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. 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