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Background: Lung cancer is the most common cause of cancer-related death worldwide and therefore there has been a growing demand for low-dose computed tomography (LDCT) protocols. Purpose: To investigate and evaluate the dose and image quality of patients undergoing lung cancer screening (LCS) using LDCT in Norway. Materials and Methods: Retrospective dosimetry data, volumetric CT dose index (CTDIvol) and dose-length product (DLP), from 70 average-size and 70 large-size patients who underwent LDCT scan for LCS were included in the survey. Effective dose and size-specific dose were calculated for each examination and were compared with the American Association of Physicists in Medicine (AAPM) requirement. For a quantitative image quality analysis, noise, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) were determined for different regions in the chest with two iterative reconstruction techniques, iDose and Iterative Model Reconstruction. Differences in dose and image quality between average-size and large-size patients were evaluated by Independent sample t test, and Wilcoxon signed rank test within the same patient group. Results: The independent sample t test revealed significant differences (p <.05) in dose values between average-size and large-size patients. Mean CTDIvol and DLP for average-size patients were 2.8 mGy and 115 mGy.cm, respectively, with appropriate increment for the large-size patients. Image quality (image noise, SNR, and CNR) did not significantly differ between patient groups when images were reconstructed with a model based iterative reconstruction algorithm. Conclusion: The screening protocol assessed in this study resulted in CTDIvol values that were compliant with AAPM recommendation. No significant differences in objective image quality were found between patient groups. [ABSTRACT FROM AUTHOR]

Background: Low-dose CT (LDCT) chest protocols have widespread clinical applications for many indications; as a result, there is a need for protocol assessment prior to standardization. Dalhousie University and Oslo Metropolitan University have a formally established cooperative relationship. Purpose: The purpose is to assess radiation dose and image quality for LDCT chest protocols in seven different hospital locations in Norway and Canada. Material and methods: Retrospective dosimetry data, volumetric CT dose index (CTDIvol), and dose length product (DLP) from 240 average-sized patients as well as CT protocol parameters were included in the survey. Effective dose (ED) and size-specific dose estimate (SSDE) were calculated for each examination. For a quantitative image quality analysis, noise, CT number, and signal-to-noise ratio (SNR) were determined for three regions in the chest. The contrast-to-noise ratio (CNR) was calculated for lung parenchyma in comparison to the subcutaneous fat. Differences in dose and image quality were evaluated by a single-factor ANOVA test. A two-sample t -test was performed to determine differences in means between individual scanners. Results: The ANOVA test revealed significant differences (p <.05) in dose values for all scanners, including identical scanner models. Statistically significant differences (p <.05) were determined in mean values of the SNR distributions between the scanners in all three measured regions in the chest, as well as the CNR values. Conclusion: The observed variations in dose and image quality measurements, even within the same hospitals and between identical scanner models, indicate a potential for protocol optimization in the involved hospitals in both countries. [ABSTRACT FROM AUTHOR]

Background: Artifacts caused by metal implants are challenging when undertaking computed tomography (CT). Dedicated algorithms have shown promising results although with limitations. Tin filtration (Sn) in combination with high tube voltage also shows promise but with limitations. There is a need to examine these limitations in more detail. The purpose of this study was to investigate the impact of different metal artefact reduction (MAR) algorithms, tin filtration, and ultra-high-resolution (UHR) scanning, alone or in different combinations in both phantom and clinical settings. Methods: An ethically approved clinical and phantom study was conducted. A modified Catphan® phantom with titanium and stainless-steel inserts was scanned with six different MAR protocols with tube voltage ranging from 80 to 150 kVp. Other scan parameters were kept identical. The differences (∆) in mean HU and standard deviation (SD) in images, with and without metal, were measured and compared. In the clinical study, three independent readers performed visual image quality assessments on eight different protocols using retrospectively acquired images. Results: Iterative MAR had the lowest ∆HU and ∆SD in the phantom study. For images of the forearm, the soft tissue noise for Sn-based 150-kVp UHR protocol with was significantly higher (p = 0.037) than for single-energy MAR protocols. All Sn-based 150-kVp protocols were rated significantly higher (p < 0.046 than the single-energy MAR protocols in the visual assessment. Conclusions: All Sn-based 150-kVp UHR protocols showed similar objective MAR in the phantom study, and higher objective MAR and significantly improved visual image quality than single-energy MAR. Relevance statement: Images with less metal artifacts and higher visual image quality may be more clinically optimal in CT examination of musculoskeletal patients with metal implants. Key points: • Metal artifact reduction algorithms and Sn filter combined with high kVp reduce artifacts. • Metal artifact reduction algorithms introduce new artifacts in certain metals. • Sn-based protocols alone may be considered as low metal artifact protocols. [ABSTRACT FROM AUTHOR]

