Susceptibility weighted imaging: a new tool in the diagnosis of prostate cancer and detection of prostatic calcification

CT-like images in MRI improve specificity of erosion detection in patients with hand arthritis: a diagnostic accuracy study with CT as standard of reference

OBJECTIVE

To compare the diagnostic accuracy of susceptibility-weighted imaging (SWI), standard T1-weighted (T1w) images and high-resolution 3D-gradient echo sequences (volumetric interpolated breath-hold examination (VIBE)) for detection of erosions in patients with peripheral arthritis using CT as standard of reference.

MATERIALS AND METHODS

A total of 36 patients were included in the study. All patients underwent CT and MRI, including SWI, VIBE and T1w sequences of the clinically more affected hand. Two trained readers scored all imaging datasets separately for erosions in a blinded fashion. Specificity, sensitivity and diagnostic accuracy of MRI sequences were calculated on a per-patient level.

RESULTS

CT was positive for erosion in 16 patients and 77 bones (Rheumatoid Arthritis MRI Score >0), T1w in 28 patients, VIBE in 25 patients and SWI in 17 patients. All MRI sequences performed with comparably high sensitivities (T1w 100%, VIBE 94% and SWI 94%). SWI had the highest specificity of 90%, followed by VIBE (50%) and T1w (40%). Both T1w and VIBE produced significantly higher sum scores than CT (341 and 331 vs 148, p<0.0001), while the sum score for SWI did not differ from CT (119 vs 148; p=0.411).

CONCLUSION

Specificity for erosion detection remains a challenge for MRI when conventional and high-resolution sequences are used but can be improved by direct bone depiction with SWI. Both T1w and VIBE tend to overestimate erosions, when CT is used as the standard of reference.

Delineation of prostatic calcification using quantitative susceptibility mapping: Spatial accuracy for magnetic resonance-only radiotherapy planning

To investigate the spatial accuracy of delineating prostatic calcifications by quantitative susceptibility mapping (QSM) in comparison with computed tomography (CT), we conducted phantom and human studies. Five differently‐sized spherical hydroxyapatites mimicking prostatic calcification (pseudo‐calcification) were arranged in the order of their sizes at the center of a plastic container filled with gelatin. This calcification phantom underwent magnetic resonance (MR) imaging, including the multiple spoiled gradient‐echo sequences (SPGR) for the QSM and CT as a reference. The volume of each pseudo‐calcification and center‐to‐center distance between the pseudo‐calcifications delineated by QSM and CT were measured. In the human study, eight patients with prostate cancer who underwent radiation therapy and had some prostatic calcifications were included. The patients underwent CT and SPGR and modified DIXON sequence for MR‐only simulation. The hybrid QSM processing combined with the complex signals in the SPGR and water and fat fraction maps estimated from the modified DIXON sequence were used to reconstruct the pelvic susceptibility map in humans. The threshold of CT numbers was set at 130 HU, while the QSM images were manually segmented in the calcification phantom and human studies. In the phantom study, there was an excellent agreement in the pseudo‐calcification volumes between QSM and CT (y = 1.02x – 7.38, R² = 0.99). The signal profiles had similar trends in CT and QSM. The center‐to‐center distances between the pseudo‐calcifications in the phantom were also identical in QSM and CT. The calcification volumes were almost identical between the QSM and CT in the human study (y = 0.95x – 9.32, R² = 1.00). QSM can offer geometric and volumetric accuracies to delineate prostatic calcifications, similar to CT. The prostatic calcification delineated by QSM may facilitate image‐guided radiotherapy in the MR‐only simulation workflow.

Susceptibility Weighted Imaging for evaluation of musculoskeletal lesions

The presence of blood or calcium in the musculoskeletal (MSK) system may be linked to specific pathological conditions. The ability of MRI for calcium detection is usually limited compared with other techniques such as CT. In a similar manner, the accuracy of MRI for detection and evaluation of hemorrhage in soft tissues is closely linked to the degree of degradation of blood products. Blood and calcium are substances that cause local inhomogeneity of the magnetic field resulting in susceptibility artifacts. To try to evaluate these substances, specific MRI sequences which are highly sensitive to these local magnetic field inhomogeneities such as Susceptibility Weighted Imaging (SWI) have been developed and successfully applied in the Central Nervous System, but scarcely used in MSK. SWI may increase the overall sensitivity of MRI to detect blood and calcium in several clinical scenarios such as degenerative joint disease or bone and soft tissue lesion assessment and discriminate between both compounds, something which is not always possible with conventional MRI approaches. In this paper, physical basis and technical adjustment for SWI acquisition at MSK are detailed reviewing the potential application of SWI in different MSK clinical scenarios.

Prostatic calcifications: Quantifying occurrence, radiodensity, and spatial distribution in prostate cancer patients

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Intraprostatic calcifications are under-recognized and under-reported in imaging.

