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Tuesday Case of the Day
Physics
Authors: A.-K. Carton, S. C. Gavenonis, E. Conant, A.D.A. Maidment
University of Pennsylvania
History: Clinical history of known invasive ductal carcinoma. Contrast-enhanced magnetic resonance
imaging (CE-MRI) is the current standard for imaging vascular characteristics of malignant breast lesions
[1, 2]. The imaging method used for Figures B and C demonstrates vascular information concordant with
breast MRI (Figure A). Name this imaging method. Figures B and C were produced with the 2
techniques currently being evaluated for this imaging method. How do these techniques differ?
Figure 1: Images acquired with techniques B & C demonstrate lesion morphology and enhancement concordant with CE-MRI (A).
Diagnosis:
The new method is contrast-enhanced digital breast
tomosynthesis (CE-DBT). In contrast to projection mammography, DBT is an x-ray
imaging technique that provides 3D images of the breast [3]. DBT is thus able to
depict 3D lesion morphology and lesion localization.
With the administration of an iodinated vascular contrast agent, it is possible to
demonstrate vascular characteristics of breast lesions, as illustrated in this case. Two
techniques for CE-DBT are being studied: temporal subtraction CE-DBT [4], and dualenergy (DE) subtraction CE-DBT [5]. Note that the CE-DBT images are single slice inplane images of the breast in MLO position.
Discussion:
Temporal subtraction CE-DBT
HE
HE
10000
1800000
1600000
1000
1400000
K-edge
1200000
100
1000000
Iodine
800000
HE
spectrum 600000
10
Breast
400000
1
Pre contrast
Post contrast
200000
0.1
0
0
10
20 keV 30
40
50
Time
Figure 2: In temporal subtraction, one pre- and one or more post-contrast tomosynthesis time points are acquired using a highenergy (HE) x-ray spectrum. Iodine-enhanced images are produced by subtracting the logarithm of the pre- and post-contrast
series [4].
# Photons
Mass Attenuation [cm2/g]
Iodine
contrast
Dual-energy subtraction CE-DBT
LE
HE
10000
1800000
Iodine
contrast
LE
spectrum
Mass Attenuation [cm2/g]
1000
LE
1600000
1400000
K-edge
1200000
100
1000000
Iodine
HE
spectrum
10
Breast
1
800000
# Photons
Discussion:
600000
400000
200000
HE
0.1
0
0
10
20
30
40
50
keV
Time
Figure 3: DE CE-DBT requires only post-contrast image series at two energies that closely bracket the K-absorption edge of
iodine. Iodine enhanced images are given by weighted difference between the logarithms of the HE and low-energy (LE) images [5].
Discussion:
Theoretically, in the absence of breast motion, temporal subtraction
is the most sensitive method for enhancement detection since background breast tissue
can be completely cancelled, whereas in DE CE-DBT background tissue cannot be
completely cancelled.
In clinical application, however, temporal subtraction is very susceptible to breast-motion
artifacts due to the relatively long time delay between the pre- and post-contrast series
[4]. With DE CE-DBT artifacts from breast motion can be significantly reduced because
the image series pair at each time point are acquired in rapid succession.
Investigation is ongoing into optimizing CE-DBT and comparing temporal CE-DBT with
dual energy CE-DBT techniques.
Temporal subtraction
DE subtraction
Figure 4: Temporal and Dual energy CE-DBT image. Note the more significant motion artifacts in the temporal
subtraction CE-DBT images; the clip inside the lesion shows a displacement of approximately 2 mm.
References/Bibliography:
1. Kuhl CK, Schild HH, Morakkabati N. Dynamic bilateral contrast-enhanced MR
imaging of the breast: trade-off between spatial and temporal resolution. Radiology
2005; 2005:789-800.
2. Schnall MD, Blume J, Bluemke DA, et al. Diagnostic architectural and dynamic
features at breast MR imaging: multicenter study. Radiology 2006; 238:42-53.
3. Niklason LT, Christian BT, Niklason LE, et al. Digital tomosynthesis in breast
imaging. Radiology 1997; 205:399-406.
4. Chen SC, Carton A-K, Albert M, Conant EF, Schnall MD, Maidment ADA. Initial
clinical experience with contrast-enhanced digital breast tomosynthesis. Academic
Radiology 2007; 14:229-238.
5. Carton AK, Ullberg C, Lindman K, Francke T, Maidment ADA, "Optimization of a
Dual-Energy Contrast-Enhanced Technique for a Photon Counting Digital Breast
Tomosynthesis System" 9th International Workshop, IWDM 2008, Tucson, AZ, USA,
July 2008.