Katja Pinker

Diffusion-weighted MR for Differentiation of Breast Lesions at 3.0 T: How Does Selection of Diffusion Protocols Affect Diagnosis?

PURPOSE To compare the diagnostic quality of diffusion-weighted (DW) imaging schemes with regard to apparent diffusion coefficient (ADC) accuracy, ADC precision, and DW imaging contrast-to-noise ratio (CNR) for different types of lesions and breast tissue. MATERIALS AND METHODS Institutional review board approval and written, informed consent were obtained. Fifty-one patients with histopathologic correlation or follow-up performed with a 3.0-T MR imager were included in this study. There were 112 regions of interest drawn in 24 malignant, 17 benign, 20 cystic, and 51 normal tissue regions. ADC maps were calculated for combinations of 10 b values (range, 0-1250 sec/mm(2)). Differences in ADC among tissue types were evaluated. The CNRs of lesions at DW imaging were compared for all b values. A repeated-measures analysis of variance was used to assess lesion differentiation. RESULTS ADCs calculated from b values of 50 and 850 sec/mm(2) were 0.99 x 10(-3) mm(2)/sec +/- 0.18 (standard deviation), 1.47 x 10(-3) mm(2)/sec +/- 0.21, 1.85 x 10(-3) mm(2)/sec +/- 0.22, and 2.64 x 10(-3) mm(2)/sec +/- 0.30 for malignant, benign, normal, and cystic tissues, respectively. An ADC threshold level of 1.25 x 10(-3) mm(2)/sec allowed discrimination between malignant and benign lesions with a diagnostic accuracy of 95% (P < .001). ADC calculations performed with multiple b values were not significantly more precise than those performed with only two. We found an overestimation of ADC for maximum b values of up to 1000 sec/mm(2). The best CNR for tumors was identified at 850 sec/mm(2). CONCLUSION Optimum ADC determination and DW imaging quality at 3.0 T was found with a combined b value protocol of 50 and 850 sec/mm(2). This provided a high accuracy for differentiation of benign and malignant breast tumors.

A combined high temporal and high spatial resolution 3 Tesla MR imaging protocol for the assessment of breast lesions: initial results.

Purpose:To develop a 3.0 Tesla breast imaging protocol that combines high temporal and spatial resolution three-dimensional MR sequences for quantitative time course and morphologic analysis of breast lesions. Materials and Methods:Thirty-four patients were included in the study (age range, 31–82; mean age, 54.3). The study protocol was approved by the Institutional Review Board and written informed consent was obtained from all patients. The magnetic resonance imaging protocol included: a coronal T1-weighted volume-interpolated-breathhold-examination sequence, focused on high temporal resolution for optimal assessment of the contrast-enhancement behavior of lesions (SI 1.7 mm isotropic; TA 3.45 minutes for 17 measurements); a coronal T1-weighted turbo fast-low-angle-shot-three-dimensional sequence, with water-excitation and fat suppression, focused on high spatial resolution for morphologic analysis (SI 1 mm isotropic; TA 2 minutes); and a repeated coronal volume-interpolated-breathhold-examination sequence for detection of washout. Lesion size and morphology were assessed. Region-of-interests for suspicious areas were manually drawn and evaluated for contrast-enhancement behavior by plotting intensity courses against time. Sensitivity and specificity with a 95% confidence interval and the negative predictive value and positive predictive value were calculated. Diagnostic accuracy was assessed. The histopathological diagnoses were used as a standard of reference. Results:Fifty-five lesions were detected in 34 patients. All malignant breast lesions were identified correctly. There were 5 false-positive lesions. The sensitivity of contrast-enhanced magnetic resonance imaging of the breast at 3 T was 100%, with a 95% confidence interval (CI) of 90.6% to 100%. The specificity was 72.2%, with a 95% CI of 49.1% to 87.5%. The positive predictive value was 0.88 and the negative predictive value was 1. Diagnostic accuracy was 91% with a 95% CI of 80.4% to 96.1%. Conclusion:Our prospective study demonstrates that the presented 3 Tesla MR imaging protocol, comprising both high temporal and high spatial resolution, enables accurate detection and assessment of breast lesions.

Effect of contrast dose and field strength in the magnetic resonance detection of brain metastases.

