Virtual monoenergetic images from dual-energy CT: systematic assessment of task-based image quality performance

Abstract

Background: To compare task-based image quality (TB-IQ) among virtual monoenergetic images (VMI) and linear-blended images (LBI) from dual-energy CT as a function of contrast task, radiation dose, size, and lesion diameter.Methods: A TB-IQ phantom (Mercury Phantom 4.0, Sun Nuclear Corporation) was imaged on a thirdgeneration dual-source dual-energy CT with 100/Sn150 kVp at three volume CT dose levels (5, 10, 15 mGy).Three size sections (diameters 16, 26, 36 cm) with subsections for image noise and spatial resolution analysis were used. High-contrast tasks (e.g., calcium-containing stone and vascular lesion) were emulated using bone and iodine inserts. A low-contrast task (e.g., low-contrast lesion or hematoma) was emulated using a polystyrene insert. VMI at 40-190 keV and LBI were reconstructed. Noise power spectrum (NPS) determined the noise magnitude and texture. Spatial resolution was assessed using the task-transfer function (TTF) of the three inserts. The detectability index (d') served as TB-IQ metric.Results: Noise magnitude increased with increasing phantom size, decreasing dose, and decreasing VMIenergy. Overall, noise magnitude was higher for VMI at 40-60 keV compared to LBI (range of noise increase, 3-124%). Blotchier noise texture was found for low and high VMIs (40-60 keV, 130-190 keV) compared to LBI. No difference in spatial resolution was observed for high contrast tasks. d' increased with increasing dose level or lesion diameter and decreasing size. For high-contrast tasks, d' was higher at 40-80 keV and lower at high VMIs. For the low-contrast task, d' was higher for VMI at 70-90 keV and lower at 40-60 keV.Conclusions: Task-based image quality differed among VMI-energy and LBI dependent on the contrast task, dose level, phantom size, and lesion diameter. Image quality could be optimized by tailoring VMIenergy to the contrast task. Considering the clinical relevance of iodine, VMIs at 50-60 keV could be proposed as an alternative to LBI.

Phantom task‐based image quality assessment of three generations of rapid kV‐switching dual‐energy CT systems on virtual monoenergetic images

“…The TTF outcomes on these two inserts showed that TTF was weakly influenced by the energy levels on the VMIs. This behavior is different from that usually found in the literature where the TTF decreases as the keV increases from 40 to 70 keV 11,29,30 . However, in these studies, the TTF was calculated with the imQuest software on a low contrast insert (acrylic or polyethylene inserts).…”

“…This behavior is different from that usually found in the literature where the TTF decreases as the keV increases from 40 to 70 keV. 11,29,30 However, in these studies, the TTF was calculated with the imQuest software on a low contrast insert (acrylic or polyethylene inserts). The low keV noise conditions and the low contrast of these inserts led to a relatively low CNR (CNR < 15).…”

Photon-Counting Detector CT With Quantum Iterative Reconstruction

“…[20][21][22] In addition, the routine clinical use of VMIs combined with iterative reconstruction from EID-CT has been limited because of their altered image impression, particularly their blotchier noise texture at low-keV levels. [23][24][25] Virtual monoenergetic images from PCD-CT combined with QIR might offer an improvement in image perception as QIR aims to replicate the noise texture of traditional filtered back projection. Moreover, based on the improved noise properties and the perfect anatomic acquisition registration, PCD-CT has the potential to improve focal liver lesion detection.…”

“…Former studies have shown the benefits of VMIs and iterative reconstruction for energy-integrating detector CT (EID-CT) with regard to image quality, lesion conspicuity, and diagnostic confidence for liver lesions, 15–19 but some studies reported that these improvements in image quality with iterative reconstruction did not necessarily translate into increased overall diagnostic accuracy 20–22 . In addition, the routine clinical use of VMIs combined with iterative reconstruction from EID-CT has been limited because of their altered image impression, particularly their blotchier noise texture at low-keV levels 23–25 . Virtual monoenergetic images from PCD-CT combined with QIR might offer an improvement in image perception as QIR aims to replicate the noise texture of traditional filtered back projection.…”

Fall incidence and associated factors in spinal cord injury patients who walk with or without an ambulatory assistive device

“…However, this methodology has been accepted by multiple researchers who studied on d' of liver lesion in CT based on acrylic insert in image quality phantom. [17][18][19][20] To the knowledge from this study that the d' of low keV VMI is inferior to that from the low-kVp SECT acquisition, the further study should be conducted to study the impact of DECT parameters on d' that may help to improve the d' on VMI images in the future. The phantom study included more clinical lesions is required to add more information relevant to our results.…”