Download Dual energy CT of renal tumors

May 14, 2008- 10:25 AM
Anno Graser, MD: Dual energy CT of renal
tumors: can virtual non-contrast images replace
the un-enhanced phase?
Invest Radiol. Quantitative
bone mineral analysis using
dual energy computed
tomography. Genant HK, et al.
1977 NovDec;12(6):5
45-51.
Dual Energy CT of Renal Tumors: Can Virtual NonContrast Images Replace the Un-Enhanced Phase?
A. Graser1, 3, T. R. C. Johnson1, M. Staehler2, K. Nikolaou1, M. F.
Reiser1, C. R. Becker1 , M. Macari3
Departments of
3 Department
1Radiology
2Urology,
and
University of Munich –
Grosshadern Campus
of Radiology, New York University Medical Center
Med Phys. Noise
considerations in dual energy
CT scanning. Kelcz F, et al.
1979 SepOct;6(5):4
18-25.
Invest Radiol. Noninvasive
quantitation of liver iron in dogs
with hemochromatosis using
dual-energy CT
scanning.Goldberg HI, et al.
1982 JulAug;17(4):
375-80.
The idea of dual energy CT
scanning isn‘t new...
1979
May;131(2):
521-3.
Radiology. Tissue signatures
with dual-energy computed
tomography. Chiro GD, et al.
1980
Aug;4(4):501-9.
J Comput Assist Tomogr.
Split-filter computed
tomography: a simple technique
for dual energy scanning. Rutt
B, et al.
1982
Nov;145(2):4936.
Radiology. Quantification of
calcium in solitary pulmonary
nodules using single- and dualenergy CT. Cann CE, Webb
WR, et al.
Dual Energy Scanning – Why now?
•
•
•
•
•
Simultaneous scan at two
different tube voltages
Material differentiation beyond
„simple“ Hounsfield units
Stable HU-units of the single
scans
Higher spatial resolution Æ less
partial volume
Faster scans Æ less motion
artifacts, no misregistration
Background: MDCT of Renal Masses
• Imaging of renal masses relies on contrast agent
uptake for
– Detection
– Characterization
– Staging
• Unenhanced CT images are acquired in addition to
nephrographic and urographic phase scans
Background: MDCT of Renal Masses
• Unenhanced images of the kidneys are used for
– Baseline density measurement of mass
– Evaluation for presence of fat
– Evaluation for presence of calcification
• Most important criterion for differentiation of
malignant from benign mass is enhancement
•Szolar DH, et al. Radiology 1997; 202:211-217
•Birnbaum BA, et al. Radiology 1996; 200:753-758
Israel GM, Bosniak MA. Radiology 2005; 236:441-450
Stanford Radiology 10th Annual Multidetector
CT Symposium
1
May 14, 2008- 10:25 AM
Anno Graser, MD: Dual energy CT of renal
tumors: can virtual non-contrast images replace
the un-enhanced phase?
Types of images from a DE
scan
Dual Energy Scanning – basic principles
• X-ray absorption of scanned materials depends on
– Photon energy of x ray beam definded by kV setting of tube
– Atomic number z of materials between tube and detector
• Attenuation of materials with high z number is much higher at 80 kV than at
140 kV
140 kV
80kV
Bone
670 HU
Iodine
296 HU
Bone
450 HU
80 kV
Iodine
144 HU
140kV
Types of images from a DE
scan
Purpose
Materials and methods:
patient population
Materials and methods:
Dual Energy CT
• 120 patients with renal masses (75 male, 45 female,
63±15 years)
– RCC (n=85)
– Angiomyolipoma (n=5)
– Oncocytoma (n=2)
– Cysts (n=18; hemorrhagic/high density: n=12)
– Sarcoma (n=1)
– Lymphoma (n=2)
– Metastasis (n=2)
Stanford Radiology 10th Annual Multidetector
CT Symposium
• Dual source 64-MDCT scanner (Siemens
Somatom Definition)
• Examination protocol
– Non contrast scan (64x0.6 mm, 200 mAs, dose
modulation)
– Dual energy nephrographic phase scan 80 s after
CM injection (14x1.2 mm; A tube: 140 kV, 96 mAs; B
tube, 80 kV, 404 mAs; dose modulation)
– Delayed scan 360 s after contrast injection (120 kV,
120 mAs, dose modulation)
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May 14, 2008- 10:25 AM
Anno Graser, MD: Dual energy CT of renal
tumors: can virtual non-contrast images replace
the un-enhanced phase?
Materials and methods:
Quantitative Analysis
• HU density measurements on native
and virtual non contrast images
–
–
–
–
–
–
Renal parenchyma (n=2)
Renal mass (n=2)
Aorta
Psoas muscle
Liver
Mesenteric fat
Results I - quantitative analysis
Materials and methods:
Qualitative Analysis
• Rating of VNC and NC
– Noise (1=none to 4=severe)
– Image quality (1=excellent to 5=unacceptable)
• B detector field of view (FOV; 1=no exclusion to
4=severe exclusion)
• Artifacts (1=none to 4=severe)
• Overall acceptance (1=fully to 3=not acceptable
as non contrast study)
Dose Measurements
Graser et al., Radiology 2008, in press
Clinical use of dual energy CT in renal masses
Stanford Radiology 10th Annual Multidetector
CT Symposium
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Anno Graser, MD: Dual energy CT of renal
tumors: can virtual non-contrast images replace
the un-enhanced phase?
Results II - qualitative analysis
May 14, 2008- 10:25 AM
Example – qualitative analysis
Moderate
exclusion
(grade 2)
due to
limited size
of B detector
Overall acceptability (1-3): 1.42±0.65. 3/100 patients rated
as „not acceptable as non contrast study“
Conclusion
Thank you very much for your attention
New York University Medical Center: M. Macari, E. Hecht, M. Godoy
Siemens Medical Solutions: B. Krauss, C. Leidecker
• Dual energy CT allows for exact assessment of CT
density in solid organs and vessels
• DECT can be used for baseline density
measurements in patients with renal masses
• Omission of unenhanced phase will result in a 35%
dose reduction
• DECT nephrographic phase imaging can be used to
generate VNC images, replacing a true non contrast
scan
Stanford Radiology 10th Annual Multidetector
CT Symposium
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