Comparable Image Quality Research Articles

Clinical validation of MR-generated synthetic CT by MRCAT for brain tumor radiotherapy.

MRI is an emerging modality in radiotherapy (RT). Accuracy synthetic CT is the prerequisite for implementing MR-only RT planning. This study validated the commercial algorithm of MR for calculating attenuation (MRCAT) in terms of image quality and dosimetric agreement. Brain tumor cases with 18 treated using intensity-modulated radiotherapy (IMRT) or volumetric modulated arc therapy (VMAT), and 15 treated using stereotactic radiosurgery (SRS) were analyzed. Synthetic CTs were resampled referencing planning CT. Treatment plan calculated on planning CT was recalculated on resampled MRCAT. Image quality of selected metrics and dosimetric agreements were assessed by dose-volume-histogram and 3D gamma analysis. For IMRT/VMAT and SRS cases, mean error were 23.42±1.05 and 28.39±3.17 HU; mean absolute error were 38.03±1.42 and 52.36±2.63 HU; root mean squared error were 89.09±6.65 and 108.38±12.23 HU; peak signal-to-noise ratio were 29.11±0.60 and 27.65±0.59dB; and structural similarity index measures were 0.88±0.00 and 0.70±0.01 respectively. No significant differences were identified for DVH metrics accounting the target coverage. Most OARs did not have significant dose deviation, except left lens with 0.70% higher in D-mean after recalculation (p<0.001). For criteria of 3mm/3%, 2mm/2%, and 1mm/1%, gamma passing rates for IMRT/VMAT were 99.92%, 99.42%, and 96.47%, while SRS were 99.86%, 99.52%, and 97.57% respectively. Correlation between passing rate and image quality metrics was established in IMRT/VMAT cases, with higher similarity yield better dosimetric agreement between planning and synthetic CT. This study has validated the MRCAT for clinical use in terms of comparable image quality and dosimetric agreement with planning CT. Further case selection and MR-compatible immobilization device would be required.

New virtual contrast enhancement boost technique can reduce the dose of intravenous contrast medium used in computer tomography angiography of the abdominal aorta.

This study aims to evaluate the image quality of computed tomography (CT) angiograms obtained using a virtual contrast augmentation technique, adding an iodine map to the contrast-enhanced images, obtained through a digital subtraction technique, reducing the dose of intravenous iodinated contrast medium compared to the conventional institutional standard technique. This prospective investigation enrolled patients previously diagnosed with abdominal aortic aneurysms, who underwent two successive computed tomography angiographies (CTAs) of the aorta. One CTA was performed employing the virtual contrast enhancement boost technique with a 40% decrease in the intravenous contrast medium dose, while the other adhered to the conventional protocol without any reduction in contrast medium volume. After imaging, both qualitative and quantitative assessments were conducted to evaluate the opacification level of the aorta and its branching vessels. The study analyzed 28 examinations from 14 subjects (two per participant). Qualitative analysis revealed that image quality was deemed adequate for diagnostic purposes, with nearly all arterial segments in both protocols rated as good or excellent. Although no statistically significant differences were detected, the average attenuation across all arterial segments in the angiograms exhibited a trend towards higher values in the virtual contrast enhancement boost technique, compared to the conventional protocol. Similarly, the signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) demonstrated comparable levels between the two methodologies. The application of virtual contrast enhancement in the acquisition of CT angiograms of the aorta maintains comparable image quality, while reducing the dosage of intravenous contrast medium by 40%. This approach suggests a potential for optimizing contrast use in vascular imaging, aligning with goals related to patient safety and radiological efficiency.

An investigation into the applicability of rapid artificial intelligence‐assisted compressed sensing in brain magnetic resonance imaging performed at 5 Tesla field strength

