Investigative Radiology最新文献

Background and objectives: Following endovascular repair of an aortic aneurysm, patients need regular surveillance using CT to exclude endoleaks. The optimal technical parameters for photon-counting detector CT (PCD-CT) have not yet been established in this clinical context. This study examines the impact of the ultra-high resolution (UHR) mode and monoenergetic reconstructions at various keV on the detection of small endoleaks in experimental settings.

Materials and methods: An aneurysm phantom model mimicking medium- and large-sized patients was scanned using PCD-CT. Monoenergetic images (MEIs) were reconstructed with standard resolution at 40, 45, 50, 55, and 60 keV and with UHR at 45, 50, and 55 keV. Three independent blinded radiologists assessed 80 CT series containing 2880 simulated endoleaks with diameters of 2, 4, and 6 mm. The observers' ratings were analyzed and compared with the jackknife alternative free-response operational characteristics (JAFROC1) method by calculating a figure-of-merit for the performance ( A1 ). The Spearman R was calculated for the correlation between A1 and objective image quality.

Results: The best readers' performance was achieved with the 50 keV UHR, 55 keV standard, 55 keV UHR, and 60 keV standard series ( A1 =0.66 to 0.72) in the medium and with the 55 keV standard, 55 keV UHR, and 60 keV standard reconstructions ( A1 = 0.40 to 0.49) in the large phantom. UHR provided higher A1 than the standard reconstruction at 50 keV for 4 to 6 mm endoleaks ( A1 , 0.82 vs. 0.72; P =0.015 in medium and 0.42 vs. 0.30; P =0.028 in large phantom) and for 6 mm endoleaks ( A1 , 0.93 vs. 0.83; P =0.002 in medium and 0.53 vs. 0.36; P =0.013 in large phantom). In both phantoms, readers' performance correlated negatively with image noise (Spearman R =-0.83; P =0.01 in the medium and Spearman R =-0.98; P <0.001 in the large phantom) and showed no correlation with the contrast-to-noise ratio of endoleaks ( P =0.91 and 0.73).

Conclusions: The 55 keV standard or UHR and 60 keV standard reconstructions yielded the best performance for detecting small endoleaks with PCD-CT. The UHR mode improved performance at 50 keV for 4 to 6 mm and 6 mm endoleaks.

Background: Despite the increasing use of MARS (metal artifact reduction sequence) MRI to investigate painful total hip arthroplasties (THA), no validated criteria exist for diagnosing femoral stem loosening.

Purpose: To evaluate MARS MRI for the diagnosis of aseptic stem loosening and determine its diagnostic accuracy.

Materials and methods: One hundred fourteen consecutive cases with THA revision surgery and MARS MRI of the hip were retrospectively included. Two blinded musculoskeletal radiologists independently assessed periprosthetic bone resorption (PPBR), bone marrow edema (BME), periosteal reaction (PR), and periprosthetic osteolysis (PO) in 14 Gruen zones (GZ). Intraoperative findings at revision surgery served as the ground truth. A predictive model was created using binomial logistic regression models to predict the probability of a loose stem with maximizing positive predictive value (PPV) and accuracy. Interobserver reliability was assessed with absolute agreement, Cohen κ and Gwet AC1.

Results: During surgery, 66 stems were fixed and 48 loose. PPBR occurred significantly more frequently in loose stems across all GZs except GZ11. Proximal PPBR was also observed in fixed stems (up to 23%), whereas middle and distal PPBR were rare (≤3%). BME was most prevalent proximally in all stems (fixed/loose: 39%/60%) with significant differences medially and distally. PR was significantly more frequent in loose stems in the middle and distal GZs. PO were rare, most occurred in GZ7. The predictive model considering proximal PPBR, mid-distal PPBR, mid-distal PR, and distal BME performed with a sensitivity of 0.708, specificity of 0.970, PPV 0.944, negative predictive value 0.821. Interobserver agreement (Gwet AC1) in the considered zones was for PPBR between 0.80 and 0.98, BME 0.91 to 0.99, PR 0.87 to 0.97.

Conclusions: MARS MRI is reproducible and accurate for assessing stem loosening. PPBR, BME, and PR can also be found in fixed THA in the proximal region, whereas they indicate loosening in the middle and distal stem region.

Objectives: To evaluate the efficacy of quantitative magnetization transfer (qMT) in quantifying interstitial fibrosis in kidney transplantation (KT) recipients, and to assess its dependence on MRI field strength (1.5T vs 3.0T), in comparison to conventional magnetization transfer imaging (MTI) performed at both 600 Hz and 1000 Hz offset frequencies.

