15 research outputs found
Investigating centering, scan length, and arm position impact on radiation dose across 4 countries from 4 continents during pandemic: mitigating key radioprotection issues
Purpose: Optimization of CT scan practices can help achieve and maintain optimal radiation protection. The aim was to assess centering, scan length, and positioning of patients undergoing chest CT for suspected or known COVID-19 pneumonia and to investigate their effect on associated radiation doses. Methods: With respective approvals from institutional review boards, we compiled CT imaging and radiation dose data from four hospitals belonging to four countries (Brazil, Iran, Italy, and USA) on 400 adult patients who underwent chest CT for suspected or known COVID-19 pneumonia between April 2020 and August 2020. We recorded patient demographics and volume CT dose index (CTDIvol) and dose length product (DLP). From thin-section CT images of each patient, we estimated the scan length and recorded the first and last vertebral bodies at the scan start and end locations. Patient mis-centering and arm position were recorded. Data were analyzed with analysis of variance (ANOVA). Results: The extent and frequency of patient mis-centering did not differ across the four CT facilities (>0.09). The frequency of patients scanned with arms by their side (11–40% relative to those with arms up) had greater mis-centering and higher CTDIvol and DLP at 2/4 facilities (p = 0.027–0.05). Despite lack of variations in effective diameters (p = 0.14), there were significantly variations in scan lengths, CTDIvol and DLP across the four facilities (p < 0.001). Conclusions: Mis-centering, over-scanning, and arms by the side are frequent issues with use of chest CT in COVID-19 pneumonia and are associated with higher radiation doses
Investigating centering, scan length, and arm position impact on radiation dose across 4 countries from 4 continents during pandemic: Mitigating key radioprotection issues
Purpose: Optimization of CT scan practices can help achieve and maintain optimal radiation protection. The aim was to assess centering, scan length, and positioning of patients undergoing chest CT for suspected or known COVID-19 pneumonia and to investigate their effect on associated radiation doses. Methods: With respective approvals from institutional review boards, we compiled CT imaging and radiation dose data from four hospitals belonging to four countries (Brazil, Iran, Italy, and USA) on 400 adult patients who underwent chest CT for suspected or known COVID-19 pneumonia between April 2020 and August 2020. We recorded patient demographics and volume CT dose index (CTDIvol) and dose length product (DLP). From thin-section CT images of each patient, we estimated the scan length and recorded the first and last vertebral bodies at the scan start and end locations. Patient mis-centering and arm position were recorded. Data were analyzed with analysis of variance (ANOVA). Results: The extent and frequency of patient mis-centering did not differ across the four CT facilities (>0.09). The frequency of patients scanned with arms by their side (11�40 relative to those with arms up) had greater mis-centering and higher CTDIvol and DLP at 2/4 facilities (p = 0.027�0.05). Despite lack of variations in effective diameters (p = 0.14), there were significantly variations in scan lengths, CTDIvol and DLP across the four facilities (p < 0.001). Conclusions: Mis-centering, over-scanning, and arms by the side are frequent issues with use of chest CT in COVID-19 pneumonia and are associated with higher radiation doses. © 202
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The role of human NKG2d receptor-ligand function in tumor immunity and immune escape
NKG2D is a unique immunoreceptor of key significance to immune surveillance of tumor cells, and it represents an attractive candidate in the development of both molecular and cell-based immunotherapies. NKG2D is a stimulatory receptor expressed by human natural killer (NK) cells, cytokine induced killer/lymphokine activated killer (CIK/LAK) cells, γδ T cells and CD8+ &agr;β T cells. The NKG2D receptor plays a pivotal role in both innate and adaptive immunity, where it stimulates the cytotoxic function of (NK) cells and CD8 + T cells upon recognition of a diverse array of MHC-related ligands. In turn, these ligands are specifically induced under pathological conditions.Current research has established a prominent role for the NKG2D receptor in the modulation of tumor immunity by both NK cells and T cells. We discovered a novel genetic modifier that limits the effectiveness of NK/T cell immunotherapy in human cancer patients. Our objective of this study was to investigate how these genetic modifiers affect NK receptor-ligand interactions and ultimately tumor cell recognition, immunity, and immune evasion. We characterized an alternate splice variant of human NKG2D that encodes a truncated receptor lacking the ligand-binding ectodomain. This truncated NKG2D variant (NKG2DTR) does not activate cytotoxicity in a ligand-dependent manner, and its enforced expression inhibits killing mediated by the full-length NKG2D isoform (NKG2DFL). Enforced expression of NKG2DTR resulted in the retention of NKG2DFL in intracellular compartments. The relative abundance of NKG2DTR transcripts varies among PBMC and activated LAK/CIK cells and NK cells of diverse donors and inversely correlates with the killing capacity of expressing cells. Furthermore, specific shRNA-mediated knockdown of the endogenous NKG2D TR isoform in human CIK cells and NK cells enhances endogenous NKG2D FL-mediated cytotoxicity. Co-immunoprecipitation studies revealed that NKG2DTR pairs with DAP10 and heterodimerizes with NKG2D FL, suggesting that its dominant negative impact on cytotoxicity is due to the formation of heterodimeric NKG2DTR/FL receptor complexes incapable of ligand binding. Thus, competitive interference via an alternatively spliced NKG2D variant constitutes a novel mechanism for regulation of NKG2D-mediated signaling and cytotoxicity in LAK/CIK cells and NK cells
Measuring cytotoxicity by bioluminescence imaging outperforms the standard chromium-51 release assay.
