Applied Radiation Dose Research Articles

A novel 3D polymer gel dosimeter based on polymethyl methacrylate gel (PMMAG) for radiotherapy: Ultrasonic evaluation

This study investigates the characteristics of a novel polymer gel dosimeter (PMMAG) for radiotherapy applications, focusing on its radiation absorption and sensitivity properties. The PMMAG dosimeters were evaluated using both UV–vis spectrophotometry and ultrasonic techniques. The results of the study, UV–vis analysis revealed a significant increase in dose response with the introduction of a cross-linker, peaking at a monomer-to-cross-linker ratio of 5:3. Sensitivity analysis indicated optimal sensitivity at this ratio, with values reaching 0.021 a.u./Gy. Ultrasound evaluation showed that the speed of sound and attenuation coefficient demonstrated a linear relationship and a strong positive correlation with an increase in the applied radiation dose, with the highest sensitivity observed at 8 Gy. The optimal sample exhibited the highest dose-response values at both 4 Gy and 8 Gy doses. Sensitivity values ranged from 2.1 to 2.75. The ultrasonic measurements demonstrated a significantly larger dynamic range in dose response curves compared to UV–vis dose-response data. It is concluded that ultrasound shows great potential as a technique for the evaluation of polymer gel dosimeters. The PMMAG can be introduced as a novel dosimeter for ionizing radiation dosimetry, validated through both optical and ultrasound assessment methods. The consistent and reliable performance of the PMMAG dosimeters makes them suitable for various applications in radiation therapy.

Ocular and the whole body radiation exposure during endoscopic retrograde cholangiopancreatography

Objective: This study aimed to analyze the average whole body radiation exposure, which changes significantly according to during endoscopic retrograde cholangiopancreatography (ERCP) difficulty and to determine whether an ocular protection device must be used by analyzing applied ocular radiation. Material and Methods: Patients >18 years of age in whom an ERCP had been indicated were prospectively included in the study. Results: A total of 1173 patients were included. Increased applied radiation dose significantly correlated with increased shot rate (Rho= 0.789, p< 0.001), ERCP duration (Rho= 0.487, p< 0.001), cost (Rho= 0.129, p< 0.001), and LOS (Rho= 0.109, p< 0.001). The whole body, skin, and eye radiation exposure doses were found to be lower than the recommended limit per year (20 mSv/year). Conclusion: Limit of ocular radiation exposure during ERCP did not exceed the recommended annual limit (20 mSv/year), and it was also detected to be much lower than that. Therefore, the use of ocular visors is not recommended.

Degradation of hydroxychloroquine in aqueous solutions under electron beam treatment

Abstract Hydroxychloroquine (HCQ), a 4-amino quinoline derivative, has antimalarial and anti-inflammatory activity and was most recently proposed in the treatment of SARS-COVID-19. Its pharmacokinetics and toxic side effects necessitate the monitoring of its presence in the environment and its removal from wastewater. In this study, HCQ was removed from an aqueous solution with a removal efficiency of between 80% and 90% under electron beam (EB) irradiation. The degradation of HCQ was propagated by reactions involving both the hydroxyl radical and aqueous electron. The degradation was observed to follow a pseudo-first-order kinetic reaction. The applied radiation dose, pH, and initial HCQ concentration were influential in the degradation efficiency under EB irradiation. Acidic and alkaline pH favored the removal of HCQ under EB irradiation. Even though the initial HCQ was successfully degraded, it was not completely mineralized. The TOC and chemical oxygen demand (COD) remained at a relatively stable level following EB irradiation of the aqueous solutions. This is attributed to the formation of other organic compounds that were not degraded under the investigated experimental conditions.

Exposure and protection protocols of dentomaxillofacial imaging applied by paediatric dentists in Europe.

