•Most of cancers enhanced within 31 s after injection on the HTR-DCE sequence.•Abbreviated protocol had better diagnostic performance to FAST and FULL protocol.•An Abbreviated protocol could have ...avoided unnecessary biopsies for 10.6%.•Acquisition time is shorter (7 min 48 s versus 13 min 54 s).
We evaluated the diagnostic value of a high temporal resolution (HTR) dynamic contrast enhanced (DCE) sequence added to a FAST protocol.
120 women (mean age = 55 years (28–88)) who underwent breast MRI between July 2016 and March 2017 and in whom a biopsy was performed (i.e., gold standard) (n = 179: 69 benign, 7 borderline and 103 malignant lesions) were retrospectively and consecutively included. Two readers classified lesions according to the Breast Imaging-Reporting and Data System (BI-RADS) by reading: a FAST protocol (T1W, T2W, T1W-fat saturated 2 min after injection) and then a FULL standard protocol. Independently they determined if lesions were visible and when (Time To Enhancement (TTE)) on the HTR-DCE sequence. An Abbreviated protocol was then built using data from the HTR-DCE sequence added to the FAST protocol.
All lesions were visible with the FAST protocol. 171/179 (95.5%) lesions were detected by reading theHTR-DCE sequence. There were a higher number of cancers rated BI-RADS 3 (PPV of malignancy of 27.6% (8/29) in FAST versus 18.7% (3/16) FULL protocol). An early enhancement on the HTR-DCE sequence (TTE < 31 s) was associated with malignancy with an OR 5.6 (CI 95%: 3.3–20.4) (p < 0.0001). Adding a TTE < 31 s to FAST analysis (AUROC = 0.826) significantly improved lesion characterization with a diagnostic gain of 10.6% (19/179) lesions correctly reclassified (p = 0.0034) compared to FAST protocol; with shorter acquisition time (7 min 48 s versus 13 min 54 s).
Adding an HTR-DCE sequence to a FAST protocol increases diagnostic performance reaching that of the FULL protocol while reducing acquisition time.
To evaluate the added value of ULTRAFAST-MR sequence to an abbreviated FAST protocol in comparison with FULL protocol to distinguish benign from malignant lesions in a population of women, regardless ...of breast MR imaging indication.
From March 10th to September 22th, 2014, we retrospectively included a total of 70 consecutive patients with 106 histologically proven lesions (58 malignant and 48 benign) who underwent breast MR imaging for preoperative breast staging (n=38), high-risk screening (n=7), problem solving (n=18), and nipple discharge (n=4) with 12 time resolved imaging of contrast kinetics (TRICKS) acquisitions during contrast inflow interleaved in a regular high-resolution dynamic MRI protocol (FULL protocol). Two readers scored MR exams as either positive or negative and described significant lesions according to Bi-RADS lexicon with a TRICKS images (ULTRAFAST), an abbreviated protocol (FAST) and all images (FULL protocol). Sensitivity, specificity, positive and negative predictive values, and accuracy were calculated for each protocol and compared with McNemar’s test.
For all readers, the combined FAST–ULTRAFAST protocol significantly improved the reading with a specificity of 83.3% and 70.8% in comparison with FAST protocol or FULL protocol, respectively, without change in sensitivity. By adding ULTRAFAST protocol to FAST protocol, readers 1 and 2 were able to correctly change the diagnosis in 22.9% (11/48) and 10.4% (5/48) of benign lesions, without missing any malignancy, respectively. Both interpretation and image acquisition times for combined FAST-ULTRAFAST protocol and FAST protocol were shorter compared to FULL protocol (p<0.001).
Compared to FULL protocol, adding ULTRAFAST to FAST protocol improves specificity, mainly in correctly reclassifying benign masses and reducing interpretation and acquisition time, without decreasing sensitivity.
Purpose
To quantitatively evaluate a superresolution technique for 3D, one‐millimeter isotropic diffusion‐weighted imaging (DWI) of the whole breasts.
Methods
Isotropic 3D DWI datasets are obtained ...using a combination of (i) a readout‐segmented diffusion‐weighted‐echo‐planar imaging (DW‐EPI) sequence (rs‐EPI), providing high in‐plane resolution, and (ii) a superresolution (SR) strategy, which consists of acquiring 3 datasets with thick slices (3 mm) and 1‐mm shifts in the slice direction, and combining them into a 1 × 1 × 1‐mm3 dataset using a dedicated reconstruction. Two SR reconstruction schemes were investigated, based on different regularization schemes: conventional Tikhonov or Beltrami (an edge‐preserving constraint). The proposed SR strategy was compared to native 1 × 1 × 1‐mm3 acquisitions (i.e. with 1‐mm slice thickness) in 8 healthy subjects, in terms of signal‐to‐noise ratio (SNR) efficiency, using a theoretical framework, Monte Carlo simulations and region‐of‐interest (ROI) measurements, and image sharpness metrics. Apparent diffusion coefficient (ADC) values in normal breast tissue were also compared.
