Radiation Dosimetry for CT Protocols

 

This document contains radiation dosimetry information from CT scans and can be used by investigators to estimate the dosimetry information required by the JRSC or RDRC for research protocols involving human subjects. For all research studies involving CT scans and requiring JRSC or RDRC approval, researchers are to provide CTDIvol , DLP, and effective dose values for the clinical exam to be given. Researchers using CT in conjunction with radiopharmaceuticals are in addition required to provide critical organ dose estimates.

 

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CT Dosimetry for Procedures not Involving Radiopharmaceuticals

In general, investigators should provide the most accurate dose estimates possible. Dosimetry of clinical protocols is provided for typical, scanner-specific protocols for scanners in the medical center for the following routine adult CT examinations:

 

 

If an investigator knows which CT scanner will be used, scanner specific information should be used to fill out the form. If this information is unknown or unavailable, the average CT scanner information provided below may be used instead.

 

Users should take special care when providing dose estimates for special CT protocols. It is the principal investigator's responsibility to provide reasonable estimates of all radiation doses a patient may incur.

 

Table 1      

Average CT Scanner

 

 

 

Scan type

CTDIvol (mGy)

DLP (mGy-cm)

Effective dose (mrem)

Adult head

59.7

1044.3

219

Adult abdomen

14

310.6

525

Adult pelvis

14

310.6

525

Adult chest

8.4

294.0

412

Adult neck

14.9

223.8

132

Pediatric abdomen

8.5

126.9

270

       

Milstein 2nd Floor - Spect-CT

 

 

 

Scan type

CTDIvol (mGy)

DLP (mGy-cm)

Effective dose (mrem)

Adult head

33.59

587.8

123

Adult abdomen

4.94

123.5

185

Adult pelvis

4.94

123.5

185

Adult chest

2.96

103.6

145

Adult neck

8.40

126.0

74

 

 

 

 

Irving 1st Floor - Siemens Sensation 16

 

 

 

Scan type

CTDIvol (mGy)

DLP (mGy-cm)

Effective dose (mrem)

Adult head

58.30

1020.25

214

Adult abdomen

9.30

232.5

349

Adult pelvis

9.30

232.5

349

Adult chest

5.58

195.3

273

Adult neck

14.58

218.7

129

 

 

 

 

Irving 1st Floor - GE Lightspeed 64 VCT

 

 

 

Scan type

CTDIvol (mGy)

DLP (mGy-cm)

Effective dose (mrem)

Adult head

85.50

1496.25

314

Adult abdomen

16.50

412.5

619

Adult pelvis

16.50

412.5

619

Adult chest

9.90

346.5

485

Adult neck

21.38

320.7

189

  

 

 

 

Milstein 8th Floor - GE Lightspeed Pro

 

 

 

Scan type

CTDIvol (mGy)

DLP (mGy-cm)

Effective dose (mrem)

Adult head

63.40

1109.5

233

Adult abdomen

20.70

517.5

776

Adult pelvis

20.70

517.5

776

Adult chest

12.42

434.7

609

Adult neck

15.85

237.75

140

 

VC-ER - Siemens Sensation 10

 

 

 

Scan type

CTDIvol (mGy)

DLP (mGy-cm)

Effective dose (mrem)

Adult head

50.16

877.8

184

Adult abdomen

13.52

338.0

507

Adult pelvis

13.52

338.0

507

Adult chest

8.11

283.85

397

Adult neck

12.54

188.1

111

Pediatric Abdomen

7.37

110.55

233

 

 

 

 

Allen Pavilion - Siemens Sensation 4

 

 

 

Scan type

CTDIvol (mGy)

DLP (mGy-cm)

Effective dose (mrem)

Adult head

61.86

1082.55

227

Adult abdomen

15.78

394.5

592

Adult pelvis

15.78

394.5

592

Adult chest

9.47

331.45

464

Adult neck

15.47

232.05

137

Pediatric Abdomen

11.40

171.0

360

 

 

 

 

CHONY 3rd Floor - GE Lightspeed VCT

 

