Abstract PD4-07: PET imaging of PARP-1 expression in breast cancer

18F-FluorThanatrace ([18F]-FTT) is a novel radiotracer shown to quantify Poly [ADP-ribose] polymerase 1 (PARP-1) expression in vitro and in vivo through a receptor-ligand interaction. A recent study at the University of Pennsylvania in women with ovarian cancer demonstrated in vivo visualization of PARP-1 expression in tumors using this radiotracer that closely correlated with an in vitro assay of PARP-1 in tumor tissue (Makvandi, M. J. Clin. Invest. 128:2116, 2018). A radioligand with PARP-1 specificity, [125I]-KX1, was also developed as a companion tool for ex vivo evaluation of PARP-1 expression and PARP inhibitor (PARPi) drug occupancy by radioligand binding assay (Makvandi, M. Cancer Res. 76:4516, 2016). As the first step in validating this biomarker in breast cancer, we performed a prospective clinical trial comparing in vivo [18F]-FTTuptake and ex vivo PARP-1 expression in women with primary breast cancer.

Methods: 24 patients with Stage I-IV primary breast cancer were imaged with [18F]-FTT prior to any therapy including surgery. We correlated in vivo uptake with ex vivo immunohistochemistry (IHC) for PARP-1 and [125I]-KX1 autoradiography in untreated surgical specimens. Tumors were analyzed for alterations in DNA repair genes, copy number-based as well as mutational signatures indicative of homologous recombination deficiency (HRD) and mutational burden, using our established protocol (Maxwell, KN, Nature Commun. 8:319, 2017).

Results: [18F]-FTT uptake was visualized above background in all primary breast tumors and known metastases. Two areas of unexpected uptake revealed an unknown contralateral breast cancer and an ovarian carcinoid, respectively. We expected that uptake might be highest in triple negative breast cancer (TNBC), where PARPi have been most heavily studied. However, a range of tracer uptake was observed in tumors independent of breast cancer subtype (hormone receptor positive/HER2 negative, TNBC, HER2+) and BRCA status. Uptake ratios (SUVmax tumor/SUV max opposite breast) ranged from 1.2-10.5 with a median 4.0. Ex vivo[125I]-KX1 autoradiography was performed on a subset of untreated primary tumors (n=5) and compared with IHC staining for PARP-1 on sequential sections. This revealed a close spatial correspondence between elevated PARP-1 expression by IHC and regions of elevated [125I]-KX1 binding radiographically. There was also a strong positive correlation between in vivo [18F]-FTT uptake and ex vivo quantitative [125I]-KX1 autoradiography (r=0.78). Genomic analysis of HRD in all tumors is pending and will be reported.

Conclusion: Initial analyses support the ability of [18F]-FTT to visualize and measure PARP-1 expression in breast cancer. This is the first step toward developing an imaging companion diagnostic to help guide PARP inhibitor treatment in breast cancer. Ongoing studies are expanding upon these results, testing the extent to which expression of PARP-1 by [18F]-FTT can predict response to PARP inhibitors and measure target engagement during therapy.

Citation Format: McDonald ES, Carlin S, Maxwell KN, Nayak A, Doot RK, Pantel AR, Farwell MD, Pryma DA, Clark AS, Shah P, DeMichele AM, Ziober A, Schubert EK, Palmer K, Lee HS, Matro J, de la Cruz L, Tchou J, Anderson DN, Feldman MD, Sheffer RE, Knollman H, Schnall MD, Makvandi M, Domchek S, Hubbard RA, Mach RH, Mankoff DA. PET imaging of PARP-1 expression in breast cancer [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr PD4-07.

Abstract PD7-05: Comparative costs of breast cancer screening with digital breast tomosynthesis versus digital mammography: A health system perspective

Background

Digital breast tomosynthesis (DBT) is being rapidly implemented in breast cancer screening and demonstrates improved specificity and sensitivity compared to screening with digital mammography (DM) alone. Prior work based on payer perspectives has demonstrated that DBT can be cost-effective. However, DBT is costlier than DM, and there are little data from a health system perspective about the comparative test performance and costs of DBT versus DM.