Evaluate exposure and protection practices regarding dentomaxillofacial imaging among pediatric dentists in Europe and determine the effect of different clinician specific characteristics on their implementation. A cross-sectional study involving an electronic questionnaire addressed to paediatric dentists, participating in a seminar on dental radiology organized by the European Academy of Paediatric Dentistry. Participants were asked to respond to questions regarding dentomaxillofacial imaging in terms of applied radiation dose, adoption of radiation protection techniques, and different patterns of radiographic studying and exchange between patients and colleagues. Data analysis was performed and distribution of responses was tested using chi-square and Fisher's exact tests. A total of 151 paediatric dentists, 119 females and 32 males, with a mean chronological age of 42.8years (s.e. 11.3years), successfully completed the questionnaire (response rate = 82%). Regardless of the type of radiograph, majority of respondents (68%), reported that they perform the radiographs themselves, while 21% reported that they refer the patients. Half of the respondents (51%), indicated requesting a small (localized) field of view (FOV) when referring for a cone beam computed tomography (CBCT) with only a small proportion (11%) reporting a large (maxillofacial) FOV. Thyroid collars and optimizing exposure settings were the most commonly reported patient protection measures used. Lastly, paediatric dentists have adopted the latest technological capacities for the study of dental images. Dentomaxillofacial imaging protection and exposure protocols used are common among paediatric dentists with none of their specific characteristics having a significant effect.

Ultra-low-dose photon-counting CT of paranasal sinus: an in vivo comparison of radiation dose and image quality to cone-beam CT.

This study investigated the differences in subjective and objective image parameters as well as dose exposure of photon-counting CT (PCCT) compared to cone-beam CT (CBCT) in paranasal sinus imaging for the assessment of rhinosinusitis and sinonasal anatomy. This single-centre retrospective study included 100 patients, who underwent either clinically indicated PCCT or CBCT of the paranasal sinus. Two blinded experienced ENT radiologists graded image quality and delineation of specific anatomical structures on a 5-point Likert scale. In addition, contrast-to-noise ratio (CNR) and applied radiation doses were compared among both techniques. Image quality and delineation of bone structures in paranasal sinus PCCT was subjectively rated superior by both readers compared to CBCT (P < .001). CNR was significantly higher for photon-counting CT (P < .001). Mean effective dose for PCCT examinations was significantly lower than for CBCT (0.038 mSv ± 0.009 vs. 0.14 mSv ± 0.011; P < .001). In a performance comparison of PCCT and a modern CBCT scanner in paranasal sinus imaging, we demonstrated that first-use PCCT in clinical routine provides higher subjective image quality accompanied by higher CNR at close to a quarter of the dose exposure compared to CBCT.

Tumor Location Impacts the Development of Radiation Necrosis in Benign Intracranial Tumors.

Radiation necrosis (RN) is a possible late complication of stereotactic radiosurgery (SRS), but only a few risk factors are known. The aim of this study was to assess tumor location in correlation to the development of radiation necrosis for skull base (SB) and non-skull base tumors. All patients treated with radiosurgery for benign neoplasms (2004-2020) were retrospectively evaluated. The clinical, imaging and medication data were obtained and the largest axial tumor diameter was determined using MRI scans in T1-weighted imaging with gadolinium. The diagnosis of RN was established using imaging parameters. Patients with tumors located at the skull base were compared to patients with tumors in non-skull base locations. 205 patients could be included. Overall, 157 tumors (76.6%) were located at the SB and compared to 48 (23.4%) non-SB tumors. Among SB tumors, the most common were vestibular schwannomas (125 cases) and meningiomas (21 cases). In total, 32 (15.6%) patients developed RN after a median of 10 (IqR 5-12) months. Moreover, 62 patients (30.2%) had already undergone at least one surgical resection. In multivariate Cox regression, SB tumors showed a significantly lower risk of radiation necrosis with a Hazard Ratio (HR) of 0.252, p < 0.001, independently of the applied radiation dose. Furthermore, higher radiation doses had a significant impact on the occurrence of RN (HR 1.372, p = 0.002). The risk for the development of RN for SB tumors appears to be low but should not be underestimated. No difference was found between recurrent tumors and newly diagnosed tumors, which may support the value of radiosurgical treatment for patients with recurrent SB tumors.

Photon-Counting Detector Computed Tomography Versus Energy-Integrating Detector Computed Tomography for Coronary Artery Calcium Quantitation.