The chromium-release assay developed in 1968 is still the most commonly used method to measure cytotoxicity by T cells and by natural killer cells. Target cells are loaded in vitro with radioactive chromium and lysis is determined by measuring chromium in the supernatant released by dying cells. Since then, alternative methods have been developed using different markers of target cell viability that do not involve radioactivity. Here, we compared and contrasted a bioluminescence (BLI)-based cytotoxicity assay to the standard radioactive chromium-release assay using an identical set of effector cells and tumor target cells. For this, we stably transduced several human and murine tumor cell lines to express luciferase. When co-cultured with cytotoxic effector cells, highly reproducible decreases in BLI were seen in an effector to target cell dose-dependent manner. When compared to results obtained from the chromium release assay, the performance of the BLI-based assay was superior, because of its robustness, increased signal-to-noise ratio, and faster kinetics. The reduced/delayed detection of cytotoxicity by the chromium release method was attributable to the association of chromium with structural components of the cell, which are released quickly by detergent solubilization but not by hypotonic lysis. We conclude that the (BLI)-based measurement of cytotoxicity offers a superior non-radioactive alternative to the chromium-release assay that is more robust and quicker to perform
Assay characteristics of the chromium release assay vs. BLI assay.
<p>The spontaneous death, maximal killing, range, and the signal to noise (max:min) ratios measured by <sup>51</sup>Cr release and BLI are shown. Results are presented as mean ± SD of three independent experiments.</p><p>* p<0.01 by Student t test.</p
Measurement of chromium release and luciferase activity in cells lysed by water or by 1% NP40.
<p>Three luciferase-transduced human cell lines (K562, UCI191 and U266) and 3 mouse cell lines (P815, YAC1, and A20) were labeled with radioactive chromium for 4 hours. The cells were lysed in water or 1% NP40 for 4 hours. (A) Chromium release in the supernatant of cells lysed in water or in 1% NP40 was determined. (B) Luciferase activity was detected by BLI in cells lysed in water or in 1% NP40 was determined. The results are represented as mean ± SD of n = 3–4 independent experiments. * p<0.001 by Wilcoxon Rank test.</p
Comparison of cytotoxicity obtained at 2 hours by the chromium release method and BLI method.
<p>Luciferase-transduced human and mouse cell lines were co-cultured with human or mouse effector cells for 2 hours at various E:T ratios. The % specific lysis of the human cell lines, (A) K562, (B) U266, and (C) UCI101 obtained by the chromium release assay (closed circles) or the BLI assay (open circles) is plotted against multiple E:T ratios. The % specific lysis of the human cell lines, (D) P815, (E) YAC1, (F) EL-4, and (G) A20 obtained by the chromium release assay (closed circles) or the BLI assay (open circles) is plotted against multiple E:T ratios. Results are represented as mean ± SD of n = 3 independent experiments. The p values obtained from the statistical analysis performed by permutated two-way ANOVA are shown in each graph.</p
Comparison of cytotoxicity obtained at 4 hours by the chromium release and BLI method.
<p>Luciferase-transduced human and mouse cell lines were co-cultured with human or mouse effector cells for 4 hours at various E: T ratios. The % specific lysis of the human cell lines, (A) K562, (B) U266, and (C) UCI101 obtained by the chromium release assay (closed circles) or the BLI assay (open circles) is plotted against multiple E:T ratios. The % specific lysis of the murine cell lines, (D) P815, (E) YAC1, (F) EL-4, and (G) A20 obtained by the chromium release assay (closed circles) or the BLI assay (open circles) is plotted against multiple E:T ratios. Results are represented as mean ± SD of n = 3 independent experiments. The p values obtained from the statistical analysis performed by permutated two-way ANOVA are shown in each graph.</p