Methods

We evaluated breast cancer screening episodes in a single health system between January 1, 2012 and December 31, 2013. A screening episode was defined as a single screening mammogram and all downstream breast diagnosis related costs for the following 1 year. Episodes were excluded if the patient had a prior diagnosis of breast cancer or reached 90 years of age before the end of the follow-up period. Test performance with respect to four outcomes – true positive (TP), true negative (TN), false positive (FP), and false negative (FN) rates – was determined by comparing the BI-RADS score assigned at screening with data about subsequent cancer diagnosis from institutional and state cancer registries. Cost data were developed using CPT codes collected from organizational billing systems and converted to the Medicare Physician Fee Payment Schedule for our region with an imputed additional charge of $60.16 for DBT. Based on this approach, a DM screening exam cost $155.66 and a DBT screening exam cost $215.82. We evaluated overall costs across a screening episode, as well as by four windows: screening, follow-up, diagnosis, and cancer treatment. Data were described using percentages, and Chi-squared and Fisher's exact tests were used to evaluate differences in test performance outcomes and costs based on screening technology.

Results

There were a total of 46,483 cost episodes during the study period, of which 24,502 (52.7%) were screened by DM and 21,981 (47.3%) were screened by DBT. Overall, there were 224 TP (0.5%), 29 FN (0.1%), 4,530 FP (9.8%), and 41,700 TN (89.7%) episodes. Compared to DM episodes, DBT episodes had lower FP (8.6% vs. 10.8%, p<0.001) and higher TN (90.9% vs. 88.7%, p<0.001) rates. There were no statistically significant differences between DBT and DM episodes with respect to TP and FN rates.

Overall, average episode costs were higher for DBT compared to DM ($378.02 vs. $286.62, p<0.001). This $91.40 difference was driven by higher average screening costs ($215.94 vs. $155.76, p<0.001), which approximated the additional charge for DBT, as well as follow-up costs ($23.67 vs. $12.11, p<0.001). There was no significant difference in costs between DBT and DM episodes within the diagnosis or cancer treatment windows.

Compared to DM episodes, DBT episodes had equivalent average episode costs per woman screened for FP ($67.75 vs. $65.71, p=0.49), FN ($4.63 vs. $5.60, p=0.69) and TP ($85.80 vs. $65.15, p=0.07) outcomes, but higher costs for TN ($219.84 vs. $150.16, p<0.001) outcomes.

Conclusion

At a single health system, screening with DBT decreased FP rates and increased TN rates compared to screening with DM. DBT costs more overall, but not on a per-woman-screened basis for FP, FN, and TP outcomes.

Citation Format: Liao GJ, Glick HA, Synnestvedt MB, Schnall MD, Conant EF. Comparative costs of breast cancer screening with digital breast tomosynthesis versus digital mammography: A health system perspective [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr PD7-05.

Dual-energy contrast-enhanced digital breast tomosynthesis--a feasibility study

Contrast-enhanced digital breast tomosynthesis (CE-DBT) is a novel modality for imaging breast lesion morphology and vascularity. The purpose of this study is to assess the feasibility of dual-energy subtraction as a technique for CE-DBT (a temporal subtraction CE-DBT technique has been described previously). As CE-DBT evolves, exploration of alternative image acquisition techniques will contribute to its optimisation. Evaluation of dual-energy CE-DBT was conducted with Institutional Review Board (IRB) approval from our institution and in compliance with federal Health Insurance Portability and Accountability Act (HIPAA) guidelines. A 55-year old patient with a known malignancy in the right breast underwent imaging with MRI and CE-DBT. CE-DBT was performed in the medial lateral oblique view with a DBT system, which was modified under IRB approval to allow high-energy image acquisition with a 0.25 mm Cu filter. Image acquisition occurred via both temporal and dual-energy subtraction CE-DBT. Between the pre- and post-contrast DBT image sets, a single bolus of iodinated contrast agent (1.0 ml kg(-1)) was administered, followed by a 60 ml saline flush. The contrast agent and saline were administrated manually at a rate of approximately 2 ml s(-1). Images were reconstructed using filtered-back projection and transmitted to a clinical PACS workstation. Dual-energy CE-DBT was shown to be clinically feasible. In our index case, the dual-energy technique was able to provide morphology and kinetic information about the known malignancy. This information was qualitatively concordant with that of CE-MRI. Compared with the temporal subtraction CE-DBT technique, dual-energy CE-DBT appears less susceptible to motion artefacts.

