Body length changes for Atlantic salmon (Salmo salar) over five decades exhibit weak spatial synchrony over a broad latitudinal gradient.

Understanding the factors that drive spatial synchrony among populations or species is important for management and recovery of populations. The range-wide declines in Atlantic salmon (Salmo salar) populations may be the result of broad-scale changes in the marine environment. Salmon undergo rapid growth in the ocean; therefore changing marine conditions may affect body size and fecundity estimates used to evaluate whether stock reference points are met. Using a dataset that spanned five decades, 172,268 individuals, and 19 rivers throughout Eastern Canada, we investigated the occurrence of spatial synchrony in changes in the body size of returning wild adult Atlantic salmon. Body size was then related to conditions in the marine environment (i.e., climate indices, thermal habitat availability, food availability, density-dependence, and fisheries exploitation rates) that may act on all populations during the ocean feeding phase of their life cycle. Body size increased during the 1980s and 1990s for salmon that returned to rivers after one (1SW) or two winters at sea (2SW); however, significant changes were only observed for 1SW and/or 2SW in some mid-latitude and northern rivers (10/13 rivers with 10 of more years of data during these decades) and not in southern rivers (0/2), suggesting weak spatial synchrony across Eastern Canada. For 1SW salmon in nine rivers, body size was longer when fisheries exploitation rates were lower. For 2SW salmon, body size was longer when suitable thermal habitat was more abundant (significant for 3/8 rivers) and the Atlantic Multidecadal Oscillation was higher (i.e., warmer sea surface temperatures; significant for 4/8 rivers). Overall, the weak spatial synchrony and variable effects of covariates on body size across rivers suggest that changes in Atlantic salmon body size may not be solely driven by shared conditions in the marine environment. Regardless, body size changes may have consequences for population management and recovery through the relationship between size and fecundity.

Technical Note: Evaluating automatic tube current modulation in CT using the standard CTDI dosimetry phantom.

PURPOSE: To assess the utility of the standard body CTDI phantom in characterizing the operation scheme of tube current modulation (TCM) systems in CT. METHODS: The body CDTI phantom was used to characterize two TCM systems: TCM1 and TCM2 , implemented in scanners from different vendors. The phantom was aligned at the gantry isocenter in two configurations. In configuration A, the facet planes of the phantom were parallel to the patient table, while in configuration B they were vertical to the patient table and parallel to the patient's long axis. Acquisitions were performed using the routine abdominal examination protocol. mA(z) profiles were recorded from images' DICOM header. The water equivalent diameter (dw ) and oval ratio (OR) were calculated as a function of z-axis location. Image noise was defined as the standard deviation (SD) of the mean Hounsfield unit value measured in a region of interest at the center of the phantom's image. Regression analysis was performed to modulated mA and SD vs dw and OR. The spatial concordance between the change in phantom size and change in mA (SCmA ) was calculated as the percent difference in the slope of mA(z) change between the 1st and 2nd half of the phantom. The corresponding spatial concordance between the change in phantom size and change in image noise (SCnoise ) was calculated. RESULTS: Modulated mA(z) along the z-axis did not substantially differentiate between configurations A and B. Correlation between ln(mA) and OR was found to be higher compared to correlation between ln(mA) and dw . SCmA was 48% for TCM1 and 33% for TCM2 . The corresponding SCnoise was 29% for TCM1 and 16% for TCM2 . CONCLUSION: Apart from routine CT dosimetry evaluations, the standard CTDI phantom positioned in configuration A or B may additionally be used by medical physicists to evaluate the performance of TCM operational characteristics.

Coverage with dosimetric concordance index (CDCI): a tool for evaluating dosimetric impact of inter-observer target variability in brachytherapy.

PURPOSE: The aim of this study was to propose an index for evaluating dosimetric impact of inter-observer target delineation variability in brachytherapy. MATERIAL AND METHODS: The coverage with dosimetric concordance index (CDCI) is expressed as CDCIcommon and CDCIpair. The CDCIcommon is the mean coverage of target volume with common volume irradiated by prescription dose among all observers and represents the condition of worst target coverage. CDCIpair is the generalized form of CDCI, which is mean target coverage with common prescription volume obtained between all possible pairs of observers and represents more realistic coverage of target with dosimetric concordance. The index was used to evaluate the dosimetric impact of target delineation variability in optimized conformal plans on target volumes of five radiation oncologists for twenty patients of multi-catheter interstitial partial breast brachytherapy. RESULTS: The mean decline of 5.6 ±3.2% and 11.3 ±5.7% in CDCIpair and CDCIcommon, respectively, was observed comparing to coverage index (CI) of target volume in all patients due to inter-observer target variability. CDCIcommon and CDCIpair were found to have significant linear correlation (r = 0.964, p < 0.000). The difference between CDC and CI increased with the mean relative target volume among observers. Significant correlation (r = 0.962, p < 0.000) was also noted for the difference (Δ) in CDCIcommon and CDCIpair with CI of target volume. CONCLUSIONS: The recommended indices and difference between the dosimetric coverage of target volume (CI) with CDCI (ΔCDCI) can be used for evaluating dosimetric impact of the inter-observer target delineation variability.

Spatial Concordance of Tumor Proliferation and Accelerated Repopulation from Pathologic Images to 3'-[18F]Fluoro-3'-Deoxythymidine PET Images: a Basic Study Guided for PET-Based Radiotherapy Dose Painting.