Materials and methods: This cross-sectional study involved 20 patients, 4 to 10 years post-KT, and 31 healthy volunteers (HV). Using 3.0T-MRI, we assessed KT and HV kidneys using MTI, qMT, blood oxygenation-level-dependent (BOLD), and diffusion-weighted imaging (DWI), and at 1.5T-MRI, we also assessed in KT renal fibrosis with MTI and qMT. In addition, we measured fibrogenic cytokine levels in KT and HV using ELISA and assessed fibrosis and cytokine expression in KT biopsy samples.

Results: KT showed renal dysfunction and higher circulating collagen-IV, MCP-1, IL-6, and NGAL than HV. At 3.0T-MRI, both the qMT index f and the MTI index magnetization-transfer ratio (MTR) measured at either 1000 Hz or 600 Hz demonstrated greater KT cortex and medulla fibrosis compared with HV, whereas DWI and BOLD signals showed no difference. Cortical and medullary MTI-MTR-600 Hz and f-qMT were comparable between 1.5T and 3.0T-MRI, whereas MTI-MTR-1000 Hz was not. Inter- and intra-observer reproducibility of qMT and MTR showed consistently high reliability across the cortex and medulla. Histologic cortical fibrosis in KT [11.12% (8.02, 15.32)] correlated directly with f-qMT at 3.0T-MRI (Spearman, P < 0.0001) but not at 1.5T-MRI, and correlated modestly with cortical and medullary MTR at 600 Hz and 1000 Hz at 1.5T but not at 3.0T-MRI. In addition, f correlated with years post-KT.

Conclusions: Both MTI-600 Hz at 1.5T-MRI and qMT at 3.0T-MRI are promising noninvasive tools for evaluating kidney allograft fibrosis, and the choice between them may depend on machine availability. Furthermore, their fidelity between 1.5T and 3.0T-MRI may facilitate clinical translation by affording comparison of renal fibrosis measured on different MRI machines.

Objectives: The aims of the study were to evaluate the spectral performance of an investigational dual-source (DS) scan mode using a tin (Sn) filter on the B-subsystem of a clinical photon-counting detector (PCD) CT system and to demonstrate improved material decomposition performance using clinical examples of bone imaging tasks.

Materials and methods: Calcium inserts (Ca 100, 200 and 300 mg/cc) were placed in water phantoms (30-, 40-, and 50-cm lateral diameter) and scanned on clinical PCD-CT (NAEOTOM Alpha, Siemens) using DS spectral scan mode (QuantumPeak). Two tube potential configurations (70/Sn150 kV and 90/Sn150 kV) were used to scan the phantoms (11 mGy to 41 mGy volume CT dose index). The phantoms were also scanned using the single-source (SS) PCD-CT scan mode at 120 kV and 140 kV tube potential, and on a DS energy-integrating detector (EID) CT (SOMATOM Force, Siemens) for quantitative comparison. CT images (from SS-PCD-CT, DS-PCD-CT, and DS-EID-CT) were reconstructed using a quantitative kernel (Qr40) at a 2-mm section thickness using iterative reconstruction strength 1. Spectral separation was quantified using the dual-energy ratio (DER) of Ca inserts and using mean absolute percent error (MAPE) of Ca mass density obtained from Ca/water material decomposition. To demonstrate clinical feasibility, 4 patients were scanned using DS-PCD-CT under an institutional review board-approved study. Bone edema maps were reconstructed from DS-PCD-CT and compared with the corresponding clinical imaging exam of the same patients (MRI or DS-EID-CT).

Results: DS-PCD-CT at 70/Sn150 kV for Ca 100 mg/cc showed the highest mean DER (2.49 and 2.56 at 30 and 40 cm, respectively) among all scan configurations. For the 50-cm phantom at Ca 100 mg/cc, DS-PCD-CT at 90/Sn150 kV showed highest mean DER (1.88), followed by DS-EID-CT at 90/Sn 150 kV (1.87) and SS-PCD-CT at 140 kV (1.78). The MAPE values for DS-PCD-CT were consistently lower across all phantom sizes (MAPE max. of 1.44%) compared to SS-PCD-CT (MAPE max. 3.97%) and DS-EID-CT (MAPE max. 3.68%). Qualitatively, patient images illustrated bone edema depiction on DS-PCD-CT comparable to clinical MR images, and more precise edema depiction compared to DS-EID-CT images at the site of fractures and intramedullary lesions, and with fewer artifacts.