PurposeTo compare the diagnostic efficacy of a standard and cumulative triple dose of magnetic resonance (MR) imaging contrast agent in the evaluation of brain metastases using a high-field 3.0 T MR unit versus a standard field 1.5 T MR unit. MethodsTwenty-two patients with suspected brain metastases were examined at both field strengths using identical postcontrast coronal 3D gradient echo with magnetization preparation, which was adjusted separately for each field strength. In both groups initially, iv injection of 0.1 mmol/kg body weight gadolinium chelate (gadodiamide) and thereafter, 0.2 mmol/kg body weight gadodiamide were administered. Subjective assessment of the images was performed independently by 3 neuroradiologists. Objective measurement of signal-to-noise and contrast-to-noise ratios was obtained. ResultsThe subjective assessment of cumulative triple-dose 3.0 T images obtained the best results compared with other sequences, detecting 84 metastases, followed by 1.5 T cumulative triple-dose enhanced images with 81 brain metastases. The objective assessment confirmed those results, showing significantly higher signal-to-noise and contrast-to-noise ratios with 3.0 T than with 1.5 T. ConclusionsCumulative triple-dose images of both field strengths were superior to standard field strengths. However, administration of gadodiamide contrast agent produces higher contrast between tumor and normal brain on 3.0 T than on 1.5 T, resulting in better detection of brain metastases and leptomeningeal involvement.

Detection of degenerative cartilage disease: comparison of high-resolution morphological MR and quantitative T2 mapping at 3.0 Tesla

OBJECTIVE The aim of the study was to investigate the association of T2 relaxation times of the knee with early degenerative cartilage changes. Furthermore the impact of unloading the knee on T2 values was evaluated. METHODS Forty-three patients with knee pain and an ICRS (International Cartilage Repair Society) cartilage defect grade <or=2 were examined with 3T magnetic resonance imaging (MRI). Morphological cartilage grading was based on high-resolution proton-density (PD), turbo-spin-echo (TSE) and three-dimensional (3D) isotropic True fast imaging with steady-state precession (FISP) images of slices covering the cartilage layer above the posterior horn of the meniscus. T2 maps were calculated from a multi-echo, spin-echo (MESE) sequence, performed at the beginning and at the end of the scan (time interval 40 min). Influence of cartilage defect grading on deep, superficial, and global T2 values as well as on T2 values for zonal variation was assessed using analysis of variance (ANOVA) and Spearman rank correlation test. Differences among both T2 measurements were compared using paired t-test. RESULTS Global and superficial T2 values significantly increased with cartilage defect grade regardless of the time elapsed from unloading (global T2: ICRS grade 0, 38.9 and 40.1 ms; grade 1, 41.2 and 44.5 ms; grade 2, 47.7 and 53.4 ms; P=0.041 and 0.008) with stronger correlation for second T2 measurement. In contrast there were no significant differences among grades in the zonal variation at any time. Significant differences for T2 values between the two subsequent measurements were consistently found. CONCLUSION T2 mapping might be a sensitive method for the detection of early cartilage degeneration. From our results we would recommend to measure T2 after unloading.

Improved diagnostic accuracy with multiparametric magnetic resonance imaging of the breast using dynamic contrast-enhanced magnetic resonance imaging, diffusion-weighted imaging, and 3-dimensional proton magnetic resonance spectroscopic imaging.

IntroductionThe purpose of this study was to compare the diagnostic accuracy of dynamic contrast-enhanced (DCE) magnetic resonance imaging (MRI) as a single parameter to multiparametric (MP) MRI with 2 (DCE MRI and diffusion-weighted imaging [DWI]) and 3 (DCE MRI, DWI, and 3-dimensional proton magnetic resonance spectroscopic imaging [3D 1H-MRSI]) parameters in breast cancer diagnosis. Materials and MethodsThis prospective study was approved by the institutional review board. Written informed consent was obtained in all patients. One hundred thirteen female patients (mean age, 52 years; range, 22–86 years) with an imaging abnormality (Breast Imaging Reporting and Data System 0, 4–5) were included in this study. Multiparametric MRI of the breast at 3 T with DCE MRI, DWI, and 3D 1H-MRSI was performed. The likelihood of malignancy was assessed for DCE MRI and MP MRI with 2 (DCE MRI and DWI) and 3 (DCE MRI, DWI, and 3D 1H-MRSI) parameters separately. Histopathology was used as the standard of reference. Appropriate statistical tests were used to assess sensitivity, specificity, and diagnostic accuracy for each assessment combination. ResultsThere were 74 malignant and 39 benign breast lesions. Multiparametric MRI with 3 MRI parameters yielded significantly higher areas under the curve (0.936) in comparison with DCE MRI alone (0.814) (P < 0.001). Multiparametric MRI with just 2 parameters at 3 T did not yield higher areas under the curve (0.808) than did DCE MRI alone (0.814). Multiparametric MRI with 3 parameters resulted in elimination of false-negative lesions and significantly reduced the false-positives ones (P = 0.002). ConclusionsMultiparametric MRI with 3 parameters increases the diagnostic accuracy of breast cancer in comparison with DCE-MRI alone and MP MRI with 2 parameters.

