| 1. |
- Almén, A, et al.
(author)
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The radiation dose to children from X-ray examinations of the pelvis and the urinary tract
- 1995
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In: British Journal of Radiology. - : British Institute of Radiology. - 0007-1285 .- 1748-880X. ; 68:810, s. 13-604
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Journal article (peer-reviewed)abstract
- X-ray examinations of the pelvis and the urinary tract are frequent examinations of children, in which a large part of the trunk is irradiated. The irradiated volume contains many of the most radiation sensitive organs and tissues. The absorbed dose to children during the examination was estimated from measurements with a dose-area product meter and thermoluminescent dosemeters (TLDs). Entrance surface dose and the dose-area product results are presented. Conversion factors between the entrance surface dose and the organ dose were derived. The energy imparted, organ dose and effective dose were determined. The entrance surface dose for one single exposure varied between 0.32 mGy and 8.6 mGy for the urinary tract examination and between 0.26 mGy and 2.89 mGy per exposure for the pelvis examination. These variations are mainly influenced by the body size of the patient. The number of images taken during one examination varied. For the urinary tract investigation, the average number of exposures was six, while the corresponding number for the pelvis examination was two. The average effective dose for a typical urinary tract investigation ranged from 0.9 mSv to 8.5 mSv and from 0.3 mSv to 1.4 mSv for the pelvis examination. The radiation dose depends greatly on the body size. The recommendations to present the results in relation to age have been followed; however, the variation of body size even within each specified age range is significant. It is suggested that doses should be quoted in relation to a more critical parameter than age.
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| 2. |
- Sundgren, P, et al.
(author)
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Elevation of the larynx on normal and abnormal cineradiogram
- 1993
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In: British Journal of Radiology. - : British Institute of Radiology. - 0007-1285 .- 1748-880X. ; 66:789, s. 72-768
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Journal article (peer-reviewed)abstract
- The relationship between bolus volume (2.5, 5, 10 and 20 ml) and larynx elevation during swallowing was assessed in 10 non-dysphagic and 10 dysphagic individuals without pharyngeal dysfunction. Laryngeal elevation in different types of pharyngeal dysfunction was assessed in 60 non-dysphagic and 75 dysphagic patients. All subjects were examined with liquid barium and cineradiography at 50 frames/s. The laryngeal elevation was measured at the moment when the bolus reached the level of the valleculae and at maximum elevation. Elevation of the larynx, both the initial and maximal, was not influenced by sex, age or presence of dysphagia. Elevation of the larynx at the moment when the bolus reached the valleculae, when expressed in per cent of maximum elevation, was lower with 10 and 20 ml bolus volumes compared with 2.5 ml bolus volume (p < 0.05) in the 10 dysphagic individuals. Pharyngeal dysfunction was associated with significantly lower initial elevation of the larynx, at the moment when the bolus reached the level of the valleculae, although the maximal laryngeal elevation was normal. Initial elevation was 30% lower (p = 0.03) in patients with aspiration of bolus material into the trachea, 22% lower (p = 0.007) in those with defective closure of the laryngeal vestibule without aspiration and 16% lower (p = 0.06) in those with incoordination of the cricopharyngeal muscle compared with patients without dysfunction.
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| 3. |
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| 4. |
- Sandborg, Michael, 1961-, et al.
(author)
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Monte Carlo study of grid performance in diagnostic radiology: factors which affect the selection of tube potential and grid ratio
- 1993
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In: British Journal of Radiology. - : British Institute of Radiology. - 0007-1285 .- 1748-880X. ; 66, s. 1164-1176
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Journal article (peer-reviewed)abstract
- A Monte Carlo computational model has been developed for the study of the performance of anti-scatter grids in diagnostic radiology. It is used here to estimate the scatter in the image plane from soft tissue phantoms (representing the patient) and to calculate image contrast and the mean absorbed dose in the phantom. Different scattering conditions, representative of various examinations, have been investigated: adult lumbar spine; small field radiography and fluoroscopy; adult chest and paediatric pelvis and chest. For each scattering condition, the combinations of tube potential and grid ratio have been found which, for a well designed grid, result in the lowest mean absorbed dose in the phantom for a fixed contrast level. In examinations which generate large amounts of scatter, the use of high grid ratios in combination with high tube potentials is favourable with regard to both mean absorbed dose in the phantom and tube charge. When less scatter is generated, either the grid ratio or the tube potential can be varied to achieve the desired contrast level. High grid ratios require shorter exposure times, but need careful alignment in the beam to prevent primary radiation cut-off. It is shown that the air gap technique can be used to reduce patient dose in examinations with small amounts of scatter, but in combinations with a lower tube potential than when a grid is used.