AbstractBackgroundBrain magnetic resonance imaging (MRI) at 5 T offers unprecedented spatial resolution but is often limited by long scan times. Acceleration techniques, such as compressed sensing (CS) and artificial intelligence‐assisted compressed sensing (ACS), have the potential to speed up the acquisition process while maintaining image quality. This study aims to evaluate and compare the performance of CS and ACS (with various acceleration factors) in brain MRI imaging at 5 T.MethodsIn this study, we enrolled 12 healthy volunteers and compared ACS‐accelerated 5 T brain MRI with conventional methods of CS. The ACS acceleration factors for the brain protocol, consisting of 3D T1‐weighted sequences and 2D T2‐weighted sequences, were optimized in a pilot study on healthy volunteers (acceleration factor, 2.06–3.41× in T2‐weighted imaging and 3.52–8.49× in T1‐weighted imaging). We evaluated the images acquired from patients using various acceleration methods on the basis of acquisition times, the signal‐to‐noise ratio (SNR), the contrast‐to‐noise ratio, subjective image quality, and diagnostic agreement.ResultsOur findings revealed that ACS acceleration significantly reduced the acquisition times for T1‐ and T2‐weighted sequences by up to 43% and 53%, respectively, compared with traditional CS at 5 T. Importantly, this acceleration was achieved while maintaining excellent image quality, demonstrated by higher or comparable SNR and contrast‐to‐noise ratio values.ConclusionsThe optimal ACS acceleration factors for 5 T brain MRI were determined to be 2.73× for 2D T2‐weighted sequences and 6.5× for 3D T1‐weighted sequences. ACS not only facilitates rapid imaging but also ensures comparable image quality and diagnostic performance, highlighting its potential to revolutionize high‐field MRI scanning.

CT radiation dose reduction with tin filter for localisation/characterisation level image quality in PET-CT: a phantom study

BackgroundThe tin filter has allowed radiation dose reduction in some standalone diagnostic computed tomography (CT) applications. Yet, ‘low-dose’ CT scans are commonly used in positron emission tomography (PET)-CT for lesion localisation/characterisation (L/C), with higher noise tolerated. Thus, dose reductions permissible with the tin filter at this image quality level may differ. The aim was to determine the level of CT dose reduction permitted with the tin filter in PET-CT, for comparable image quality to the clinical reference standard (CRS) L/C CT images acquired with standard filtration.Materials and methodsA whole-body CT phantom was scanned with standard filtration in CRS protocols, using 120 kV with 20mAs-ref for bone L/C (used in 18F-Sodium Fluoride (NaF) PET-CT) and 40mAs-ref for soft tissue L/C (used in 18F-Fluorodeoxyglucose (FDG) PET-CT), followed by tin filter scans at 100 kV (Sn100kV) and 140 kV (Sn140kV) with a range of mAs settings. For each scan, effective dose (ED) in an equivalent-sized patient was calculated, and image quality determined in 5 different tissues through quantitative (contrast-to-noise ratio) and qualitative (visual) analyses. The relative dose reductions which could be achieved with the tin filter for comparable image quality to CRS images were calculated.ResultsQuantitative analysis demonstrated dose savings of 50–76% in bone, 27–51% in lung and 8–61% in soft tissue with use of the tin filter at Sn100kV. Qualitative analysis demonstrated dose reductions using Sn100kV in general agreement with the dose reductions indicated by quantitative analysis. Overall, CT dose reductions of around 85% were indicated for NaF bone PET-CT, allowing whole-body CT at just 0.2mSv ED, and a 30–40% CT dose reduction for FDG PET-CT using Sn100kV (1.7-2.0mSv), providing comparable image quality to current CRS images with standard filtration. Sn140kV demonstrated limited value in CT dose reduction.ConclusionsLarge CT dose reductions can be made using the tin filter at Sn100kV, when imaging bone, lung and soft tissue at L/C level CT image quality in PET-CT. As well as reducing the risk of inducing a cancer in later life, such dose reductions may also impact PET-CT practice, such as justifying cross-sectional over planar imaging or justifying PET-CT in younger patients.

Comparative analysis of image quality and diagnostic performance among SS-EPI, MS-EPI, and rFOV DWI in bladder cancer.

To compare image quality and diagnostic performance among SS-EPI diffusion weighted imaging (DWI), multi-shot (MS) EPI DWI, and reduced field-of-view (rFOV) DWI for muscle-invasive bladder cancer (MIBC). This retrospective study included 73 patients with bladder cancer who underwent multiparametric MRI in our referral center between August 2020 and February 2023. Qualitative image assessment was performed in 73; and quantitative assessment was performed in 66 patients with maximum lesion diameter > 10mm. The diagnostic performance of the imaging finding of muscle invasion was evaluated in 47 patients with pathological confirmation of MIBC. T2-weighted imaging, SS-EPI DWI, MS-EPI DWI, rFOV DWI, and dynamic contrast-enhanced imaging were acquired with 3T-MRI. Qualitative image assessment was performed by three readers who rated anatomical distortion, clarity of bladder wall, and lesion conspicuity using a four-point scale. Quantitative assessment included calculation of SNR and CNR, and grading of the presence of muscle layer invasion according to the VI-RADS diagnostic criteria. Wilcoxon matched pairs signed rank test was used to compare qualitative and quantitative image quality. McNemar test and receiver-operating characteristic analysis were used to compare diagnostic performance. Anatomical distortion was less in MS-EPI DWI, rFOV DWI, and SS-EPI DWI, in that order with significant difference. Clarity of bladder wall was greater for MS-EPI DWI, SS-EPI DWI, and rFOV DWI, in that order. There were significant differences between any two combinations of the three DWI types, except between SS-EPI DWI and MS-EPI in Reader 1. Lesion conspicuity, diagnostic performance, SNR and CNR were not significantly different among the three DWI types. Among the three DWI sequences evaluated, MS-EPI DWI showed the least anatomical distortion and superior bladder wall delineation but no improvement in diagnostic performance for MIBC. MS-EPI DWI may be considered for additional imaging if SS-EPI DWI is of poor quality.

