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Image-Guided Radiation Therapy (IGRT) and Motion Management
Published in Eric Ford, Primer on Radiation Oncology Physics, 2020
Another technique to manage and reduce respiratory motion during treatment is respiratory gating. In this technique the linac beam is turned on and off in cycle with the breathing trace as shown in Figure 21.2.2C. The breathing trace is monitoring during treatment with a device such as the marker block. When the patient respiration enters some predefined window a trigger signal is sent to the linac to turn it on. If gating is employed it is important to use a CT scan in treatment planning that represents the position in the gating window during treatment.
Magnetic Resonance Imaging
Published in Suzanne Amador Kane, Boris A. Gelman, Introduction to Physics in Modern Medicine, 2020
Suzanne Amador Kane, Boris A. Gelman
To image the heart with conventional MRI, physicians have used an idea called gating. The electrical signal associated with each heartbeat (the electrocardiogram or EKG) is monitored, and used to take an MRI scan repeatedly only during a certain stage of the heartbeat. The total scan accumulates from many separate snapshots to reduce blurring, while gathering an image of adequate quality. However, this idea cannot be used with an irregular heartbeat and it does not totally eliminate blurring due to motion. EPI can freeze a very fast image of the heart, taking either scans of many different planes or rapidly compiling a film loop of the heart as it beats. These movies of the heart are taken at roughly the best speeds achievable with ultrafast CT (20–30 frames per second) and ultrasound (30 frames per second), though about four times slower than cardiac angiography with x-rays. (For comparison, ordinary video signals are 30 frames per second.) This ability to resolve fast motions also allows cardiologists to measure blood flow, to visualize regions of the heart's muscle with inadequate blood supply (a possible sign of impending heart attack), or to see abnormalities in blood flow associated with a defective valve.
Cardiovascular system
Published in A Stewart Whitley, Jan Dodgeon, Angela Meadows, Jane Cullingworth, Ken Holmes, Marcus Jackson, Graham Hoadley, Randeep Kumar Kulshrestha, Clark’s Procedures in Diagnostic Imaging: A System-Based Approach, 2020
A Stewart Whitley, Jan Dodgeon, Angela Meadows, Jane Cullingworth, Ken Holmes, Marcus Jackson, Graham Hoadley, Randeep Kumar Kulshrestha
To overcome this limitation and make it possible to use cross-sectional imaging for cardiac investigation requires either pharmacological control of the heart rate (with drugs such as beta blockers) or ultra-rapid imaging times to freeze cardiac movement, or cardiac gating. Gating is a method of timing image acquisition to coincide with a selected part of the cardiac cycle so that the heart is in the same part of its cycle at each acquisition, thus negating the effect of movement. Gating requires a regular heart rhythm, which may also necessitate drug control. These techniques and improvements in equipment specification have brought CT and MRI into the forefront of cardiac imaging, as both are relatively non-invasive investigations.
Diabetes type 2: relationships between lysosomal exocytosis of circulating normal-sized platelets and in vitro ɑ-thrombin-evoked platelet responses
Published in Annals of Medicine, 2023
Maria Edvardsson, Magnus Oweling, Petter Järemo
A flow cytometry protocol, first described by Ramström’s research group, was used without substantial alterations [4]. The antibodies and probes used are listed in Table 2. Platelets were recognized by forward scatter (size) and GPIIb receptor fluorescence, and normal-sized populations, as determined by flow cytometry gating, were studied. The probes and antibodies were added to the density subpopulations (Table 2) as described previously [4,26] and we did not extract platelets from the polyvinylpyrrolidone-coated silica. Gating has been extensively explained elsewhere [26] but is also shown in Figure 1. It demonstrates an individual sample after α-thrombin (10 U/mL) provocation and shows the gating of the GPIIb positive populations (normal-sized platelets, small platelets, and vesicles). In all samples, the proportions of positive corpuscles (%) were evaluated, and mean fluorescence intensities were not determined. The management of different controls has been described in detail [4]. After 10 min at room temperature the reactions were stopped by dilution in HEPES-Ca2+. Flow cytometry particle acquisition ended either after counting >5000 corpuscles or after 2 min. Thus, the number of assessed particles differed depending on the subpopulation corpuscle count.
The progression of radiation injury in a Wistar rat model of partial body irradiation with ∼5% bone marrow shielding
Published in International Journal of Radiation Biology, 2023
Tyler Beach, James Bakke, Ed Riccio, Harold S. Javitz, Denise Nishita, Shweta Kapur, Deborah I. Bunin, Polly Y. Chang
Images were obtained prior to irradiation and at approximately 42-, 84-, 126-, and 180-days post irradiation using the Bruker (Billerica, MA) 7 T PharmaScan small animal MRI, 16 cm bore, 60 mm body coil, with ParaVision 6.0.1 software. Respiratory gating was applied during image acquisition. For MRI analysis, visual verification of areas with increased signal intensity and tissue density, indicating congestion, inflammation or fibrosis were recorded. The mean signal intensity of three separate, manually delineated lung sections captured around the mid-point of the thorax were recorded per animal using Image J. At each timepoint, group means were compared to both the pre-irradiation mean for that group and to the age matched control group for that timepoint. Two different scans were performed:
A diversity outbred F1 mouse model identifies host-intrinsic genetic regulators of response to immune checkpoint inhibitors
Published in OncoImmunology, 2022
Justin B. Hackett, James E. Glassbrook, Maria C. Muñiz, Madeline Bross, Abigail Fielder, Gregory Dyson, Nasrin Movahhedin, Jennifer McCasland, Claire McCarthy-Leo, Heather M. Gibson
PBMC populations from DOB6F1 mice were performed on a BD LSRII flow cytometer (Becton Dickinson, Franklin Lakes, NJ). The following panel was used: Viability (Ghost DyeTM Violet 510, TONBO biosciences, CD3ε APC780 (clone 17A2), CD19 BV 605 (clone 6D5), CD4 AF 488 (clone RM4-5), CD8 BB700 (clone 53–6.7), FoxP3 eFluor 660 (clone FJK-16s). PBLs samples were gated based on viable singlets. B-cells were CD19+/CD3−, CD3+ defined pan T cells, CD4 T cells (CD3+/CD19−/CD4+), CD8 (CD3+/CD19−/CD8+), Double negative T cells (CD3+/CD4−/CD8−), Regulatory T cells (CD3+/CD19−/CD4+/FoxP3+). Example gating can be found in Fig. S7.