Background: Total body weight (TBW) is a frequently used contrast media (CM) strategy for dose calculation in enhanced CT, yet it is suboptimal as it lacks consideration of patient characteristics, such as body fat percentage (BFP) and muscle mass. Alternative CM dosage strategies are suggested by the literature. Our objectives were to analyze the CM dose impact when adjusting to body composition using methods of obtaining lean body mass (LBM) and body surface area (BSA) along with its correlation with demographic factors in contrast enhanced chest CT examinations. Methods: Eighty-nine adult patients referred for CM thoracic CT were retrospectively included, categorized as either normal, muscular, or overweight. Patient body composition data was used to calculate the CM dose according to LBM or BSA. LBM was calculated with the James method, Boer method, and bioelectric impedance (BIA). BSA was calculated using the Mostellar formula. We then correlated the corresponding CM doses with demographic factors. Results: BIA demonstrated the highest and lowest calculated CM dose in muscular and overweight groups respectively, compared to other strategies. For the normal group, the lowest calculated CM dose was achieved using TBW. The calculated CM dose was more closely correlated with BFP using the BIA method. Conclusions: The BIA method is more adaptive to variations in patient body habitus especially in muscular and overweight patients and is most closely correlated to patient demographics. This study could support utilizing the BIA method for calculating LBM for a body-tailored CM dose protocol for enhanced chest CT examinations. Relevance statement: The BIA-based method is adaptive to variations in body habitus especially in muscular and overweight patients and is closely correlated to patient demographics for contrast-enhanced chest CT. Key points: • Calculations based on BIA showed the largest variation in CM dose. • Lean body weight using BIA demonstrated the strongest correlation to patient demographics. • Lean body weight BIA protocol may be considered for CM dosing in chest CT. [ABSTRACT FROM AUTHOR]

Background: Computed tomography (CT) contributes to 60% of the collective dose in medical imaging. Literature has demonstrated that patient dose varies across regions and countries. Establishing diagnostic reference levels (DRLs) contributes to the optimization of clinical practices and radiation protection. Purpose: To survey the dose indices (CTDIvol and dose-length product) for frequently performed CT examinations from the chosen hospitals in Norway and Canada and to determine local DRLs (LDRLs) based on the collected data. Material and Methods: The survey included eight scanners from two Norwegian hospitals and four scanners from four Canadian hospitals. Dosimetry data were collected for the following routine CT examinations: head, contrast-enhanced thorax, and abdomen and pelvis. Overall 480 adult average-sized patients from Norway and 360 from Canada were included in the survey. The LDRLs were determined as the 75th percentile of distributions of median values of dose indicators from different CT scanners. The differences in dose between scanners were determined using single-factor ANOVA. Results: The LDRLs determined in Norway were higher overall than in Canada. The obtained values were compared to the national DRLs. The dose from several scanners in Norway exceeded national Norwegian DRLs, while Canadian LDRLs were below the Canadian reference levels. The differences between the means of the dose distributions from each scanner were statistically significant (p < 0.05) for all examinations with exception of identical scanners located in the same hospital and using the same protocols. Conclusion: Observed dose variations even in the same hospital, or from the same scanner model confirmed the need for CT protocol optimization. [ABSTRACT FROM AUTHOR]