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| 5. |
- Sandborg, Michael, 1961-, et al.
(author)
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Monte Carlo study of grid performance in diagnostic radiology: task dependent optimisation for screen-film imaging
- 1994
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In: British Journal of Radiology. - : British Institute of Radiology. - 0007-1285 .- 1748-880X. ; 67, s. 76-85
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Journal article (peer-reviewed)abstract
- An optimization of anti-scatter grid design using Monte Carlo techniques in diagnostic radiology is presented. The criterion for optimization was to find the combinations of the grid parameters (lead strip width, grid ratio and strip density) and tube potential which result in the lowest mean absorbed dose in the patient at fixed image contrast. The optimization was performed in three irradiation geometries, representing different scattering conditions (paediatric examinations, and two adult lumbar spine examinations) and was restricted to grids using fibre materials in covers and interspaces. Grid designs currently available were studied, as were designs which use thinner strips (< 30 µm) and higher grid ratios (> 18). It was found that grids with widely different strip densities (strips cm–1) and grid ratios can have good performance provided that they are used with appropriate strip width and tube potential. With increasing amounts of scatter, the optimal grid requires thicker strips and higher grid ratios. Increasing the strip density and using thinner strips and higher grid ratios are generally required. Grids with low strip density (25 strips cm–1) were found to be less sensitive to alterations in strip width. Optimal grids for paediatric radiology require thinner strips (10–20 µm) than those in currently available grids. Grids on the market are best suited for examinations of the adult body in anteroposterior (AP) view. In the adult lateral view, representing the largest scattering volume, higher grid ratios (> 18) than those in existing grids would be optimal. Examples of good grid designs are given for each examination.
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| 6. |
- Sandborg, Michael, 1961-, et al.
(author)
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Selection of anti-scatter grids for different imaging tasks: the advantage of low atomic number cover and interspace materials
- 1993
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In: British Journal of Radiology. - : British Institute of Radiology. - 0007-1285 .- 1748-880X. ; 66, s. 1151-1163
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Journal article (peer-reviewed)abstract
- A Monte Carlo computer program has been developed for the study of anti-scatter grids used in diagnostic radiology. The program estimates the scatter from soft tissue phantoms representative of either adult or paediatric examinations and uses dose increase, signal-to-noise ratio improvement and contrast improvement factors to study grid performance. It has been used to quantify the advantage of replacing grids with aluminium covers and interspaces by grids using materials of low atomic number for these components. Two approaches are used. First, the aluminium and low atomic number alternatives are compared for five grid ratios at fixed strip density and width and for tube potentials of 50, 70, 100 and 150 kV. Second, 44 commercially available grids are compared for three different imaging situations (lumbar spine, chest and paediatric). The results demonstrate that grids made with carbon fibre cover and cotton fibre interspace result in greater improvements in contrast and signal-to-noise ratio, and lower dose increase factors, than do grids made with aluminium. The dose reduction varies with irradiation conditions and is generally larger at lower tube potentials, higher grid ratios and lower strip densities. A typical reduction in mean absorbed dose in the patient is 30% in an adult lumbar spine (AP view) at 70 kV with a grid with 36 strips per centimetre and ratio 12.
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| 7. |
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| 8. |
- Adrian, Gabriel, et al.
