The first clinical photon-counting detector CT system demonstrated superior spatial resolution relative to current CT systems and improved noise properties and multi-energy temporal resolution relative to similarly configured, energy-integrating detector CT. Key Results1. The high-resolution mode of the photon-counting detector (PCD) CT demonstrated 125-micron in-plane spatial resolution and 0.3 mm longitudinal resolution, the smallest reported to date for a clinical CT system.2. The PCD CT system provided 66-msec temporal resolution multi-energy imaging in dual-source mode.3. Noise reduction (up to 47%) or dose reduction (up to 30%) were achieved in study participants using the PCD CT system relative to a similar CT system equipped with conventional detectors.

Purpose Myocardial tissue stiffness plays an important role in cardiac function. A non-invasive quantitative imaging technique capable of measuring myocardial stiffness could aid in disease diagnosis, therapy monitoring, and disease prognostic strategies. We recently developed a high frequency cardiac magnetic resonance elastography (MRE) technique capable of making non-invasive stiffness measurements. Hence our objective was to evaluate if cardiac Magnetic Resonance Elastography (MRE) can measure increased stiffness in patients with cardiac amyloidosis. Materials and Methods 16 volunteers and 22 patients with cardiac amyloidosis were enrolled in this study, after IRB approval and obtaining formal written consent. All subjects were imaged head first in the supine position in a 1.5-Tesla closed-bore MR imager (Optima MR450W; GE Healthcare, Milwaukee, WI, USA). 3D MRE was performed using 5 mm isotropic resolution oblique short-axis slices and a vibration frequency of 140Hz to obtain global quantitative in vivo left ventricular stiffness measurements. The median stiffness was compared between the two cohorts. An octahedral shear strain signal-to-noise ratio (OSS-SNR) threshold of 1.17 was used to exclude exams with insufficient motion amplitude. Results Five volunteers and 6 patients had to be excluded from the study because they fell below the 1.17 OSS-SNR threshold. The myocardial stiffness of cardiac amyloid patients (median: 11.4 kPa, min: 9.2, max: 15.7) was significantly higher (p = 0.0008) than normal controls (median: 8.2 kPa, min: 7.2, max: 11.8). Conclusions This study demonstrates the feasibility of 3D high-frequency cardiac MRE as a contrast-agent-free diagnostic imaging technique for cardiac amyloidosis.

Photon-counting detector (PCD) CT is a new CT technology utilizing a direct conversion X-ray detector, where incident X-ray photon energies are directly recorded as electronical signals. The design of the photon-counting detector itself facilitates improvements in spatial resolution (via smaller detector pixel design) and iodine signal (via count weighting) while still permitting multi-energy imaging. PCD-CT can eliminate electronic noise and reduce artifacts due to the use of energy thresholds. Improved dose efficiency is important for low dose CT and pediatric imaging. The ultra-high spatial resolution of PCD-CT design permits lower dose scanning for all body regions and is particularly helpful in identifying important imaging findings in thoracic and musculoskeletal CT. Improved iodine signal may be helpful for low contrast tasks in abdominal imaging. Virtual monoenergetic images and material classification will assist with numerous diagnostic tasks in abdominal, musculoskeletal, and cardiovascular imaging. Dual-source PCD-CT permits multi-energy CT images of the heart and coronary arteries at high temporal resolution. In this special review article, we review the clinical benefits of this technology across a wide variety of radiological subspecialties.

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