Molecular imaging of cancer: MR spectroscopy and beyond.

Proton magnetic resonance spectroscopic imaging is a non-invasive diagnostic tool for the investigation of cancer metabolism. As an adjunct to morphologic and dynamic magnetic resonance imaging, it is routinely used for the staging, assessment of treatment response, and therapy monitoring in brain, breast, and prostate cancer. Recently, its application was extended to other cancerous diseases, such as malignant soft-tissue tumours, gastrointestinal and gynecological cancers, as well as nodal metastasis. In this review, we discuss the current and evolving clinical applications of proton magnetic resonance spectroscopic imaging. In addition, we will briefly discuss other evolving techniques, such as phosphorus magnetic resonance spectroscopic imaging, sodium imaging and diffusion-weighted imaging in cancer assessment.

Three-dimensional Proton MR Spectroscopic Imaging at 3 T for the Differentiation of Benign and Malignant Breast Lesions

PURPOSE To evaluate the diagnostic accuracy of quantitative, three-dimensional (3D) magnetic resonance (MR) spectroscopic imaging at 3 T for the differentiation of benign and malignant breast lesions, on the basis of choline (Cho) signal-to-noise ratio (SNR) threshold levels, in a clinically feasible measurement time. MATERIALS AND METHODS Institutional review board approval and written informed consent were obtained from all subjects. Fifty female patients (mean age, 50 years; age range, 25-82 years) with mammographic or ultrasonographic (US) abnormalities were successfully examined in the prone position with a 3-T MR system by using a dedicated breast coil. Lesions were verified by either histopathologic examination or follow-up of at least 24 months. For 3D MR spectroscopic imaging, a point-resolved spectroscopic sequence (repetition time msec/echo time msec, 750/145; field of view, 12 × 12 × 12 cm(3); matrix size, 12 × 12 × 12, interpolated to 16 × 16 × 16; acquisition time, 11 minutes 17 seconds) was used. The maximum Cho SNR was assessed in all lesions and correlated with the histopathologic results. RESULTS Thirty-two malignant and 12 benign lesions were confirmed in 43 patients with histopathologic examination. Seven patients without biopsy underwent imaging follow-up. In 31 of 32 (97%) malignant and 10 of 19 (53%) benign lesions, Cho was detected. The median Cho SNR in malignant lesions was 5.7, compared with 2.0 in benign lesions. With a Cho SNR threshold level of 2.6, 3D MR spectroscopic imaging provided a sensitivity of 97% and a specificity of 84% for the differentiation of benign and malignant breast lesions. CONCLUSION At 3T, 3D MR spectroscopic imaging yields high diagnostic sensitivity and specificity for discrimination of benign and malignant breast lesions within reasonable measurement times. This technique allows the study of heterogeneous and multicentric breast tumors and simplifies acquisition planning.

MR contrast agent at high-field MRI (3 Tesla).

Tumor-to-brain contrast after gadolinium administration using MP-RAGE and T1-SE scans in patients with primary and secondary brain tumors was significantly higher at 3 T than at 1.5 T. The subjective assessment of cumulative triple-dose 3 Tesla images obtained the best results in the detection of brain metastases compared with other sequences followed by 1.5 T cumulative triple-dose enhanced images. In macroadenomas of the hypophysis, contrast-enhanced 3 T MRI was superior to standard MRI in the diagnosis of cavernous sinus infiltration and in visualization of cranial nerves within the cavernous sinus. Due to higher spatial resolution, contrast-enhanced MR venography at 3 T showed more details in and around tumors than at 1.5 T, additionally enhanced by stronger susceptibility weighting and higher signal-to-noise ratio at 3 T. In summary, administration of gadolinium-based contrast agent produces higher contrast between tumor and normal brain at 3 T than at 1.5 T, helps to detect more cerebral metastases at 3 T versus 1.5 T in single and cumulative triple dose, improves the evaluation of macroadenomas of the hypophysis, and makes MR venography at 3 T clinically attractive with increase in spatial resolution within the same measurement time, thus providing more detailed information.