Results
The SR images resulted in an SNR gain above 3 compared to native 1 × 1 × 1‐mm3 using the same acquisition duration (acquisition gain 3 and reconstruction gain >1). Beltrami‐SR provided the best results in terms of SNR and image sharpness. The ADC values in normal breast measured from Beltrami‐SR were preserved compared to low‐resolution images (1.91 versus 1.97 ×10–3 mm2/s, P = .1).
Conclusion
A combination of rs‐EPI and SR allows 3D, 1‐mm isotropic breast DWI data to be obtained with better SNR than a native 1‐mm isotropic acquisition. The proposed DWI protocol might be of interest for breast cancer monitoring/screening without injection.
Cine cardiac MRI sequences require repeated breath-holds, which can be difficult for patients with ischemic heart disease (IHD).
The purpose of the study was to compare a free-breathing accelerated ...cine sequence using deep learning (DL) reconstruction and a standard breath-hold cine sequence in terms of image quality and left ventricular (LV) measurements in patients with IHD undergoing cardiac MRI.
This prospective study included patients undergoing 1.5- or 3-T cardiac MRI for evaluation of IHD between March 15, 2023, and June 21, 2023. Examinations included an investigational free-breathing cine short-axis sequence with DL reconstruction (hereafter, cine-DL sequence). Two radiologists (reader 1 R1 and reader 2 R2), in blinded fashion, independently assessed left ventricular ejection fraction (LVEF), left ventricular end-diastolic volume (LVEDV), left ventricular end-systolic volume (LVESV), and subjective image quality for the cine-DL sequence and a standard breath-hold balanced SSFP sequence; R1 assessed artifacts.
The analysis included 26 patients (mean age, 64.3 ± 11.7 SD years; 14 men, 12 women). Acquisition was shorter for the cine-DL sequence than the standard sequence (mean ± SD, 0.6 ± 0.1 vs 2.4 ± 0.6 minutes;
< .001). The cine-DL sequence, in comparison with the standard sequence, showed no significant difference for LVEF for R1 (mean ± SD, 51.7% ± 14.3% vs 51.3% ± 14.7%;
= .56) or R2 (53.4% ± 14.9% vs 52.8% ± 14.6%;
= .53); significantly greater LVEDV for R2 (mean ± SD, 171.9 ± 51.9 vs 160.6 ± 49.4 mL;
= .01) but not R1 (171.8 ± 53.7 vs 165.5 ± 52.4 mL;
= .16); and no significant difference in LVESV for R1 (mean ± SD, 88.1 ± 49.3 vs 86.0 ± 50.5 mL;
= .45) or R2 (85.2 ± 48.1 vs 81.3 ± 48.2 mL;
= .10). The mean bias between the cine-DL and standard sequences by LV measurement was as follows: LVEF, 0.4% for R1 and 0.7% for R2; LVEDV, 6.3 mL for R1 and 11.3 mL for R2; and LVESV, 2.1 mL for R1 and 3.9 mL for R2. Subjective image quality was better for cine-DL sequence than the standard sequence for R1 (mean ± SD, 2.3 ± 0.5 vs 1.9 ± 0.8;
= .02) and R2 (2.2 ± 0.4 vs 1.9 ± 0.7;
= .02). R1 reported no significant difference between the cine-DL and standard sequences for off-resonance artifacts (3.8% vs 23.1% examinations;
= .10) and parallel imaging artifacts (3.8% vs 19.2%;
= .19); blurring artifacts were more frequent for the cine-DL sequence than the standard sequence (42.3% vs 7.7% examinations;
= .008).
A free-breathing cine-DL sequence, in comparison with a standard breath-hold cine sequence, showed very small bias for LVEF measurements and better subjective quality. The cine-DL sequence yielded greater LV volumes than the standard sequence.
A free-breathing cine-DL sequence may yield reliable LVEF measurements in patients with IHD unable to repeatedly breath-hold.
ClinicalTrials.gov NCT05105984.
Purpose
Amide proton transfer‐weighted (APTw) MRI at 3T provides a unique contrast for brain tumor imaging. However, APTw imaging suffers from hyperintensities in liquid compartments such as cystic ...or necrotic structures and provides a distorted APTw signal intensity. Recently, it has been shown that heuristically motivated fluid suppression can remove such artifacts and significantly improve the readability of APTw imaging.