PURPOSE: To assess tumor cell proliferation and repopulation during fractionated radiotherapy and investigate the spatial concordance of cell proliferation and repopulation according to the uptake of 3'-[18F]fluoro-3'-deoxythymidine ([18F]FLT). PROCEDURES: Mice bearing A549 xenograft tumors were assigned to five irradiated groups, including 3 fraction (f)/6 days (d), 6f/12d, 9f/18d, 12f/24d, and 18f/36d with 2 Gy/f irradiations performed every other day and one non-irradiated group. Serial [18F]FLT positron emission tomography (PET) scans were performed at different time points as the groups finished the radiotherapy. The maximum of standard uptake values (SUVmax) were measured to confirm the likely time of tumor repopulation. A layer-by-layer comparison between SUVmax of PET images and Ki-67 LI of pathology images, including the thresholds at which maximum overlap occurred between FLT-segmented areas and cell proliferation areas were conducted to evaluate the spatial correlation. RESULTS: The SUVmax decreased in the 3f/6d group (P = 0.000) compared to the non-irradiated group, increased in the 6f/12d group and then gradually reduced with prolonged treatment. Proliferation changes in 6f/12d group on pathology images were also confirmed. Significant correlations were found between the SUVmax and Ki-67 LI in each in vitro tumor of cell proliferation group and accelerated repopulation group (both of the P < 0.001). Furthermore, the mean overlap region rates (ORRs) were 56.21 % and 57.82 % in the proliferation group and repopulation group, respectively. The data represented the preferable registration. CONCLUSIONS: [18F]FLT PET is a promising imaging surrogate of tumor proliferative response to fractionated radiotherapy and may help make an adaptive radiation oncology treatment plan to realize radiotherapy dose painting.

Prevalence and spatial concordance of visual field deterioration in fellow eyes of glaucoma patients.

PURPOSE: To examine the prevalence of visual field deterioration in contralateral eyes of patients with worsening open-angle glaucoma and to evaluate the spatial concordance of visual field deterioration between both eyes. METHODS: One hundred sixteen open-angle glaucoma patients who underwent 8 or more visual field examinations over ≥ 6 years of follow-up were included. The rates of the fast and slow components of visual field decay for each of 52 visual field test locations were calculated with point-wise exponential regression analysis. The spatial concordance of visual field deterioration in contralateral eyes was evaluated with a concordance ratio (calculated as the number of overlapping locations divided by the total number of deteriorating locations) and by comparing the rate of decay in corresponding modified glaucoma hemifield test clusters. RESULTS: The average visual field mean deviation (± standard deviation [SD]) was -8.5 (± 6.4) dB and the mean (± SD) follow-up time was 9.0 (± 1.6) years. Sixty-three patients had mild damage, 23 had moderate damage, and 30 had severe damage. The mean concordance ratio (± SD) was 0.46 (± 0.32) for the mild group, 0.33 (± 0.27) for the moderate group, and 0.35 (± 0.21) for the severe group. Thirty-one patients (27%) had deterioration in concordant locations (p < 0.05). Visual field deterioration was greater in the superior hemifield than the inferior hemifield (p < 0.05) when evaluated with both the concordance ratio and modified glaucoma hemifield test cluster analysis methods. CONCLUSIONS: There is only fair spatial concordance with regard to visual field deterioration between the both eyes of an individual. We conclude that testing algorithms taking advantage of inter-eye spatial concordance would not be particularly advantageous in the early detection of glaucomatous deterioration.

Prevalence and Spatial Concordance of Visual Field Deterioration in Fellow Eyes of Glaucoma Patients

PURPOSE: To examine the prevalence of visual field deterioration in contralateral eyes of patients with worsening open-angle glaucoma and to evaluate the spatial concordance of visual field deterioration between both eyes. METHODS: One hundred sixteen open-angle glaucoma patients who underwent 8 or more visual field examinations over > or =6 years of follow-up were included. The rates of the fast and slow components of visual field decay for each of 52 visual field test locations were calculated with point-wise exponential regression analysis. The spatial concordance of visual field deterioration in contralateral eyes was evaluated with a concordance ratio (calculated as the number of overlapping locations divided by the total number of deteriorating locations) and by comparing the rate of decay in corresponding modified glaucoma hemifield test clusters. RESULTS: The average visual field mean deviation (+/-standard deviation [SD]) was -8.5 (+/-6.4) dB and the mean (+/-SD) follow-up time was 9.0 (+/-1.6) years. Sixty-three patients had mild damage, 23 had moderate damage, and 30 had severe damage. The mean concordance ratio (+/-SD) was 0.46 (+/-0.32) for the mild group, 0.33 (+/-0.27) for the moderate group, and 0.35 (+/-0.21) for the severe group. Thirty-one patients (27%) had deterioration in concordant locations (p < 0.05). Visual field deterioration was greater in the superior hemifield than the inferior hemifield (p < 0.05) when evaluated with both the concordance ratio and modified glaucoma hemifield test cluster analysis methods. CONCLUSIONS: There is only fair spatial concordance with regard to visual field deterioration between the both eyes of an individual. We conclude that testing algorithms taking advantage of inter-eye spatial concordance would not be particularly advantageous in the early detection of glaucomatous deterioration.