Differentiation of benign and malignant breast lesions by in-vivo three-dimensional diffuse optical tomography

Abstract #805

Background: Diffuse optical tomography (DOT) uses near-infrared light to non-invasively image total hemoglobin concentration and blood oxygen saturation in the human breast. Given its low cost, ease of use, and possibility of repeated measured over time, DOT is a promising adjunctive imaging modality for screening, diagnosis and monitoring of neoadjuvant therapy. In this study we explored the performance of DOT to differentiate benign and malignant breast lesions.
 Method and Materials: Forty-seven women with clinical or mammographic abnormalities were prospectively recruited for DOT. Most patients underwent gadolinium-enhanced MRI examination. Three-dimensional oxy-, deoxy-hemoglobin, total hemoglobin concentration, blood oxygen saturation and scattering coefficient images of each breast were reconstructed. Tumor-to-normal (T/N) ratios of these parameters were computed by defining tumor regions with guidance from MRI and radiology reports. In addition, optical index was constructed based on these parameters to maximize the T/N contrast. Only the biopsy-proven lesions were selected (51 breast lesions) and classified into three groups: benign lesions (N=10), malignant lesions where DOT preceded core biopsy (N=20) and malignant lesions where DOT was performed after core-biopsy (N=21). We fit a mixed effects model that estimated the mean optical T/N ratios and optical index for each group, and using the resulting standard errors developed 95% confidence intervals and tested the hypothesis that each optical contrast parameter was unity.
 Results: Malignant cancers showed statistically significant higher total hemoglobin concentration, scattering, oxy-hemoglobin concentration and optical index (P=0.01-0.04) compared to normal tissue. Furthermore, malignant lesions exhibited a two-fold average increase in an optical index derived from the endogenous optical parameters (95% CI: 1.4 - 2.4). To test whether bleeding due to core biopsy influence DOT results, we compared if there was statistically significant differences between two groups measured before or after core-biopsy. There were no statistically significant differences in these groups, suggesting that post biopsy hemorrhage did not alter the DOT results. Benign tumors did not show statistical significance in all of the T/N ratios. AUC of total hemoglobin concentration, scattering, oxy-hemoglobin and optical index suggested good discriminatory power with values between 0.90 and 0.99.
 Discussion: The data demonstrates the feasibility of differentiating benign and malignant lesions by quantitative three-dimensional DOT when the tumor location information is provided by other imaging modality. The main drawback of this study is the small number of benign lesions, which warrants further study. DOT technology is still at its developing stage and needs more investigation to find its niche in breast imaging.

Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 805.

Comparison of MRI endpoints for assessing breast cancer response to neoadjuvant treatment: preliminary findings of the American College of Radiology Imaging Network (ACRIN) trial 6657

Abstract #6043

Background: ACRIN 6657, the imaging component of the I-SPY trial (CALGB 150007/150012), is a multi-center study testing the ability of MRI to provide in-vivo quantification of breast tumor response to neoadjuvant chemotherapy, for early prediction of response and stratification of risk-of-recurrence following treatment. We report results from preliminary analysis comparing MRI variables for correlation with pathologic response and disease progression. Methods: Women with ≥3 cm invasive breast cancer receiving an anthracycline-cyclophosphamide (AC) neoadjuvant chemotherapy regimen followed by a taxane (T) were enrolled between May 2002 and March 2006. Contrast-enhanced MRI was performed prior to start of treatment (baseline), following 1 cycle of AC chemotherapy (t2), between AC and T regimens (t3), and after all chemotherapy but prior to surgery (t4). MRI assessments included tumor longest diameter (MRLD), tumor volume (MRVol), and signal enhancement ratio (SER), a measure of contrast enhancement kinetics. Clinical size (cSize) and mammographic longest diameter (MGLD) were also recorded. Linear dimension was measured by the radiologist for MGLD and MRLD; MRVol was calculated by computer using SER thresholds. Pathologic residual disease size (pSize) and residual cancer burden (RCB) index were evaluated following surgery. Results: 237 patients were enrolled at 9 institutions. 216 patients with complete imaging formed the preliminary analysis set. At time of analysis 42 patients had progressed or died with mean time-to-progression of 21 months; 174 patients were progression-free with mean follow-up time of 42 months. At t4, MRVol was more strongly correlated with pSize than MRLD, SER or cSize (r=.61 vs .28, .24 and .43), while SER showed a stronger correlation with RCB than MRLD, MRVol or cSize (r = .45 vs .30, .31 and .37). MGLD at t4 did not show a significant correlation with either pSize or RCB. Early measurements of tumor size change from baseline by MRVol at t2, and MRVol, MRLD and SER at t3, all showed significant correlation with RCB. In univariate logistic regressions, all t4 measurements were found to be predictive of disease progression. Conclusion: Among clinical and imaging measurements of residual breast tumor size, MRI appears to most accurately reflect pathologic extent of disease following neoadjuvant treatment. Preliminary findings also suggest that tumor size and contrast kinetics measured by MRI may be useful early predictors of treatment response. ACRIN 6657 is continuing to collect follow-up data toward the primary aim testing MRI for stratification of post-treatment risk groups according to 3-year disease-free survival. This work is funded by NIH/ACRIN Grant U01 CA79778S2, CALGB Grants CA31946 and CA33601, and NCI SPORE Grant CA58207.

Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 6043.

The impact of FDG PET in the staging of breast cancer

530

Background: To evaluate the impact of whole-body fluorine-18-fluorodeoxyglucose (FDG) positron emission tomography (PET) in staging breast cancer beyond the breast and axilla. Methods: 200 women, mean age 51 yrs (range 28–81) with breast cancer were enrolled in an IRB approved multi-modality imaging trial from 3/02 to 5/05. After imaging with film screen mammography ± ultrasound (US), patients underwent digital mammography, whole breast US, magnetic resonance imaging (MRI), and whole body FDG PET. Imaging reports and patient charts were reviewed and distant lesions were classified: 1 = no uptake; 2 = physiologic uptake; 3 = non-suspicious uptake; 4 = suspicious uptake without work-up; 5 = suspicious uptake with work-up. Decisions to forego work-up in class 4 lesions were clinical. Class 5 PET lesions were evaluated by confirmatory studies, including computed tomography (CT), MRI, x-ray (XR), bone scan (BS), or pathology. Patients also underwent standard staging with chest XR and BS per clinical judgment. Results: 189/200 (95%) women received PET scans. PET identified 71 distant areas of increased uptake in 42/189 (22%) women. 59/71 (83%) lesions were considered suspicious in 33/42 (79%) women: 50/59 (85%) lesions were class 5 and 9/59 (15%) class 4. Of the 50 class 5 lesions, 19 (38%) were true positive (TP) for neoplastic disease, 2 (4%) were TP for non-neoplastic disease, and 29 (58%) were false positive (FP). The positive predictive value (PPV) for class 5 lesions was 40%. The 19 TP distant sites of malignancy occurred in 6/189 (3%) patients; 4 of these patients (67%) also had TP distant sites identified by standard staging procedures. PET alone identified TP distant disease in 2/189 (1%) women. PET identified 29 FP findings in 22/189 (12%) patients. FP findings prompted 17 CTs, 8 XRs, 2 MRIs, and 1 BS. MRI revealed 2 additional neoplasms that had been false negatives (FN) by PET in 2/189 (1%) women. Conclusions: Whole-body FDG-PET added little additional information in staging our patients with known primary breast cancer, based on low PPV and equivalent TP and FN rates. Additionally, the high FP rate of PET in these patients may prompt unnecessary, costly, and invasive follow-up studies.

No significant financial relationships to disclose.

Pulmonary MR angiography with contrast agent at 4 Tesla: a preliminary result

In this study, pulmonary MR angiography (MRA) using a tailored coil at 4 Tesla in conjunction with an intravenous injection of contrast agent is described. Three-dimensional gradient-echo images were obtained during the intravenous injection of 0.05, 0.1, and 0.2 mmol/kg body weight of gadodiamide to investigate the signal enhancement effect of the contrast agent in pulmonary arteries qualitatively and quantitatively. In the qualitative analysis, the subsegmental branches were visualized on every dose. In the quantitative analysis, the average contrast-to-noise ratios (CNRs) of the main pulmonary arteries increased in a dose-dependent manner. However, the CNRs of segmental arteries did not increase as the dose of contrast agent increased, as observed at 1.5 Tesla MRI. These observations demonstrate the feasibility of delineating the pulmonary vasculature using a contrast agent; however, our results also suggest possible high-field-related disabilities that need to be overcome before high-field (> or =4 Tesla) MRI can be used to full advantage.