Theory and Methods
In this work, we show that the fluid suppression can actually be understood by the known concept of spillover dilution, which itself can be derived from the Bloch‐McConnell equations in comparison to the heuristic approach. Therefore, we derive a novel post‐processing formula that efficiently removes fluid artifact, and explains previous approaches. We demonstrate the utility of this APTw assessment in silico, in vitro, and in vivo in brain tumor patients acquired at MR scanners from different vendors.
Results
Our results show a reduction of the CEST signals from fluid environments while keeping the APTw‐CEST signal intensity almost unchanged for semi‐solid tissue structures such as the contralateral normal appearing white matter. This further allows us to use the same color bar settings as for conventional APTw imaging.
Conclusion
Fluid suppression has considerable value in improving the readability of APTw maps in the neuro‐oncological field. In this work, we derive a novel post‐processing formula from the underlying Bloch‐McConnell equations that efficiently removes fluid artifact, and explains previous approaches which justify the derivation of this metric from a theoretical point of view, to reassure the scientific and medical field about its use.
Purpose
Risk stratification of patients with type 2 diabetes mellitus (T2D) remains suboptimal. We hypothesized that myocardial perfusion entropy (MPE) quantified from SPECT myocardial perfusion ...images may provide incremental prognostic value in T2D patients independently from myocardial ischemia.
Methods
T2D patients with very high and high cardiovascular risk were prospectively included (
n
= 166, 65 ± 12 years). Stress perfusion defect was quantified by visual evaluation of SPECT MPI. SPECT MPI was also used for the quantification of rest and stress MPE. The primary end point was major adverse cardiac events (MACEs) defined as cardiac death, myocardial infarction (MI), and myocardial revascularization > 3 months after SPECT.
Results
Forty-four MACEs were observed during a 4.6-year median follow-up. Significant differences in stress MPE were observed between patients with and without MACEs (4.19 ± 0.46 vs. 3.93 ± 0.40;
P
≤ .01). By Kaplan-Meier analysis, the risk of MACEs was significantly higher in patients with higher stress MPE (log-rank
P
≤ 01). Stress MPE and stress perfusion defect (SSS ≥ 4) were significantly associated with the risk of MACEs (hazard ratio 2.77 and 2.06, respectively,
P
< .05 for both) after adjustment for clinical and imaging risk predictors as identified from preliminary univariate analysis. MPE demonstrated incremental prognostic value over clinical risk factors, stress test EKG and SSS as evidenced by nested models showing improved Akaike information criterion (AIC), reclassification (global continuous net reclassification improvement NRI: 63), global integrated discrimination improvement (IDI: 6%), and discrimination (change in c-statistic: 0.66 vs 0.74).
Conclusions
Stress MPE provided independent and incremental prognostic information for the prediction of MACEs in diabetic patients.
Trial registration number
NCT02316054 (12/12/2014).
Le cancer du sein est aujourd’hui le cancer le plus fréquent chez la femme ainsi que la première cause de décès féminin par cancer. Actuellement, l’IRM mammaire n’est réalisée qu’en seconde intention ...lorsque les autres modalités d’imagerie ne suffisent pas à poser un diagnostic. Dans le cas des populations à risque, l’IRM mammaire est recommandée comme examen de dépistage annuel en raison de sa très haute sensibilité de détection. Par IRM, la détection d’un cancer du sein se fait à la suite de l’injection d’un produit de contraste qui permet de visualiser les lésions mammaires en hypersignal. La majeure partie du diagnostic repose sur l’analyse morphologique de ces lésions ; une acquisition hautement résolue spatialement est donc nécessaire. Malgré l’utilisation des techniques d’accélération courantes, le volume de données à acquérir reste important et la résolution temporelle de l’examen d’IRM mammaire est aujourd’hui aux alentours d’une minute. Cette faible résolution temporelle limite donc intrinsèquement la spécificité de l’examen d’IRM mammaire. Un examen avec une haute résolution temporelle permettrait l’utilisation de modèles pharmacocinétiques donnant accès à des paramètres physiologiques spécifiques des lésions. L’approche proposée dans ce travail de thèse est le développement d’une séquence IRM permettant à la fois la reconstruction classique d’images, telle que celle utilisée en routine clinique pour le diagnostic, ainsi qu’une reconstruction accélérée d’images avec une plus haute résolution temporelle permettant ainsi l’application de modèles pharmacocinétiques. Le développement de cette séquence a été réalisé en modifiant l’ordre d’acquisition du domaine de Fourier de la séquence utilisée en clinique, afin qu’il soit aléatoire et permette la reconstruction a posteriori de domaines sous-échantillonnés acquis plus rapidement. Des acquisitions sur des objets tests, sur des volontaires et sur des patientes ont montré que l’acquisition aléatoire ne modifiait pas les images obtenues par reconstruction classique permettant ainsi le diagnostic conventionnel. Une attention particulière a été portée pour permettre la suppression de graisse nécessaire à l’acquisition des images d’IRM mammaire. Les reconstructions des domaines sous-échantillonnés sont réalisées via des reconstructions Compressed Sensing permettant la suppression des artéfacts de sous-échantillonnage. Ces reconstructions Compressed Sensing ont été développées et testées sur des fantômes numériques reproduisant des IRMs mammaires. Le potentiel de cette nouvelle acquisition a enfin été testé sur une lésion artificielle mammaire, développée à cet effet, et reproduisant des prises de contraste mammaires