(author)
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The FLASH effect depends on oxygen concentration
- 2019
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In: British Journal of Radiology. - : British Institute of Radiology. - 1748-880X .- 0007-1285. ; 93:1106
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Journal article (peer-reviewed)abstract
- OBJECTIVE: Recent in vivo results have shown prominent tissue sparing effect of radiotherapy with ultra-high dose rates (FLASH) compared to conventional dose rates (CONV). Oxygen depletion has been proposed as the underlying mechanism, but in vitro data to support this have been lacking. The aim of the current study was to compare FLASH to CONV irradiation under different oxygen concentrations in vitro. METHODS: Prostate cancer cells were irradiated at different oxygen concentrations (relative partial pressure ranging between 1.6 and 20%) with a 10 MeV electron beam at a dose rate of either 600 Gy/s (FLASH) or 14 Gy/min (CONV), using a modified clinical linear accelerator. We evaluated the surviving fraction of cells using clonogenic assays after irradiation with doses ranging from 0 to 25 Gy. RESULTS: Under normoxic conditions, no differences between FLASH and CONV irradiation were found. For hypoxic cells (1.6%), the radiation response was similar up to a dose of about 5-10 Gy, above which increased survival was shown for FLASH compared to CONV irradiation. The increased survival was shown to be significant at 18 Gy, and the effect was shown to depend on oxygen concentration. CONCLUSION: The in vitro FLASH effect depends on oxygen concentration. Further studies to characterize and optimize the use of FLASH in order to widen the therapeutic window are indicated. ADVANCES IN KNOWLEDGE: This paper shows in vitro evidence for the role of oxygen concentration underlying the difference between FLASH and CONV irradiation.
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| 9. |
- Al-Okshi, Ayman, et al.
(author)
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A meta-review of effective doses in dental and maxillofacial cone beam CT using the ROBIS tool.
- 2021
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In: British Journal of Radiology. - : British Institute of Radiology. - 0007-1285 .- 1748-880X. ; 94:1123
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Journal article (peer-reviewed)abstract
- OBJECTIVES: To apply the ROBIS tool for assessment of risk of bias (RoB) in systematic reviews (SRs) in a meta-review on effective doses (EDs) in dental and maxillofacial cone beam CT.METHODS: Three electronic databases and reference lists of included SRs were searched. Eligible SRs were classified as having low, high or unclear RoB. Findings of SRs were synthesised and data from primary studies combined to relate ED to field of view (FOV) and operating potential (kV).RESULTS: Seven SRs were included: three displayed low RoB, three high and one had unclear RoB. Only one SR related ED to image quality. Deficiencies in reporting of eligibility criteria, study selection and synthesis of results in SRs were identified. FOV height had a significant relationship with ED, explaining 27.2% of its variability. Median ED for three FOV categories differed significantly. Operating potential had a weak relationship with ED, with no significant difference in median ED between three operating potential groups.CONCLUSION: The ROBIS tool should have a role for meta-reviews of different aspects of radiology. The disappointing results for RoB might be remedied by developing standards to improve the quality of reporting of primary dosimetry studies and of SRs. Future dosimetry studies should always relate ED to image quality or diagnostic accuracy.ADVANCES IN KNOWLEDGE: This meta-review is the first to implement ROBIS for SRs of ED and identified that trustworthiness of some SRs is questionable. The percentage change in average ED per cm increase in FOV height could be calculated, emphasizing the importance of FOV as a determinant of ED in CBCT.
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| 10. |
- Al-Okshi, Ayman, et al.
(author)
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Effective dose of cone beam computed tomography (CBCT) of the facial skeleton : a systematic review
- 2015
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In: British Journal of Radiology. - : British Institute of Radiology. - 0007-1285 .- 1748-880X. ; 88:1045
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Research review (peer-reviewed)abstract
- Objective: To estimate effective dose of cone beam CT (CBCT) of the facial skeleton with focus on measurement methods and scanning protocols. Methods: A systematic review, which adhered to the preferred reporting items for systematic reviews (PRISMA) Statement, of the literature up to April 2014 was conducted. Data sources included MEDLINE®, The Cochrane Library and Web of Science. A model was developed to underpin data extraction from 38 included studies. Results: Technical specifications of the CBCT units were insufficiently described. Heterogeneity in measurement methods and scanning protocols between studies made comparisons of effective doses of different CBCT units and scanning protocols difficult. Few studies related doses to image quality. Reported effective dose varied across studies, ranging between 9.7 and 197.0 mSv for field of views (FOVs) with height #5cm, between 3.9 and 674.0 mSv for FOVs of heights 5.1–10.0 cm and between 8.8 and 1073.0 mSv for FOVs .10 cm. There was an inconsistency regarding reported effective dose of studies of the same CBCT unit with the same FOV dimensions. Conclusion: The review reveals a need for studies on radiation dosages related to image quality. Reporting quality of future studies has to be improved to facilitate comparison of effective doses obtained from examinations with different CBCT units and scanning protocols. A model with minimum data set on important parameters based on this observation is proposed. Advances in knowledge: Data important when estimating effective dose were insufficiently reported in most studies. A model with minimum data based on this observation is proposed. Few studies related effective dose to image quality.