A deformable finite element model of the breast for predicting mechanical deformations under external perturbations

RATIONALE AND OBJECTIVES

Live guidance during needle breast procedures is not currently possible with high-field-strength (1.5-T), superconducting magnetic resonance (MR) imaging. The physician can calculate only the approximate location and extent of a tumor in the compressed patient breast before inserting the needle, and the tissue specimen removed at biopsy may not actually belong to the lesion of interest. The authors developed a virtual reality system for guiding breast biopsy with MR imaging, which uses a deformable finite element model of the breast.

MATERIALS AND METHODS

The geometry of the model is constructed from MR data, and its mechanical properties are modeled by using a nonlinear material model. This method allows the breast to be imaged with or without mild compression before the procedure. The breast is then compressed, and the finite element model is used to predict the position of the tumor during the procedure. Three breasts of patients with cancer were imaged with and without compression. Deformable models of these breasts were built, virtually compressed, and used to predict tumor positions in the real compressed breasts. The models were also used to register MR data sets of the same patient breast imaged with different amounts of compression.

RESULTS

The model is shown to predict reasonably well the displacement by plate compression of breast lesions 5 mm or larger.

CONCLUSION

A deformable model of the breast based on finite elements with nonlinear material properties can help in modeling and predicting breast deformation. The entire procedure lasts less than half an hour, making it clinically practical.

Simultaneous acquisition of multiple resolution images for dynamic contrast enhanced imaging of the breast

An imaging technique is described that allows the reconstruction of a series of images at high temporal rates, while simultaneously providing images at high spatial resolution. The method allows one to arbitrarily choose from among several combinations of temporal/spatial resolutions during postprocessing. This flexibility is accomplished by strategically interleaving multiple undersampled projection reconstruction datasets (or subapertures), in which each set can be used to reconstruct a high temporal resolution image. Images with increasingly higher spatial resolutions can subsequently be formed by combining two or more subaperture datasets. The technique is demonstrated in vivo to assess the kinetics of contrast enhancement and to visualize the architectural features of suspicious breast lesions.

An apparatus for MR-guided breast lesion localization and core biopsy: design and preliminary results

System design and initial results are presented from a new unilateral MR-guided breast lesion localization and core biopsy system. Over 150 imaging studies, an accuracy study on phantoms with 50 localization wire deployments and 33 core biopsy trials, and 19 clinical procedures are reported. The mean spatial accuracy from the lesion center for a 20-gauge (G) needle (N = 13) was within 1.2 +/- 1.4 mm (SD) and for a 14G biopsy (N = 4) 0.8 +/- 1.1 mm. For sampling using a 16G core through a 14G needle, the mean accuracy was 5.6 mm (N = 2). The needle guide geometry imposed a small, calculable targeting error. For phantom measurements using the 20G device, the mean geometry-induced error was 0.73 +/- 0.43 mm. However, this contribution was, on average, 42% of the mean measured 2.35 +/- 1.65 mm offset. The new device design provided an accurate and simple guidance method for localization or core biopsy of MR-visible breast lesions.

Dynamic observation of pulmonary perfusion using continuous arterial spin-labeling in a pig model

The continuous arterial spin-labeling (CASL) method of perfusion MRI is used to observe pulmonary perfusion dynamically in an animal model. Specifically, a respiratory-triggered implementation of the CASL method is used with approximate spatial resolution of 0.9 x 1.8 x 5.0 mm (0.008 cc) and 2-minute temporal resolution. Perfusion MRI is performed dynamically during repeated balloon occlusion of a segmental pulmonary artery, as well as during pharmacological stimulation. A total of three Yorkshire pigs were studied. The results demonstrate the ability of the endogenous spin-labeling method to characterize the dynamic changes in pulmonary perfusion that occur during important physiological alterations.