Comprehensive Image Quality Evaluation and Motion Phantom Studies of an Ultra-Fast (6-Second) Cone-Beam Computed Tomography Imaging System on a Ring Gantry Linear Accelerator

PurposeTo evaluate the image quality of an ultra-fast CBCT system - Varian HyperSight. MethodsIn this evaluation, five-studies were performed to assess the image quality of HyperSight CBCT. First, a HyperSight CBCT image quality evaluation was performed and compared with Siemens simulation-CT and Varian TrueBeam CBCT. Second, a visual comparison of image quality among simulation-CTs, HyperSight CBCT and TrueBeam CBCT was performed for a head-and-neck patient, and patients with metal dental fillings and prosthesis. Third, the HU vs electron density curve of HyperSight CBCT was compared with GE and Siemens simulation-CTs. Fourth, Siemens simulation-CT and HyperSight CBCT scans were acquired on the Catphan setting-up at different locations inside the bore (±10cm in all three principal directions from the center), and the HU variations for different materials were evaluated. Fifth, a 4D lung tumor phantom study was performed to assess moving tumor alignment during image registration. ResultsSignificant improvement of image contrast, HU constancy, and noise level on HyperSight CBCT was observed compared to TrueBeam CBCT. Significant image quality improvement was observed on HyperSight CBCT for patients with dental fillings and prosthesis compared to simulation-CT without metal artifact reduction. The linear fit trend-line of HU vs electron density curves for GE simulation-CT, Siemens simulation-CT and HyperSight CBCT showed 0.6% difference for HU value below 2000. The maximum HU difference for HyperSight CBCT when Catphan positioned within ±10cm in all three principal directions was ≤98 on bone 50%, and ≤29 other than bone, and was ≤31 on bone 50%, and ≤17 other than bone for Siemens simulation-CT. Both tumor shape and tumor alignment discrepancies on CBCT scans were observed in 4D phantom study. ConclusionsThis evaluation shows significant image improvement of HyperSight CBCT over conventional CBCT on image contrast, HU constancy, and noise level with scatter correction and metal artifact reduction reconstruction methods. HyperSight CBCT has similar image quality to simulation-CTs, and shows the potential application for treatment planning. The rapid acquisition of HyperSight CBCT showed both tumor shape and tumor alignment discrepancies of moving target. Careful considerations of patient respiratory motion monitoring and target matching are highly recommended.

Contrast-enhanced thin-slice abdominal CT with super-resolution deep learning reconstruction technique: evaluation of image quality and visibility of anatomical structures.

To compare image quality and visibility of anatomical structures on contrast-enhanced thin-slice abdominal CT images reconstructed using super-resolution deep learning reconstruction (SR-DLR), deep learning-based reconstruction (DLR), and hybrid iterative reconstruction (HIR) algorithms. This retrospective study included 54 consecutive patients who underwent contrast-enhanced abdominal CT. Thin-slice images (0.5mm thickness) were reconstructed using SR-DLR, DLR, and HIR. Objective image noise and contrast-to-noise ratio (CNR) for liver parenchyma relative to muscle were assessed. Two radiologists independently graded image quality using a 5-point rating scale for image noise, sharpness, artifact/blur, and overall image quality. They also graded the visibility of small vessels, main pancreatic duct, ureters, adrenal glands, and right adrenal vein on a 5-point scale. SR-DLR yielded significantly lower objective image noise and higher CNR than DLR and HIR (P < .001). The visual scores of SR-DLR for image noise, sharpness, and overall image quality were significantly higher than those of DLR and HIR for both readers (P < .001). Both readers scored significantly higher on SR-DLR than on HIR for visibility for all structures (P < .01), and at least one reader scored significantly higher on SR-DLR than on DLR for visibility for all structures (P < .05). SR-DLR reduced image noise and improved image quality of thin-slice abdominal CT images compared to HIR and DLR. This technique is expected to enable further detailed evaluation of small structures.