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| 11. |
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| 12. |
- Almén, Anja, et al.
(author)
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Paediatric diagnostic reference levels for common radiological examinations using the European guidelines
- 2022
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In: British Journal of Radiology. - : British Institute of Radiology. - 0007-1285 .- 1748-880X. ; 95:1130
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Journal article (peer-reviewed)abstract
- Objective: The purpose of this study was to explore the feasibility to determine regional diagnostic reference levels (RDRLs) for paediatric conventional and CT examinations using the European guidelines and to compare RDRLs derived from weight and age groups, respectively. Methods: Data were collected from 31 hospitals in 4 countries, for 7 examination types for a total of 2978 patients. RDRLs were derived for each weight and age group, respectively, when the total number of patients exceeded 15. Results: It was possible to derive RDRLs for most, but not all, weight-based and age-based groups for the seven examinations. The result using weight-based and age-based groups differed substantially. The RDRLs were lower than or equal to the European and recently published national DRLs. Conclusion: It is feasible to derive RDRLs. However, a thorough review of the clinical indications and methodologies has to be performed previous to data collection. This study does not support the notion that DRLs derived using age and weight groups are exchangeable. Advances in knowledge: Paediatric DRLs should be derived using weight-based groups with access to the actual weight of the patients. DRLs developed using weight differ markedly from those developed with the use of age. There is still a need to harmonize the method to derive solid DRLs for paediatric radiological examinations.
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| 13. |
- Alobeidi, Hanan, et al.
(author)
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Minimizing contrast media dose in CT pulmonary angiography with high-pitch technique
- 2020
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In: British Journal of Radiology. - : John Wiley & Sons. - 0007-1285 .- 1748-880X. ; 93:1111
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Journal article (peer-reviewed)abstract
- OBJECTIVES: To perform CT pulmonary angiography (CTPA) using a minimal amount of iodinated contrast media.METHODS: 47 patients (25 females) with mean age 69 years (range 41-82 years) referred for contrast-enhanced chest CT were prospectively included in this Phase IV clinical drug trial. All participants underwent a study specific CTPA in addition to the chest CT. The participants received 80 mg I/kg body weight Iohexol contrast media using a preparatory saline bolus, a dual flow contrast/saline bolus and a saline flush, and a scanner protocol with 80 kVp dual source high-pitch mode. Three readers independently assessed the image quality on the 3-point scale non-diagnostic, adequate or good-excellent image quality. Additionally, the pulmonary arterial contrast opacification was measured.RESULTS: On average, the patients received 16.8 ml Iohexol 350 mg I/mL (range 12-20 ml). Mean patient weight was 71 kg (range 50-85 kg). Identically for all readers, pulmonary embolism (PE) was detected in 1/47 participants. The median number of examinations visually scored concerning pulmonary embolism as good-excellent was 47/47 (range 44-47); adequate 0/47 (0-3) and non-diagnostic 0/47 (range 0-0). The proportion adequate or better examinations was for all readers 47/47, 100% [95% confidence interval 92-100%]. The mean attenuation ± standard deviation in the pulmonary trunk was 325 ± 72 Hounsfield unit (range 165-531 Hounsfield unit).CONCLUSIONS: Diagnostic CTPA with 17 ml contrast media is possible in non-obese patients using low kVp, high pitch and carefully designed contrast media administration.ADVANCES IN KNOWLEDGE: By combining several procedures in a CTPA protocol, the contrast media dose can be minimized.
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| 14. |
- Andersson, Karin M., 1989-, et al.