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Intraprostatic calcifications are common in patients with prostate cancer.

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They commonly occur within tumors or in the vicinity of tumors.

Background

To evaluate the prevalence, density, and distribution of prostate calcification in patients with prostate cancer.

Methods

Patients who underwent both Gallium-68 PSMA PET/CT and MRI of the prostate over the course of a year were selected for analysis. The CT images with visible calcifications within the prostate were included and calcifications automatically isolated using a threshold of 130 HU. The corresponding multiparametric MRI was assessed and the peripheral zone, transition zone, MRI-visible tumor, and urethra manually contoured. The contoured MRI and CT images were registered using rigid registration, and calcifications mapped automatically to the MRI contours.

Results

A total of 85 men (age range 50–88, mean 69 years, standard deviation 7.2 years) were assessed. The mean serum Prostate Specific Antigen PSA was 16.7, range 0.12 to 94.4. Most patients had intermediate-risk disease (68%; Gleason grade group 2 and 3), 26% had high-risk disease (Gleason grade group 4 and 5), and 6% had low-risk disease (Gleason grade group 1). Forty-six patients out of 85 (54%) had intraprostatic calcification. Calcification occurred more in transition zone than the peripheral zone (65% vs. 35%). The mean density of the calcification was 227 HU (min 133, max 1,966 HU). In 12 patients, the calcification was within an MRI-visible tumor, in 24 patients, there were calcifications within a 9 mm distance of the tumor border, and in 9 patients, there were calcifications located between the urethra and tumor.

Conclusions

Calcifications are common in patients with prostate cancer. Their density and location may make them a significant consideration when planning treatment or retreatment with some types of minimally invasive therapy.

Value of susceptibility-weighted imaging for the assessment of angle measurements reflecting hip morphology

Radiographs are the clinical first line imaging modality for evaluating hip morphology and pathology. MRI offers additional information and is the method of choice to evaluate soft tissue, bone marrow and preradiographic signs of osteoarthritis. Radiographs are used to measure the most morphometric parameters. The aim of this study was to compare susceptibility weighted MRI (SWMR) with radiographs to evaluate hip morphology. 40 Patients were examined with standard MR-sequences, coronal SWMR and radiographs in anteroposterior pelvic view. Coronal maximum intensity projection (MIP) images of both hips were automatically reconstructed on SWMR and T1weighted images. Sharp´s angle, Tönnis angle, lateral center–edge angle of Wiberg and caput-collum-diaphyseal angle were measured on coronal SWMR MIP-images, T1weighted MIP-images and radiographs. Measurements were compared by linear regression analysis and Bland-Altmann Plots, using radiographs as reference standard. Additionally, a ratio between the signal intensity of muscles and bone on SWMR and T1weighted MIP-images was calculated and compared between these two sequences. SWMR enables the reliable assessment of Sharp´s angle (SWMR: R² = 0.80; T1weighted: R² = 0.37), Tönnis angle (SWMR: R² = 0.86; T1weighted: not measurable), lateral center–edge angle of Wiberg (SWMR: R² = 0.88; T1weighted: R² = 0.40) and caput-collum-diaphyseal angle (SWMR: R² = 0.38; T1weighted: R² = 0.18) compared to radiographs with a higher accuracy than conventional MR imaging. The ratio between the intensity of muscles and bone was significant higher on SWMR (2.00 and 2.02) than on T1weighted MIP-images (1.6 and 1.42; p < 0.001).

Susceptibility-weighted MR imaging to improve the specificity of erosion detection: a prospective feasibility study in hand arthritis

OBJECTIVE

To evaluate the diagnostic potential of susceptibility-weighted imaging (SWI) for the detection of erosions of the hand, compared to T1-weighted (T1w) magnetic resonance imaging (MRI). Computed tomography (CT) was used as a reference standard.

MATERIALS AND METHODS

We prospectively investigated 37 patients with suspected arthritic activity of the hand. All patients underwent T1w, SWI, and CT on the same day. Patients were randomized to MRI or CT first. CT, T1w, SWI, and T1w/SWI were scored for erosions according to OMERACT RAMRIS guidelines. Specificity, sensitivity, and diagnostic accuracy were separately calculated for T1w, SWI, and T1w/SWI on a per-patient and per-bone basis using CT as reference. The one-tailed McNemar test was performed to test the number of erosion-positive patients in T1w, SWI, and T1w/SWI for non-inferiority. Measured erosion sizes were compared using Pearson's test.

RESULTS

CT was positive for erosions in 16 patients and 55 bones. SWI and T1w/SWI had superior diagnostic accuracy (91.2 and 93.8%) compared to T1w (87.8%) driven by a higher specificity (93.8 and 96.5%) compared to T1w (88.8%). On the patient level, SWI and T1w/SWI showed non-inferiority (p = 0.11 and p = 0.38) but not T1w alone (p < 0.0001). The lesion size on CT correlated better with SWI (Pearson's r = 0.92) compared to T1w (r = 0.69).