Photon-counting detector (PCD) computed tomography (CT) offers improved spatial and contrast resolution, which can impact quantitative measurements. This work aims to determine in human subjects the effect of dual-source PCD-CT on the quantitation of coronary artery calcification (CAC) compared with dual-source energy-integrating detector (EID) CT in both 1- and 3-mm images. This prospective study enrolled patients receiving a clinical EID-CT CAC examination to undergo a research PCD-CT CAC examination. Axial images were reconstructed with a 512 × 512 matrix, 200-mm field of view, 3-mm section thickness/1.5-mm interval using a quantitative kernel (Qr36). Sharper kernels (Qr56/QIR strength 4 for PCD and Qr49/ADMIRE strength 5 for EID) were used to reconstruct images with 1-mm section thickness/0.5-mm interval. Pooled analysis was performed for all calcifications with nonzero values, and volume and Agatston scores were compared between EID-CT and PCD-CT. A Wilcoxon signed-rank test was performed with P < 0.05 considered statistically significant. In 21 subjects (median age, 58 years; range, 50-75 years; 13 male [62%]) with a total of 42 calcified arteries detected at 3 mm and 46 calcified arteries at 1-mm images, EID-CT CAC volume and Agatston scores were significantly lower than those of PCD-CT ( P ≤ 0.001). At 3-mm thickness, the mean (standard deviation) volume and Agatston score for EID-CT were 55.5 (63.4) mm 3 and 63.8 (76.9), respectively, and 61.5 (69.4) mm 3 and 70.4 (85.3) for PCD-CT ( P = 0.0001 and P = 0.0013). At 1-mm thickness, the mean (standard deviation) volume and score for EID-CT were 50.0 (56.3) mm 3 and 61.1 (69.3), respectively, and 59.5 (63.9) mm 3 and 72.5 (79.9) for PCD-CT ( P < 0.0001 for both). The applied radiation dose (volume CT dose index) for the PCD-CT scan was 2.1 ± 0.6 mGy, which was 13% lower than for the EID-CT scan (2.4 ± 0.7 mGy, P < 0.001). Relative to EID-CT, PCD-CT demonstrated a small but significant increase in coronary artery calcium volume and Agatston score.

Dose response assessment of conventional Fricke: a relationship between UV-Visible and nuclear magnetic resonance techniques

Conventional Fricke is an aqueous ferrous sulfate solution that has been widely studied in the field of chemical dosimetry. The feasibility of its use has become attractive for high dose measurements that are of clinical interest in the field of radiotherapy and for industrial purposes, in the irradiation of blood bags and the sterilization of surgical material. The derivation of the absorbed dose of Fricke depends on the radiation-induced oxidation of iron (II) ions (Fe2+) present in the aqueous solution to iron (III) ions (Fe3+), which occurs after exposure to ionising radiation. In this paper, it is proposed to evaluate the dose response of the Fricke dosimeter using two different analytical techniques, ultraviolet-visible spectrophotometry (UV-Vis) and nuclear magnetic resonance spectroscopy (NMR). Twelve groups of samples were analysed in triplicate, irradiated with doses between 0 and 800 Gy, using a cobalt-60 source (60Co). The dose rate of Fricke dosimeters was evaluated against the practical values obtained. The different methods allowed an analytical correlation of the species of oxidised iron (Fe3+) using a linearity curve as a function of the applied radiation dose.

Diagnostic Value of Computed Tomography Angiography in Suspected Acute Ischemic Stroke Patients With Respect to National Institutes of Health Stroke Scale Score.

Noncontrast computed tomography (NCCT) plus computed tomography angiography (CTA) is the standard imaging modality for acute stroke. We investigated whether there is an additional diagnostic value of supra-aortic CTA in relation to National Institutes of Health Stroke Scale (NIHSS) and resultant effective radiation dose. In this observational study, 788 patients with suspected acute stroke were included and divided into 3 NIHSS groups: group 1, NIHSS 0-2; group 2, NIHSS 3-5; and group 3, NIHSS ≥ 6.Computed tomography scans were assessed for findings of acute ischemic stroke and vascular pathologies in 3 regions. Final diagnosis was obtained from medical records. Effective radiation dose was calculated based on the dose-length product. Seven hundred forty-one patients were included. Group 1 had 484 patients, group 2 had 127 patients, and group 3 had 130 patients. Computed tomography diagnosis of acute ischemic stroke was made in 76 patients. In 37 patients, a diagnosis of acute stroke was made based on pathologic CTA findings in case of an unremarkable NCCT. Stroke occurrence was the lowest in groups 1 and 2, with 3.6% and 6.3%, respectively, compared with 12.7% in group 3. If both NCCT and CTA were positive, the patient was discharged with a stroke diagnosis. Male sex had the highest effect on the final stroke diagnosis. The mean effective radiation dose was 2.6 mSv. In female patients with NIHSS 0-2, additional CTA rarely contains relevant additional findings decisive for treatment decisions or overall patient outcomes; therefore, CTA in this patient group might yield less impactful findings, and the applied radiation dose could be lowered by approximately 35%.