(author)
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Metal artefact reduction in CT imaging of hip prostheses-an evaluation of commercial techniques provided by four vendors
- 2015
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In: British Journal of Radiology. - : British Institute of Radiology. - 0007-1285 .- 1748-880X. ; 88:1052
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Journal article (peer-reviewed)abstract
- Objective: The aim of this study was to evaluate commercial metal artefact reduction (MAR) techniques in X-ray CT imaging of hip prostheses.Methods: Monoenergetic reconstructions of dual-energy CT (DECT) data and several different MAR algorithms, combined with single-energy CT or DECT, were evaluated by imaging a bilateral hip prosthesis phantom. The MAR images were compared with uncorrected images based on CT number accuracy and noise in different regions of interest.Results: The three MAR algorithms studied implied a general noise reduction (up to 67%, 74% and 77%) and an improvement in CT number accuracy, both in regions close to the prostheses and between the two prostheses. The application of monoenergetic reconstruction, without any MAR algorithm, did not decrease the noise in the regions close to the prostheses to the same extent as did the MAR algorithms and even increased the noise in the region between the prostheses.Conclusion: The MAR algorithms evaluated generally improved CT number accuracy and substantially reduced the noise in the hip prostheses phantom images, both close to the prostheses and between the two prostheses. The study showed that the monoenergetic reconstructions evaluated did not sufficiently reduce the severe metal artefact caused by large orthopaedic implants.Advances in knowledge: This study evaluates several commercially available MAR techniques in CT imaging of large orthopaedic implants.
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| 15. |
- Andersson, Karin M., 1989-, et al.
(author)
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Visual grading evaluation of commercially available metal artefact reduction techniques in hip prosthesis computed tomography
- 2016
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In: British Journal of Radiology. - London, United Kingdom : British Institute of Radiology. - 0007-1285 .- 1748-880X. ; 89:1063
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Journal article (peer-reviewed)abstract
- Objectives: To evaluate metal artefact reduction (MAR) techniques from four computed tomography (CT) vendors in hip prosthesis imaging.Methods: Bilateral hip prosthesis phantom images, obtained by using MAR algorithms for single energy CT data or dual energy CT (DECT) data and by monoenergetic reconstructions of DECT data, were visually graded by five radiologists using ten image quality criteria. Comparisons between the MAR images and a reference image were performed for each scanner separately. Ordinal probit regression analysis was used.Results: The MAR algorithms in general improved the image quality based on the majority of the criteria (up to between 8/10 and 10/10) with a statistically improvement in overall image quality (P<0.001). However, degradation of image quality, such as new artefacts, was seen in some cases. A few monoenergetic reconstruction series improved the image quality (P<0.004) for one of the DECT scanners, but it was only improved for some of the criteria (up to 5/10). Monoenergetic reconstructions resulted in worse image quality for the majority of the criteria (up to 7/10) for the other DECT scanner.Conclusions: The MAR algorithms improved the image quality of the hip prosthesis CT images. However, since additional artefacts and degradation of image quality were seen in some cases, all algorithms should be carefully evaluated for every clinical situation. Monoenergetic reconstructions were in general concluded to be insufficient for reducing metal artifacts. Advances in knowledge: Qualitative evaluation of the usefulness of several MAR techniques from different vendors in CT imaging of hip prosthesis.
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| 16. |
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| 17. |
- Aznar, MC, et al.
(author)
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In vivo absorbed dose measurements in mammography using a new real-time luminescence technique
- 2005
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In: British Journal of Radiology. - : British Institute of Radiology. - 1748-880X .- 0007-1285. ; 78:928, s. 328-334
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Journal article (peer-reviewed)abstract
- A dosimetry system based on radioluminescence (RL) and optically stimulated luminescence (OSL) from carbon doped aluminium oxide (Al2O3:C) crystals was developed for in vivo absorbed dose measurements in mammography. A small cylindrical crystal of Al2O3:C (diameter 0.48 mm and length 2 mm) was coupled to the end of a 1 mm diameter optical fibre cable. Owing to their small size and characteristic shape, these probes can be placed on the body surface in the field of view during the examination, without compromising the reading of the mammogram. Our new technique was tested with a mammography unit (Siemens Mammomat 3000) and screen-film technique over a range of clinically relevant X-ray energies. The results were compared with those obtained from an ionization chamber usually used for the determination of absorbed dose in mammography. The reproducibility of measurements was around 3% (1 standard deviation) at 4.5 mGy for both RL and OSL data. The dose response was found to be linear between 4.5 mGy and 30 mGy. The energy dependence of the system is around 18% between 23 kV and 35 kV. In vivo measurements were performed during three patient examinations. It was shown that entrance and exit doses could be measured. The presence of the small probes did not significantly interfere with the diagnostic quality of the images. Entrance doses estimated by RL/OSL results agreed within 3% with entrance surface dose values calculated from the ionization chamber measurements. These results indicate a considerable potential for use in routine control and in vivo dose measurements in mammography.