Comprehensive image quality comparison of conventional and new flat panel detectors under bedside chest radiography beam conditions.

Recently, a novel wireless flat-panel detector with auto-exposure control has become available. This study aimed to elucidate the potential advantages of the new detector over conventional detectors through a comprehensive analysis of the physical image quality characteristics. Measurements were conducted on two models: new (720C) and conventional (710C) versions; this assessment was performed by assuming the beam quality for bedside chest radiography, utilizing a portable device for X-ray exposure. The detective quantum efficiency (DQE) was computed based on the presampled modulation transfer function (MTF) and normalized noise power spectrum. The validity of the DQE results was verified through the visualization of the analog blurring components and a detailed analysis of the noise components. The spatial frequency at which the presampled MTF value reached 10% was 5.2 cycles/mm for 720C and 3.9 cycles/mm for 710C. The full width at half-maximum of the spatial spreading of analog components was estimated at 0.09mm for 720C and 0.14mm for 710C by the visualization. Regarding the DQE, 720C was superior under low-dose conditions despite no significant differences being observed under high-dose conditions. The new detector demonstrated superior resolution characteristics compared with the conventional detector and an improvement in the DQE under low-dose conditions. However, similar to the conventional detector, a significant dose dependence caused by a structural factor was confirmed for the DQE. These results suggest the existence of an appropriate dose range for maximizing detector performance and provide insights crucial for optimization tasks in the X-ray imaging.

Cardiac functional assessment using prospectively electrocardiography-triggered computed tomography in children with congenital heart disease: Comparison of radiation dose and image quality between heart rate-dependent single-extended and heart rate-independent dual-focused scans

PurposeTo evaluate radiation dose (RD) reduction potential of heart rate-independent dual-focused scan of prospectively electrocardiography (ECG)-triggered computed tomography (CT) for cardiac functional assessment in children with congenital heart disease (CHD), RD and image quality of the scan mode were compared to those of heart rate-dependent single-extended scan. MethodsThis study encompassed 1,252 prospectively ECG-triggered pediatric cardiothoracic CT examinations, including single-focused (a reference in matched comparisons), single-extended (younger patients), and dual-focused (older patients) scans. Propensity score matching was used to reduce the confounding effect of age and sex in two matched groups (MPs) (younger MP: single-focused vs. single-extended; older MP: single-focused vs. dual-focused). CT RD, image noise, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) of the MPs were compared. ResultsThe effective dose of single-extended (1.4 ± 0.5 mSv) and dual-focused (1.1 ± 0.4 mSv) scans were approximately 2.0–3.2 times higher than (depending on heart rate) and approximately 1.8 times (irrespective of heart rate) that of the age- and sex-matched single-focused scans (0.6 ± 0.2 mSv), respectively. Image noise and SNR of single-extended and dual-focused scans were similar to those of the age- and sex-matched single-focused scans (p values > 0.05). The CNR was also comparable between single-focused and single-extended scans (younger MP) (p > 0.05), but a slightly lower CNR of the dual-focused scans compared to single-focused scans was observed in the older MP (p < 0.02). ConclusionFor cardiac functional assessment in children with CHD, heart rate-independent dual-focused prospectively ECG-triggered scan can reduce CT RD, especially at lower heart rates, with comparable image quality, compared to heart rate-dependent single-extended scan.

Myocardial Fibrosis Assessment at 3-T versus 5-T Myocardial Late Gadolinium Enhancement MRI: Early Results.

