<p>Low-dose computed tomography of urolithiasis in obese patients: a feasibility study to evaluate image reconstruction algorithms</p>

Abstract

Purpose: Retrospective evaluation and comparison of image quality generated by low-dose computed tomography (LDCT) from obese patients with urolithiasis using alternative reconstruction algorithms. Materials and methods: Twenty-five obese patients (body mass index [BMI]>25 kg/m 2 ) underwent LDCT scans for suspected urolithiasis. The scans were recompiled using filtered-back projection (FBP), statistical iterative reconstruction (iDose) and iterative model-based reconstruction (IMR). Dose-length product (DLP) and patient details were obtained from the CT dose report and clinical charts, respectively. Objective image noise was assessed by measuring the SD of Hounsfield units (HUs) in defined locations. Additionally, subjective image evaluation was independently performed by two radiologists using a 3-point Likert scale. The inter-reviewer agreement of image quality was calculated. Results: Ureteral concretions were observed in all CT scans, two of which revealed bilateral stones. The assessed patients’ mean BMI was 29.29±3.74 kg/m 2 , and the DLP of the CT scans was 100.04±10.00 mGy*cm. All scans were rated diagnostic with the iDose and iterative model-based reconstructions, whereas 41% of the scans performed with FBP reconstruction were nondiagnostic. With respect to image quality, IMR was superior to iDose and FBP, both in the objective ( P <0.001) and overall subjective ( P ≤0.008) evaluation of the respective data sets. The inter-reviewer agreement for overall image quality was “almost perfect” for IMR, “substantial” for iDose and “moderate” for FBP (κ values of 1.0, 0.6 and 0.46, respectively). Conclusion: Using iterative image reconstruction algorithms, LDCT of urolithiasis is feasible in overweight patients with a BMI between 25 and 35 kg/m 2 . Due to higher image quality, IMR is the preferred algorithm for scan reconstruction as it may help to avoid repeated examinations due to initial nondiagnostic scans.

Clinical Low Dose Photon Counting CT for the Detection of Urolithiasis: Evaluation of Image Quality and Radiation Dose

“…Recently published studies based on modern dual-energy CT scanners with optimized scan protocols for the detection and evaluation of kidney and ureter stones report on effective doses of slightly over 3 mSv [ 10 , 14 , 29 , 30 , 31 ]. Although a direct comparison of these studies with the present study appears inappropriate, it nevertheless points to the great potential of PCD detectors to reduce the radiation dose for patients.…”

“…The reduction of radiation dose is often achieved by reducing the tube charge current [ 7 ]. Other approaches, among many others, are based on an increased pitch factor, an additional tin filtration or iterative reconstructions [ 8 , 9 , 10 , 11 , 12 , 13 , 14 ].…”

Detection and size measurements of kidney stones on virtual non-contrast reconstructions derived from dual-layer computed tomography in an ex vivo phantom setup

“…While the used phantom diameter of 280 mm is close to the diameter of the general body phantom (320 mm) used for CT dosimetry, the homogeneous attenuation of water does not represent in vivo conditions and possibly results in an underestimation of radiation dose as compared to the in-vivo setting [33]. Furthermore, it is known that the detection of kidney stones on TNC is hampered in patients with high body mass indices due to a decrease in image quality, which is yet to be shown for VNC [34]. Last, the ex vivo conditions resulted in a bias as to in which position a stone would be expected and will therefore likely overestimate detection rates as compared to a true patient study.…”

Manual kidney stone size measurements in computed tomography are most accurate using multiplanar image reformatations and bone window settings

“…Determination of most reliable measurement techniques and standardization of these procedures are key for obtaining precise and comparable results throughout different studies and in clinical routine 7 , 20 – 22 . While in recent years there has been rapid development towards reducing radiation dose using various image reconstruction techniques, the influence of these more refined techniques on kidney stone size measurements are largely elusive 5 – 7 , 10 .…”