 

 

Scan type

CTDIvol (mGy)

DLP (mGy-cm)

Effective dose (mrem)

Adult head

58.60

1025.5

215

Adult abdomen

17.97

449.25

674

Adult pelvis

17.97

449.25

674

Adult chest

10.78

377.3

528

Adult neck

14.65

219.75

130

Pediatric Abdomen

6.63

99.24

209

 

 

 

 

Milstein 3rd Floor - Siemens Volume Zoom 4

 

 

 

Scan type

CTDIvol (mGy)

DLP (mGy-cm)

Effective dose (mrem)

Adult head

66.00

1155.0

243

Adult abdomen

13.30

332.5

499

Adult pelvis

13.30

332.5

499

Adult chest

7.98

279.3

391

Adult neck

16.50

247.5

146

 

 

Organ Doses for Procedures Involving Radiopharmaceuticals

Investigators using radiopharmaceuticals for research studies requiring JRSC or RDRC approval are required to provide critical organ dose information. The table below provides dose estimates using an average CT scanner at the medical center from routine adult CT examinations to all organs defined in ICRP 103. These organ dose estimates are provided by the ImPACT CT Patient Dosimetry Calculator.

 

For researchers using PET/CT, the CT dose estimates below should not be used

 

Table 2      
                            CT Examination Type  
  Abdomen Pelvis Chest Neck Head
Organ Organ Dose (mrad) Organ Dose (mrad) Organ Dose (mrad) Organ Dose (mrad) Organ Dose (mrad)
Gonads 99 1000 1 0 0
Bone Marrow 360 510 360 120 400
Colon 800 1100 8 0 0
Lung 300 3 1300 44 23
Stomach 1900 67 120 1 1
Bladder 50 2100 0 0 0
Breast 74 3 1200 8 6
Liver 1800 44 180 3 2
Oesophagus (Thymus) 54 0.96 1500 38 20
Thyroid 6 0.26 220 2300 550
Skin 310 320 240 160 420
Bone Surface 570 530 690 400 1600
Brain 0 0 11 280 4900
Salivary Glands (Brain) 0 0 11 280 4900
Adrenals 1700 20 230 2 1
Small Intestine 930 1100 8 0 0
Kidney 2100 76 50 2 0
Pancreas 1700 39 180 2 2
Spleen 1800 35 140 38 2
Thymus 54 1 1500 0 20
Uterus / Prostate (Bladder) 110 2000 1 130 0.025
Muscle 390 490 260 1 190
Gall Bladder 1900 130 65 11 1
Heart 370 5 1300 0 6
ET region (Thyroid) 6 0 220 2300 550
Lymph nodes (Muscle) 390 490 260 130 190
Oral mucosa (Brain) 0 0 11 280 4900
Eye lenses 0 0 15 600 5500
Testes 4 400 0 0 0
Ovaries 190 1700 2 0 0
Uterus 170 1800 2 0 0
Prostate 50 2100 0 0 0

 

Dose Estimates for Pediatric Patients

The effective dose estimates given above are for adults. These dose estimates can be used to estimate the effective dose to pediatric patients by using the scaling factors given below. These scaling factors, provided by Kersheed, may be used to provide an estimate of the dose to pediatric patients based on the dose received by an adult.

 

Table 3      

 

Head and Neck

Chest

Abdomen & Pelvis

Adult

1.0

1.0

1.0

15 y

1.1

1.0 - 1.1

1.0 - 1.1

10 y

1.2 - 1.3

1.1 - 1.4

1.2 - 1.5

5 y

1.6 - 1.7

1.2 - 1.6

1.2 - 1.6

1 y

2.2

1.3 - 1.9

1.3 - 2.0

Newborn (0 y)

2.3 - 2.6

1.4 - 2.2

1.4 - 2.4

Typical normalized effective doses to pediatric patients relative to adults

 

Example for Dose Estimation Not Involving Radiopharmaceuticals

Consider a research protocol requiring two abdominal CT scans to be performed on the GE Lightspeed 64 VCT (Irving 1st Floor).