Background Cardiac MRI at 5 T has recently become available and potentially improves tissue contrast enhancement at gadolinium chelate-enhanced T1-weighted imaging. Purpose To evaluate the feasibility of 5-T myocardial late gadolinium enhancement (LGE) MRI in assessing myocardial fibrosis by comparing image quality and LGE quantification with reference-standard 3-T myocardial LGE MRI. Materials and Methods Consecutive patients with confirmed myocardial fibrosis on previous 3-T MRI scans between January 2023 and July 2023 prospectively underwent follow-up imaging from August 2023 to November 2023. Each participant underwent follow-up 5-T imaging using an identical dose of contrast agent. Radiologist scoring of image quality using a Likert scale (range, 1-5), signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), contrast ratio, and semiautomatic quantitative LGE assessment were obtained and reported as medians and IQRs. Paired Wilcoxon signed rank tests were used to compare characteristics derived at 3-T and 5-T imaging. Results A total of 18 participants (mean age, 49 years ± 17 [SD]; nine male participants) were included, with a mean interval of 6.2 months ± 2.3 between undergoing 3-T and 5-T MRI. Median image quality scores were 4.0 (IQR, 3.0-4.2) at 3 T and 4.0 (IQR, 3.0-4.4) at 5 T (P = .45). SNR at 5 T was higher than at 3 T (183.7 [IQR, 147.2-255.9] vs 125.8 [IQR, 108.2-171.6], respectively; P = .002). Median CNR at 5 T was higher than at 3 T in normal myocardium (50.8 [IQR, 35.4-67.9] vs 16.5 [IQR, 11.3-24.6], respectively) and pericardial fat (21.4 [IQR, 7.1-29.3] vs -5.0 [IQR, -16.4 to -2.3], respectively) (both P < .001). There was no evidence of a difference in the percentage of LGE quantified between 5 T and 3 T (median, 11.8% [IQR, 7.7%-20.5%] vs 12.6% [IQR, 6.6%-20.4%], respectively; P = .81). Conclusion Myocardial LGE MRI at 5 T was found to be feasible, with no evidence of differences in subjective image quality and myocardial fibrosis quantification compared with 3-T myocardial LGE MRI. Furthermore, with use of identical contrast agent doses, SNRs and CNRs were improved at 5 T. Published under a CC BY 4.0 license. Supplemental material is available for this article. See also the editorial by Czum in this issue.

Benefits of front coating crystalline scintillator screens for phase-contrast synchrotron micro-tomography.

Transparent crystalline scintillators such as cerium-doped YAG or LuAG are widely used in X-ray imaging for the indirect detection of X-rays. The application of reflective coatings on the front side to improve the optical gain is common practice for flat panel detectors with CsI or Gd2O2S powder scintillators but still largely unknown for crystalline scintillators such as LuAG. This work shows experimentally and quantitatively how a black and reflective coating on the X-ray side of a 2 mm LuAG:Ce scintillator improves the image quality compared to a 2 mm LuAG:Ce scintillator without a coating. The measurements have been done for two different distances, with 2 m and 29.7 m on the BM18 beamline of the European Synchrotron. The Modulation Transfer Function (MTF) and the Signal-to-Noise-Ratio (SNR2) power spectrum as well as contrast-to-noise ratio are used for comparing image quality. Propagation-based phase contrast strongly enhances the SNR2 amplitudes (gain ≈10 from 2 m to 29.7 m object-detector distance) of the raw images' spectrum independent of the scintillator coating. For both detector positions, the reflective coating is able to raise SNR2 by up to 80% through the improved optical gain, while black coating does the opposite (decrease SNR2 by 20%) with respect to no coating. With the tested optical setups, changes in MTF /sharpness between the coatings are minor. Comparing CNR2 in CT scans of a multi-material sample, in this case an electric motor, we observe the reflective coating yielding better material contrast for plastic and air. Application and effect of Wiener-deconvolution, along with Paganin-type phase retrieval, are also discussed in the context of CT image quality.

Comparison of image quality and lesion conspicuity between conventional and deep learning reconstruction in gadoxetic acid-enhanced liver MRI

ObjectiveTo compare the image quality and lesion conspicuity of conventional vs deep learning (DL)-based reconstructed three-dimensional T1-weighted images in gadoxetic acid-enhanced liver magnetic resonance imaging (MRI).MethodsThis prospective study (NCT05182099) enrolled participants scheduled for gadoxetic acid-enhanced liver MRI due to suspected focal liver lesions (FLLs) who provided signed informed consent. A liver MRI was conducted using a 3-T scanner. T1-weighted images were reconstructed using both conventional and DL-based (AIRTM Recon DL 3D) reconstruction algorithms. Three radiologists independently reviewed the image quality and lesion conspicuity on a 5-point scale.ResultsFifty participants (male = 36, mean age 62 ± 11 years) were included for image analysis. The DL-based reconstruction showed significantly higher image quality than conventional images in all phases (3.71–4.40 vs 3.37–3.99, p < 0.001 for all), as well as significantly less noise and ringing artifacts than conventional images (p < 0.05 for all), while also showing significantly altered image texture (p < 0.001 for all). Lesion conspicuity was significantly higher in DL-reconstructed images than in conventional images in the arterial phase (2.15 [95% confidence interval: 1.78, 2.52] vs 2.03 [1.65, 2.40], p = 0.036), but no significant difference was observed in the portal venous phase and hepatobiliary phase (p > 0.05 for all). There was no significant difference in the figure-of-merit (0.728 in DL vs 0.709 in conventional image, p = 0.474).ConclusionDL reconstruction provided higher-quality three-dimensional T1-weighted imaging than conventional reconstruction in gadoxetic acid-enhanced liver MRI.Critical relevance statementDL reconstruction of 3D T1-weighted images improves image quality and arterial phase lesion conspicuity in gadoxetic acid-enhanced liver MRI compared to conventional reconstruction.Key PointsDL reconstruction is feasible for 3D T1-weighted images across different spatial resolutions and phases.DL reconstruction showed superior image quality with reduced noise and ringing artifacts.Hepatic anatomic structures were more conspicuous on DL-reconstructed images.Graphical