Breast cancer is nowadays the first cause of female cancer and the first cause of female death by cancer. Breast MRI is only performed in second intention when other imaging modalities cannot lead to a confident diagnosis. In high risk women population, breast MRI is recommended as an annual screening tool because of its higher sensitivity to detect breast cancer. Breast MRI needs contrast agent injection to visualize enhancing lesions and the diagnosis is mostly based on morphological analysis of these lesions. Therefore, an acquisition with high spatial resolution is needed. Despite the use of conventional MRI acceleration techniques, the volume of data to be acquired remains quite large and the temporal resolution of the exam is around one minute. This low temporal resolution may be the cause of the low specificity of breast MRI exam. Breast MRI with higher temporal resolution will allow the use of pharmacokinetic models to access physiological parameters and lesion specifications. The main aim of this work is to develop a MRI sequence allowing a flexible use of the acquired data at the reconstruction stage. On the one hand, the images can be reconstructed with a conventional reconstruction like the protocol used in clinical routine. On the other hand, the new MRI sequence will also allow the reconstruction of images with a higher temporal resolution allowing the use of pharmacokinetic models. The development of this sequence was done by modifying the acquisition order in the Fourier domain. A random acquisition of the Fourier domain will allow the reconstruction of sub-sampled domains acquired faster. We paid attention to fat suppression efficiency with this new Fourier domain acquisition order. Tests were performed on phantom, female volunteers and patients. These tests showed that the random acquisition did not impact the quality of images (MRI signal and lesion morphology) obtained by conventional reconstruction thus allowing the conventional diagnosis. The reconstructions of the sub-sampled Fourier domains were made using Compressed Sensing reconstructions to remove sub-sampling artifacts. These reconstructions were developed and tested on digital phantoms reproducing breast MRI. The potential of this new MRI acquisition was tested on an artificial enhancing breast lesion developed especially for this purpose
The first confirmed case of COVID-19 in Quebec, Canada, occurred at Verdun Hospital on February 25, 2020. A month later, a localized outbreak was observed at this hospital. We performed tiled ...amplicon whole genome nanopore sequencing on nasopharyngeal swabs from all SARS-CoV-2 positive samples from 31 March to 17 April 2020 in 2 local hospitals to assess viral diversity (unknown at the time in Quebec) and potential associations with clinical outcomes. We report 264 viral genomes from 242 individuals-both staff and patients-with associated clinical features and outcomes, as well as longitudinal samples and technical replicates. Viral lineage assessment identified multiple subclades in both hospitals, with a predominant subclade in the Verdun outbreak, indicative of hospital-acquired transmission. Dimensionality reduction identified two subclades with mutations of clinical interest, namely in the Spike protein, that evaded supervised lineage assignment methods-including Pangolin and NextClade supervised lineage assignment tools. We also report that certain symptoms (headache, myalgia and sore throat) are significantly associated with favorable patient outcomes. Our findings demonstrate the strength of unsupervised, data-driven analyses whilst suggesting that caution should be used when employing supervised genomic workflows, particularly during the early stages of a pandemic.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Throughout the SARS-CoV-2 pandemic, several variants of concern (VOCs) have been identified, many of which share recurrent mutations in the spike glycoprotein's receptor-binding domain (RBD). This ...region coincides with known epitopes and can therefore have an impact on immune escape. Protracted infections in immunosuppressed patients have been hypothesized to lead to an enrichment of such mutations and therefore drive evolution towards VOCs. Here, we present the case of an immunosuppressed patient that developed distinct populations with immune escape mutations throughout the course of their infection. Notably, by investigating the co-occurrence of substitutions on individual sequencing reads in the RBD, we found quasispecies harboring mutations that confer resistance to known monoclonal antibodies (mAbs) such as S:E484K and S:E484A. These mutations were acquired without the patient being treated with mAbs nor convalescent sera and without them developing a detectable immune response to the virus. We also provide additional evidence for a viral reservoir based on intra-host phylogenetics, which led to a viral substrain that evolved elsewhere in the patient's body, colonizing their upper respiratory tract (URT). The presence of SARS-CoV-2 viral reservoirs can shed light on protracted infections interspersed with periods where the virus is undetectable, and potential explanations for long-COVID cases.
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