Radiation doses and accuracy of navigated pedicle screw placement in cervical and thoracic spine surgery: a comparison of sliding gantry CT and mobile cone-beam CT in a homogeneous cohort.

Multiple solutions for navigation-guided pedicle screw placement are currently available. Intraoperative imaging techniques are invaluable for spinal surgery, but often there is little attention paid to patient radiation exposure. This study aimed to compare the applied radiation doses of sliding gantry CT (SGCT)- and mobile cone-beam CT (CBCT)-based pedicle screw placement for spinal instrumentation. The authors retrospectively analyzed 183 and 54 patients who underwent SGCT- or standard CBCT-based pedicle screw placement, respectively, for spinal instrumentation at their department between June 2019 and January 2020. SGCT uses an automated radiation dose adjustment. Baseline characteristics, including the number of screws per patient and the number of instrumented levels, did not significantly differ between the two groups. Although the accuracy of screw placement according to Gertzbein-Robbins classification did not differ between the two groups, more screws had to be revised intraoperatively in the CBCT group (SGCT 2.7% vs CBCT 6.0%, p = 0.0036). Mean (± SD) radiation doses for the first (SGCT 484.0 ± 201.1 vs CBCT 687.4 ± 188.5 mGy*cm, p < 0.0001), second (SGCT 515.8 ± 216.3 vs CBCT 658.3 ± 220.1 mGy*cm, p < 0.0001), third (SGCT 531.3 ± 237.5 vs CBCT 641.6 ± 177.3 mGy*cm, p = 0.0140), and total (SGCT 1216.9 ± 699.3 vs CBCT 2000.3 ± 921.0 mGy*cm, p < 0.0001) scans were significantly lower for SGCT. This was also true for radiation doses per scanned level (SGCT 461.9 ± 429.3 vs CBCT 1004.1 ± 905.1 mGy*cm, p < 0.0001) and radiation doses per screw (SGCT 172.6 ± 110.1 vs CBCT 349.6 ± 273.4 mGy*cm, p < 0.0001). The applied radiation doses were significantly lower using SGCT for navigated pedicle screw placement in spinal instrumentation. A modern CT scanner on a sliding gantry leads to lower radiation doses, especially through automated 3D radiation dose adjustment.

Experimental assessment of impedance-based structural health monitoring in radioactive environment

This work presents an experimental study of the influence of radiation on structural health monitoring systems based on the electromechanical impedance method using low-cost piezoelectric diaphragms. For application of the method, the baseline was obtained without radiation and then compared by damage indices after application of radiation. Considering applications in nuclear power plants, the irradiation and calculation of damage indices were performed in the range of 10 kGy–60 kGy at 10 kGy intervals. Impedance measurements were performed in seven frequency bands between 0 and 65 kHz. The results show that, due to the change in the impedance signatures, the damage indices values increase according to the total applied radiation dose, which may indicate a false indication of damage. Besides, results indicate that there are frequency bands less sensitive to radiation and a threshold can be defined to distinguish radiation from structural damage.

High resolution propagation-based lung imaging at clinically relevant X-ray dose levels