CONCLUSIONS

Adding SWI to a standard MRI protocol has the potential to improve erosion detection in hands by increasing specificity. SWI depicts bony erosions more accurately compared to standard MRI techniques.

Observed high incidence of prostatic calculi with the potential to act as natural fiducials for prostate image guided radiotherapy

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Prostatic calculi are a frequent radiological finding and may aid prostate IGRT.

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Incidence of prostatic calculi in a population of radiotherapy patients is reported.

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Significant proportion of patients have calculi detectable on radiotherapy images.

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Prostatic calculi may reduce the need for surgically implanted markers.

Purpose

This study aims to quantify the incidence and distribution of prostatic calculi in a population of prostate radiotherapy patients and assess their potential role in prostate image guided radiotherapy (IGRT).

Methods & materials

A retrospective analysis of trans-rectal ultrasound (TRUS), computed tomography (CT) planning and treatment verification cone beam CT (CBCT) scans from radical prostate radiotherapy patients (external beam and brachytherapy) between 2012 and 2014 was undertaken by a single experienced observer. An internationally validated schema from the Prostate Imaging Reporting and Data system (PIRADS) was used to map the location of calculi. The association of calculi with patient and disease characteristics was explored. Data was analysed using SPSS (IBM version 22.0) using descriptive statistical methods and logistic binary regression analysis.

Results

389 scan sets from 254 patients were included in the analysis. The overall incidence of calculi was 85% (n = 218) of which 79% (n = 201) were intra-prostatic calculi. The mean number of intra-prostatic calculi was 2 (range 1–10) and the mean size of calculi was 3.7 mm (range 0.5–15 mm). Calculi were most frequently observed in the posterior of the mid-gland (PI-RADs 3p, 9p) and posterior of the apex (PI-RADs 5p, 11p). 99% (n = 135) of CT planning scans with a corresponding CBCT had calculi in the same PIRADs location and all calculi were visible at the last fraction. There was no statistically significant association of calculi and N stage, M stage or Gleason score.

Conclusions

A significant proportion of prostate radiotherapy patients have prostatic calculi detectable on pre radiotherapy imaging. Calculi observed on CT were also detectable on CBCT in 99% of cases and remain visible at the end of treatment. These findings add to the growing evidence base supporting the potential of calculi as an alternative to fiducial markers to aid prostate IGRT.

Differentiation of Predominantly Osteoblastic and Osteolytic Spine Metastases by Using Susceptibility-weighted MRI

Purpose To evaluate the use of susceptibility-weighted MRI for the differentiation of predominantly osteoblastic and osteolytic spine metastases. Materials and Methods For this prospective study, 53 study participants (mean age, 54.5 years ± 14.3 [range, 22-88 years]; 27 men with a mean age of 55.3 years ± 12.7 [range, 22-72 years] and 26 women with a mean age of 53.8 years ± 15.7 [range, 23-88 years]) with clinically suspected spine metastases underwent imaging with standard MRI sequences, susceptibility-weighted MRI, and CT. Sensitivities and specificities of MRI sequences for the detection of predominantly osteoblastic and osteolytic metastases were determined by using CT as the reference standard. The metastases-to-vertebral body signal intensity ratio (MVR) was calculated to compare modalities. Phantom measurements were obtained to correlate bone densities between MRI sequences and CT. Results A total of 64 metastases (38 predominantly osteoblastic, 26 predominantly osteolytic) were detected. Susceptibility-weighted MRI achieved a sensitivity of 100% (38 of 38) and specificity of 96% (25 of 26) for predominantly osteoblastic metastases and a sensitivity of 96% (25 of 26) and specificity of 100% (38 of 38) for predominantly osteolytic metastases. Standard MRI sequences achieved a sensitivity of 89% (34 of 38) and specificity of 73% (19 of 26) for predominantly osteoblastic metastases and a sensitivity of 73% (19 of 26) and specificity of 92% (35 of 38) for predominantly osteolytic metastases. MVR measurements obtained with susceptibility-weighted MRI demonstrated a strong correlation with those obtained with CT (R² = 0.75), whereas those obtained with T1-weighted MRI, T2-weighted MRI, and turbo inversion-recovery magnitude MRI showed a weak to moderate correlation (R² = 0.00, R² = 0.35, and R² = 0.39, respectively). Susceptibility-weighted MRI showed a strong correlation with CT with regard to metastases size (R² = 0.91). In phantom measurements, susceptibility-weighted MRI enabled the reliable differentiation of different degrees of mineralization (R² = 0.92 compared with CT). Conclusion Susceptibility-weighted MRI enables the reliable differentiation between predominantly osteoblastic and osteolytic spine metastases with a higher accuracy than standard MRI sequences. © RSNA, 2018 Online supplemental material is available for this article. See also the editorial by Schweitzer in this issue.

