Abstract Purpose Multiparametric MRI (mpMRI) has an emerging role in prostate cancer (PC) diagnostics. In addition, clinical information are reliable predictors for significant PC (sPC). We analyzed ...if the negative predictive value (NPV) of mpMRI to rule out sPC could be improved by using clinical factors, especially prostate specific antigen (PSA)-density. Methods 1040 consecutive men with suspicion of PC underwent mpMRI first, followed by transperineal systematic and MRI/TRUS-fusion-guided biopsy. Logistic regression analyses were performed to test different clinical factors as predictors of sPC and to build nomograms. To simplify these for clinical use, patients were stratified to three PSA-density groups (1: <0.07, 2: 0.07-0.15; 3: >0.15). After stratification, NPVs for PI-RADS Likert score<3 were calculated. sPC was defined as Gleason score (GS)≥3+4. High-grade PC was defined as GS≥4+3. Results Overall, 451 men were diagnosed with sPC and 187 had a GS≥4+3. In ROC curve analyses the predictive power of the developed nomogram for sPC showed a higher AUC compared to PI-RADS alone (0.79 vs. 0.75, p<0.001). The NPV to harbor sPC increased for men with unsuspicious MRI from 79% up to 89% when these men had a PSA-density ≤0.15. In the repeat biopsy setting the NPV for sPC increased from 83% to 93%. The NPV to harbor high-grade PC increased from 92% up to 98% in the entire cohort. Conclusion Using PSA-density in combination with mpMRI improves the NPV of PI-RADS scoring. By increasing the probability of ruling-out sPC, approximately 20% of unnecessary biopsies could be avoided safely.
Objectives
The purpose of this study was to investigate the association of relaxation-compensated chemical exchange saturation transfer (CEST) MRI with overall survival (OS) and progression-free ...survival (PFS) in newly diagnosed high-grade glioma (HGG) patients.
Methods
Twenty-six patients with newly diagnosed high-grade glioma (WHO grades III–IV) were included in this prospective IRB-approved study. CEST MRI was performed on a 7.0-T whole-body scanner. Association of patient OS/PFS with relaxation-compensated CEST MRI (amide proton transfer (APT), relayed nuclear Overhauser effect (rNOE)/NOE, downfield-rNOE-suppressed APT (dns-APT)) and diffusion-weighted imaging (apparent diffusion coefficient) were assessed using the univariate Cox proportional hazards regression model. Hazard ratios (HRs) and corresponding 95% confidence intervals were calculated. Furthermore, OS/PFS association with clinical parameters (age, gender, O6-methylguanine-DNA methyltransferase (MGMT) promotor methylation status, and therapy: biopsy + radio-chemotherapy vs. debulking surgery + radio-chemotherapy) were tested accordingly.
Results
Relaxation-compensated APT MRI was significantly correlated with patient OS (HR = 3.15,
p
= 0.02) and PFS (HR = 1.83,
p
= 0.009). The strongest association with PFS was found for the dns-APT metric (HR = 2.61,
p
= 0.002). These results still stand for the relaxation-compensated APT contrasts in a homogenous subcohort of
n
= 22 glioblastoma patients with isocitrate dehydrogenase (IDH) wild-type status. Among the tested clinical parameters, patient age (HR = 1.1,
p
= 0.001) and therapy (HR = 3.68,
p
= 0.026) were significant for OS; age additionally for PFS (HR = 1.04,
p
= 0.048).
Conclusion
Relaxation-compensated APT MRI signal intensity is associated with overall survival and progression-free survival in newly diagnosed, previously untreated glioma patients and may, therefore, help to customize treatment and response monitoring in the future.
Key Points
• Amide proton transfer (APT) MRI signal intensity is associated with overall survival and progression in glioma patients.
• Relaxation compensation enhances the information value of APT MRI in tumors.
• Chemical exchange saturation transfer (CEST) MRI may serve as a non-invasive biomarker to predict prognosis and customize treatment.
Abstract
Roentgen’s photographs with the “new kind of rays” triggered a worldwide storm of enthusiasm in all social circles. It was a stroke of luck that the photographic dry plates available to him ...were also sensitive to invisible X-rays. The discovery, research and utilization of X-rays are based on methods for making them visible, from fluorescent screens to photographic plates and digital X-ray detectors. From this point of view, this paper aims to outline the 125-year success story of X-ray imaging from its discovery to the recent development of photon-counting detectors. The scientific-historical view during the transition from the 19
th
to the 20
th
century reveals an impressive period of profound scientific and social upheaval in which revolutionary discoveries and technological developments led to enormous progress in medicine. The cross-fertilization of physics and medicine and their combination with inventiveness, engineering and entrepreneurial spirit created the impressive possibilities of today’s imaging diagnostics. This contribution accompanies the Roentgen Lecture the author gave on November 13, 2020 in Roentgen’s birth house as part of its inauguration and the closing ceremony of the 101
st
Congress of the German Roentgen Society in Remscheid-Lennep.