Absorption-based clinical computed tomography (CT) is the current imaging method of choice in the diagnosis of lung diseases. Many pulmonary diseases are affecting microscopic structures of the lung, such as terminal bronchi, alveolar spaces, sublobular blood vessels or the pulmonary interstitial tissue. As spatial resolution in CT is limited by the clinically acceptable applied X-ray dose, a comprehensive diagnosis of conditions such as interstitial lung disease, idiopathic pulmonary fibrosis or the characterization of small pulmonary nodules is limited and may require additional validation by invasive lung biopsies. Propagation-based imaging (PBI) is a phase sensitive X-ray imaging technique capable of reaching high spatial resolutions at relatively low applied radiation dose levels. In this publication, we present technical refinements of PBI for the characterization of different artificial lung pathologies, mimicking clinically relevant patterns in ventilated fresh porcine lungs in a human-scale chest phantom. The combination of a very large propagation distance of 10.7 m and a photon counting detector with 100,upmu hbox {m} pixel size enabled high resolution PBI CT with significantly improved dose efficiency, measured by thermoluminescence detectors. Image quality was directly compared with state-of-the-art clinical CT. PBI with increased propagation distance was found to provide improved image quality at the same or even lower X-ray dose levels than clinical CT. By combining PBI with iodine k-edge subtraction imaging we further demonstrate that, the high quality of the calculated iodine concentration maps might be a potential tool for the analysis of lung perfusion in great detail. Our results indicate PBI to be of great value for accurate diagnosis of lung disease in patients as it allows to depict pathological lesions non-invasively at high resolution in 3D. This will especially benefit patients at high risk of complications from invasive lung biopsies such as in the setting of suspected idiopathic pulmonary fibrosis (IPF).

Influence of heart rate and heart rate variability on the feasibility of ultra-fast, high-pitch coronary photon-counting computed tomography angiography

Coronary computed tomography angiography has become a mainstay in diagnosing coronary artery disease and is increasingly used in screening symptomatic patients. Recently, photon-counting computed tomography (PCCT) has been introduced into clinical practice, offering higher spatial and temporal resolution. As the applied radiation dose is highly dependent on the choice of scan mode and is lowest using the ultra-fast high-pitch (FLASH) mode, guidelines for their application are needed. From a retrospective study investigating the properties of a novel photon-counting computed tomography, all patients who underwent FLASH-mode PCCT angiography were selected between January and April 2022. This resulted in a study population of 46 men and 27 women. We recorded pre- and intrascan ECG readings and calculated heart rate (maximum heart rate 73 bpm) as well heart rate variability (maximum HRV 37 bpm) as measured by the standard deviation of the heart rate. Diagnostic quality and motion artifacts scores were recorded for each coronary artery segment by consensus between two readers. We found a highly significant association between heart rate variability and image quality (p < 0.001). The heart rate itself was not independently associated with image quality. Both heart rate and heart rate variability were significantly associated with the presence of motion artifacts in a combined model. Scan heart rate variability—but not heart rate itself—is a highly significant predictor of reduced image quality on high-pitch coronary photon-counting computed tomography angiography. This may be due to better scanner architecture and an increased temporal resolution compared to conventional energy-integrating detector computed tomography, which has to be addressed in a comparison study in the future.

RADT-29. THE IMPACT OF TUMOR LOCATION AT THE SKULL BASE ON RADIATION NECROSIS IN PATIENTS UNDERGOING STEREOTACTIC RADIOSURGERY: AN ANALYSIS OF 205 PATIENTS

Abstract Background Skull base (SB) surgery and radiosurgery (SRS) are an interdisciplinary concept and represent an individualized treatment option for various skull base tumors. Radiation necrosis (RN) is a possible sequela of SRS, but despite few accepted risk factors, there is very limited data on the influence of tumor location. The aim of this study was to assess tumor location in correlation to the development of radiation necrosis for skull-base tumors. METHODS All patients treated with radiosurgery for meningioma, vestibular schwannoma and other benign neoplasms between January 2004 and November 2020 were retrospectively evaluated. The clinical, imaging and medication data were gained from the patients’ charts. The diagnosis of RN was established retrospectively using imaging parameters. Patients with tumors located at the skull base were compared to patients with tumors of other location. RESULTS A total of 205 patients could be included in this study. 157 neoplasms (76.6%) were localized at the SB, while the remaining 48 (23.4%) were non-SB. 32 (15.6%) of all patients developed RN after median 10 (IqR 5-12) months during a median follow-up of 24 (IqR 6-62) months. SB-tumors showed a significantly lower risk of radiation necrosis with a Hazard Ratio (HR) of 0.252, p &amp;lt; 0.001, independently of the applied radiation dose. Furthermore, higher radiation doses had a significant impact on the occurrence of RN (HR 1.372, p = 0.002). No significant difference could be shown for age, previous resection or previous radiosurgery. Administered dose of dexamethasone did not correlate with the risk of radiation necrosis. CONCLUSION The risk for development of RN for SB-tumors appears to be low. No difference between recurrent and newly diagnosed tumors was found, which may underpin the value of radiosurgical treatment for patients with recurrent SB-tumors. For extensive tumors of the SB, combinations of surgery and radiosurgery represents a valuable approach.