Background: Administration of contrast medium (CM) is an important image quality factor in computed tomography (CT) of the chest. There is no clear evidence or guidelines on CM strategies for chest CT, thus a consensus approach is needed. Purpose: To survey the potential impact on differences in chest CT protocols, with emphasis on strategies for the administration of CM. Material and Methods: A total of 170 respondents were included in this survey, which used two different approaches: (i) an online survey was sent to the members of the European Society of Thoracic Imaging (ESTI); and (ii) an email requesting a copy of their CT protocol was sent to all hospitals in Norway, and university hospitals in Sweden and Denmark. The survey focused on factors affecting CM protocols and enhancement in chest CT. Results: The overall response rate was 24% (n = 170): 76% of the respondents used a CM concentration of ≥350 mgI/mL; 52% of the respondents used a fixed CM volume strategy. Fixed strategies for injection rate and delay were also the most common approach, practiced by 73% and 57% of the respondents, respectively. The fixed delay was in the range of 20–90 s. Of the respondents, 56% used flexible tube potential strategies (kV). Conclusion: The chest CT protocols and CM administration strategies employed by the respondents vary widely, affecting the image quality. The results of this study underline the need for further research and consensus guidelines related to chest CT. [ABSTRACT FROM AUTHOR]

Introduction: Several studies have demonstrated the psychological impact of the COVID‐19 pandemic on health care providers. However, there is little known about how the COVID‐19 pandemic has impacted radiation therapists (RTs) in Norway or Canada. The aim of this investigation was to study the psychological impact of working during the COVID‐19 pandemic among RTs in Canada and Norway. Methods: Online surveys were administered to a convenience sample of RTs and RT department managers. Approximately 2000 and 300 RTs were invited to participate from Canada and Norway, respectively. The RT survey collected information on demographics, work‐related stressors, psychological impact, quality of life, and workplace support programmes. The RT manager survey collected information on departmental changes, patient volumes, staff shortages and redeployment, personal protective equipment, and infection control measures. Descriptive analysis, group comparisons and logistic regression were used to examine the impact of COVID‐19 on RTs in the two countries, while open‐ended questions were examined through thematic analysis. Results: Work‐related stress and anxiety were prevalent among Canadian (n = 155) and Norwegian RTs (n = 124), with Canadian RTs reporting higher levels. Fear of transmission, changes in PPE usage, and changes in staffing were reported as the most frequent work‐related stressors. Themes related to working during the pandemic included: generalised anxiety; physical, emotional and cognitive symptoms of stress; and loneliness, as well as negative impact on health and quality of relationships. Survey findings from RT department managers in Canada (n = 12) and Norway (n = 13) suggest that the pandemic had an organisational impact on RT departments due to implemented infection control measures and changes in staffing. Conclusion: The COVID‐19 pandemic has led to similar stressors amongst Canadian and Norwegian RTs but relatively higher levels of psychological impact among Canadian RTs. Findings demonstrate the importance of mental health support programmes in the workplace to mitigate the psychological impact of the COVID‐19 pandemic on RTs. [ABSTRACT FROM AUTHOR]

Brain metastases (BM) occur in about 30% of all patients with non-small cell lung cancer (NSCLC). BM treatment guidelines recommend more frequent use of stereotactic radiotherapy (SRT). Overall, studies report no difference in overall survival (OS) comparing SRT to whole-brain radiotherapy (WBRT). We examined survival after radiotherapy for BM in a population-based sample from the South-Eastern Norway Regional Health Authority treated 2006-2018. We reviewed electronic medical records of 2140 NSCLC patients treated with SRT or WBRT for BM from 2006–2018. Overall survival (OS) was compared to predicted survival according to the prognostic systems DS-GPA and Lung-molGPA. Use of SRT increased during the period, from 19% (2006–2014) to 45% (2015–2018). Median OS for all patients was 3.0 months, increasing from 2.0 (2006) to 4.0 (2018). Median OS after SRT was 7.0 months (n = 435) and 3.0 months after WBRT (n = 1705). Twenty-seven percent of SRT patients and 50% of WBRT patients died within 90 days after start of RT. Age ≥70, male sex, KPS ≤70, non-adenocarcinoma histology, ECM present, multiple BM, and WBRT were associated with shorter survival (p <.001). Actual mOS corresponded best with predicted mOS by DS-GPA and Lung-molGPA for the SRT group. Overall survival after radiotherapy (RT) for BM improved during the study period, but only for patients treated with SRT. Survival after WBRT remains poor; its use should be questioned. DS-GPA and Lung-molGPA seem most useful in predicting prognosis considered for SRT. [ABSTRACT FROM AUTHOR]