Conclusions: DS-PCD-CT showed superior spectral performance for calcium imaging tasks compared to SS-PCD-CT and DS-EID-CT.

Objectives: Development of molecular therapies for liver fibrosis is slowed by a lack of noninvasive methods addressing questions of target expression, target engagement, and treatment response. Integrin α v β 6 is a biomarker of liver fibrosis that is upregulated in livers of patients with primary sclerosing cholangitis. It activates latent TGF-β and plays a critical role in regulating extracellular matrix expression, especially collagen. In this study, our aim was to use combined α v β 6 integrin-targeted positron emission tomography (PET) and collagen-specific magnetic resonance imaging (MRI) to measure target expression/engagement and liver fibrosis reduction with a α v β 6 integrin inhibitor.

Materials and methods: We conducted a treatment study in bile duct-ligated (BDL) rats using a small molecule inhibitor to α v β 6 /α v β 1 . 68 Ga-DOTA-R01-MG, an α v β 6 -specific PET probe, was used to noninvasively measure α v β 6 expression and target engagement in the liver. CM-101, a type I collagen MRI probe, was used to quantify fibrosis.

Results: 68 Ga-DOTA-R01-MG PET showed 3-fold higher liver uptake in BDL rats compared with sham rats at 17 days after surgery. Pretreatment with high dose α v β 6 /α v β 1 inhibitor 1 hour before imaging significantly decreased liver PET uptake in BDL rats (31%, P  = 0.012). Two weeks of daily dosing with an α v β 6 /α v β 1 inhibitor attenuated α v β 6 expression in BDL rat liver as assessed by α v β 6 PET (0.27 ± 0.07 percent injected dose [%ID]/mL compared with 0.40 ± 0.09 %ID/mL in vehicle-treated group, P  = 0.014) and reduced liver fibrosis as assessed by collagen MRI (liver relaxation rate change ΔR 1  = 0.14 ± 0.11 vs 0.36 ± 0.06, P  = 0.0037). Imaging findings were confirmed by histology (collagen proportionate area 10.7 ± 2.8% vs 22.5 ± 6.1%, P  < 0.001).

Conclusions: A single imaging protocol combining molecular MRI and PET can be used to effectively monitor integrin inhibitor treatment by measuring target expression/engagement and treatment outcomes. Multimodality molecular imaging may be valuable in accelerating drug development in molecular therapies for liver fibrosis.

Objectives: The introduction of photon-counting detector computed tomography (PCCT) has allowed for significant dose reductions compared to energy-integrating-detector CT, making it particularly relevant for applications such as lung cancer screening. Coronary artery calcification is an important incidental finding in lung cancer screening, warranting attention in this context. This study aims to assess the impact of dose reduction to levels comparable to that of a chest radiography on opportunistic evaluation of coronary artery calcification on PCCTs of the chest.

Materials and methods: Sixty-eight out of 115 patients with age >45 years and body mass index ≤30 kg/m 2 undergoing noncontrast low- and chest-radiography-comparable-dose PCCT in the same session were included. Scans were performed at 100 kVp with image quality settings 12 (low-dose) and 2 (radiography-comparable-dose). Visual calcium scoring was conducted by 2 readers using 2 scoring approaches (CAD-RADS 2.0 and Shemesh). Semiautomated quantitative analysis was performed using commercially available software. Image quality was evaluated using 5-point Likert scales.

Results: Sixty-eight patients (65.9 ± 8.6 years; 49 men) were subjected to evaluation. CTDI was lower for radiography-dose scans (0.11 mGy vs 0.68 mGy; P  < 0.001). Image quality was found to be inferior for radiography-dose scans (4.01 vs 2.03; P  < 0.001). In both visual scoring approaches, coronary calcification was scored significantly lower in radiography-dose scans ( P  < 0.001 for both) with almost perfect reader agreement (CAD-RADS score Cohen's kappa =0.82; Shemesh score Cohen's kappa =0.81), most importantly reclassification from mild to absent occurred for CAD-RADS score in 31%/21% of cases and for Shemesh score in 23%/15% of cases (reader 1/reader 2). Semiautomated assessment showed no significant differences between low and radiography dose ( P  = 0.121). Strong correlation between scores (Pearson's r = 0.98, P  < 0.001) with good agreement (Cohen's kappa =0.61) was found.