Changing the Patient's Position: Pitfalls and Benefits for Radiation Dose and Image Quality of Computed Tomography in Polytrauma.

For computed tomography (CT), representing the diagnostic standard for trauma patients, image quality is essential. The positioning of the patient's arms next to the abdomen causes artifacts and is also considered to increase radiation exposure. The aim of this study was to evaluate the effect of various positionings during different CT examination steps on the extent of artifacts as well as radiation dose using iterative reconstruction (IR). 354 trauma-CTs were analyzed retrospectively. All datasets were reconstructed using IR and three different examination protocols were applied. Arm elevation led to a significant improvement of the image quality across all examination protocols (p &lt; 0.001). Variation in arm positioning during image acquisition did not lead to a reduction of radiation dose (p = 0.123). Only elevation during scout acquisition resulted in the reduction of radiation exposure (p &lt; 0.001). To receive high-quality CT images, patients should be placed with elevated arms for the trunk scan, as artifacts remain even with the IR. Arm repositioning during the examination itself had no effect on the applied radiation dose because its modulation refers to the initial scout obtained. In order to achieve a dose effect by different positioning, a two-scout protocol (dual scout) should be used.

Metal artifact reduction in ultra-high-resolution cone-beam CT imaging with a twin robotic X-ray system

Cone-beam computed tomography (CBCT) has been shown to be a powerful tool for 3D imaging of the appendicular skeleton, allowing for detailed visualization of bone microarchitecture. This study was designed to compare artifacts in the presence of osteosynthetic implants between CBCT and multidetector computed tomography (MDCT) in cadaveric wrist scans. A total of 32 scan protocols with varying tube potential and current were employed: both conventional CBCT and MDCT studies were included with tube voltage ranging from 60 to 140 kVp as well as additional MDCT protocols with dedicated spectral shaping via tin prefiltration. Irrespective of scanner type, all examinations were conducted in ultra-high-resolution (UHR) scan mode. For reconstruction of UHR-CBCT scans an additional iterative metal artifact reduction algorithm was employed, an image correction tool which cannot be used in combination with UHR-MDCT. To compare applied radiation doses between both scanners, the volume computed tomography dose index for a 16 cm phantom (CTDIvol) was evaluated. Images were assessed regarding subjective and objective image quality. Without automatic tube current modulation or tube potential control, radiation doses ranged between 1.3 mGy (with 70 kVp and 50.0 effective mAs) and 75.2 mGy (with 140 kVp and 383.0 effective mAs) in UHR-MDCT. Using the pulsed image acquisition method of the CBCT scanner, CTDIvol ranged between 2.3 mGy (with 60 kVp and 0.6 mean mAs per pulse) and 61.0 mGy (with 133 kVp and 2.5 mean mAs per pulse). In essence, all UHR-CBCT protocols employing a tube potential of 80 kVp or more were found to provide superior overall image quality and artifact reduction compared to UHR-MDCT (all p < .050). Interrater reliability of seven radiologists regarding image quality was substantial for tissue assessment and moderate for artifact assessment with Fleiss kappa of 0.652 (95% confidence interval 0.618–0.686; p < 0.001) and 0.570 (95% confidence interval 0.535–0.606; p < 0.001), respectively. Our results demonstrate that the UHR-CBCT scan mode of a twin robotic X-ray system facilitates excellent visualization of the appendicular skeleton in the presence of metal implants. Achievable image quality and artifact reduction are superior to dose-comparable UHR-MDCT and even MDCT protocols employing spectral shaping with tin prefiltration do not achieve the same level of artifact reduction in adjacent soft tissue.

Hearing Loss in Cancer Patients with Skull Base Tumors Undergoing Pencil Beam Scanning Proton Therapy: A Retrospective Cohort Study.

