Gemstone Spectral Imaging Images Research Articles

Virtual unehanced image in the single-source dual energy CT for evaluation of renal cell carcinoma:a preliminary study

To qualitatively and quantitatively evaluate the feasibility of CT virtual unenhanced (VUE) spectral imaging in renal cell carcinoma. Thirty-six patients with histopathologically proven renal cell carcinoma underwent gemstone spectral imaging (GSI) including ture unenhanced (TUE), arterial, cortex and medullary phase acquisitions. The triphasic GSI dataset was sent to workstation and 3 sets of VUE images (including VUE a, VUE c, VUE m) were obtained by subtract iodine from iodine-water images in the triphasic enhanced GSI images, respectively. The quality of VUE s and TUE images was evaluated on a five-point scale.Interobserver agreement with regard to image quality was assessed using Cohen's Kappa, and four groups of image quality was compared with ANOVA analysis. The contrast-to-noise ratio (CNR) of mass-to-kidney in the TUE and VUE s images was calculated, and difference between these four datasets was compared with ANOVA analysis. Using appearance of masses on triphasic images as a standard, the masses detection ratio of four groups was calculated and compared with chi-square test. Interobserver agreement with regard to image quality was excellent (κ>0.600). There was no significant difference among the image quality of TUE and triphasic images of VUEs (P>0.05). The CNR of TUE (0.7 ± 0.6) was significant worse than that of triphasic images (1.7 ± 1.0, 1.9 ± 1.2, 2.5 ± 1.4, respectively) (P<0.05). There was no significant difference among the CNR of triphasic images (P>0.05). VUE images obtain from triphasic phases may be a surrogate for conventional unenhanced scan in renal cell carcinoma diagnosis.

Feasibility Study of Using Gemstone Spectral Imaging (GSI) and Adaptive Statistical Iterative Reconstruction (ASIR) for Reducing Radiation and Iodine Contrast Dose in Abdominal CT Patients with High BMI Values.

PurposeTo prospectively investigate the effect of using Gemstone Spectral Imaging (GSI) and adaptive statistical iterative reconstruction (ASIR) for reducing radiation and iodine contrast dose in abdominal CT patients with high BMI values.Materials and Methods26 patients (weight > 65kg and BMI ≥ 22) underwent abdominal CT using GSI mode with 300mgI/kg contrast material as study group (group A). Another 21 patients (weight ≤ 65kg and BMI ≥ 22) were scanned with a conventional 120 kVp tube voltage for noise index (NI) of 11 with 450mgI/kg contrast material as control group (group B). GSI images were reconstructed at 60keV with 50%ASIR and the conventional 120kVp images were reconstructed with FBP reconstruction. The CT values, standard deviation (SD), signal-noise-ratio (SNR), contrast-noise-ratio (CNR) of 26 landmarks were quantitatively measured and image quality qualitatively assessed using statistical analysis.ResultsAs for the quantitative analysis, the difference of CNR between groups A and B was all significant except for the mesenteric vein. The SNR in group A was higher than B except the mesenteric artery and splenic artery. As for the qualitative analysis, all images had diagnostic quality and the agreement for image quality assessment between the reviewers was substantial (kappa = 0.684). CT dose index (CTDI) values for non-enhanced, arterial phase and portal phase in group A were decreased by 49.04%, 40.51% and 40.54% compared with group B (P = 0.000), respectively. The total dose and the injection rate for the contrast material were reduced by 14.40% and 14.95% in A compared with B.ConclusionThe use of GSI and ASIR provides similar enhancement in vessels and image quality with reduced radiation dose and contrast dose, compared with the use of conventional scan protocol.

