Ultra-high-resolution photon-counting detector computed tomography of the lungs: Phantom and clinical assessment of radiation dose and image quality

• Published in: Clinical imaging 2023-12, Vol.104, p.110008-110008, Article 110008
• Main Authors: Chamberlin, Jordan H., Smith, Carter D., Maisuria, Dhruw, Parrish, Joe, van Swol, Elizabeth, Mah, Eugene, Emrich, Tilman, Schoepf, U. Joseph, Varga-Szemes, Akos, O'Doherty, Jim, Munden, Reginald F., Tipnis, Sameer V., Baruah, Dhiraj, Kabakus, Ismail M.
• Format: Article
• Language: English
• Subjects: Photon-counting-detector computed tomography; Pulmonary imaging; Ultra-high-resolution
• ISSN: 0899-7071; 1873-4499
• DOI: 10.1016/j.clinimag.2023.110008

Photon-counting-detector computed tomography (PCD-CT) offers enhanced noise reduction, spatial resolution, and image quality in comparison to energy-integrated-detectors CT (EID-CT). These hypothesized improvements were compared using PCD-CT ultra-high (UHR) and standard-resolution (SR) scan-modes. Phantom scans were obtained with both EID-CT and PCD-CT (UHR, SR) on an adult body-phantom. Radiation dose was measured and noise levels were compared at a minimum achievable slice thickness of 0.5 mm for EID-CT, 0.2 mm for PCD-CT-UHR and 0.4 mm for PCD-CT-SR. Signal-to-noise ratios (SNR) and contrast-to-noise ratios (CNR) were calculated for five tissue densities. Additionally, data from 25 patients who had PCD-CT of chest were reconstructed at 1 mm and 0.2 mm (UHR) slice-thickness and compared quantitatively (SNR) and qualitatively (noise, quality, sharpness, bone details). Phantom PCD-CT-UHR and PCD-CT-SR scans had similar measured radiation dose (16.0mGy vs 15.8 mGy). Phantom PCD-CT-SR (0.4 mm) had lower noise level in comparison to EID-CT (0.5 mm) (9.0HU vs 9.6HU). PCD-CT-UHR (0.2 mm) had slightly higher noise level (11.1HU). Phantom PCD-CT-SR (0.4 mm) had higher SNR in comparison to EID-CT (0.5 mm) while achieving higher resolution (Bone 115 vs 96, Acrylic 14 vs 14, Polyethylene 11 vs 10). SNR was slightly lower across all densities for PCD-CT UHR (0.2 mm). Interestingly, CNR was highest in the 0.2 mm PCD-CT group; PCD-CT CNR was 2.45 and 2.88 times the CNR for 0.5 mm EID-CT for acrylic and poly densities. Clinical comparison of SNR showed predictably higher SNR for 1 mm (30.3 ± 10.7 vs 14.2 ± 7, p = 0.02). Median subjective ratings were higher for 0.2 mm UHR vs 1 mm PCD-CT for nodule contour (4.6 ± 0.3 vs 3.6 ± 0.1, p = 0.02), bone detail (5 ± 0 vs 4 ± 0.1, p = 0.001), image quality (5 ± 0.1 vs 4.6 ± 0.4, p = 0.001), and sharpness (5 ± 0.1 vs 4 ± 0.2). Both UHR and SR PCD-CT result in similar radiation dose levels. PCD-CT can achieve higher resolution with lower noise level in comparison to EID-CT. •Photon counting CT ultra-high resolution imaging provides higher resolution with reasonable noise and comparable radiation dose, improving lung evaluation.•Photon counting CT ultra-high resolution outperforms high resolution Energy-Integrating CT in noise reduction, achieving higher image quality and resolution for pulmonary structures.•Ultra-high resolution photon counting CT offers increased sharpness, bone detail, and nodule contour compared to standard rec