Simple SummaryMost patients with skull base tumors require radiation therapy as part of their overall treatment, preferably with protons. However, vital and healthy organs, such as the cochlea, are often located in the immediate anatomical vicinity of the tumor. Despite the high precision of the proton beam, irradiating the cochlea is often unavoidable, resulting in an increased risk of hearing loss. To assess the frequency and severity of changes in hearing after proton therapy, we performed a retrospective study in a cohort of 51 patients undergoing proton therapy for skull base tumors. We observed that a hearing threshold shift correlates to the applied radiation dose intensity to the cochlea. In addition, advancing age, hearing sensitivity before proton therapy, and the time elapsed after the end of proton therapy are independently associated with the deterioration of the hearing threshold after proton therapy. These results are essential to adequately inform patients about the treatment’s impact and side effects.To assess the incidence and severity of changes in hearing threshold in patients undergoing high-dose pencil-beam-scanning proton therapy (PBS-PT). This retrospective cohort study included fifty-one patients (median 50 years (range, 13–68)) treated with PBS-PT for skull base tumors. No chemotherapy was delivered. Pure tone averages (PTAs)were determined before (baseline) and after PBS-PT as the average hearing thresholds at frequencies of 0.5, 1, 2, and 4 kHz. Hearing changes were calculated as PTA differences between pre-and post-PBS-PT. A linear mixed-effects model was used to assess the relationship between the PTA at the follow-up and the baseline, the cochlea radiation dose intensity, the increased age, and the years after PBS-PT. Included patients were treated for chordoma (n = 24), chondrosarcoma (n = 9), head and neck tumors (n = 9), or meningioma (n = 3), with a mean tumor dose of 71.1 Gy (RBE) (range, 52.0–77.8), and a mean dose of 37 Gy (RBE) (range, 0.0–72.7) was delivered to the cochleas. The median time to the first follow-up was 11 months (IQR, 5.5–33.7). The PTA increased from a median of 15 dB (IQR 10.0–25) at the baseline to 23.8 (IQR 11.3–46.3) at the first follow-up. In the linear mixed-effect model, the baseline PTA (estimate 0.80, 95%CI 0.64 to 0.96, p ≤ 0.001), patient’s age (0.30, 0.03 to 0.57, p = 0.029), follow-up time (2.07, 0.92 to 3.23, p ≤ 0.001), and mean cochlear dose in Gy (RBE) (0.34, 0.21 to 0.46, p ≤ 0.001) were all significantly associated with an increase in PTA at follow-up. The applied cochlear dose and baseline PTA, age, and time after treatment were significantly associated with hearing loss after proton therapy.

Phase III randomised controlled trial on PSMA PET/CT guided hypofractionated salvage prostate bed radiotherapy of biochemical failure after radical prostatectomy for prostate cancer (PERYTON-trial): study protocol

BackgroundSalvage external beam radiotherapy (sEBRT) for patients with a biochemical recurrence (BCR) after radical prostatectomy provides a 5-year biochemical progression-free survival up to 60%. Multiple studies have shown that dose escalation to the primary prostate tumour improves treatment outcome. However, data is lacking on the role of dose escalation in the recurrent salvage setting. The main objective of the PERYTON-trial is to investigate whether treatment outcome of sEBRT for patients with a BCR after prostatectomy can be improved by increasing the biological effective radiation dose using hypofractionation. Moreover, patients will be staged using the PSMA PET/CT scan, which is superior to conventional imaging modalities in detecting oligometastases.MethodsThe PERYTON-study is a prospective multicentre open phase III randomised controlled trial. We aim to include 538 participants (269 participants per treatment arm) with a BCR after prostatectomy, a PSA-value of < 1.0 ng/mL and a recent negative PSMA PET/CT scan. Participants will be randomised in a 1:1 ratio between the conventional fractionated treatment arm (35 × 2 Gy) and the experimental hypofractionated treatment arm (20 × 3 Gy). The primary endpoint is the 5-year progression-free survival after treatment. The secondary endpoints include toxicity, quality of life and disease specific survival.DiscussionFirstly, the high rate of BCR after sEBRT may be due to the presence of oligometastases, for which local sEBRT is inappropriate. With the use of the PSMA PET/CT before sEBRT, patients with oligometastases will be excluded from intensive local treatment to avoid unnecessary toxicity. Secondly, the currently applied radiation dose for sEBRT may be too low to achieve adequate local control, which may offer opportunity to enhance treatment outcome of sEBRT by increasing the biologically effective radiotherapy dose to the prostate bed.Trial registrationThis study is registered at ClinicalTrials.gov (Identifier: NCT04642027). Registered on 24 November 2020 – Retrospectively registered. The study protocol was approved by the accredited Medical Ethical Committee (METc) of all participating hospitals (date METc review: 23-06-2020, METc registration number: 202000239). Written informed consent will be obtained from all participants.

