Low-Threshold Testing for SARS-CoV-2 (COVID-19) in Long-Term Care Facilities Early in the First Pandemic Wave, the Twente Region, the Netherlands: A Possible Factor in Reducing Morbidity and Mortality.

During the first wave of the COVID-19 pandemic, there was a shortage of SARS-CoV-2 diagnostic tests, and testing patients with mild symptoms (low-threshold testing) was not recommended in the Netherlands. Despite these guidelines, to protect those who were most at risk, low-threshold testing was advocated and offered to the majority of long-term care institutions in the Twente region. In this manner, 144 healthcare workers and 96 residents tested SARS-CoV-2-positive and were isolated before the same service was provided nationwide by public health services. Strikingly, excess mortality rate in the Twente region 1 month after the introduction of this strategy was found to be 62%-89% lower than that in neighboring regions, which may be explained by this divergent testing strategy. In an emerging pandemic, early implementation of a liberal testing policy may be more effective than restricted testing in settings with a high death rate.

Comparing signal-to-noise ratio for prostate imaging at 7T and 3T.

BACKGROUND: In MRI, the signal-to-noise ratio (SNR) theoretically increases with B0 field strength. However, because of attenuation of the radiofrequency (RF) fields at 7T, it is not certain if this SNR gain can be realized for prostate imaging. PURPOSE/HYPOTHESIS: To investigate the SNR gain in prostate imaging at 7T as compared with 3T. It is expected that SNR will improve for prostate imaging at 7T compared with 3T. STUDY TYPE: Prospective. SUBJECTS: Four healthy volunteers and one prostate cancer patient. FIELD STRENGTH/SEQUENCE: All subjects were scanned at 3T and at 7T using optimal coil setups for both field strengths. For all volunteers, proton density-weighted images were acquired for SNR analysis and actual flip angle imaging (AFI) B1+| maps were acquired for correction of measured SNR values. In the patient, a T2 -weighted (T2 w) image was acquired at 3T and at 7T. ASSESSMENT: SNR was calculated in the prostate region for all volunteers. SNR was normalized for flip angle, receiver bandwidth, and voxel volume. SNR was also calculated for different sensitivity encoding (SENSE) acceleration factors. STATISTICAL TESTING: SNR values are represented as the arithmetic mean of SNR values in the prostate. Estimated SNR in the T2 w image is calculated as the arithmetic mean of the signal intensity (SI) divided by the standard deviation of the SI in a specified zone. Tumor-to-tissue contrast is calculated as (SItumor +SIzone )/( SItumor -SIzone ). RESULTS: An increase in SNR ranging from 1.7-fold to 2.8-fold was measured in the prostate at 7T in comparison to 3T for four volunteers. At 7T, it is possible to achieve a 4-fold SENSE acceleration in the left-right direction with similar SNR to a nonaccelerated 3T image. T2 w imaging was done at 3T and 7T in one patient, where improved tumor-to-tissue contrast was demonstrated at 7T. DATA CONCLUSION: SNR improves for prostate imaging at 7T as compared with 3T. LEVEL OF EVIDENCE: 2 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2019;49:1446-1455.

Correlation between genomic index lesions and mpMRI and 68Ga-PSMA-PET/CT imaging features in primary prostate cancer.

Magnetic resonance imaging (MRI) and prostate specific membrane antigen (PSMA)- positron emission tomography (PET)/computed tomography (CT)-imaging of prostate cancer (PCa) are emerging techniques to assess the presence of significant disease and tumor progression. It is not known, however, whether and to what extent lesions detected by these imaging techniques correlate with genomic features of PCa. The aim of this study was therefore to define a genomic index lesion based on chromosomal copy number alterations (CNAs) as marker for tumor aggressiveness in prostate biopsies in direct correlation to multiparametric (mp) MRI and 68Ga-PSMA-PET/CT imaging features. CNA profiles of 46 biopsies from five consecutive patients with clinically high-risk PCa were obtained from radiologically suspicious and unsuspicious areas. All patients underwent mpMRI, MRI/TRUS-fusion biopsy, 68Ga-PSMA-PET/CT and a radical prostatectomy. CNAs were directly correlated to imaging features and radiogenomic analyses were performed. Highly significant CNAs (≥10 Mbp) were found in 22 of 46 biopsies. Chromosome 8p, 13q and 5q losses were the most common findings. There was an strong correspondence between the radiologic and the genomic index lesions. The radiogenomic analyses suggest the feasibility of developing radiologic signatures that can distinguish between genomically more or less aggressive lesions. In conclusion, imaging features of mpMRI and 68Ga-PSMA-PET/CT can guide to the genomically most aggressive lesion of a PCa. Radiogenomics may help to better differentiate between indolent and aggressive PCa in the future.

