Calculating Organ Dose from
Fluoroscopy
Parham Alaei, Ph.D.
Department of Therapeutic Radiology-Radiation Oncology
University of Minnesota
Minneapolis, Minnesota
Imaging Symposium: Patient Dose in Fluoroscopy: Estimating
Patient-Specific Radiation Dose from Fluoroscopy
2011 Joint AAPM/COMP Meeting
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Is there a need to calculate patientspecific organ dose?
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Effective dose for long, complex interventional
procedures could exceed 50 mSv
Possibility of modeling organ dose prior to
procedure to avoid radiosensitive organs
Estimate biological response
Compare with and add the dose to that from
other techniques/technologies (CT, etc.)
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Outline:
Brief review of methods of organ dose
computation from fluoroscopy
 Use of a treatment planning system for organ
dose calculation in fluoroscopy
 Magnitude of organ doses encountered in a
sample procedure
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Common organ dose calculation methods:
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DAP-derived
Dose-Area Product
(DAP) Measurements
Organ Doses Calculated
By MC Modeling
Dose Conversion
Coefficients (DCCs)
[organ doses per unit
DAP]
Calculate Organ Dose
Calculate Effective Dose
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Common organ dose calculation methods:

DAP-derived
Phys. Med. Biol. 54 (2009) 3613–3629
… if patient size is neglected when choosing a DCC, the organ and
effective dose will be underestimated to an underweight patient and will
be overestimated to an overweight patient, with errors as large as 113%
for certain projections.
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Common organ dose calculation methods:
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Extrapolation/interpolation from entrance/exit
dose

Entrance surface dose (ESD) to organ dose
conversion using MC-generated tables (NRPB R262
and NRPB SR262)
Computational/MC
 CDRH organ dose handbooks
 A combination of above
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*NRPB: National Radiological Protection Board (UK)
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Using a Treatment Planning System:
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Commonly used in radiation therapy
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Pros:
Ability to get a “customized” dose distribution for a
patient, accounting for beam quality, patient anatomy,
size, heterogeneities, …
 Ability to segment organs and obtain dose statistics
within each organ

