared 43 patients treated with SRS to 12 patients treated with resection + SRS. The primary study outcome was unfavorable combined endpoint, defined as worsening or new clinical symptoms, and/or tumor radiological progression. SRS (38.81 ± 5.3) and resection + SRS (67.14 ± 11.8) groups had similar clinical follow-ups. Results At the time of SRS, the tumor volumes of SRS (mean ± standard error; 1.83 ± 0.35 mL) and resection + SRS (2.51 ± 0.75 mL) groups were similar. SRS (12.15 ± 0.08 Gy) and resection + SRS (12.16 ± 0.14 Gy) groups received similar radiation doses. SRS group (42/43, 98%) had better local tumor control than the resection + SRS group (10/12, 83%, p = 0.04). Most of SRS (32/43, 74%) and resection + SRS (10/12, 83%) group patients reached a favorable combined endpoint following SRS ( p = 0.52). Considering surgical associated side effects, only 2/10 patients of the resection + SRS group reached a favorable endpoint ( p < 0.001). Patients of SRS group, who are > 34 years old ( p = 0.02), have larger tumors (> 4 mL, 0.04), internal auditory canal (IAC) segment tumor involvement ( p = 0.01) were more likely to reach an unfavorable endpoint. Resection + SRS group patients did not show such a difference. Conclusion While resection is still needed for larger tumors, SRS offers better clinical and radiological outcomes compared to resection followed by SRS for facial schwannomas. Younger age, smaller tumors, and non-IAC situated tumors are factors that portend a favorable outcome.

ESTABLISHMENT OF THE IN VITRO DOSE-RESPONSE CALIBRATION CURVE FOR X-RAY-INDUCED MICRONUCLEI IN HUMAN LYMPHOCYTES.

The cytokinesis-block micronucleus assay has proven to be a reliable technique for biological dosimetry. This study aimed to establish the dose-response curve for X-ray-induced micronucleus. Peripheral blood samples from three healthy donors were irradiated with various doses and scoring criteria by the micronuclei (MN) in binucleated cells. The results showed that the frequency of MN increased with the elevation of radiation dose. CABAS and Dose Estimate software were used to fit the MN and dose into a linear quadratic model, and the results were compared. The linear and quadratic coefficients obtained by the two software were basically the same and were comparable with published curves of similar radiation quality and dose rates by other studies. The dose-response curve established in this study can be used as an alternative method for in vitro dose reconstruction and provides a reliable tool for biological dosimetry in accidental or occupational radiation exposures.

Assessment of image quality in photon-counting detector computed tomography of the wrist – An ex vivo study

PurposeThe aim of this study was to evaluate the effect of reconstruction parameters on image quality in wrist imaging using photon-counting detector CT (PCD-CT) and to compare the results with images from an energy-integrating detector CT (EID-CT). MethodsTwelve cadaveric wrist specimens were examined using a prototype PCD-CT and a clinical EID-CT using similar radiation dose. Reconstruction parameters were matched between scanners. Also, sharper reconstruction kernels, a larger matrix size, and smaller slice thicknesses were evaluated for PCD-CT. Image noise, contrast-to-noise ratio (CNR) and image sharpness in trabecular structures were quantitatively measured. Image quality with respect to the visibility of cortical and trabecular bone structures was assessed by six radiologists using visual grading methods. ResultsImages obtained with PCD-CT had lower noise (42.6 ± 3.9 HU vs 75.1 ± 6.3 HU), higher CNR (38.9 ± 4.5 vs 19.0 ± 2.4) and higher trabecular sharpness (63.5 ± 6.0 vs 53.7 ± 8.5) than those obtained with EID-CT using similar scan and reconstruction parameters (p < 0.001). The image sharpness in trabecular structures was further improved by using sharper kernels, despite higher noise levels. Radiologists had a strong preference for PCD-CT images both in terms of spatial resolution and suitability for bone imaging. Visual grading analysis showed an improved visibility of cortical bone, trabeculae and nutritive canals (p < 0.005). ConclusionPCD-CT offers improved image quality regarding bone structures in the wrist relative to EID-CT systems, particularly when sharper reconstruction kernels, smaller slice thickness and a larger image matrix size are used.