Key Points:
The development of computed tomography was a milestone in the methodological advancement of imaging with X-rays.
In the detector pixel invisible X-rays are converted into digital electrical impulses, which the computer uses to create images.
Photon-counting detectors could have significant diagnostic advantages for clinical applications.
Citation Format
Schlemmer H, The Eye of the CT Scanner: The story of learning to see the invisible or from the fluorescent screen to the photon-counting detector. Fortschr Röntgenstr 2021; 193: 1034 – 1048
Zusammenfassung
Röntgens Fotografien mit der „neuen Art von Strahlen“ lösten einen weltweiten Begeisterungssturm in allen gesellschaftlichen Kreisen aus. Dabei war es ein Glücksfall, dass die ihm zu Verfügung stehenden fotografischen Trockenplatten auch für die unsichtbaren X-Strahlen empfindlich waren. Entdeckung, Erforschung und Nutzbarmachung von Röntgenstrahlen beruhen auf Methoden zur deren Sichtbarmachung, vom Fluoreszenzschirm über die Fotoplatte bis hin zum digitalen Röntgendetektor. Aus diesem Blickwinkel heraus möchte diese Arbeit die 125-jährige Erfolgsgeschichte der Röntgenbildgebung von der Entdeckung bis zur jüngsten Entwicklung photonenzählender Detektoren skizzieren. Die wissenschaftshistorische Betrachtung am Übergang des 19. zum 20. Jahrhundert offenbart eine eindrucksvolle Zeit tiefgreifender wissenschaftlicher und gesellschaftlicher Umbrüche, in der revolutionäre Entdeckungen und technologische Entwicklungen zu gewaltigen Fortschritten der Medizin führten. Die gegenseitige Befruchtung von Physik und Medizin und deren Verquickung mit Erfindergeist, Ingenieurskunst und unternehmerischem Geschick schufen die eindrucksvollen Möglichkeiten der bildgebenden Diagnostik von heute. Diese Arbeit begleitet die Röntgenvorlesung, die der Autor am 13. November 2020 im Röntgen-Geburtshaus im Rahmen von dessen Eröffnung sowie des feierlichen Abschlusses des 101. Deutschen Röntgenkongresses in Remscheid-Lennep gehalten hat.
Kernaussagen:
Die Entwicklung der Computertomografie markiert einen Meilenstein der methodischen Weiterentwicklung der Bildgebung mit Röntgenstrahlen.
Im Detektorpixel werden die unseren Sinnen unzugänglichen Röntgenstrahlen in digitale elektrische Impulse umgewandelt, aus denen der Computer die Bilder errechnet.
Photonenzählende Röntgendetektoren lassen deutliche diagnostische Vorteile für klinische Anwendungen erwarten.
Zitierweise
Schlemmer H, The Eye of the CT Scanner: The story of learning to see the invisible or from the fluorescent screen to the photon-counting detector. Fortschr Röntgenstr 2021; 193: 1034 – 1049
Purpose
Dynamic glucose‐enhanced (DGE)‐MRI based on chemical exchange‐sensitive MRI, that is, glucoCEST and gluco‐chemical exchange‐sensitive spin‐lock (glucoCESL), is intrinsically prone to ...motion‐induced artifacts because the final DGE contrast relies on the difference of images, which were acquired with a time gap of several mins. In this study, identification of different types of motion‐induced artifacts led to the development of a 3D acquisition protocol for DGE examinations in the human brain at 7 T with improved robustness in the presence of subject motion.
Methods
DGE‐MRI was realized by the chemical exchange‐sensitive spin‐lock approach based either on relaxation rate in the rotating frame (R1ρ)‐weighted or quantitative R1ρ imaging. A 3D image readout was implemented at 7 T, enabling retrospective volumetric coregistration of the image series and quantification of subject motion. An examination of a healthy volunteer without administration of glucose allowed for the identification of isolated motion‐induced artifacts.
Results
Even after coregistration, significant motion‐induced artifacts remained in the DGE contrast based on R1ρ‐weighted images. This is due to the spatially varying sensitivity of the coil and was found to be compensated by a quantitative R1ρ approach. The coregistered quantitative approach allowed the observation of a clear increase of the DGE contrast in a patient with glioblastoma, which did not correlate with subject motion.
Conclusion
The presented 3D acquisition protocol enables DGE‐MRI examinations in the human brain with improved robustness against motion‐induced artifacts. Correction of motion‐induced artifacts is of high importance for DGE‐MRI in clinical studies where an unambiguous assignment of contrast changes due to an actual change in local glucose concentration is a prerequisite.