Non-contrast-enhanced MR-angiography of the abdominal arteries: intraindividual comparison between relaxation-enhanced angiography without contrast and triggering (REACT) and 4D contrast-enhanced MR-angiography.

To evaluate Relaxation-Enhanced Angiography without Contrast and Triggering (REACT), a novel 3D isotropic flow-independent non-contrast-enhanced magnetic resonance angiography (non-CE-MRA) for imaging of the abdominal arteries, by comparing image quality and assessment of vessel stenosis intraindidually with 4D CE-MRA. Thirty patients (mean age 35.7 ± 16.8years; 20 females) referred for the assessment of the arterial abdominal vasculature at 3T were included in this retrospective, single-centre study. The protocol comprised both 4D CE-MRA and REACT (navigator-triggering, Compressed SENSE factor 10, nominal scan time 02:54min, and reconstructed voxel size 0.78 × 0.78 × 0.85 mm3). Two radiologists independently evaluated 14 abdominal artery segments for stenoses, anatomical variants, and vascular findings (aortic dissection, abdominal aorta aneurysms and its branches). Subjective image quality was assessed using a 4-point Likert scale (1 = non-diagnostic, 4 = excellent). REACT had a total acquisition time of 5:36 ± 00:40min, while 4D CE-MRA showed a total acquisition time (including the native scan and bolus tracking sequence) of 3:45 ± 00:59min (p = 0.001). Considering 4D CE-MRA as the reference standard, REACT achieved a sensitivity of 87.5% and specificity of 100.0% for relevant (≥ 50%) stenosis while detecting 89.5% of all vascular findings other than stenosis. For all vessels combined, subjective vessel quality was slightly higher in 4D CE-MRA (3.0 [IQR: 2.0; 4.0.]; P = 0.040), although comparable to REACT (3.0 [IQR: 2.0; 3.5]). In a short scan time of about 5min, REACT provides good diagnostic performance for detection of relevant stenoses, variants, and vascular findings of the abdominal arteries, while yielding to 4D CE-MRA comparable image quality.

Image Quality Comparison of Three 3D Mobile X-Ray Imaging Guidance Devices Used in Spine Surgery: A Phantom Study.

An image-quality CT phantom was scanned with three different 3D X-ray imaging guidance devices in the operating theatre: O-Arm, Loop-X, and Airo TruCT. Default acquisition and reconstruction parameters for lumbar spine procedures were used on each device. The tube current was set to a dose level of around 27 mGy. A task-based image quality assessment was performed by calculating the noise power spectrum (NPS) and task transfer function (TTF). A detectability index (d') was calculated for three simulated bone lesions. The noise magnitude of the O-Arm was higher than the Airo TruCT, and the Loop-X had higher noise than the Airo TruCT. The highest average NPS frequency was for the O-Arm images, and the lowest was for the Loop-X. The TTFs at 50% values were similar for the Airo TruCT and Loop-X devices. Compared to Airo TruCT, the TTF at 50% value increased with the O-Arm by 53.12% and 41.20% for the Teflon and Delrin inserts, respectively. Compared to Airo TruCT, the d' value was lower with Loop-X by -26.73%, -27.02%, and -23.95% for lytic lesions, sclerotic lesions, and high-density bone, respectively. Each 3D-imaging spine surgery guidance device has its own strengths and weaknesses in terms of image quality. Cone-beam CT systems apparently offer the best compromise between noise and spatial resolution for spine surgery.