Towards intrinsic R2* imaging in the prostate at 3 and 7tesla.

PURPOSE: Hypoxia is an important marker for resistance to therapy. In this study, we quantify the macroscopic effects of R2* mapping in prostate cancer patients incorporating susceptibility matching and field strengths effects. MATERIALS AND METHODS: 91 patients were scanned without endorectal coil (ERC) at 3T. Only when rectal gas was absent, data was included for analysis. Another group of 10 patients was scanned using a susceptibility matched ERC. To assess the residual contamination of R2 and macroscopic field non-uniformities, a group of 10 patients underwent ultra-high resolution 7T MRI. RESULTS: Of the patients scanned at 3T 60% presented rectal gas and were excluded, due to susceptibility artifacts. At 3T the tumor was significantly different (P<0.01) from the healthy surrounding tissue in R2* values at intrapatient level. Using the measured median R2* value of 24.9s-1 at 3T and 43.2s-1 at 7T of the peripheral zone, the minimum contribution of macroscopic susceptibility effects is 15% at 3T. CONCLUSION: R2* imaging might be a promising tool for hypoxia imaging, particularly when minimizing macroscopic susceptibility effects contaminating intrinsic R2* of tissue, such as rectal gas. At 3T macroscopic effects still contribute 15% in the R2* value, compared to ultra-high resolution R2* mapping at 7T.

Requirements for static and dynamic higher order B0 shimming of the human breast at 7 T.

The increased magnetic susceptibility effects at higher magnetic fields increase the demands for shimming of the B0 field for in vivo MRI and MRS. Both static and dynamic techniques have been developed to compensate for susceptibility-induced field inhomogeneities. In this study, we investigate the impact of and need for both static and dynamic higher order B0 shimming of magnetic field homogeneities in clinical breast MRI at 7 T. Both global and local field variations at lipid-tissue interfaces were observed in the magnetic field using TE-optimized B0 mapping at 7 T. With static B0 shimming, a field homogeneity of 39 ± 11 Hz (n = 48) was reached in a single breast using second-order shimming. Further compensation of the residual local field inhomogeneities caused by lipid-tissue interfaces does not seem to be feasible with shallow spherical harmonic fields. For bilateral shimming, the shimming quality was significantly less at 62 ± 15 Hz (n = 22) over both breasts, even after (simulated) fourth-order shimming. In addition, a substantial time-dependent field instability of 30 Hz peak to peak, with significant higher order field contributions, was observed during regular breathing. In conclusion, TE-optimized B0 field mapping reveals substantial field variations in the lipid-rich environment of the human breast, in both space and time. The static field variations could be partially minimized by third-order B0 shimming, providing sufficient lipid suppression. However, in order to fully benefit from the increased spectral dispersion at high fields, the significant magnetic field variations during breathing need to be considered.

(31) P MR spectroscopic imaging combined with (1) H MR spectroscopic imaging in the human prostate using a double tuned endorectal coil at 7T.