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Cons:
Extensive initial setup/commissioning
 Need a CT scan of the patient
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Convergence of diagnostic and therapeutic
radiology
Depth dose curves of various diagnostic
beams (HVL: ~2-4 mm AL)
From: Fetterly et. al Med. Phys. 28 (2),
2001
Depth dose curve of Elekta XVI cone
beam CT beam (HVL: ~7 mm Al)
From: Spezi et. al Med. Phys. 36 (1),
2009
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Convergence of diagnostic and therapeutic
radiology
kV cone beam CT dose distribution
Previous work in modeling
diagnostic beams using
radiation therapy treatment
planning system
Med. Phys. 26 (8), August 1999
Med. Phys. 27 (12), December 2000
Med. Phys. 28 (2), February 2001
Beam Modeling in the treatment planning
system (Philips Pinnacle)
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Collecting and importing depth dose/cross profiles
Selecting modeling parameters (beam spectra, etc.)
Simulating heel effect
Obtaining the best match between measured and
modeled data
Med. Phys. 28 (2), February 2001
Depth dose and cross profile data of a 120 kVp beam
Measured:
Modeled:
Modeled beams
CT scan
Dose distribution within body
Kilovoltage beam dose distribution in phantom
One 120 kVp beam
Three 100 kVp beams
Kilovoltage beam dose distribution in phantom
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Dose Volume Histograms:
One 120 kVp beam
Left lung
Heart
Three 100 kVp beams
Right lung
Heart
Lungs
Modeling a cardiac
angiography procedure using
a treatment planning system
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Sample calculation-Cardiac angiography procedure
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Data obtained from a Siemens Artis Zee unit*
Acquisition Protocol
Dose Area
Product (Gym2)
Dose (RP)
(Gy)
FOV area
(cm^2)
dose rate
(cGy/min)
Positioner Primary
Angle (deg)
Positioner
Secondary
Angle (deg)
Beam on time (s)
KVP (kV)
FL Low LD
0.000059
0.00522
113.0
4.9
0.0
0
6.4
81.0
FL Low LD
0.000036
0.00447
80.5
2.9
40.6
-0.6
9.2
81.0
FL Low LD
0.0001985
0.03502
56.7
17.7
52.0
-30.8
11.9
112.0
Coro HDR Low
0.0006967
0.12294
56.7
145.6
52.0
-30.8
5.1
124.0
FL Low LD
0.000017
0.0027
63.0
4.9
41.2
21.7
3.3
82.0
Coro HDR Low
0.0002776
0.04377
63.4
46.9
41.2
21.7
5.6
101.0
FL Low LD
0.000011
0.00199
55.3
3.6
-25.7
30.6
3.3
81.0
Coro HDR Low
0.0002164
0.03796
57.0
43.8
-25.7
30.6
5.2
97.0
FL Low LD
0.000037
0.0065
56.9
6.6
-23.8
-28.9
5.9
88.0
Coro HDR Low
0.0002409
0.04247
56.7
51.0
-23.8
-28.9
5.0
104.0
FL Low LD
0.000056
0.00755
74.2
1.7
11.6
-4
26.7
81.0
FL Low LD
0.0001024
0.01389
73.7
3.3
27.1
-4
25.3
81.0
FL Low LD
0.000007
0.00098
71.4
4.9
37.9
15.3
1.2
81.0
Coro HDR Low
0.0002946
0.04139
71.2
46.6
37.9
15.3
5.3
99.0
FL Low LD
0.00001
0.00178
56.2
5.3
-2.6
38.1
2.0
85.0
Coro HDR Low
0.0002478
0.04316
57.4
45.7
-2.6
38.1
5.7
98.0
*Courtesy Ken Fetterly, Mayo Clinic
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Sample calculation-Cardiac angiography procedure
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Data as entered into the treatment planning system
Beam #
Field Size
Gantry
Couch
Time (Min.)
Beam Type
1
10.6
180
0
0.11
Fluoro 81
2
9.0
221
1
0.15
Fluoro 81
3
7.5
232
31
0.20
Fluoro 112
4
7.5
232
31
0.08
Cine 120
5
7.9
221
-22
0.06
Fluoro 81
6
8.0
221
-22
0.09
Cine 100
7
7.4
154
-31
0.06
Fluoro 81
8
7.6
154
-31
0.09
Cine 100
9
7.5
156
29
0.10
Fluoro 81
10
7.5
156
29
0.08
Cine 100
11
8.6
192
4
0.44
Fluoro 81
12
8.6
207
4
0.42
Fluoro 81
13
8.5
218
-15
0.02
Fluoro 81
14
8.4
218
-15
0.09
Cine 100
15
7.5
177
-38
0.03
Fluoro 81
16
7.6
177
-38
0.09
Cine 100
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Sample calculation-Cardiac procedure
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Sample calculation-Cardiac procedure
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Sample calculation-Cardiac procedure
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Sample calculation-Cardiac procedure
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Sample calculation-Cardiac procedure
16 Beams incident on Rando phantom
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Sample calculation-Cardiac procedure
16 Beams incident on Rando phantom
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Sample calculation-Cardiac procedure
16 Beams incident on Rando phantom
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Sample calculation-Cardiac procedure
16 Beams incident on Rando phantom
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Sample calculation-Cardiac procedure
16 Beams incident on a male chest CT dataset
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Sample calculation-Cardiac procedure
16 Beams incident on a female chest CT dataset
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Limitations of the method:
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Skin dose calculations not accurate:
Difficulty in measuring and modeling dose on surface
and shallow depths
 Uncertainty in algorithms’ calculation accuracy on
surface
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Bone dose underestimated
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Algorithm developed for megavoltage beams
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Results could be improved by post processing
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Future directions:
New algorithms for dose calculation in kilovoltage
beams (kV CBCT, fluoroscopy, CT, etc.)
 This will lead to accurate calculation of dose to
bone and bone marrow
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Acknowledgement:
Ken Fetterly, Ph.D.
Mayo Clinic
Questions?
E-mail: alaei001@umn.edu