360° CZT-SPECT/CT cameras: 99mTc- and 177Lu-phantom-based evaluation under clinical conditions

PurposeFor the first time, three currently available 360° CZT-SPECT/CT cameras were compared under clinical conditions using phantom-based measurements.MethodsA 99mTc- and a 177Lu-customized NEMA IEC body phantom were imaged with three different cameras, StarGuide (GE Healthcare), VERITON-CT versions 200 (V200) and 400 (V400) (Spectrum Dynamics Medical) under the same clinical conditions. Energy resolution and volumetric sensitivity were evaluated from energy spectra. Vendors provided the best reconstruction parameters dedicated to visualization and/or quantification, based on their respective software developments. For both 99mTc- and 177Lu-phantoms, noise level, quantification accuracy, and recovery coefficient (RC) were performed with 3DSlicer. Image quality metrics from an approach called “task-based” were computed with iQMetrix-CT on 99mTc visual reconstructions to assess, through spatial frequencies, noise texture in the background (NPS) and contrast restitution of a hot insert (TTF). Spatial resolution indices were calculated from frequencies corresponding to TTF10% and TTF50%.ResultsDespite the higher sensitivity of VERITON cameras and the enhanced energy resolution of the V400 (3.2% at 140 keV, 5.2% at 113 keV, and 3.6% at 208 keV), StarGuide presents comparable image quality. This highlights the need to differentiate sensitivity from count quality, which is influenced by hardware design (collimator, detector block) and conditions image quality as well as the reconstruction process (algorithms, scatter correction, noise regulation). For 99mTc imaging, the quantitative image optimization approach based on RCmean for StarGuide versus RCmax for V200 and V400 systems (RCmean/RCmax: 0.9/1.8; 0.5/0.9; 0.5/0.9 respectively—Ø37 mm). SRTB10/50 showed nearly equivalent spatial resolution performances across the different reconstructed images. For 177Lu imaging, the 113 keV imaging of the V200 and V400 systems demonstrated strong performances in both image quality and quantification, while StarGuide and V400 systems offer even better potential due to their ability to exploit signals from both the 113 and 208 keV peaks. 177Lu quantification was optimized according to RCmax for all cameras and reconstructions (1.07 ± 0.09—Ø37 mm).ConclusionsThe three cameras have equivalent potential for 99mTc imaging, while StarGuide and V400 have demonstrated higher potential for 177Lu. Dedicated visual or quantitative reconstructions offer better specific performances compared to the unified visual/quantitative reconstruction. The task-based approach appears to be promising for in-depth comparison of images in the context of system characterization/comparison and protocol optimization.

Feasibility of knee magnetic resonance imaging protocol using artificial intelligence-assisted iterative algorithm protocols: comparison with standard MRI protocols.

To evaluate the image quality and diagnostic performance of AI-assisted iterative algorithm protocols (AIIA) in accelerated fast spin-echo magnetic resonance imaging (MRI) versus standard (SD) fast spin-echo MRI for clinical 3.0 T rapid knee scans. The accelerated sequence, which includes fat-suppression proton density-weighted imaging (FS-PDWI), T2-weighted imaging (T2WI), and T1-weighted imaging (T1WI), was used in conjunction with the SD sequence in 61 patients who underwent MRI scans. SD images were processed using standard reconstruction techniques, while accelerated images utilized AIIA reconstruction. Quantitative assessments of image quality were conducted, measuring noise levels, signal-to-noise ratio (SNR) and contrast signal-to-noise ratio (CNR). Additionally, subjective evaluations were performed using a Likert five-point scale to assess image quality. The SD group completed the entire knee scan in 466 s, while the AIIA group completed the scan in 312 s. Compared to the SD group, the AIIA group had a noticeably higher SNR of T1WI in the femur and subpatellar fat pad (p = 0.04, 0.001). On the other hand, T2WI femur SNR was noticeably higher in the SD group (p = 0.004). Measurements of SNR, CNR and other noise levels showed no statistically significant changes. Compared to the SD group, the AIIA group had significantly higher subjective image quality scores for every sequence (p < 0.05). There was a modest to large intraclass correlation value (ICC = 0.65-0.90) for the anomalies that were examined among readers. Both the AIIA and SD procedures were shown to have comparable diagnostic performance for meniscal and cruciate ligament rupture (p > 0.05). Images processed using AIIA reconstruction were acquired faster while maintaining comparable image quality and diagnostic capability, meeting the requirements for clinical diagnosis.