Performance of Magnetic Resonance Susceptibility-Weighted Imaging for Detection of Calcifications in Patients With Hepatic Echinococcosis

OBJECTIVE

We evaluated the performance of susceptibility-weighted imaging (SWI) for identification of hepatic calcifications in alveolar echinococcosis and cystic echinococcosis.

METHODS

The SWI images of 58 lesions in 40 patients (age, 49 ± 14 y) with alveolar echinococcosis (n = 22) or cystic echinococcosis (n = 18) were reviewed for calcifications. First, calcifications were suggested by visual assessment. Second, ratios of minimum intralesional intensity and mean lumbar muscle intensity were recorded. Computed tomography (CT) served as the criterion standard.

RESULTS

Thirty-seven lesions showed calcifications on CT. Susceptibility-weighted imaging provided a sensitivity of 89.2% (95% confidence interval [CI], 50.1-75.7) and a specificity of 57.1% (95% CI, 34.4-77.4) for calcifications detected by visual assessment. Receiver operating characteristic curves demonstrated a sensitivity of 67.6% and a specificity of 85.0% for an intensity ratio of 0.61. A specificity of 100% (95% CI, 80.8-100) and a sensitivity of 84.5% (95% CI, 67.3-93.2) were achieved by SWI for calcifications with a density greater than 184 HU in CT.

CONCLUSIONS

Identification of hepatic calcifications is possible with SWI. Susceptibility-weighted imaging offers the potential to reduce the need for of CT imaging for evaluation of echinococcosis.

Detecting prostate cancer and prostatic calcifications using advanced magnetic resonance imaging

Prostate cancer and prostatic calcifications have a high incidence in elderly men. We aimed to investigate the diagnostic capabilities of susceptibility-weighted imaging in detecting prostate cancer and prostatic calcifications. A total number of 156 men, including 34 with prostate cancer and 122 with benign prostate were enrolled in this study. Computed tomography, conventional magnetic resonance imaging, diffusion-weighted imaging, and susceptibility-weighted imaging were performed on all the patients. One hundred and twelve prostatic calcifications were detected in 87 patients. The sensitivities and specificities of the conventional magnetic resonance imaging, apparent diffusion coefficient, and susceptibility-filtered phase images in detecting prostate cancer and prostatic calcifications were calculated. McNemar's Chi-square test was used to compare the differences in sensitivities and specificities between the techniques. The results showed that the sensitivity and specificity of susceptibility-filtered phase images in detecting prostatic cancer were greater than that of conventional magnetic resonance imaging and apparent diffusion coefficient (P < 0.05). In addition, the sensitivity and specificity of susceptibility-filtered phase images in detecting prostatic calcifications were comparable to that of computed tomography and greater than that of conventional magnetic resonance imaging and apparent diffusion coefficient (P < 0.05). Given the high incidence of susceptibility-weighted imaging (SWI) abnormality in prostate cancer, we conclude that susceptibility-weighted imaging is more sensitive and specific than conventional magnetic resonance imaging, diffusion-weighted imaging, and computed tomography in detecting prostate cancer. Furthermore, susceptibility-weighted imaging can identify prostatic calcifications similar to computed tomography, and it is much better than conventional magnetic resonance imaging and diffusion-weighted imaging.

Energy Dispersive X-ray (EDX) microanalysis: A powerful tool in biomedical research and diagnosis

The Energy Dispersive X-ray (EDX) microanalysis is a technique of elemental analysis associated to electron microscopy based on the generation of characteristic Xrays that reveals the presence of elements present in the specimens. The EDX microanalysis is used in different biomedical fields by many researchers and clinicians. Nevertheless, most of the scientific community is not fully aware of its possible applications. The spectrum of EDX microanalysis contains both semi-qualitative and semi-quantitative information. EDX technique is made useful in the study of drugs, such as in the study of drugs delivery in which the EDX is an important tool to detect nanoparticles (generally, used to improve the therapeutic performance of some chemotherapeutic agents). EDX is also used in the study of environmental pollution and in the characterization of mineral bioaccumulated in the tissues. In conclusion, the EDX can be considered as a useful tool in all works that require element determination, endogenous or exogenous, in the tissue, cell or any other sample.

