CT Dose Physics - Advanced Health Education Center
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Transcript of CT Dose Physics - Advanced Health Education Center
Where CT Dose Is Recorded?
DICOM Standards
Extracting CT Dose from Dose Page orDICOM Header
What is RDSR?
Radiation Dose Structured Report (RDSR)
CT Radiation Dose Reporting (DoseSR)
What is a Dose SR Template?
CT Radiation Dose SR IOD Template Structure
A RDSR Viewer
RDSR Converted toplain text format
http://www.aapm.org/pubs/reports/default.asp#tg204.
(https://shop.acr.org/Default.aspx?TabID=55&ProductId=12363982)(https://shop.acr.org/Default.aspx?TabID=55&ProductId=88190170).
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Facility ID=999999 Page 15 Jul-Dec 2015 Facility ID=999999 Page 27 Jul-Dec 2015
BIOLOGICAL EFFECTS OF RADIATION IN TIME PERSPECTIVE
Time of onset of clinical signs Time of onset of clinical signsof skin injury depending onn injury dependin
dose received
Radiation may cause mutations, that is, changes in the reproductive cells that transmit inherited characteristics from one generation to the next. Practically all radiation-induced mutations are harmful, and the deleterious effects persist in successive generations.
Cancer GeneDNA
Carcinogen
LowProliferation
Normal Cancer Gene
HighProliferation
Permanently MutatedCancer Gene
Proliferation Decreases Mutation Repair
Time For Repair Before
DNA Duplication
Little Time For Repair Before DNA Duplication
Within a Cell
In Each Daughter Cell In Each Daughter Cell
Jacoby Roth several hours after receiving 151 CT scans in a 68-minute period. Image courtesy of Roth family attorney Don Stockett.
INTERNATIONAL COMMISSION ON RADIOLOGICAL PROTECTION
INTERNATIONAL COMMISSION ON RADIOLOGICAL PROTECTION
z-overscanning
z-overscanning
Ref. Medscape.com
Ref. Medscape.com
Ref. Impactscan.org
Ref: www.gehealthcare.org
INTERNATIONAL COMMISSION ON RADIOLOGICAL PROTECTION
Computed Tomography
A CT image is a pixel-by-pixel map of X-ray beam attenuation(essentially density) in Hounsfield Units (HU)
HUwater = 0
Bright = “hyperattenuating” or “hyperdense”
Computed TomographyTypical HU Values:
Air –1000Fat –100 to –40Water 0Watery fluid (e.g. CSF) 0–20White matter 20–35Gray matter 30–40Blood clot 55–75Calcification >150Bone 1000Metallic foreign body >1000
Brain
421
4 = 100
2 = 10
1 = 01
The more detectors a CT scanner detector has, the more slices per rotation it is able to acquire. The number of slices per rotation is equal to the number of detectors.
0.4s RT (200mAs)
1s RT (200mAs)
Use of Scout Image for Modulation
Tube Current Modulation - Overview Implementation Issues
200mA
150mA
130mA
150mA
180mA
210mA
200mA
170mA
180mA
200mA
150mA130mA150mA180mA
210mA200mA
170mA
180mA
Tube Current Modulation Methods
Several MethodsAngular modulation (in plane (x-y) )Longitudinal modulation (along patient length, z-axis)Combination (x, y and z) modulationTemporal (ECG-gated) modulation
A/P vs P/A vs Lateral scout?
Bottom Line
Combination (x,y and z)
0.4s RT (200mAs)
1s RT (200mAs)
et al.
e.g.
Statistical iterative reconstructioniterative reconstruction
Courtesy: M. Kalra