OTHR-31. The molecular profile of secondary meningiomas in survivors of childhood non-central nervous system (CNS) cancers

Abstract INTRODUCTION: Secondary meningiomas are a late effect in children who received cranial irradiation, frequently with a long latency. The molecular genetic profile of primary meningiomas is well studied; however, few studies describe the genomic landscape of radiation-induced meningiomas (RIM). METHODS: Patients followed at the Stollery Children’s Hospital (Edmonton, Canada) with a history of non-CNS malignancies who received cranial irradiation and then developed meningiomas between 1971 and 2013 were identified. Whole exome sequencing (WES), RNA sequencing as well as DNA methylation profiling were performed for patients with available tumor tissue and germline DNA. RESULTS: Of 96 patients who received cranial irradiation for non-CNS tumors, 16 (16.7%) developed symptomatic meningiomas. This patient cohort is unique; all 16 patients identified received 2000-2400 cGy of cranial irradiation, suggesting a threshold dose. 9/16 (56%) had WHO Grade 2 meningiomas or greater and 7/16 (44%) of meningiomas infiltrated other tissues. Post-surgical recurrences occurred in 43%. Patients experienced considerable morbidities directly attributable to the meningiomas or their treatment. 14 patients had samples suitable for further analysis. NF2 mutations were identified in 50% (8; 4 DNA,4 fusion). Other meningioma related genes with mutations identified in other cohorts were not identified. Copy number alternations were noted in all 16 patients in chromosomes 1p and 22q. 850k methylation analysis with PCA as well as UMAP and tSNE did not demonstrate clustering. Ongoing additional studies include examining tumor mutation burden and the radiation mutational profile. CONCLUSIONS: This study examined the RIM in a cohort of patients having received similar doses of radiation for their childhood cancer. There is increased risk of radiation-induced meningioma in survivors of non-CNS cancers given ≥ 2000 cGy during childhood. To date, our findings are consistent with previously described primary and RIM mutations. Enhanced knowledge in secondary meningiomas is crucial for accurate patient counselling, prognostication, and treatment.

Dental imaging using an ultra-high resolution photon-counting CT system

Clinical photon-counting CT (PCCT) offers a spatial resolution of about 200 µm and might allow for acquisitions close to conventional dental CBCTs. In this study, the capabilities of this new system in comparison to dental CBCTs shall be evaluated. All 8 apical osteolysis identified in CBCT were identified by both readers in all three PCCT scan protocols. Mean visibility scores showed statistical significant differences for root canals(p = 0.0001), periodontal space(p = 0.0090), cortical(p = 0.0003) and spongious bone(p = 0.0293) in favor of high and medium dose PCCT acquisitions. Overall, both devices showed excellent image quality of all structures assessed. Interrater-agreement showed high values for all protocols in all structures. Bland–Altman plots revealed a high concordance of both modalities with the reference measurements. In vitro, ultra-high resolution PCCT can reliably identify different diagnostic entities and structures relevant for dental diagnostics similar to conventional dental CBCT with similar radiation dose. Acquisitions of five cadaveric heads were performed in an experimental CT-system containing an ultra-high resolution PC detector (0.25 mm pixel size in isocenter) as well as in a dental CBCT scanner. Acquisitions were performed using dose levels of 8.5 mGy, 38.0 mGy and 66.5 mGy (CTDI16cm) in case of PCCT and of 8.94 mGy (CTDI16cm) in case of CBCT. The quality of delineation of hard tissues, root-canals, periodontal-space as well as apical osteolysis was assessed by two readers. Mean visibility scores and interrater-agreement (overall agreement (%)) were calculated. Vertical bone loss (bl) and thickness (bt) of the buccal bone lamina of 15 lower incisors were measured and compared to reference measurements by ore microscopy and clinical probing.

Safety and Feasibility of Ultrasound-Guided Access for Coronary Interventions through Distal Left Radial Route.

Aims Left distal transradial arterial approach (ldTRA) is a new interventional route that spares right radial artery (RRA) for use in haemodialysis and as bypass graft. Vasant Kunj Left dIstal Transradial ArtEry approach (VKLITE) study aimed to assess the feasibility and safety of ldTRA access during coronary angiography (CAG) and percutaneous coronary intervention (PCI). Methods and Results Between April 2018 and June 2020, 108 patients were enrolled and underwent CAG ± PCI via ultrasound guided ldTRA. Arterial puncture, CAG, and PCI were successful in 96.3% (104/108), 92.1% (93/101), and 94.1% (32/34) patients, respectively. Access site crossover rate was 14/108 (13.0%). Mean puncture, procedure, and haemostasis time (minutes) were 6.7 ± 7.1, 55.7 ± 32.8, and 23.1 ± 11.9. Median total fluoroscopic time was 6.6 minutes (IQR-14.2), and median total radiation dose was 39.2 Gy-cm2 (IQR-97.0). Local haematoma occurred in 11 patients (10.2%) with major haematoma in 1.9%, all recovering within three weeks. Mean pain score was 2.4 ± 2.3, and patient satisfaction score was 9.0 ± 1.3. LdTRA access compared with RRA access (n = 121) showed significantly increased mean procedure time (55.7 ± 32.8 vs. 43.9 ± 26.0 minutes, p = 0.01) and median total fluoroscopic time (6.6 [IQR-14.2] vs. 4.7 [IQR-8.2] minutes, p = 0.02), with similar median total radiation dose (39.2 [IQR-97.0] vs. 43.8 [IQR-54.5] Gy-cm2, p = 0.56). No radial artery loss, dissection, pseudoaneurysm, arteriovenous fistula, or nerve injury was noted. Conclusions LdTRA access is feasible with few complications during CAG/PCI. Patient comfort and satisfaction makes it a desirable route for coronary interventions.