Diagnostic performance of susceptibility-weighted magnetic resonance imaging for the detection of calcifications: A systematic review and meta-analysis

Since its introduction, susceptibility-weighted-magnetic resonance imaging (SW-MRI) has shown the potential to overcome the insensitivity of MRI to calcification. Previous studies reporting the diagnostic performance of SW-MRI and magnetic resonance imaging (MRI) for the detection of calcifications are inconsistent and based on single-institution designs. To our knowledge, this is the first meta-analysis on SW-MRI, determining the potential of SW-MRI to detect calcifications. Two independent investigators searched MEDLINE, EMBASE and Web of Science for eligible diagnostic accuracy studies, which were published until March 24, 2017 and investigated the accuracy of SW-MRI to detect calcifications, using computed tomography (CT) as a reference. The QUADAS-2 tool was used to assess study quality and methods for analysis were based on PRISMA. A bivariate diagnostic random-effects model was applied to obtain pooled sensitivities and specificities. Out of the 4629 studies retrieved by systematic literature search, 12 clinical studies with 962 patients and a total of 1,032 calcifications were included. Pooled sensitivity was 86.5% (95%-confidence interval (CI): 73.6–93.7%) for SW-MRI and 36.7% (95%–CI:29.2–44.8%) for standard MRI. Pooled specificities of SW-MRI (90.8%; 95%–CI:81.0–95.8%) and standard MRI (94.2; 95%–CI:88.9–96.7%) were comparable. Results of the present meta-analysis suggest, that SW-MRI is a reliable method for detecting calcifications in soft tissues.

Susceptibility-weighted imaging: current status and future directions

Susceptibility-weighted imaging (SWI) is a method that uses the intrinsic nature of local magnetic fields to enhance image contrast in order to improve the visibility of various susceptibility sources and to facilitate diagnostic interpretation. It is also the precursor to the concept of the use of phase for quantitative susceptibility mapping (QSM). Nowadays, SWI has become a widely used clinical tool to image deoxyhemoglobin in veins, iron deposition in the brain, hemorrhages, microbleeds and calcification. In this article, we review the basics of SWI, including data acquisition, data reconstruction and post-processing. In particular, the source of cusp artifacts in phase images is investigated in detail and an improved multi-channel phase data combination algorithm is provided. In addition, we show a few clinical applications of SWI for the imaging of stroke, traumatic brain injury, carotid vessel wall, siderotic nodules in cirrhotic liver, prostate cancer, prostatic calcification, spinal cord injury and intervertebral disc degeneration. As the clinical applications of SWI continue to expand both in and outside the brain, the improvement of SWI in conjunction with QSM is an important future direction of this technology. Copyright © 2016 John Wiley & Sons, Ltd.

Overview of quantitative susceptibility mapping

Magnetic susceptibility describes the magnetizability of a material to an applied magnetic field and represents an important parameter in the field of MRI. With the recently introduced method of quantitative susceptibility mapping (QSM) and its conceptual extension to susceptibility tensor imaging (STI), the non-invasive assessment of this important physical quantity has become possible with MRI. Both methods solve the ill-posed inverse problem to determine the magnetic susceptibility from local magnetic fields. Whilst QSM allows the extraction of the spatial distribution of the bulk magnetic susceptibility from a single measurement, STI enables the quantification of magnetic susceptibility anisotropy, but requires multiple measurements with different orientations of the object relative to the main static magnetic field. In this review, we briefly recapitulate the fundamental theoretical foundation of QSM and STI, as well as computational strategies for the characterization of magnetic susceptibility with MRI phase data. In the second part, we provide an overview of current methodological and clinical applications of QSM with a focus on brain imaging. Copyright © 2016 John Wiley & Sons, Ltd.

Diagnostic accuracy of susceptibility-weighted magnetic resonance imaging for the evaluation of pineal gland calcification

Objectives

To determine the diagnostic performance of susceptibility-weighted magnetic resonance imaging (SWMR) for the detection of pineal gland calcifications (PGC) compared to conventional magnetic resonance imaging (MRI) sequences, using computed tomography (CT) as a reference standard.

Methods

384 patients who received a 1.5 Tesla MRI scan including SWMR sequences and a CT scan of the brain between January 2014 and October 2016 were retrospectively evaluated. 346 patients were included in the analysis, of which 214 showed PGC on CT scans. To assess correlation between imaging modalities, the maximum calcification diameter was used. Sensitivity and specificity and intra- and interobserver reliability were calculated for SWMR and conventional MRI sequences.

Results

SWMR reached a sensitivity of 95% (95% CI: 91%-97%) and a specificity of 96% (95% CI: 91%-99%) for the detection of PGC, whereas conventional MRI achieved a sensitivity of 43% (95% CI: 36%-50%) and a specificity of 96% (95% CI: 91%-99%). Detection rates for calcifications in SWMR and conventional MRI differed significantly (95% versus 43%, p<0.001). Diameter measurements between SWMR and CT showed a close correlation (R² = 0.85, p<0.001) with a slight but not significant overestimation of size (SWMR: 6.5 mm ± 2.5; CT: 5.9 mm ± 2.4, p = 0.02). Interobserver-agreement for diameter measurements was excellent on SWMR (ICC = 0.984, p < 0.0001).

Conclusions

Combining SWMR magnitude and phase information enables the accurate detection of PGC and offers a better diagnostic performance than conventional MRI with CT as a reference standard.