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| 18. |
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| 19. |
- Borga, Magnus, 1965-
(author)
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MRI adipose tissue and muscle composition analysis : a review of automation techniques
- 2018
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In: British Journal of Radiology. - London, United Kingdom : British Institute of Radiology. - 0007-1285 .- 1748-880X. ; 91:1089
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Research review (peer-reviewed)abstract
- MRI is becoming more frequently used in studies involving measurements of adipose tissue and volume and composition of skeletal muscles. The large amount of data generated by MRI calls for automated analysis methods. This review article presents a summary of automated and semi-automated techniques published between 2013 and 2017. Technical aspects and clinical applications for MRI-based adipose tissue and muscle composition analysis are discussed based on recently published studies. The conclusion is that very few clinical studies have used highly automated analysis methods, despite the rapidly increasing use of MRI for body composition analysis. Possible reasons for this are that the availability of highly automated methods has been limited for non-imaging experts, and also that there is a limited number of studies investigating the reproducibility of automated methods for MRI-based body composition analysis.
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| 20. |
- Brandberg, John, 1966, et al.
(author)
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Accurate tissue area measurements with considerably reduced radiation dose achieved by patient-specific CT scan parameters
- 2008
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In: British Journal of Radiology. - : British Institute of Radiology. - 1748-880X .- 0007-1285. ; 81:970, s. 801-8
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Journal article (peer-reviewed)abstract
- A low-dose technique was compared with a standard diagnostic technique for measuring areas of adipose and muscle tissue and CT numbers for muscles in a body composition application. The low-dose technique was intended to keep the expected deviation in the measured area of adipose and muscle tissue to <1% of the total tissue area. The largest diameter of the patient determined the parameters for the low-dose technique. 17 patients - chosen to cover a wide range of diameters (31-47 cm) for both abdomen and thighs - were examined using both techniques. Tissue areas were compared, as were CT numbers for muscle tissue. Image noise was quantified by standard deviation measurements. The area deviation was <1%, except in the smallest subjects, in whom it was <2%. The integral radiation dose of the low-dose technique was reduced to 2-3% for diameters of 31-35 cm and to 7.5-50% for diameters of 36-47 cm as compared with the integral dose by the standard diagnostic technique. The CT numbers of muscle tissue remained unchanged with reduced radiation dose. Image noise was on average 20.9 HU (Hounsfield units) for subjects with diameters of 31-35 cm and 11.2 HU for subjects with diameters in the range of 36-47 cm. In conclusion, for body composition studies with CT, scan protocols can be adjusted so that the integral dose is lowered to 2-60% of the standard diagnostic technique at our centre without adversely altering area measurements of adipose and muscle tissue and without altering CT numbers of muscle tissue.
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| 21. |
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| 22. |
- Båth, Magnus, 1974, et al.
(author)
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Visual grading characteristics (VGC) analysis: a non-parametric rank-invariant statistical method for image quality evaluation.
- 2007
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In: The British journal of radiology. - : British Institute of Radiology. - 1748-880X .- 0007-1285. ; 80:951, s. 169-76
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Journal article (peer-reviewed)abstract
- Visual grading of the reproduction of important anatomical structures is often used to determine clinical image quality in radiography. However, many visual grading methods incorrectly use statistical methods that require data belonging to an interval scale. The rating data from the observers in a visual grading study with multiple ratings is ordinal, meaning that non-parametric rank-invariant statistical methods are required. This paper describes such a method for determining the difference in image quality between two modalities called visual grading characteristics (VGC) analysis. In a VGC study, the task of the observer is to rate his confidence about the fulfilment of image quality criteria. The rating data for the two modalities are then analysed in a manner similar to that used in receiver operating characteristics (ROC) analysis. The resulting measure of image quality is the VGC curve, which--for all possible thresholds of the observer for a fulfilled criterion--describes the relationship between the proportions of fulfilled image criteria for the two compared modalities. The area under the VGC curve is proposed as a single measure of the difference in image quality between two compared modalities. It is also described how VGC analysis can be applied to data from an absolute visual grading analysis study.