PURPOSE: Improved diagnostic sensitivity could be obtained in cancer detection and staging when individual compounds of the choline pool can be detected. Therefore, a novel coil design is proposed, providing the ability to acquire both (1) H and (31) P magnetic resonance spectroscopic imaging (MRSI) in patients with prostate cancer. METHODS: A two-element (1) H/(31) P endorectal coil was designed by adjusting a commercially available 3T endorectal coil. The two-element coil setup was interfaced as a transceiver to a whole body 7T MR scanner. Simulations and phantom measurements were performed to compare the efficiency of the coil. (1) H MRSI and (31) P MRSI were acquired in vivo in prostate cancer patients. RESULTS: The efficiency of the (1) H/(31) P coil is comparable to the dual channel (1) H coil previously published. Individually distinguishable phospholipid metabolites in the in vivo (31) P spectra were: phosphoethanolamine, phosphocholine, phosphate, glycerophosphoethanolamine, glycerophosphocholine, phosphocreatine, and adenosine triposphate. (1) H MRSI was performed within the same scan session, visualizing choline, polyamines, creatine, and citrate. CONCLUSION: (1) H MRSI and (31) P MRSI can be acquired in the human prostate at 7T within the same scan session using an endorectal coil matched and tuned for (1) H (quadrature) and (31) P (linear) without the need of cable traps and with negligible efficiency losses in the (1) H and (31) P channel.

SPECIAL semi-LASER with lipid artifact compensation for 1H MRS at 7 T.

The measurement of full metabolic profiles at ultrahigh fields including low concentrated or fast-relaxing metabolites is usually achieved by applying short echo time sequences. One sequence beside stimulated echo acquisition mode that was proposed in this regard is spin echo full intensity-acquired localized spectroscopy. Typical problems that are still persistent for spin echo full intensity-acquired localized spectroscopy are B(1) inhomogeneities especially for signal acquisition with surface coils and chemical shift displacement artifacts due to limited B(1) amplitudes when using volume coils. In addition, strong lipid contaminations in the final spectrum can occur when only a limited number of outer volume suppression pulses is used. Therefore, an adiabatic short echo time (= 19 ms) spin echo full intensity-acquired localized spectroscopy semilocalization by adiabatic selective refocusing sequence is presented that is less sensitive to strong B(1) variations and that offers increased excitation and refocusing pulse bandwidths than regular spin echo full intensity acquired localized spectroscopy. Furthermore, the existence of the systematic lipid artifact is identified and linked to unfavorable effects due to the preinversion localization pulse. A method to control this artifact is presented and validated in both phantom and in vivo measurements. The viability of the proposed sequence was further assessed for in vivo measurements by scanning 17 volunteers using a surface coil and moreover acquiring additional volume coil measurements. The results show well-suppressed lipid artifacts, good signal-to-noise ratio, and reproducible fitting results in accordance with other published studies.

Quantitative 31P magnetic resonance spectroscopy of the human breast at 7 T.

This study presents quantified levels of phosphorylated metabolites in glandular tissue of human breast using (31)P magnetic resonance spectroscopy at 7 T. We used a homebuilt (1)H/(31)P radiofrequency coil to obtain artifact-free (31)P MR spectra of glandular tissue of healthy females by deploying whole breast free induction decay (FID) detection with adiabatic excitation and outer volume suppression. Using progressive saturation, the estimated apparent T(1) relaxation time of (31)P spins of phosphocholine and phosphoethanolamine was 4.4 and 5.7 s, respectively. Quantitative measures for phosphocholine and phosphoethanolamine levels in glandular tissue were established based on MR imaging. We used a 3D (1)H image of the breast to segment the glandular tissue; this was matched to a 3D (31)P image of the B1- field of the (31)P coil to correct for differences in glandular tissue volume and B(1) inhomogeneity of the (31)P coil. The (31)P MR spectra were calibrated using a phantom with known concentration. Average levels of phosphocholine and phosphoethanolamine in 11 volunteers were 0.84 ± 0.21 mM and 1.18 ± 0.41 mM, respectively. In addition, data of three patients with breast cancer showed higher levels of phosphocholine and phosphoethanolamine compared with healthy volunteers. This may indicate a potential role for the use of (31)P magnetic resonance spectroscopy for characterization, prognosis, and treatment monitoring in breast cancer.