T1 (Gd) Gives Comparable Information as Delta T1 Relaxation Rate in dGEMRIC Evaluation of Cartilage Repair Tissue

Objectives:To evaluate the relationship between T1 after intravenous contrast administration (T1Gd) and &Dgr; relaxation rate (&Dgr;R1) = (1/T1(Gd) − 1/T1o) in the delayed Gadolinium-Enhanced MRI of cartilage (dGEMRIC) evaluation of cartilage repair tissue. Materials and Methods:Thirty single MR examinations from 30 patients after matrix-associated autologous chondrocyte transplantations of the knee joint with different postoperative intervals were examined using an 8-channel knee-coil at 3T. T1 mapping using a 3D GRE sequence with a 35/10° flip angle excitation pulse combination was performed before and after contrast administration (dGEMRIC technique). T1 postcontrast (T1(Gd)) and the &Dgr;R1 (relative index of pre- and postcontrast R1 value) were calculated for repair tissue and the weight-bearing normal appearing control cartilage. For evaluation of the different postoperative intervals, MR exams were subdivided into 3 groups (up to 12 months, 12–24 months, more than 24 months). For statistical analysis Spearman correlation coefficients were calculated. Results:The mean value for T1 postcontrast was 427 ± 159 ms, for &Dgr;R1 1.85 ± 1.0; in reference cartilage 636 ± 181 ms for T1 postcontrast and 0.83 ± 0.5 for &Dgr;R1.The correlation coefficients were highly significant between T1 (Gd) and &Dgr;R1 for repair tissue (0.969) as well as normal reference cartilage (0.928) in total, and for the reparative cartilage in the early, middle postoperative, and late postoperative interval after surgery (R values: −0.986, −0.970, and −0.978, respectively). Using either T1(Gd) or &Dgr;R1, the 2 metrics resulted in similar conclusions regarding the time course of change of repair tissue and control tissue, namely that highly significant (P > 0.01) differences between cartilage repair tissue and reference cartilage were found for all follow-up groups. Additionally, for both metrics highly significant differences (P < 0.01) between early follow up and the 2 later postoperative groups for cartilage repair tissue were found. No statistical differences were found between the 2 later follow-up groups of reparative cartilage either for T1 (Gd) or &Dgr;R1. Conclusion:The high correlation between T1 (Gd) and &Dgr;R1 and the comparable conclusions reached utilizing metric implies that T1 mapping before intravenous administration of MR contrast agent is not necessary for the evaluation of repair tissue. This will help to reduce costs, inconvenience for the patients, simplifies the examination procedure, and makes dGEMRIC more attractive for follow-up of patients after cartilage repair surgeries.

Improved Differentiation of Benign and Malignant Breast Tumors with Multiparametric 18Fluorodeoxyglucose Positron Emission Tomography Magnetic Resonance Imaging: A Feasibility Study

Purpose: To assess whether multiparametric 18fluorodeoxyglucose positron emission tomography magnetic resonance imaging (MRI) (MP 18FDG PET-MRI) using dynamic contrast-enhanced MRI (DCE-MRI), diffusion-weighted imaging (DWI), three-dimensional proton MR spectroscopic imaging (3D 1H-MRSI), and 18FDG-PET enables an improved differentiation of benign and malignant breast tumors. Experimental Design: Seventy-six female patients (mean age, 55.7 years; range, 25–86 years) with an imaging abnormality (BI-RADS 0, 4–5) were included in this Institutional Review Board (IRB)-approved study. Patients underwent fused PET-MRI of the breast with 18FDG-PET/CT and MP MRI at 3T. The likelihood of malignancy was assessed for all single parameters, for MP MRI with two/three parameters, and for MP 18FDG PET-MRI. Histopathology was used as the standard of reference. Appropriate statistical tests were used to assess sensitivity, specificity, and diagnostic accuracy for each assessment combination. Results: There were 53 malignant and 23 benign breast lesions. MP 18FDG PET-MRI yielded a significantly higher area under the cure (AUC) of 0.935 than DCE-MRI (AUC, 0.86; P = 0.044) and the combination of DCE-MRI and another parameter (AUC, 0.761–0.826; P = 0.013–0.020). MP 18FDG PET-MRI showed slight further improvement to MP MRI with three parameters (AUC, 0.925; P = 0.317). Using MP 18FDG PET-MRI there would have been a reduction of the unnecessary breast biopsies recommended by MP imaging with one or two parameters (P = 0.002–0.011). Conclusion: This feasibility study shows that MP 18FDG PET-MRI enables an improved differentiation of benign and malignant breast tumors when several MRI and PET parameters are combined. MP 18FDG PET-MRI may lead to a reduction in unnecessary breast biopsies. Clin Cancer Res; 20(13); 3540–9. ©2014 AACR.