Image Quality and Radiation Dose of Contrast-Enhanced Chest-CT Acquired on a Clinical Photon-Counting Detector CT vs. Second-Generation Dual-Source CT in an Oncologic Cohort: Preliminary Results

Abstract

Our aim was to compare the image quality and patient dose of contrast-enhanced oncologic chest-CT of a first-generation photon-counting detector (PCD-CT) and a second-generation dual-source dual-energy CT (DSCT). For this reason, one hundred consecutive oncologic patients (63 male, 65 ± 11 years, BMI: 16–42 kg/m2) were prospectively enrolled and evaluated. Clinically indicated contrast-enhanced chest-CT were obtained with PCD-CT and compared to previously obtained chest-DSCT in the same individuals. The median time interval between the scans was three months. The same contrast media protocol was used for both scans. PCD-CT was performed in QuantumPlus mode (obtaining full spectral information) at 120 kVp. DSCT was performed using 100 kV for Tube A and 140 kV for Tube B. “T3D” PCD-CT images were evaluated, which emulate conventional 120 keV polychromatic images. For DSCT, the convolution algorithm was set at I31f with class 1 iterative reconstruction, whereas comparable Br40 kernel and iterative reconstruction strengths (Q1 and Q3) were applied for PCD-CT. Two radiologists assessed image quality using a five-point Likert scale and performed measurements of vessels and lung parenchyma for signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and in the case of pulmonary metastases tumor-to-lung parenchyma contrast ratio. PCD-CT CNRvessel was significantly higher than DSCT CNRvessel (all, p < 0.05). Readers rated image contrast of mediastinum, vessels, and lung parenchyma significantly higher in PCD-CT than DSCT images (p < 0.001). Q3 PCD-CT CNRlung_parenchyma was significantly higher than DSCT CNRlung_parenchyma and Q1 PCD-CT CNRlung_parenchyma (p < 0.01). The tumor-to-lung parenchyma contrast ratio was significantly higher on PCD-CT than DSCT images (0.08 ± 0.04 vs. 0.03 ± 0.02, p < 0.001). CTDI, DLP, SSDE mean values for PCD-CT and DSCT were 4.17 ± 1.29 mGy vs. 7.21 ± 0.49 mGy, 151.01 ± 48.56 mGy * cm vs. 288.64 ± 31.17 mGy * cm and 4.23 ± 0.97 vs. 7.48 ± 1.09, respectively. PCD-CT enables oncologic chest-CT with a significantly reduced dose while maintaining image quality similar to a second-generation DSCT for comparable protocol settings.

Technical Basics and Clinical Benefits of Photon-Counting CT

“…The authors attributed this result, which is well in line with, 54 to the improved weighting of low-energy x-ray quanta leading to higher iodine contrast, aided by the absence of electronic noise and improved iterative reconstruction. In a similar study of 100 oncologic chest patients, 56 a mean radiation dose reduction of more than 40% at maintained image quality compared with second-generation DSCT was demonstrated (mean CTDI vol /DLP = 4.17 mGy/151.0 mGy  cm for PCD-CT and 7.21 mGy/288.6 mGy  cm for DSCT).…”

Photon Counting Computed Tomography with the Radiation Dose of a Chest X-Ray: Feasibility and Diagnostic Yield

“…Dose reduction has always been an issue in CT, and the PC-CT offers new possibilities in this realm. Clinical studies on this topic revealed a 43-50% reduction of the radiation dose while retaining equal image quality in PC-CT [7][8][9][10][11]. With a minor reduction in radiation dose, the signal-to-noise ratio improves with a better image quality [10].…”

Evaluation of low-contrast detectability of photon-counting-detector CT using channelized Hotelling observer and an ACR accreditation phantom

“…Photon-counting-detector (PCD) CT has been shown to have a higher spatial resolution [1][2][3] and iodine contrast-tonoise ratio (CNR) [3][4][5], improved detectability for iodine and high-contrast inserts [3,6], and reduced radiation dose compared to EID-CT [1,2,7,8]. The first whole-body clinical PCD-CT scanner has two major scan modes: standard resolution (SR) and ultra-high-resolution (UHR), which acquire data using different detector pixel sizes, and different reconstructions: spectral mode at a given virtual monochromatic energy (VMI) and non-spectral mode at different threshold energies (e.g., threshold low (T3D)).…”