Benign prostatic hyperplasia after prostatic arterial embolization in a canine model: A 3T multiparametric MRI and whole-mount step-section pathology correlated longitudinal study

PURPOSE

To explore the morphological and functional characteristics of prostatic arterial embolization (PAE) in a canine model of benign prostatic hyperplasia (BPH) with 3T multiparametric magnetic resonance imaging (mp-MRI) and whole-mount step-section pathology correlation.

MATERIALS AND METHODS

Eight adult male beagle dogs with hormone-induced BPH underwent 3T mp-MRI before and 1, 3, and 6 months after PAE, with subsequent whole-mount step-section pathologic assessment. Images were acquired using T₁ -weighted images (T₁ WI), T₂ WI, 3D-SPACE, diffusion-weighted imaging (DWI), susceptibility-weighted imaging (SWI), T₂ -mapping, and dynamic contrast-enhanced (DCE) sequences. Variance analysis was performed to assess statistical differences in prostatic volume (PV), apparent diffusion coefficient (ADC), and T₂ values. Pearson correlation analysis was performed to correlate ADC, T₂ , and PV.

RESULTS

The PV decreased from baseline to 1, 3, and 6 months after PAE from (25.88 ± 7.09) cm³ to (6.48 ± 2.08) cm³ , (6.48 ± 3.39) cm³ , (6.20 ± 2.88) cm³ . The ADC values sequentially decreased from baseline to 1, 3, and 6 months after PAE from (1497.06 ± 222.72) × 10^-6 mm² /s to (1056.00 ± 189.46) × 10^-6 mm² /s, (950.48 ± 77.85) × 10^-6 mm² /s, (980.98 ± 107.78) × 10^-6 mm² /s. The T₂ values decreased from baseline to 1, 3, and 6 months after PAE were (83.74 ± 5.29) msec, (68.72 ± 5.66) msec, (53.96 ± 15.04) msec, (49.81 ± 13.34) msec, respectively. ADC and T₂ values were positively correlated with PV (r = 0.823 and 0.744, respectively). Microhemorrhages and hemosiderin were found on SWI after PAE.

CONCLUSION

3T mp-MRI may facilitate noninvasive assessment of morphological and functional changes of BPH after PAE.

LEVEL OF EVIDENCE

1 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2017;46:1220-1229.

Use of Susceptibility-Weighted Imaging (SWI) in the Detection of Brain Hemorrhagic Metastases from Breast Cancer and Melanoma

PURPOSE

Susceptibility-weighted imaging (SWI) has significantly increased our sensitivity in detecting hemorrhagic brain lesions. We sought to explore the prevalence of intratumoral hemorrhage as detected by SWI in brain metastases from melanoma and breast cancer.

METHODS

Lesions with a size of 0.1 cm were categorized as micrometastases, whereas larger lesions were categorized as macrometastases. Susceptibility-weighted imaging findings on locations corresponding to enhancing lesions were categorized as either positive or negative based on presence/absence of signal dropout. The percentage of SWI positivity was then estimated as a function of lesion size. Two-tailed Fisher exact test was performed to examine differences in the contingency tables.

RESULTS

Magnetic resonance imaging studies from 73 patients with 1173 brain metastases, which enhanced on postcontrast T1-weighted imaging (T1WI) were selected for analysis. Of these lesions, 952 had SWI data available, and 342 of 952 were micrometastases. Only 10 of the 342 micrometastases and 410 (67.2%) of the 610 macrometastases were SWI positive (P < 0.0001). When examined by tumor type, 76.9% (melanoma) versus 55.6% (breast cancer) were SWI positive (P < 0.0001), regardless of tumor size. All melanoma lesions (8/8) and only 1 of 15 breast cancer lesions larger than 1.5 cm were SWI positive.

CONCLUSION

With the use of combined SWI and contrast-enhanced high-resolution T1 imaging, we found that presence of intratumoral brain hemorrhage is uncommon in micrometastases but common in metastases greater than 0.1 cm from breast cancer or melanoma. Large metastases commonly harbored hemorrhage, and this occurred more frequently in patients with melanoma than with breast cancer.

Assessment of intracranial meningioma-associated calcifications using susceptibility-weighted MRI

PURPOSE

To determine the diagnostic accuracy of susceptibility-weighted MRI (SW-MRI) for the detection of intracranial meningioma-associated calcifications compared with standard MR sequences, using computed tomography (CT) as a reference standard.

MATERIALS AND METHODS

354 patients, who had received both a CT and a 1.5 Tesla clinical brain MRI with SW-MRI sequences between January 2014 and July 2016, were retrospectively evaluated and 316 patients were included. Calcification diameter was used to assess correlation between imaging modalities. Sensitivity and specificity as well as intra- and interobserver agreement were calculated for SW-MRI and standard MRI sequences when compared with reference standard CT.