Aim: To evaluate the patterns of loco-regional recurrences in head and neck cancer patients METHODS: Twenty-six out of 112 patients treated with primary or postoperative 3D CRT or IMRT for their primary and recurrent disease between 2007 and 2013 were included. The CT images of recurrent disease were rigidly registered with the primary CT images for each patient. To assess overlaps and overlap localization, the recurrence volume overlapping with the primary target volume was identified. For relapses occurring in the regional lymph nodes, the epicenter distance in recurrences and primary volumes and dose in recurrences were also identified. The recurrences were defined as in-field, marginal or out-of-field.Results: The majority of the failures occurred within 1 year after completed primary treatment. The dose differences in recurrence volume were not statistically significant when patients were treated with IMRT or 3D CRT. Recurrence in 15/26 of the included patients occurred in the regional lymph nodes located fully or partly inside the primary target volume or the elective lymph node region. The majority of recurrences were recognized as in-field, independent of the primary treatment.Conclusion: Recurrence in the majority of the patients occurred in the regional lymph nodes located in high dose area. The cause of recurrence may be due to inadequate total dose in the primary treatment and/or lack of optimal primary diagnosis leading to inadequate primary target delineation. [ABSTRACT FROM AUTHOR]

Background: To test seven different strategies for recruitment in a randomized controlled trial, to report documented response data from each strategy, and to discuss recruitment challenges.Methods: We used 5 opt-in (potential participants have to do something active to contact or be contacted by the researcher) and 2 opt-out (potential participants have the option to decline being contacted about a study) recruitment strategies from February 2013 until July 2014 to contact 1562 cancer patient candidates for participation in a randomized controlled trial. For each of these cancer patients a caregiver was also invited to take part in the study.Results: Of the 1562 candidates, 22.6 % were ineligible on initial contact, 56.7 % declined to participate on initial contact, and 8.9 % agreed orally to participate but did not complete the enrollment. The 2 opt-out strategies, on-site recruitment and routine care letters recruitment, yielded the highest number of recruited participants with 79 dyads and 58 dyads respectively, constituting 42.7 % and 31.4 % of the total number of enrolled candidates. The 5 opt-in recruitment approaches yielded 49 dyads for the study. Almost half of these dyads were recruited using the approach termed "relying on providers at the hospital."Conclusions: In this study, opt-out recruitment strategies appeared to be the most effective.Trial Registration: Registration number NCT01867723 , registered February 2012. [ABSTRACT FROM AUTHOR]

Purpose. To explore the relationship between radiotherapy (RT) dose levels in the arm/shoulder region and arm/shoulder morbidity in breast cancer patients. Material and methods. This study included 183 breast cancer patients who had received locoregional RT with or without chemotherapy and/or hormone treatment during the period 1998-2002. Individual RT dose level, reflected by dose-volume histograms (DVHs), for the shoulder joint and joining structures were obtained from archived CT-based RT plans. Individual median, mean and maximum arm/shoulder RT dose levels were extracted. Arm/shoulder morbidity was assessed 29-58 months after breast cancer treatment using the following clinical endpoints: arm pain, arm stiffness, swollen arm, use of arm, numbness, shoulder flexion and shoulder abduction difference, fibrosis and breast cancer-related lymphedema. The relationship between arm/shoulder RT dose level and these clinical endpoints was assessed by Spearman's correlation and multivariate logistic regression. Results. Ninety-one percent of the included patients had some degree of arm/shoulder morbidity. Neither mean nor maximum RT dose level was associated with clinical endpoints. However, significant correlations (p < 0.05) were found between DVHs and arm stiffness, arm pain, use of arm and shoulder abduction difference, when arm/shoulder RT dose levels were approximately 15 Gy. Conclusions. Three-dimensional conformal locoregional RT for breast cancer results in long-term arm/shoulder morbidity. To minimize this risk, large shoulder volumes receiving RT doses of approximately 15 Gy should be reduced. [ABSTRACT FROM AUTHOR]