Dual-energy computed tomography of cruciate ligament injuries in acute knee trauma

To examine dual-energy computed tomography (DECT) in evaluating cruciate ligament injuries. More specifically, the purpose was to assess the optimal keV level in DECT gemstone spectral imaging (GSI) images and to examine the usefulness of collagen-specific color mapping and dual-energy bone removal in the evaluation of cruciate ligaments and the popliteus tendon. At a level 1 trauma center, a 29-month period of emergency department DECT examinations for acute knee trauma was reviewed by two radiologists for presence of cruciate ligament injuries, visualization of the popliteus tendon and the optimal keV level in GSI images. Three different evaluating protocols (GSI, bone removal and collagen-specific color mapping) were rated. Subsequent MRI served as a reference standard for intraarticular injuries. A total of 18 patients who had an acute knee trauma, DECT and MRI were found. On MRI, six patients had an ACL rupture. DECT's sensitivity and specificity to detect ACL rupture were 79% and 100%, respectively. The DECT vs. MRI intra- and interobserver proportions of agreement for ACL rupture were excellent or good (kappa values 0.72-0.87). Only one patient had a PCL rupture. In GSI images, the optimal keV level was 63 keV. GSI of 40-140 keV was considered to be the best evaluation protocol in the majority of cases. DECT is a usable method to evaluate ACL in acute knee trauma patients with rather good sensitivity and high specificity. GSI is generally a better evaluation protocol than bone removal or collagen-specific color mapping in the evaluation of cruciate ligaments and popliteus tendon.

Reduction of metal artifacts from alloy hip prostheses in computer tomography.

The objective of this study was to evaluate the feasibility of reducing artifacts from large metal implants with gemstone spectral imaging (GSI) and metal artifact reduction software (MARS). Twenty-three in-vivo cobalt-chromium-molybdenum alloy total hip prostheses were prospectively scanned by fast kV-switching GSI between 80 and 140 kVp. The computed tomography images were reconstructed with monochromatic energy and with/without MARS. Both subjective and objective measurements were performed to assess the severity of metal artifacts. Increasing photon energy was associated with reduced metal artifacts in GSI images (P < 0.001). Combination of GSI with MARS further diminished the metal artifacts (P < 0.001). Artifact reduction at 3 anatomical levels (femoral head, neck, and shaft) were evaluated, with data showing that GSI and MARS could reduce metal artifacts at all 3 levels (P = 0.011, P < 0.001, and P = 0.003, respectively). Nevertheless, in certain cases, GSI without MARS produced more realistic images for the clinical situation. Proper usage of GSI with/without MARS could reduce the computed tomography artifacts of large metal parts and improve the radiological evaluation of postarthroplasty patients.

Objective characterization of GE Discovery CT750 HD scanner: Gemstone spectral imaging mode

To objectively characterize the performance of the gemstone spectral imaging (GSI) mode of GE CT750 HD scanner from a user's perspective. A regular scan protocol that approximates the adult abdomen scan protocol frequently used in the authors' institute was selected as the baseline, and a GSI protocol (preset 11) that is similar to the regular protocol and has a moderate dose level (CTDI(vol) = 26.27 mGy) was compared to the baseline protocol. The resolving power of both protocols was characterized in terms of modulation transfer functions and high contrast resolution bar readings. Their noise characteristics were studied through noise power spectra, and their low contrast detectability was compared via contrast-to-noise ratio. Material decomposition capability of GSI was evaluated by scanning iodine solutions of 9-24 mg/ml iodine concentration in a Gammex CT phantom and by examining the estimated iodine concentration. In addition, a formula describing the dependency of HU in iodine enhanced area on GSI monochromatic energies and iodine concentrations was provided and the theoretical values were compared with the measured results. The resolutions levels of 50%, 10%, and 5% MTF of GSI monochromatic images at 65 keV agree with those of the regular protocol within 0.1 1p/cm. GSI monochromatic images at 65 keV demonstrated the lowest noise level among GSI images of different monochromatic energies and showed very similar noise magnitude and noise power distribution as compared to the regular protocol images. The CNR of 60 and 65 keV GSI monoimages are approximately 100% of those of the regular protocol images. Estimated iodine concentration levels agreed with the actual values within 2% when the iodine solutions were placed at 3, 9, 12 o'clock positions of the phantom; when iodine solutions were placed at the phantom center and at 6 o'clock position, higher discrepancies of 2%-10% were observed. The observed dependency of HU on keV and iodine concentration levels agreed with the expectation from x-ray attenuations. Equivalent performances were observed in the comparison between GSI 65 keV monochromatic images and images from a regular abdomen scan protocol. This suggests the possibility of GSI to be employed in routine abdominal scans, which would potentially offer more information through its capabilities of material decomposition.