Conclusions: Coronary artery calcifications are underestimated on radiography-dose PCCT visually, whereas semiautomatic analysis provides more robust results. Visual underestimation of coronary artery calcification in low-dose imaging is further amplified with the additional dose reduction to radiography-comparable dose levels, indicating that while estimation of high cardiovascular risk is feasible, exclusion of such risk is not possible.

Objective: The aim of the study is to compare the image quality and homogeneity of vessel enhancement in high-pitch CT-angiography of the aorta (CTA) prior to transcatheter aortic valve implantation between bolus tracking with a fixed trigger delay and bolus tracking with a patient-specific trigger delay.

Materials and methods: In this retrospective study, consecutive patients who received a CTA of the aorta prior to transcatheter aortic valve implantation between January 2023 and June 2024 were included. Patients were imaged using either bolus tracking and a fixed trigger delay (Group A; 15 seconds) or bolus tracking and a patient-specific trigger delay (Group B; FAST Bolus; Siemens Healthineers AG). The same contrast injection and scan protocol were used in both groups. Vessel enhancement was measured at multiple craniocaudal locations. Subjective image quality was assessed by 2 readers using 5-point Likert scales. Likert scores were analyzed using Wilcoxon rank-sum tests. Enhancement was assessed with a mixed-effects model.

Results: Sixty-five patients (28 females) were assessed in each group. Patient demographics (both 74 ± 12 years; P  = 0.58, body mass index: 26.0 vs 26.2 kg/m 2 ; P  = 0.79) and radiation dose (CTDI vol : 3.4 vs 3.5 mGy; P  = 0.55) did not differ significantly between the two groups. Mean CT attenuation was 489 HU versus 469 HU in the ascending aorta and 428 HU versus 464 HU in the common femoral artery for fixed and patient-specific delays, respectively. Enhancement in the femoral arteries was significantly lower in the fixed delay group ( P  < 0.05), while there was no significant difference at other vessel locations. Diagnostic image quality and enhancement at the femoral artery were rated significantly better for the patient-specific trigger delay by one reader (both P  < 0.05).

Conclusions: Bolus tracking with a patient-specific trigger delay improved the craniocaudal homogeneity of vessel enhancement and subjective image quality at the distal access site as compared to bolus tracking with a fixed trigger delay in high-pitch CTA prior to TAVI.

Objectives: Spontaneous coronary artery dissection (SCAD) is a rare cause of acute coronary syndrome and myocardial infarction. Accurate diagnosis is crucial for appropriate management. This study aimed to compare late enhancement (LE) imaging using photon-counting detector (PCD)-CT with cardiac MRI in patients with SCAD in the acute phase and during follow-up and to introduce a novel approach for visualizing myocardial extracellular volume (ECV) distribution in the myocardium.

Materials and methods: This single-center prospective study enrolled patients with SCAD diagnosed with invasive coronary angiography. LE iodine imaging with spectral dual-source PCD-CT and cardiac MRI was performed early after symptom onset and at short-term follow-up. CT included coronary angiography and LE imaging (5 minutes after contrast). LE CT was assessed using the combination of conventional LE images, overlay images, polar maps, and with newly developed atlas maps. Atlas maps represent 2-dimensional maps with prefiltering applied to enable a simpler and more intuitive reading of ECV distribution across the myocardium. Cardiac MRI served as the reference standard for identifying pathologic myocardial segments based on late gadolinium enhancement (LGE) and edema on T2-weighted and T2-mapping images. Agreement between modalities was evaluated using Cohen's κ.

Results: Seventeen patients (median age, 44 years [interquartile range, 36-52]; 11 women) underwent 24 LE CT and cardiac MRI scans. Sixteen patients (median age, 44 years; 10 women) underwent acute phase imaging (median 6 days after symptom onset), and 8 patients (median age, 45 years; 6 women) underwent follow-up imaging (median 120 days after symptom onset). Atlas maps were helpful in detecting segments with pathological ECV and to adjudicate corresponding myocardial segments. Agreement between LE CT with LGE cardiac MRI was strong in the acute phase (κ = 0.832), improving to almost perfect when comparing LE-CT with both LGE and edema in cardiac MRI (κ = 0.944). At follow-up imaging, agreement further improved as edema resolved (κ = 0.956).

Conclusions: LE imaging with PCD-CT demonstrated strong agreement with cardiac MRI for detecting myocardial injury in SCAD, which further improved at follow-up when edema resolved. Newly introduced atlas maps proved useful for a simple and intuitive visualization of myocardial injury.