First Clinical Photon-counting Detector CT System: Technical Evaluation.

Background The first clinical CT system to use photon-counting detector (PCD) technology has become available for patient care. Purpose To assess the technical performance of the PCD CT system with use of phantoms and representative participant examinations. Materials and Methods Institutional review board approval and written informed consent from four participants were obtained. Technical performance of a dual-source PCD CT system was measured for standard and high-spatial-resolution (HR) collimations. Noise power spectrum, modulation transfer function, section sensitivity profile, iodine CT number accuracy in virtual monoenergetic images (VMIs), and iodine concentration accuracy were measured. Four participants were enrolled (between May 2021 and August 2021) in this prospective study and scanned using similar or lower radiation doses as their respective clinical examinations performed on the same day using energy-integrating detector (EID) CT. Image quality and findings from the participants' PCD CT and EID CT examinations were compared. Results All standard technical performance measures met accreditation and regulatory requirements. Relative to filtered back-projection reconstructions, images from iterative reconstruction had lower noise magnitude but preserved noise power spectrum shape and peak frequency. Maximum in-plane spatial resolutions of 125 and 208 µm were measured for HR and standard PCD CT scans, respectively. Minimum values for section sensitivity profile full width at half maximum measurements were 0.34 mm (0.2-mm nominal section thickness) and 0.64 mm (0.4-mm nominal section thickness) for HR and standard PCD CT scans, respectively. In a 120-kV standard PCD CT scan of a 40-cm phantom, VMI iodine CT numbers had a mean percentage error of 5.7%, and iodine concentration had root mean squared error of 0.5 mg/cm3, similar to previously reported values for EID CT. VMIs, iodine maps, and virtual noncontrast images were created for a coronary CT angiogram acquired with 66-msec temporal resolution. Participant PCD CT images showed up to 47% lower noise and/or improved spatial resolution compared with EID CT. Conclusion Technical performance of clinical photon-counting detector (PCD) CT is improved relative to that of a current state-of-the-art CT system. The dual-source PCD geometry facilitated 66-msec temporal resolution multienergy cardiac imaging. Study participant images illustrated the effect of the improved technical performance. © RSNA, 2022 Online supplemental material is available for this article. See also the editorial by Willemink and Grist in this issue.

CT imaging of esophageal foreign bodies in children: a pictorial essay.

Foreign body (FB) ingestion is common in children, particularly from 6months to 3years of age. As young children may be unable to provide a clinical history and the ingestion is often unwitnessed, imaging plays an important role in diagnosis, predicting outcomes and detecting complications that require surgical intervention. Since 2015, our institution's diagnostic algorithm for suspected airway foreign bodies has included a noncontrast airway FB CT (FB-CT) with the z-axis coverage spanning from the larynx to the proximal segmental bronchi of the lower lung zones. The effective dose of radiation from this FB-CT airway protocol is typically less than 1mSv, compared to an effective dose of just under 1mSv to up to 3mSv for a fluoroscopic esophagram in children under 10years of age and 1-3mSv for a routine pediatric CT chest. In using the FB-CT airway protocol at our institution, we observed that esophageal rather than airway FBs were sometimes encountered on these exams. However, the confidence among radiologists for definitively diagnosing an esophageal foreign body on noncontrast CT was variable. Consequently, we created a teaching module of positive cases for our group of 21 pediatric body radiologists to increase their diagnostic confidence. This pictorial essay illustrates our institutional experience and can help others to confidently diagnose esophageal foreign bodies using a dedicated CT foreign body imaging protocol. At a similar radiation dose to a fluoroscopic esophagram, CT provides the additional advantage of an expedited diagnosis without the need for a radiologist on site.

Acute, Low-Dose Neutron Exposures Adversely Impact Central Nervous System Function.

