DIAGNOSTIC VALUE OF DUAL ENERGY SPECTRAL CT FOR PROSTATE

DIAGNOSTIC VALUE OF DUAL ENERGY SPECTRAL CT
FOR PROSTATE
Xiaofei Zhang, Department of Radiology of Renji Hospital
CLINICAL BACKGROUND
*Prostate cancer(Pca) is the most common cancer in men . Both benign
prostate hyperplasia(BPH) and PCa rank among the 10 most diagnosed
diseases over the age of 65.
*Main diagnostic tools: Digital rectal examination, PSA level, and
transrectal sonographically guided biopsy(golden standard).
*Disadvantages of biopsies:Even after preventive antibiotics, some
patients suffer septic complications and may require aggressive therapy.
A reliable noninvasive method would have considerable impact.
Many imaging methods have been investigated on the aspect of MRI, CT.
MRI: false positive rate
Pca
Imflamation
Adnomal
BPH
The T2-weighted MR imaging employed for the diagnosis of
Pca is based on the finding of low signal intensity foci in the
peripheral zone. It is limited by false-positive findings.
Conventional CT Plain scanning
* Conventional CT for the investigation of
prostate disease is rare.
* Parenchyma,urethral portion and
capsule of the prostate cannot be
distinguished because of similar tissue
density.
* The basal part of prostate and the
basal part of bladder cannot be
distinguished because of partial volume
effect.
Conventional CT enhanced scanning
BPH
Pca
* One previous study to evaluate the role of conventional enhanced
CT demonstrated that it only accurately revealed 58% peripheral
zone cancer sites.
* Regardless of pathologic features, each lesion (BPH or PCa)
appeared contrast enhanced in the peripheral zone and were
hardly been differentiated in a naked eye .
Enlightenings of Dynamic Contrast
Enhanced MRI
1 DCE MR imaging is useful in distinguishing malignant from
benign because prostate cancer enhances earlier than healthy
prostatic tissue .
2 PCa has a large network of immature blood vessels with
abnormally higher leakability. Although, the microvessl density
of BPH is also high , the vessels have normal leakability.
3 The enhancing order of different prostatic tissue:
Pca>BPH>normal transitional zone>normal peripheral zone is
hardly enhanced during all phases.
4
Dual energy spectral CT
Monochromatic
Images
Material
Decomposition
Spectral Tools
(Discovery CT 750 HD,GE health care)
• with energies ranging from 40 to 140 keV
• Reduce beam hardening artifact and
improve spatial resolution
• used to quantitatively estimate
the iodine content in lesions
• Spectral HU curve, optimal CNR,
scatter plot, effective Z
Case1
male patient with age of 78
Left: PCA
Right: BPH
Proven by biopsy
T2 weighted MR image
Monochromatic CT Image
Case1
HU curve
Aterial Phase(AP), Venous Phase(VP), Parenchymal Phase (PP)
The tendency of Pca HU curve is of great difference to that of BPH in AP and VP.
Owing to the enhancement of BPH lesion in PP, the HU curves of different
lesions cannot be greatly discriminated.
Case2
60 male
Pca
Normalized HU Curve
Suspicious lymph node
The HU curves of the two lesions have similar tendency, indicating that the
abnormal lymph node may be caused by metastasis of Pca lesion.
Patients
Inclusive criteria
Exclusive criteria
• Between August 2011 and August 2012, 56
consecutive patients with elevated PSA levels or
positive digital rectal examination selected to
undergo multi-phase CT scanning of the prostate
before undergoing US-guided biopsy.
• contraindications to enhanced CT imaging
• contraindications to biopsy: poor general health
condition
• biopsy prior to CT scanning
• previous diagnosis of acute prostatitis, hemorrhage
• history of prostate cancer
Three types of images were obtained from the single spectral CT acquisition
Polychromatic
energy image
monochromatic images
obtained at energies ranging
from 40 to 140 keV
iodine-based material
decomposition images
QUANTITATIVE PARAMETERS
Monochromatic
images
Iodine-based
material
decomposition images
•1the CT values
•2the Differences in CT values
(DCTVA=CTVP-CTAP and DCTPV=CTPP-CTVP) on
the 75keV monochoromatic image set
•3normalized Lesion iodine concentration
(NIC = ICles/Icm )
Since in pelvic CT, the 120kvp scanning has an average energy of about
75Kev.
Parameter
PCa (n=27)
BPH (n=25)
P Value
CTAP(HU)
68.75±15.82
62.88±16.79
0.50
CTVP(HU)
92.75±15.79
90.59±18.16
0.81
CTPP(HU)
90.48±11.35
87.92±1.68
0.68
DCTVA(HU)
25.6±14.3
28.0±13.7
0.74
DCTPV(HU)
-1.3±9.5
-1.9±11.2
0.92
* In terms of CT values and CT value changes (DCTVA and DCTPV) at the conventional CT
imaging(120kVp=75kev), there were no significant differences between PCa group and BPH
group.
* CONCLUSION1:Conventionnal CT values and CT value changes do not have
considerable impact on distinguishing malignant from benign.
NIC = ICles/Icm
(Normalized Iodine Concentration to minimize variations in patients, scan timings)
Parameter
PCa (n=27)
BPH (n=25)
P Value
NIC (AP)※
1.90±0.30
0.99±0.32
0.00
NIC (VP) ※
2.46±0.40
1.89±0.41
0.00
NIC Box plots
*In terms of normalized iodine concentration(NIC), there were significant
differences between PCa and BPH group in AP and VP(p<0.05)
* All lines of 25th percentile, medium, 75th percentile in PCa were higher
than those in BPH .
• The NIC curve dentency for PCa is quite different from that of BPH,
with a fast washout after the enhancement.
• On the other hand, CT value changes during the three phases were
very similar between PCa and BPH.
sensitivity
specificity
Conventional enhanced CT
70%
71%
Dynamic enhanced MRI
80%
70%(high false positive)
Iodine concentrations threshold
value of GSI
80%
81%
* ROC analyses indicate when the value 1.25 ( NIC) in AP was used as
threshold, the sensitivity and specificity reached 80% and 81%.
* CONCLUSION2: NIC has moderately significant discriminatory power ,
better than Conventional enhanced CT and Dynamic enhanced MRI.
THANKS FOR YOUR ATTENTION
[email protected]
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