Download - 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.

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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


z-overscanning

z-overscanning

Ref. Medscape.com

Ref. Medscape.com

Ref. Impactscan.org

Ref: www.gehealthcare.org


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