RESULTS

Fifty patients had positive findings for intracranial meningioma-associated calcifications on CT scans. SW-MRI reached a sensitivity of 94% (95% confidence interval [CI]: 83-99%) and a specificity of 95% (95% CI: 92-98%) for the detection of meningioma-associated calcifications, while standard MRI yielded a sensitivity of 64% (95% CI: 49-77%) and a specificity of 94% (95% CI: 90-96%). Diameter measurements between SW-MRI and CT showed a close correlation (R²  = 0.99; P < 0.001) with a slight overestimation of size, which, however, did not reach significance level (SW-MRI: 8.2 mm ± 7.1; CT: 6.8 mm ± 6.4; P = 0.29). Compared with standard MRI, SW-MRI showed a better interobserver agreement for size measurements of calcifications.

CONCLUSION

SW-MRI enables a reliable detection of intracranial meningioma-associated calcifications by using CT as a reference and offers a higher diagnostic accuracy than standard MRI.

LEVEL OF EVIDENCE

3 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2017;46:1177-1186.

Potential of quantitative susceptibility mapping for detection of prostatic calcifications

PURPOSE

To evaluate whether quantitative susceptibility (QSM) may be used as an alternative to computed tomography (CT) to detect calcification in prostate cancer patients.

MATERIALS AND METHODS

Susceptibility map calculation was performed using 3D gradient echo magnetic resonance imaging (MRI) data from 26 patients measured at 3T who previously received a planning CT of the prostate. Phase images were unwrapped using Laplacian-based phase unwrapping, the background field was removed with the V-SHARP method, and susceptibility maps were calculated with the iLSQR method. Two blinded readers were asked to identify peri- and intraprostatic calcifications.

RESULTS

Average mean and minimum susceptibility values (referenced to iliopsoas muscle) of calcifications were -0.249 ± 0.179 ppm and -0.551 ± 0.323 ppm, and average mean and maximum intensities in CT images were 319 ± 164 HU and 679 ± 392 HU. Twenty-one and 17 out of 22 prostatic calcifications were identified using susceptibility maps and magnitude images, respectively, as well as more than half of periprostatic phleboliths depicted by CT. Calcifications in the prostate and its periphery were quantitatively differentiable from noncalcified prostate tissue in CT (mean values for calcifications / for noncalcified tissue: 71 to 649 / -1 to 83 HU) and in QSM (mean values for calcifications / for noncalcified tissue: -0.641 to 0.063 / -0.046 to 0.181 ppm). Moreover, there was a significant correlation between susceptibility values and CT image intensities for calcifications (P < 0.004).

CONCLUSION

Prostatic calcifications could be well identified with QSM. Susceptibility maps can be easily obtained from clinical prostate MR protocols that include a 3D gradient echo sequence, rendering it a promising technique for detection and quantification of intraprostatic calcifications.

LEVEL OF EVIDENCE

1 J. Magn. Reson. Imaging 2017;45:889-898.

Susceptibility-weighted magnetic resonance imaging for the evaluation of deep infiltrating endometriosis: preliminary results

BACKGROUND

Knowledge of the precise sites of deep infiltrating endometriosis (DIE) lesions is essential for preoperative workup and treatment. Susceptibility-weighted imaging (SWI) has high sensitivity for blood products and have recently been applied in abdominal imaging.

PURPOSE

To determine the value of SWI in the diagnosis of DIE.

MATERIAL AND METHODS

Forty-three clinically suspected DIE patients with sonographically diagnosed ovarian endometriomas who had tenderness or palpable nodule(s) on rectovaginal examination were referred to pelvic magnetic resonance imaging (MRI) including SWI. Two patients were excluded from the study because of low quality of SWI series. Twenty-eight patients who were offered laparoscopic endometriosis surgery (LES) preferred medical treatment over surgical approach. Thirteen out of 41 participants had LES. Lesions were evaluated for their locations, signal intensities on T1-weighted (T1W) and T2-weighted (T2W) images, and presence of signal voids on SWI using 3T MRI and correlated with LES findings.

RESULTS

A total of 18 endometriosis foci were laparoscopically removed from 13 patients. DIE lesions removed at laparoscopy were located at the uterosacral ligament (9/18), rectovaginal region (4/18), retrocervical region (2/18), and fallopian tubes (3/18). Eleven out of 18 (61%) DIE foci were detected by their high-signal intensities on T1W images whereas 16 out of 18 (89%) DIE foci were detected by signal voids on SWI.

CONCLUSION

SWI imaging with its high sensitivity to blood products, contributes to the diagnosis of DIE by depicting different phases of hemorrhage not seen by conventional MRI sequences.

Diagnosis of Calcific Tendonitis of the Rotator Cuff by Using Susceptibility-weighted MR Imaging

PURPOSE

To evaluate the diagnostic performance of susceptibility-weighted imaging (SWI) and standard shoulder joint magnetic resonance (MR) sequences in comparison to that of conventional radiography for the identification of calcifications in the rotator cuff in patients with calcific tendonitis.