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| 23. |
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| 24. |
- Chakwizira, Arthur, et al.
(author)
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Mathematical modelling of the synergistic combination of radiotherapy and indoleamine-2,3-dioxygenase (IDO) inhibitory immunotherapy against glioblastoma
- 2018
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In: British Journal of Radiology. - : British Institute of Radiology. - 0007-1285 .- 1748-880X. ; 91:1087
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Journal article (peer-reviewed)abstract
- Objective: Recent research has shown that combining radiotherapy and immunotherapy can counteract the ability of cancer to evade and suppress the native immune system. To optimise the synergy of the combined therapies, factors such as radiation dose and fractionation must be considered, alongside numerous parameters resulting from the complexity of cancer-immune system interactions. It is instructive to use mathematical models to tackle this problem. Methods: In this work, we adapted a model primarily to describe the synergistic effect between single-fraction radiotherapy and immunotherapy (1-methyl tryptophan) observed in previous experiments with glioblastoma-carrying rats. We also showed how the model can be used to generate hypotheses on the outcome of other treatment fractionation schemes. Results: The model successfully reproduced the results of the experiments. Moreover, it provided support for the hypothesis that, for a given biologically effective dose, the efficacy of the combination therapy and the synergy between the two therapies are favoured by the administration of radiotherapy in a hypofractionated regime. Furthermore, for a double-fraction irradiation regimen, the synergy is favoured by a short time interval between the treatment fractions. Conclusion: It was concluded that the model could be fitted to reproduce the experimental data well within its uncertainties. It was also demonstrated that the fitted model can be used to form hypotheses to be validated by further pre-clinical experiments. Advances in knowledge: The results of this work support the hypothesis that the synergetic action of combined radiotherapy and immunotherapy is favoured by using a hypofractionated radiation treatment regimen, given over a short time interval.
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| 25. |
- Cooper, Christian R, et al.
(author)
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FLASH irradiation induces lower levels of DNA damage ex vivo, an effect modulated by oxygen tension, dose, and dose rate
- 2022
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In: British Journal of Radiology. - : British Institute of Radiology. - 1748-880X .- 0007-1285. ; 95:1133
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Journal article (peer-reviewed)abstract
- OBJECTIVE: FLASH irradiation reportedly produces less normal tissue toxicity, while maintaining tumour response. To investigate oxygen's role in the 'FLASH effect', we assessed DNA damage levels following irradiation at different oxygen tensions, doses and dose rates.METHODS: Samples of whole blood were irradiated (20 Gy) at various oxygen tensions (0.25-21%) with 6 MeV electrons at dose rates of either 2 kGy/s (FLASH) or 0.1 Gy/s (CONV), and subsequently with various doses (0-40 Gy) and intermediate dose rates (0.3-1000 Gy/s). DNA damage of peripheral blood lymphocytes (PBL) were assessed by the alkaline comet assay.RESULTS: Following 20 Gy irradiation, lower levels of DNA damage were induced for FLASH, the difference being significant at 0.25% (p < 0.05) and 0.5% O2 (p < 0.01). The differential in DNA damage at 0.5% O2 was found to increase with total dose and dose rate, becoming significant for doses ≥20 Gy and dose rates ≥30 Gy/s.CONCLUSION: This study shows, using the alkaline comet assay, that lower levels of DNA damage are induced following FLASH irradiation, an effect that is modulated by the oxygen tension, and increases with the total dose and dose rate of irradiation, indicating that an oxygen related mechanism, e.g. transient radiation-induced oxygen depletion, may contribute to the tissue sparing effect of FLASH irradiation.ADVANCES IN KNOWLEDGE: This paper is first to directly show that FLASH-induced DNA damage is modulated by oxygen tension, total dose and dose rate, with FLASH inducing significantly lower levels of DNA damage for doses ≥20 Gy and dose rates ≥30 Gy/s, at 0.5% O2.
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