Purpose: To evaluate cardiac doses in breast cancer patients with stage II/III treated with 4-field radiotherapy based on computed tomography (CT) dose planning. Methods and Materials: Based on archived CT images, whole heart and cardiac chamber radiation doses were analyzed in 216 (111 left-sided and 105 right-sided) mastectomized or lumpectomized breast cancer patients treated at a single institution, the Norwegian Radium Hospital, between 2000-2002. Individual dose volume histograms for the whole heart and for the four cardiac chambers were obtained, and mean, median and maximum doses to these structures were calculated. The dose (Gy) delivered to the 5% of the volume of each cardiac structure (D5%), and the volume percentage of each structure receiving ≥ 25 Gy (V25Gy) were reported. Normal tissue complication probability (NTCP) calculations were used to estimate the risk for ischemic heart disease (IHD). Results: Cohort-based medians of the whole heart mean dose (Dmean) for left- and right-sided tumors were 3.2 Gy and 1.3 Gy, respectively, with similar ventricular but lower atrial values. The atrial doses did not differ according to laterality of the breast tumor. In 13 patients with left-sided cancer, 5% of the heart volume was exposed to >25 Gy. The NTCP estimates were generally low, with a maximum of 2.8%. Conclusions: During adjuvant CT-based locoregional radiotherapy of women with breast cancer, the cardiac radiation doses are, at the group level, below recommended threshold values (D5% < 25 Gy), though individual patients with left-sided disease may exceed these limits. [ABSTRACT FROM AUTHOR]

Purpose: To assess the impact of using breathing adapted radiotherapy on contralateral breast (CB) dose, to relate the thorax shape with the dose to the organs at risk (OARs) and to predict the risk for induced malignancies in CB using linear and non-linear models, following tangential irradiation of breast. Material and methods. Sixteen patients with stage I-II breast cancer treatment planned with tangential fields using deep inspiration breath hold (DIBH) and free breathing (FB) techniques were included in this analysis. The dose results mainly based on DVH analysis were compared. Four parameters were defined to describe thoracic shape. Excess relative risk (ERR) for cancer induction in CB, employing linear and non-linear models was calculated. Results. Average CB volumes exposed to a dose of 1 Gy is 1.3 times higher in DIBH plans than in FB plans. No significant difference in average V3Gy and V5Gy for DIBH and FB plans is observed. The average mean CB dose for DIBH and FB plans is 0.33 and 0.28 Gy, respectively. No correlation between thorax shape parameters and mean OARs dose is observed. The estimated average mean ERR with linear model is lower in FB plans (0.12) than for the DIBH plans (0.14). The estimated ERR with non-linear model is 0.14 for DIBH plans and 0.15 for FB plans. Conclusion. No significant difference in CB dose between DIBH and FB plans is observed. The four thorax shape parameters defined in this study can not be related to the dose at OARs using DIBH and FB radiation techniques. The ERR estimates for secondary CB cancer are nearly the same for FB and DIBH planning when using a linear and non-linear risk prediction models. [ABSTRACT FROM AUTHOR]

Purpose. To investigate the impact of using different radiation therapy techniques on contra-lateral breast (CB) dose, and also dose to other involved organs at risk such as heart and lungs following radiation therapy of breast and regional lymph nodes. Furthermore, to predict the risk for induced malignancies in CB using linear and non linear models. Material and methods. Eight patients with stage II-III breast cancer were included in this analysis. It was focused on three treatment techniques; conventional radiotherapy technique forwardly planed, IMRT and volumetric modulated arc (RapidArc) techniques, inversely planed. The CC algorithm was employed to calculate the standard treatment plans whereas for the IMRT and RapidArc treatment plans AAA algorithm was adopted. The dose results based on mostly DVH analysis were compared. The excess relative risk (ERR) for cancer induction in CB, employed both linear and non-linear models, was estimated. Results. A better homogeneity and conformation in PTV was observed in the RapidArc plans. The highest minimum dose to PTV was observed in the conventional plans while no difference was observed for minimum significant doses D98% and D99% where DX% is the dose received by X% of the PTV volume. In terms of organ sparing, the IMRT and RapidArc plans spare ipsilateral-lung better, but a 40% lower mean dose in the contra-lateral lung in the conventional plans is observed. The mean dose to the contra-lateral breast was lowest for the RapidArc plans as well as the V10Gy and the maximum dose. The mean predicted ERR for the eight patients were lower for the conventional and RA plans than for the IMRT plans assuming a linear dose-risk relationship. The mean predicted ERR when using a non linear model was lower for all the three techniques (with lowest ERR for RapidArc plans). Conclusions. From a clinical perspective, it should be concluded that all three solutions investigated in the study can offer high quality treatment of patients. Further comparative analysis of the two algorithms used in the present study, however, should be performed especially on the peripheral organ dose. The impact of CB exposure to a low-dose radiation on minimizing the risk of radiation induced malignancy in CB can be interpreted differently when using linear or non linear models to predict ERR. In general, no detriment was observed when using RapidArc compared to conventional treatments while a potentially higher risk could be associated to IMRT treatments with fixed gantry. [ABSTRACT FROM AUTHOR]