Optimization of bromine-based radical initiators using leucomalachite green and solvents in PRESAGE® dosimeter

This study has two main objectives. The first objective is to create an ideal dosimeter with improved sensitivity and tissue-like equivalent characteristics. Formulas F1 and F2 were fabricated for this specific purpose. The second objective is to investigate the effect of two bromine-based radical initiators and the effect of adding two types of solvents to PRESAGE® formula on the radiological properties and dose sensitivity of PRESAGE® dosimeter. Formulas F3, F4, F5, F6, and F7 were fabricated for this investigation. In total, seven different PRESAGE® dosimeters containing up to 2 wt% of tetrabromomethane (CBr4) and 1,1,1,2-tetrabromoethane (C2H2Br4) radical initiators were fabricated. They were irradiated with either 250 or 100-kVp X-rays ranging from 0 to 40 Gy. Their optical density changes pre and post irradiation were measured using a spectrophotometer. Besides, radiological properties and sensitivity of PRESAGE® dosimeters were investigated for different percentages of radical initiators and varying amounts of cyclohexanone with a fixed amount of dimethyl sulfoxide (DMSO; 2 wt%). Using Monte Carlo methods, the relative depth doses in water of F2, F3, and F5 were calculated for 50, 100, and 300- kVp X-ray beams and 1.25 MeV from cobalt-60. For all PRESAGE® formulas, an excellent linear correlation between dose response and applied radiation dose was observed. CBr4 showed much higher sensitivity than C2H2Br4 even when using the same weight percentage. The formula F2 exhibited improved sensitivity to radiation than the presented PRESAGE® dosimeter formula named as MOD3, along with radiological properties close to water. The PRESAGE® formula F5 showed a sensitivity increase of 46.1% with addition of DMSO; however, it showed an increase in effective atomic number by ∼1%. The PRESAGE® formula F2 is equivalent to water than formulas F3 and F5 in terms of depth-dose response and can be used in both kilo- and megavoltage beams without correction factors. The PRESAGE® dosimeters with CBr4 as a radical initiator can be used if high sensitivity is required. However, an effective atomic number is not water-equivalent when using a considerable amount of radical initiator (>0.50 wt%).

The Fusion of MRI and CT in the Planning of Brachytherapy for Cancer of the Uterine Cervix

Introduction: tumors of the uterine cervix are among the most common carcinomas in women. Intracervical brachytherapy is an indispensable part of curative treatment. Although the tumor is significantly more recognizable in MRI than in CT, the practical application of MRI in brachytherapy planning is still difficult. The present study examines the technical possibilities of merging CT and MRI. Materials and Methods: the treatment files and imaging of all 53 patients who had been irradiated by image-guided adaptive brachytherapy (IGABT) between January 2019 and August 2021 at the Department of Radiotherapy of the Hannover Medical School were evaluated, retrospectively. Patients were treated first with an external beam radiotherapy (EBRT) combined with simultaneous chemotherapy. After an average of 4.2 weeks, the preparation for IGABT began. The clinical target volume (CTV) for brachytherapy was contoured first in an MRI acquired before starting EBRT (MRI 1) and once more in a second MRI just before starting IGABT (MRI 2). Then, after inserting the intravaginal applicator, a CT-scan was acquired, and the CTV was contoured in the CT. Finally, the recordings of MRI 1, MRI 2, and the CT were merged, and the congruence of CTVs was quantitatively evaluated. Results: the CTV delineated in MRI 2 was, on average, 28% smaller than that in MRI 1 after an average applied radiation dose of 42 Gy. The CTV delineated in the CT covered an average of no more than 80.8% of the CTV delineated in MRI 2. The congruence of CTVs was not superior in patients with a smit sleeve in the cervical channel, with a 3D-volumetric MRI or with a contrast-enhanced sequence for MRI. Conclusion: the anatomical shape and position of the uterus is significantly changed by introducing a vaginal applicator. Despite the superior delimitability of the tumor in MRI, brachytherapy cannot be reliably planned by the image fusion of an MRI without a vaginal applicator.