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NC HPS Meeting 10/18-19/2001 Boone, NC. Measurement of Effective Dose Equivalent Using a Newborn Phantom L. Barnes 1 , T. Yoshizumi 1,2 , D. Frush 2 , V. Varchena 3 , M. Sarder 1 , E. Paulson 2 1 Radiation Safety Office, 2 Department of Radiology, - PowerPoint PPT Presentation
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Measurement of Effective Dose Equivalent Using a Newborn Phantom
L. Barnes 1, T. Yoshizumi 1,2, D. Frush 2, V. Varchena3, M. Sarder 1, E. Paulson 2
1 Radiation Safety Office, 2 Department of Radiology,3Computerized Imaging Reference Systems, Inc.
Duke University Medical Center Durham, NC
NC HPS MeetingNC HPS Meeting10/18-19/200110/18-19/2001Boone, NCBoone, NC
Measurement of Effective Dose Equivalent Measurement of Effective Dose Equivalent Using a Newborn PhantomUsing a Newborn Phantom
Topics1. Why pediatric CT dosimetry?2. Scope of study3. Materials and Methods4. Results5. Conclusions
Why pediatric CT dosimetry?Why pediatric CT dosimetry? Only 40% of CT users adjust techniques for
patient size (preliminary NEXT data) NEXT =Committee on Nationwide Evaluation of
X-ray Trend, CRCPD Don’t have organ dose data in multi-detector
CT scanners (your guess is as good as mine) Dose indices such as CTDI and the dose-
length product do not represent actual organ dose and are of limited value in risk assessment
Problems created by news media frenzy in recent months
American Journal of Roentgenology 2001:176;303-306American Journal of Roentgenology 2001:176;303-306
2. Scope of study2. Scope of study
Measure Effective Dose Equivalent using single and multi-detector CT scanners for chest and abdomen CT protocols;
Two protocols were selected: Chest and Abdomen;
Scan parameters (kVp, mA, sec, pitch, etc.) were selected to represent High, Medium, and Low techniques.
Dosimeters Harshaw TLD-100 Harshaw auto TLD reader QS 5500
CT scanners GE QXi (multi-detector) and CTi (single
detector) Anthropomorphic phantom
Newborn phantom, CIRS, Inc., Norfolk, VA.
3. Materials and Methods3. Materials and Methods
Brief description of phantomBrief description of phantom
Atom newborn phantom (Model 703-D) CIRS, Norfolk, VA
Cost: ~ $ 9K Joint effort between Duke
and CIRS
Brief description of phantomBrief description of phantom
Dosimeter distributionDosimeter distribution TLD locations in
organs pre-drilled Designed for TLD-
100 (3mm x 3 mm x 1 mm)
Newborn Abdomen CT ProtocolNewborn Abdomen CT ProtocolDose Comparison: CT/i vs QX/i Dose Comparison: CT/i vs QX/i
CTII. High3 mm, pitch 1.0140 kVp;120 mA, 0.8 sec
II. Medium5 mm, pitch 1.5140 kVp; 90 mA; 0.8 sec
III. Low5 mm, pitch 2.0120 kVp; 70 mA; 0.8 sec
QXII. High 2.5/7.5 HQ140 kVp; 100 mA, 0.8 sec
II. Medium3.75/11.25 HQ140 kVp; 70 mA, 0.8 sec
III. Low5.0/22.5 HS120 kVp; 60 mA, 0.5 sec
Calculation of Effective Dose EquivalentCalculation of Effective Dose Equivalent
ICRP Report No. 26 (1977)Effective Dose Equivalent = T WT HTWhere WT = weighting factor; HT = dose equivalent.
Selected Organs (Newborn Phantom – CIRS, Norfolk, VA) –see Chart (Rt).
Organs Slice #Thyroid 6
BM/Mandible 5
BM/Femor 14
Testes 14
BM/Pelvis 12
Intestine 12
Ovaries 12
Kidney 11
Intestine 11
Liver 10
Stomach 10
Lungs 9
BM/Spine 9
BM/Rib 8
Lungs 7
BM/Spine 7
Effective Dose EquivalentNewborn Phantom
QXI vs CTI
High Medium Low0.0
0.5
1.0
1.5
2.0
2.5
3.0QXICTI2.3
1.51.3
0.82
0.35 0.32
Abdomen Scan Protocol
Effe
ctiv
e Do
seEq
uiva
lent
(mSv
)
Newborn Newborn Chest CTChest CT Protocol ProtocolDose Comparison: CT/i vs QX/i plusDose Comparison: CT/i vs QX/i plus
CTII. High
3 mm, pitch 1.0140 kVp;100 mA, 0.8 sec
II. Low5 mm, pitch 2.0120 kVp; 50 mA; 0.8 sec
QXI PlusI. High
2.5/7.5 HQ, 140 kVp, 80 mA, 0.8 sec
II. Med3.75/1.25 HQ, 140 kVp, 50 mA, 0.8 sec
III. Low5.0/22.5 HS120 kVp; 40 mA, 0.5 sec
Calculation of Effective Dose EquivalentCalculation of Effective Dose Equivalent ICRP Report No. 26 (1977)
Effective Dose Equivalent = T WT HT
Where WT = weighting factor; HT = dose equivalent.
Selected Organs (Newborn Phantom – CIRS, Norfolk, VA) –see Chart (Rt).
Organs Slice #BM/Mandible 5Thyroid 6Lungs 7BM/Spine 7BM/Rib 8Lungs 9BM/Spine 9Liver 10Stomach 10kidney 11Intestine Upper 11Ovaries 12BM/Pelvis 12Testes 14BM/Femor 14BM/ UPPER ARM ARMBM/ LOWER ARM ARMBM/RADIUS+ULNA ARM
EDE (female)
Effective Dose Equivalent(Chest)
Newborn PhantomQXI (plus) vs CTI
High Med Low0.0
0.2
0.4
0.6
0.8QXICTI
0.70
0.11
0.59
0.075
0.40
Chest Scan Protocol
Effe
ctiv
e Do
seEq
uiva
lent
(mSv
)
For abdomen protocol, the effective dose equivalent between high and low scan techniques differed a factor of 7 for QXi and that of 5 for CTi.
For chest protocol, the effective dose equivalent between high and low scan techniques differed a factor of 6 for QXi and 8 for CTi.
It is important to adjust scan techniques for the size and weight of a patient.
A multi-detector scanner (QXi) resulted in substantially higher dose than a single-detector scanner (CTi).
5. Conclusions5. Conclusions