Purpose. To facilitate a discussion about the impact of dose heterogeneity on the risk for secondary contralateral breast (CB) cancer predicted with linear and non linear models associated with primary breast irradiation. Methods and materials. Dose volume statistics of the CB calculated for eight patients using a collapsed cone algorithm were used to predict the excess relative risk (ERR) for cancer induction in CB. Both linear and non-linear models were employed. A sensitivity analysis demonstrating the impact of different parameter values on calculated ERR for the eight patients was also included in this study. Results. A proportionality assumption was established to make the calculations with a linear and non-linear model comparable. ERR of secondary cancer predicted by the linear model varied considerably between the patients, while the predicted ERR for the same patients using the non-linear model showed very small variation. The predicted ERRs by the two models were indistinguishable for small doses, i.e. below ∼3 Gy. The sensitivity analysis showed that the quadratic component of the radiation-induction pre-malignant cell term is negligible for lower dose level. The ERR is highly sensitive to the value of α1 and α2. Conclusions. Optimization of breast cancer radiation therapy, where also the risk for radiation induced secondary malignancies in the contralateral breast is taken into account, requires robust and valid risk assessment. The linear dose-risk model does not account for the complexity in the mechanisms underlying the development of secondary malignancies following exposure to radiation; this is particularly important when estimating risk associated with highly heterogeneous dose distributions as is the case in the contralateral breast of women receiving breast cancer irradiation. [ABSTRACT FROM AUTHOR]

Background: We investigated the impact of varying contrast medium (CM) densities and x-ray tube potentials on contrast enhancement (CE), image quality and radiation dose in thoracic computed tomography (CT) using two different scanning techniques. Methods: Seven plastic tubes containing seven different CM densities ranging from of 0 to 600 HU were positioned inside a commercial chest phantom with padding, representing three different patient sizes. Helical scans of the phantom in single-source mode were obtained with varying tube potentials from 70 to 140 kVp. A constant volume CT dose index (CTDIvol) depending on phantom size and automatic dose modulation was tested. CE (HU) and image quality (contrast-to-noise ratio, CNR) were measured for all combinations of CM density and tube potential. A reference threshold of CE and kVp was defined as ≥ 200 HU and 120 kVp. Results: For the medium-sized phantom, with a specific CE of 100–600 HU, the diagnostic CE (200 HU) at 70 kVp was ~ 90% higher than at 120 kVp, for both scan techniques (p < 0.001). Changes in CM density/specific HU together with lower kVp resulted in significantly higher CE and CNR (p < 0.001). When changing only the kVp, no statistically significant differences were observed in CE or CNR (p ≥ 0.094), using both dose modulation and constant CTDIvol. Conclusions: For thoracic CT, diagnostic CE (≥ 200 HU) and maintained CNR were achieved by using lower CM density in combination with lower tube potential (< 120 kVp), independently of phantom size. [ABSTRACT FROM AUTHOR]

A correction to the article "Recruitment challenges in clinical research including cancer patients and their caregivers. A randomized controlled trial study and lessons learned," by Karin Sygna, Safora Johansen, and Cornelia M. Ruland in the 2015 issue is presented.