Purpose To evaluate a radiomics model of Breast Imaging Reporting and Data System (BI-RADS) 4 and 5 breast lesions extracted from breast-tissue-optimized kurtosis magnetic resonance (MR) imaging for ...lesion characterization by using a sensitivity threshold similar to that of biopsy. Materials and Methods This institutional study included 222 women at two independent study sites (site 1: training set of 95 patients; mean age ± standard deviation, 58.6 years ± 6.6; 61 malignant and 34 benign lesions; site 2: independent test set of 127 patients; mean age, 58.2 years ± 6.8; 61 malignant and 66 benign lesions). All women presented with a finding suspicious for cancer at x-ray mammography (BI-RADS 4 or 5) and an indication for biopsy. Before biopsy, diffusion-weighted MR imaging (b values, 0-1500 sec/mm
) was performed by using 1.5-T imagers from different MR imaging vendors. Lesions were segmented and voxel-based kurtosis fitting adapted to account for fat signal contamination was performed. A radiomics feature model was developed by using a random forest regressor. The fixed model was tested on an independent test set. Conventional interpretations of MR imaging were also assessed for comparison. Results The radiomics feature model reduced false-positive results from 66 to 20 (specificity 70.0% 46 of 66) at the predefined sensitivity of greater than 98.0% 60 of 61 in the independent test set, with BI-RADS 4a and 4b lesions benefiting from the analysis (specificity 74.0%, 37 of 50; 60.0% nine of 15) and BI-RADS 5 lesions showing no added benefit. The model significantly improved specificity compared with the median apparent diffusion coefficient (P < .001) and apparent kurtosis coefficient (P = .02) alone. Conventional reading of dynamic contrast material-enhanced MR imaging provided sensitivity of 91.8% (56 of 61) and a specificity of 74.2% (49 of 66). Accounting for fat signal intensity during fitting significantly improved the area under the curve of the model (P = .001). Conclusion A radiomics model based on kurtosis diffusion-weighted imaging performed by using MR imaging machines from different vendors allowed for reliable differentiation between malignant and benign breast lesions in both a training and an independent test data set.
RSNA, 2018 Online supplemental material is available for this article.
OBJECTIVEThe aim of this study was to compare changes in the signal intensity (SI) ratio of the dentate nucleus (DN) to the pons, DN to cerebrospinal fluid (CSF), and globus pallidus (GP) to thalamus ...on unenhanced T1-weighted magnetic resonance imaging (MRI) scans after serial injections of the macrocyclic gadolinium-based contrast agent gadobutrol.
MATERIALS AND METHODSThirty patients who had received at least 5 MRI examinations (plus an additional last MRI for reference) with the exclusive use of gadobutrol, resulting in a total cumulative dose of 54.1 ± 30.4 mL gadobutrol, were analyzed retrospectively. Signal intensity ratio differences were calculated for DN-to-pons, DN-to-CSF, and GP-to-thalamus ratios by subtracting the SI ratio at the first MRI from the SI ratio at the last MRI scan. One-sample t tests were employed to examine if they differed from 0. Regression and correlational analyses were performed to examine whether the SI ratio differences were predicted by a number of control variables.
RESULTSSignal intensity ratio differences did not differ significantly from 0, neither for the DN-to-pons ratio (−0.0035 ± 0.0476, P = 0.69), the DN-to-CSF ratio (−0.0539 ± 0.3217, P = 0.37), nor the GP-to-thalamus ratio (−0.0020 ± 0.0211, P = 0.60). None of the control variables predicted changes in SI ratios.
CONCLUSIONSIn contrast to a recently published study, we did not find signal increases in the DN or in the GP after serial injections of gadobutrol, even though the total dose applied here was considerably larger than in the respective study. This finding adds further support to the hypothesis that the molecular structure of a gadolinium-based contrast agent as either macrocyclic or linear is a crucial factor for its potential to cause gadolinium deposition in the brain. Future studies should further assess this hypothesis by additional animal investigations as well as histopathological and clinical correlation studies.