MR imaging of the breast for the detection, diagnosis, and staging of breast cancer

With the introduction of contrast agents, advances in surface coil technology, and development of new imaging protocols, contrast agent-enhanced magnetic resonance (MR) imaging has emerged as a promising modality for detection, diagnosis, and staging of breast cancer. The reported sensitivity of MR imaging for the visualization of invasive cancer has approached 100%. There are many examples in the literature of MR imaging--demonstrated mammographically, sonographically, and clinically occult breast cancer. Often, breast cancer detected on MR images has resulted in a change in patient care. Despite these results, there are many unresolved issues, including no defined standard technique for contrast-enhanced breast MR imaging, no standard interpretation criteria for evaluating such studies, no consensus on what constitutes clinically important enhancement, and no clearly defined clinical indications for the use of MR imaging. Furthermore, this technology remains costly, and issues of cost-effectiveness and cost competition from percutaneous biopsy have yet to be fully addressed. These factors along with the lack of commercially available MR imaging--guided localization and biopsy systems have slowed the transfer of this imaging technology from research centers to clinical breast imaging practices. Technical requirements, potential clinical applications, and potential pitfalls and limitations of contrast-enhanced MR imaging as a method to help detect, diagnose, and stage breast cancer will be described.

The evaluation of human breast lesions with magnetic resonance imaging and proton magnetic resonance spectroscopy

PURPOSE

MR spectroscopy (MRS) assists in lesion characterization and diagnosis when combined with magnetic resonance imaging (MRI). Cancerous lesions demonstrate elevated composite choline levels arising from increased cellular proliferation. Our study investigated if MR spectroscopy of the breast would be useful for characterizing benign and malignant lesions.

MATERIALS AND METHODS

Single voxel proton MR spectroscopy (MRS) was acquired as part of an MR imaging protocol in 38 patients referred upon surgical consultation. The MR spectra were read independently in a blinded fashion without the MR images by three spectroscopists. The MRI exam was interpreted in two settings: (a) as a clinical exam with detailed histories and results from previous imaging studies such as mammography or ultrasound included and (b) as a blinded study without prior histories or imaging results.

RESULTS

Elevated choline levels were demonstrated by MRS in 19 of the 23 confirmed cancer patients. The sensitivity and specificity for determining malignancy from benign breast disease with MRS alone were 83 and 87%, respectively, while a blinded MRI review reported 95 and 86%, respectively.

CONCLUSIONS

Proton MR spectroscopy provides a noninvasive, biochemical measure of metabolism. The technique can be performed in less than 10 min as part of an MRI examination. MRI in combination with MRS may improve the specificity of breast MR and thereby, influence patient treatment options. This may be particularly true with less experienced breast MRI readers. In exams where MRI and MRS agree, the additional confidence measure provided by MRS may influence the course of treatment.

A combined architectural and kinetic interpretation model for breast MR images

RATIONALE AND OBJECTIVES

The purpose of this study was to integrate contrast material kinetic and architectural data from magnetic resonance (MR) images and to assess the improvement in diagnostic accuracy.

MATERIALS AND METHODS

MR imaging data from a diagnostic cohort of 100 patients (50 malignant and 50 benign cases) were analyzed.

RESULTS

Qualitative classification of the enhancement curve was the most predictive kinetic feature. Receiver operating characteristic (ROC) curves were calculated for the architectural model alone and for the architectural model combined with the qualitative kinetic classification. The results demonstrated a statistically significant increase in ROC area (P = .03) of the combined model compared with that of the architectural model alone.

CONCLUSION

The addition of qualitative classification of the time-signal intensity curve to an architectural interpretation model results in significant improvement in model performance as measured by the area under the ROC curve.