MATERIALS AND METHODS

The institutional review board approved this prospective study. Written informed consent was obtained from all subjects. Fifty-four patients clinically suspected of having calcific tendonitis of the rotator cuff were included. On radiographs (the standard of reference), 27 patients had positive calcification findings, and 27 did not. Standard MR sequences and SWI, including magnitude and phase imaging, were performed. The diameter of calcifications was measured to assess intermodality correlations. Sensitivity, specificity, and intra- and interobserver agreement were calculated. Phantom measurements were performed to assess the detection limit of SWI.

RESULTS

Fifty-six calcifications were detected with radiography in 27 patients. Most (55 calcifications, 98%) could be identified as calcifications by using SWI. Standard T1- and T2-weighted sequences were used to identify 33 calcifications (59%). SWI yielded a sensitivity of 98% (95% confidence interval [CI]: 0.943, 1) and specificity of 96% (95% CI: 0.886, 1) for the identification of calcifications when compared with radiography. Standard rotator cuff MR sequences yielded a sensitivity of 59% (95% CI: 0.422, 0.758) and specificity of 67% (95% CI: 0.493, 0.847). Diameter measurements demonstrated a high correlation between SWI and radiography (R(2) = 0.90), with overestimation of lesion diameter at SWI (mean ± standard deviation for SWI, 7.6 mm ± 5.4; for radiography, 5.3 mm ± 5.1). SWI yielded higher interobserver agreement (R(2) = 0.99, P < .001; 95% CI: 0.989, 0.996) compared with standard MR sequences (R(2) = 0.67, P = .62; 95% CI: 0.703, 0.899). In phantom experiments, SWI and computed tomography were used to identify small calcifications that were missed at radiography.

CONCLUSION

SWI enables the reliable detection of calcifications in the rotator cuff in patients with calcific tendonitis by using conventional radiography as a reference and offers better sensitivity and specificity than standard rotator cuff MR sequences.

Susceptibility-Based Differentiation of Intracranial Calcification and Hemorrhage in Pediatric Patients

Differential diagnosis of intracranial hemorrhage versus calcification on conventional magnetic resonance images (MRIs) is often challenging. Although computed tomography (CT) confirms calcification, phase information obtained during susceptibility-weighted imaging can be useful in distinguishing between 2 pathologies. Fourteen patients previously diagnosed to have hemorrhage or calcification with imaging were included in the study retrospectively. Phase shift values of hemorrhage and calcification were compared by using Student t test. The pathologies identified were tuberous sclerosis, Sturge-Weber syndrome, craniopharyngioma, congenital cytomegalovirus, subependymal hemorrhages, and hemorrhagic microembolic infarction. Calcifications appeared hypointense whereas hemorrhages were hyperintense on phase maps (left-handed magnetic resonance system). Statistical comparison of phase shift values yielded significant difference between hemorrhage versus calcification (P < .01). Phase maps were found to offer valuable data to differentiate 2 pathologies when used complementary to conventional magnetic resonance images. Considering the relatively higher risks of radiation exposure in children, susceptibility-weighted imaging with phase maps may help to waive radiation exposure from CT.

Susceptibility weighted imaging: differentiating between calcification and hemosiderin

Objective

To present a detailed explanation on the processing of magnetic susceptibility weighted imaging (SWI), demonstrating the effects of echo time and sensitive mask on the differentiation between calcification and hemosiderin.

Materials and Methods

Computed tomography and magnetic resonance (magnitude and phase) images of six patients (age range 41– 54 years; four men) were retrospectively selected. The SWI images processing was performed using the Matlab’s own routine.

Results

Four out of the six patients showed calcifications at computed tomography images and their SWI images demonstrated hyperintense signal at the calcification regions. The other patients did not show any calcifications at computed tomography, and SWI revealed the presence of hemosiderin deposits with hypointense signal.

Conclusion

The selection of echo time and of the mask may change all the information on SWI images, and compromise the diagnostic reliability. Amongst the possible masks, the authors highlight that the sigmoid mask allows for contrasting calcifications and hemosiderin on a single SWI image.

Prostate cancer research in China

Prostate cancer (PCa) research in China has been on a rocketing trend in recent years. The first genome-wide association study (GWAS) in China identified two new PCa risk associated single nucleotide polymorphisms (SNPs). Next generation sequencing is beginning to be used, yielding novel findings: gene fusions, long non-coding RNAs and other variations. Mechanisms of PCa progression have been illustrated while various diagnosis biomarkers have been investigated extensively. Personalized therapy based on genetic factors, nano-medicine and traditional Chinese medicine has been the focus of experimental therapeutic research for PCa. This review intends to shed light upon the recent progress in PCa research in China and points out the possible breakthroughs in the future.