Clinical photon-counting CT (PCCT) offers a spatial resolution of about 200 µm and might allow for acquisitions close to conventional dental CBCTs. In this study, the capabilities of this new system ...in comparison to dental CBCTs shall be evaluated. All 8 apical osteolysis identified in CBCT were identified by both readers in all three PCCT scan protocols. Mean visibility scores showed statistical significant differences for root canals(p = 0.0001), periodontal space(p = 0.0090), cortical(p = 0.0003) and spongious bone(p = 0.0293) in favor of high and medium dose PCCT acquisitions. Overall, both devices showed excellent image quality of all structures assessed. Interrater-agreement showed high values for all protocols in all structures. Bland-Altman plots revealed a high concordance of both modalities with the reference measurements. In vitro, ultra-high resolution PCCT can reliably identify different diagnostic entities and structures relevant for dental diagnostics similar to conventional dental CBCT with similar radiation dose. Acquisitions of five cadaveric heads were performed in an experimental CT-system containing an ultra-high resolution PC detector (0.25 mm pixel size in isocenter) as well as in a dental CBCT scanner. Acquisitions were performed using dose levels of 8.5 mGy, 38.0 mGy and 66.5 mGy (CTDI16cm) in case of PCCT and of 8.94 mGy (CTDI16cm) in case of CBCT. The quality of delineation of hard tissues, root-canals, periodontal-space as well as apical osteolysis was assessed by two readers. Mean visibility scores and interrater-agreement (overall agreement (%)) were calculated. Vertical bone loss (bl) and thickness (bt) of the buccal bone lamina of 15 lower incisors were measured and compared to reference measurements by ore microscopy and clinical probing.
Purpose
In clinics, only iodine‐ and barium‐based contrast agents are currently used for contrast‐enhanced x‐ray computed tomography (CT). Recently, the introduction of new photon‐counting (PC) ...detectors increased the interest in developing new contrast agents based on heavier elements. These elements may provide more contrast and spectral information compared to iodine and barium thanks to their k‐edges at higher energies. In this paper, the potential of high‐Z elements in contrast‐enhanced CT was evaluated for different patient sizes and x‐ray spectra using a PC detector.
Methods
An adult liver phantom with five high‐Z element solutions (iodine, gadolinium, ytterbium, tungsten, and bismuth) was scanned with a whole‐body photon‐counting computed tomography (PCCT) prototype. For each element, the contrast‐to‐noise ratio at unit concentration and at unit dose (CNRCD) was evaluated in low threshold images (T0=20keV) as function of the tube voltage (80, 100, 120, and 140 kV) and in bin images (tube voltage = 120 kV) as function of the higher threshold (T0=20keV and T1∈50,90keV). Simulations were performed for validation with measurements and to investigate more elements (cerium and gold), different patient sizes (infant, adult, and obese), and spectrum filtration (with and without 0.4‐mm tin filter). The dose reductions associated with the CNRCD improvements over iodine were quantified as well.
Results
CNRCD improvements and dose reductions depend on the investigated scenario. For the infant phantom, dose reductions around 30% were reached using cerium or gadolinium in combination with the tin filter. For the adult and obese phantom, reductions around 50% were provided by gadolinium or ytterbium in combination with the tin filter. Independently of the high‐Z element, the CNRCD of two optimally combined bin images was higher than the CNRCD of the low threshold image. Good agreement was found between measurements and simulations.
Conclusions
Between the investigated elements, gadolinium resulted to have the highest potential as novel contrast agent in PCCT, providing significant dose reductions for all patient sizes. Compared to the other elements, the implementation of gadolinium as CT contrast agent may be facilitated since it is already deployed as contrast agents for magnetic resonance imaging.
Purpose To determine the effect of more than 20 serial injections of macrocyclic gadolinium-based contrast agents (GBCAs) on the signal intensity (SI) of the dentate nucleus (DN) on unenhanced ...T1-weighted magnetic resonance (MR) images. Materials and Methods In this retrospective, institutional review board-approved study, 33 patients who underwent at least 20 consecutive MR imaging examinations (plus an additional MR imaging for reference) with the exclusive use of macrocyclic GBCAs gadoterate meglumine and gadobutrol were analyzed. SI ratio differences were calculated for DN-to-pons and DN-to-middle cerebellar peduncle (MCP) ratios by subtracting the SI ratio at the first MR imaging examination from the SI ratio at the last MR imaging examination. One-sample t tests were used to examine if the SI ratio differences differed from 0, and Bayes factors were calculated to quantify the strength of evidence for each test. Results Patients underwent a mean of 23.03 ± (standard deviation) 4.20 GBCA administrations (mean accumulated dose, 491.21 mL ± 87.04 of a 0.5 M GBCA solution) with an average of 12.09 weeks ± 2.16 between every administration. Both ratio differences did not differ significantly from 0 (DN-to-pons ratio: -0.0032 ± 0.0154, P = .248; DN-to-MCP ratio: -0.0011 ± 0.0093, P = .521), and one-sided Bayes factors provided substantial to strong evidence against an SI ratio increase (Bayes factor for DN-to-pons ratio = 0.09 and that for DN-to-MCP ratio = 0.12). Conclusion The study indicates that 20 or more serial injections of macrocyclic GBCAs administered with on average 3 months between each injection are not associated with an SI increase in the DN.
RSNA, 2016.
PDF