Deep learning reconstruction of diffusion-weighted brain MRI for evaluation of patients with acute neurologic symptoms

Purpose: We aimed to evaluate whether the deep-learning (DL) accelerated diffusion weighted image (DWI) is clinically feasible for evaluating patients with acute neurologic symptoms, regarding its shorter study time and acceptable image quality. Materials and methods: In this retrospective study, brain images obtained at DWI with a b-value of 0 s/mm2 and DWI with a b-value of 1000 s/mm2 (DWI 1000) from 321 consecutive patients with acute stroke-like symptom were reconstructed with and without DL algorithm. We compare the diagnostic performance between DL-DWI and conventional DWI for detecting brain lesions, including acute infarction. We assessed the diagnostic accuracy of conventional DWI and DL-DWI and compared the results. Qualitative analysis based on image quality was assessed and compared using a five-point visual scoring system. Apparent diffusion coefficients (ADCs) from DWI with and without DL were also compared. Results: The mean acquisition time for the DL-DWI (49 s) was significantly shorter (P < 0.001) than conventional DWI (165 s). Both DWI with and without DL showed similar performance in diagnosing brain lesions especially sensitivity (98.8% in both DWI and DL-DWI) and specificity (99.5% in both DWI and DL-DWI). Overall image quality, gray-white matter and deep gray matter differentiation of two sequences were similar. DL DWI showed more artifacts than DWI. Lesion conspicuity, especially smaller than 5 mm, was better with DL DWI than conventional DWI (p = 0.03). ADC values of white matter, deep gray matter, and pons with DL were lower than conventional DWI. Conclusions: Compared to conventional DWI, DL-DWI achieved comparable image quality and brain lesion visualization for acute neurological symptoms, with a significantly shorter scan time.

124 - Deep Learning Reconstructed Reduced Field-of-View Diffusion Weighted Imaging in Rectal Cancer: Comparison of Image Quality

124 - Deep Learning Reconstructed Reduced Field-of-View Diffusion Weighted Imaging in Rectal Cancer: Comparison of Image Quality

Design and Evaluation of a Weighted Periodic Sparse Array for Low-Complexity 1-D Phased Array Ultrasound Imaging Systems.

A sparse array offers a significant reduction in the complexity of ultrasonic imaging systems by decreasing the number of active elements and associated electrical circuits needed to form a focused beam. Consequently, for 1-D arrays, it has been adopted in the development of miniaturized systems such as portable, handheld, or smartphone-based systems. Previously, we developed an analytic method that can design a pair of 1-D periodic sparse arrays (PSAs) satisfying three specific constraints, which are the array size, desired grating lobe level, and sparseness factor (SF). In this study, we further developed our method by incorporating aperture weighting functions, which take the form of tapered rectangular functions to introduce null points on the beam pattern. These null points effectively suppress grating lobes generated by a matching pair of arrays. The design process commences with determining transmit and receive PSA patterns, followed by deriving corresponding aperture weighting functions. First, aperture functions of a base and weighting arrays are convolved, which is then upsampled to the targeted array size. Finally, the upsampled aperture is convolved to an aperture function of a subarray, resulting in weighted PSAs (wPSAs). Pulsed wave (PW) simulation confirmed improved grating lobe suppression with wPSAs compared to PSAs. Phantom imaging experiments using a 1-D phased array validated the enhanced contrast due to suppressed grating lobes but at the cost of small degradation in lateral resolution. The signal-to-noise ratio (SNR) also gradually declined with the greater SFs, but no significant difference in SNR was observed between wPSAs and PSAs. Finally, in vivo echocardiography imaging highlighted the clinical potential of wPSAs, particularly with high SFs. Overall, these results suggest that wPSAs can effectively enhance contrast compared to PSAs under the given SF or, alternatively, wPSA with greater SFs can achieve comparable image quality to PSAs with lower SFs. In conclusion, the wPSA approach holds promise for further reducing the complexity of ultrasound imaging systems.

Applications of artificial intelligence in radiology

Artificial intelligence (AI) is increasingly finding its way into routine radiological work. Presentation of the current advances and applications of AI along the entire radiological patient journey. Systematic literature review of established AI techniques and current research projects, with reference to consensus recommendations. The applications of AI in radiology cover awide range, starting with AI-supported scheduling and indications assessment, extending to AI-enhanced image acquisition and reconstruction techniques that have the potential to reduce radiation doses in computed tomography (CT) or acquisition times in magnetic resonance imaging (MRI), while maintaining comparable image quality. These include computer-aided detection and diagnosis, such as fracture recognition or nodule detection. Additionally, methods such as worklist prioritization and structured reporting facilitated by large language models enable arethinking of the reporting process. The use of AI promises to increase the efficiency of all steps of the radiology workflow and an improved diagnostic accuracy. To achieve this, seamless integration into technical workflows and proven evidence of AI systems are necessary. Applications of AI have the potential to profoundly influence the role of radiologists in the future.