A recognized risk of long-duration space travel arises from the elevated exposure astronauts face from galactic cosmic radiation (GCR), which is composed of a diverse array of energetic particles. There is now abundant evidence that exposures to many different charged particle GCR components within acute time frames are sufficient to induce central nervous system deficits that span from the molecular to the whole animal behavioral scale. Enhanced spacecraft shielding can lessen exposures to charged particle GCR components, but may conversely elevate neutron radiation levels. We previously observed that space-relevant neutron radiation doses, chronically delivered at dose-rates expected during planned human exploratory missions, can disrupt hippocampal neuronal excitability, perturb network long-term potentiation and negatively impact cognitive behavior. We have now determined that acute exposures to similar low doses (18 cGy) of neutron radiation can also lead to suppressed hippocampal synaptic signaling, as well as decreased learning and memory performance in male mice. Our results demonstrate that similar nervous system hazards arise from neutron irradiation regardless of the exposure time course. While not always in an identical manner, neutron irradiation disrupts many of the same central nervous system elements as acute charged particle GCR exposures. The risks arising from neutron irradiation are therefore important to consider when determining the overall hazards astronauts will face from the space radiation environment.

STATIONARY INTRAORAL TOMOSYNTHESIS IN PROXIMAL CARIES DETECTION: AN EX-VIVO STUDY

<h3>BACKGROUND</h3> Research on radiographic detection of proximal caries has shown high specificity but low sensitivity, especially for early caries lesions. Stationary intraoral tomosynthesis (s-IOT) shows promise in caries detection, utilizing multibeam carbon nanotube source array technology and a direct intraoral detector to acquire images at similar radiation dose to standard bitewings and generating stacks of parasagittal image slices with an iterative reconstruction algorithm. <h3>OBJECTIVE(S)</h3> This study aimed to compare the diagnostic accuracy of s-IOT and conventional digital bitewing modalities for the detection of proximal caries lesions. <h3>STUDY DESIGN</h3> Extracted permanent posterior teeth (n = 64) with proximal surfaces scored between 0 and 4 in the International Caries Detection Assessment System were mounted in phantom heads for imaging. Eight observers, each with 2 or more years of radiology specialty training, scored surfaces on a 5-point Likert scale for caries presence and depth using s-IOT images and digital bitewings, in a standardized viewing format. Fifty percent of specimens will be repeated for intra-examiner reliability assessment. Results will be compared with a histologic gold standard and analyzed by logistic regression and receiver operating curve (Az value). The study is currently in progress, with final results expected by August 2020. <h3>RESULTS</h3> Pilot test results with 3 observers showed s-IOT to have a sensitivity of 49.6% and specificity of 86.1%, with interobserver agreement of 0.433. The conventional bitewing modality had a sensitivity of 47.9% and specificity of 83.3%, with interobserver agreement of 0.380. <h3>DISCUSSION/CONCLUSIONS</h3> Based on preliminary data, the 2 imaging modalities showed small differences between sensitivity, specificity, and interobserver kappa reliability, indicating that s-IOT is comparable to digital bitewings for the detection of proximal caries.

RARE-15. THE MOLECULAR PROFILE OF SECONDARY MENINGIOMAS IN SURVIVORS OF CHILDHOOD NON-CENTRAL NERVOUS SYSTEM CANCERS

IntroductionCranial irradiation remains part of childhood cancer therapy and secondary meningiomas are a late effect. Secondary meningiomas are reported in patients who received low and high dose cranial irradiation and arise ~ 20 years post exposure. The molecular and genetic profile of primary meningiomas has been well studied; however, only a few studies describe these in radiation-induced meningiomas (RIM). MethodsWe identified patients followed at the Childhood Cancer Survivor Clinic, Stollery Children’s Hospital who had a history of non-central nervous system malignancies and received cranial irradiation who developed meningiomas between clinic inception in 1971 and June 2013. Whole exome sequencing (WES) as well as DNA methylation profiling were performed for patients where tumor and germline DNA were available. ResultsOf 96 patients who received cranial irradiation, 16 (16.7%) developed symptomatic meningiomas. This patient cohort is unique; all 16 patients received 2000–2400 cGy, suggesting a threshold dose. 9/16 (56%) had WHO Grade 2 meningiomas or greater and 7/16 (44%) were infiltrative. Post-surgical recurrences occurred in 43%. Patients experienced considerable morbidities directly attributable to the meningiomas or their treatment. 14 patients had samples suitable for further analysis. Preliminary results revealed that NF2 mutations were the most common (5). Other meningioma related genes with mutations identified in our patient cohort include TRAF7, AKT3, MSH4 (2), KMT2C (2), TET1 (2), KDM6A, and MLH3. Copy number alternations were noted with increased frequency on chromosomes 1p, 22q, 19q. 850k methylation analysis did not conclusively show any clustering. Ongoing studies include assessment of tumor mutation burden, RNAseq, and the mutational profile. ConclusionsThis study examined RIM in patients who received similar doses of radiation for their childhood cancer. To date, our findings are consistent with previously described primary and RIM mutations. Enhanced knowledge in secondary meningiomas is crucial for accurate patient counseling, prognostication, and treatment.