 

JRSC form 5c is to be used, since this protocol does not include radiopharmaceuticals. CTDIvol, DLP, and effective dose for the GE Lightspeed 64 VCT are read off of table 1 above. Form 5c, page 3 would be as follows:

 

 

Exam

 

CTDIvol (mGy)

 

DLP (mGy-cm)

Effective Dose per exam  (mrem)

Total No. of Exams per Study

Total Effective Dose per Study (mrem)

 Abdominal CT

 16.5

412.5

619

 2

1238

 

 

 

 

 

 

 

 

 

 

 

 

 

Example for Dose Estimation Involving Radiopharmaceuticals: F-18 FDG

As an example, consider a patient injected with 10 mCi of F-18 FDG in a single study. Assume that the patient will also receive one abdominal CT examinations as a part of the study.

In order to determine the critical organ, the radiation dosimetry for the radiopharmaceutical was first calculated on the nuclear medicine FAQ page. In this case the critical organ is the bladder.

Organ dose information is only provided for the average CT scanner. For this scanner the CTDIvol is 14 mGy, the DLP is 310.6 mGy-cm, and the effective dose per exam is 525. The organ dose can be obtained from table 2 above.

 

 

 

2. Radiation Dosimetry

c)     CT:

 

Exam

CTDIvol

(mGy)

DLP

(mGy-cm)

Critical Organ

Critical Organ Absorbed Dose (mrad)

Effective Dose per exam  (mrem)

Total No. of Exams per Study

Critical Organ Absorbed Dose per Study (mrad)

Total Effective Dose per Study (mrem)

 Abdominal CT

 14

 310.6

 Bladder

 50

 525

 1

 50

525

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 


 

LIST OF SCANNERS AND CT EXAMINATIONS INCLUDED IN THIS REPORT

 

CT Scanner

Location

Abdomen

Head

Pediatric

Philips Spect-CT

Milstein

2nd Floor

120kVp,

50 mAs,

Helical, 16x1.5

Pitch .938

120kVp,

150mAs,

Axial, SL5

Pitch 1

 

n/a

Siemens Sensation 16

Irving

1st Floor

120kVp,

160mA, 1s,

Helical, 16x1.5,

Pitch 1.25

120kVp,

300mA, 1s,

Axial, 12x1.5

 

n/a

GE LightSpeed 64 VCT

Irving

1st Floor

120kVp,

250 mA, 1s,

Helical, 32x5, Pitch 1.375

120kVp,

400mA, 1s,

Axial, 32x0.625

 

n/a

GE LightSpeed Pro

Milstein

8th Floor

120kVp,

350 mA, 0.5s,

Helical, SL5.0,

Pitch .938

120kVp,

300mAs,

Axial,

SL5.0/5.0

 

n/a

Siemens Sensation 10

VC

ER

120kVp,

200 eff mAs*,

Helical,

SL5.0/6*3/12,

Pitch 0.65

120kVp,

300mAs,

Axial,

SL5.0/5.0

120kVp,

55mAs,

Helical,

SL5.0/3.0/18.0

Pitch 1,

25-34kg

Siemens Sensation 4

Allen Pavilion

120kVp,

200 eff mAs*,

Helical,

SL5.0/2.5/8.8, Pitch 0.88

120kVp,

300mAs,

Axial,

SL5.0/2.5

120kVp,

75mAs,

Helical,

SL3.0/2.5/10.0

Pitch 1.0

25-34kg

GE Lightspeed VCT

CHONY

3rd Floor

120kVp, 210mAs, Helical, SL5.0/39.37, Pitch .984

120kVp, 210mAs, Axial, SL5.0/4i

120 kVp, 135mA, .4s,

Pitch 1.375

31.5-40 lbs

Siemens Volume Zoom 4

Milstein

3rd Floor

120 kVp,

200 mA, 1s, Helical, 4x2.5,

Pitch 2

120kVp, 300mA, 1s,

Axial, 4x2.5

 

n/a

 

 

 

* Effective mAs = mAs/pitch