Development, standardization, and testing of a lexicon for reporting contrast-enhanced breast magnetic resonance imaging studies

The purpose of this study was to develop, standardize, and test reproducibility of a lexicon for reporting contrast-enhanced breast magnetic resonance imaging (MRI) examinations. To standardize breast MRI lesion description and reporting, seven radiologists with extensive breast MRI experience developed consensus on technical detail, clinical history, and terminology reporting to describe kinetic and architectural features of lesions detected on contrast-enhanced breast MR images. This lexicon adapted American College of Radiology Breast Imaging and Data Reporting System terminology for breast MRI reporting, including recommendations for reporting clinical history, technical parameters for breast MRI, descriptions for general breast composition, morphologic and kinetic characteristics of mass lesions or regions of abnormal enhancement, and overall impression and management recommendations. To test morphology reproducibility, seven radiologists assessed morphology characteristics of 85 contrast-enhanced breast MRI studies. Data from each independent reader were used to compute weighted and unweighted kappa (kappa) statistics for interobserver agreement among readers. The MR lexicon differentiates two lesion types, mass and non-mass-like enhancement based on morphology and geographical distribution, with descriptors of shape, margin, and internal enhancement. Lexicon testing showed substantial agreement for breast density (kappa = 0.63) and moderate agreement for lesion type (kappa = 0.57), mass margins (kappa = 0.55), and mass shape (kappa = 0.42). Agreement was fair for internal enhancement characteristics. Unweighted kappa statistics showed highest agreement for the terms dense in the breast composition category, mass in lesion type, spiculated and smooth in mass margins, irregular in mass shape, and both dark septations and rim enhancement for internal enhancement characteristics within a mass. The newly developed breast MR lexicon demonstrated moderate interobserver agreement. While breast density and lesion type appear reproducible, other terms require further refinement and testing to lead to a uniform standard language and reporting system for breast MRI. J. Magn. Reson. Imaging 2001;13:889-895.

Update of breast MR imaging architectural interpretation model

PURPOSE

To (a) validate a breast magnetic resonance (MR) interpretation model, (b) expand the tree-shaped prediction model to increase specificity without decreasing sensitivity, and (c) reevaluate the model's diagnostic performance.

MATERIALS AND METHODS

Two hundred sixty-two new patients with palpable or mammographic abnormalities underwent MR imaging, and pathologic evaluation was performed. They were entered prospectively into the model, which yielded 454 patients in the construction (training) and validation (test) phases. Predictive values for previously published terminal nodes or branch points of the model were compared between the training and test data sets. Ductal enhancement morphology, regional enhancement micronodularity, regional enhancement degree, and focal mass T2 signal intensity were evaluated for model expansion. Diagnostic performance characteristics of the model were recalculated.

RESULTS

For previously published nodes, absence of a lesion visible at MR imaging, smooth masses, lobulated masses with nonenhancing internal septations, and lobulated masses with minimal or no enhancement had negative predictive values (NPVs) for malignancy similar in both data sets (96% vs 99%, 100% vs 93%, 100% vs 98%, and 100% vs 100%). Irregular masses with internal septations (100% vs 0%) and spiculated masses with no or minimal enhancement (100% vs 50%) did not. Nonseptated enhancing lobulated masses with low T2 signal intensity were added as a benign terminal node (NPV, 100%). Mild regional enhancement (NPV, 92%) was added but not considered a terminal node. Sensitivity, specificity, NPV, positive predictive value, and accuracy of the expanded model were 96%, 80%, 96%, 78%, and 87%, respectively.

CONCLUSION

Additional investigation yielded a slightly modified model, but the diagnostic performance characteristics remain high, similar to those originally published.

An overview of interpretation strategies for breast MR imaging

This article provides an overview of the different approaches to the interpretation of breast MR imaging. It provides an overview of the use of architectural features for breast MR imaging interpretation. It also includes a discussion of the various types of contrast kinetic data that are used for breast MR imaging interpretation. Approaches to combine architectural and kinetic features are also discussed. This article serves as an introduction to the other articles in this issue that discuss specific interpretation and strategies.

MR imaging-guided interventions in the breast

MR imaging of the breast has high sensitivity for the detection of invasive breast cancer. However, not all enhancing lesions are malignant. A needle localization or biopsy system is necessary to differentiate false positive benign enhancing lesions from the true carcinomas. In this article, the techniques, pitfalls, and potential clinical indications for MR imaging-guided needle localization and percutaneous biopsy are discussed.

Endoluminal magnetic resonance imaging in the evaluation of urethral diverticula in women

OBJECTIVES

Accurate determination of the size and extent of urethral diverticula can be important in planning operative reconstruction and repair. Voiding cystourethrography (VCUG) is currently the most commonly used study in the preoperative evaluation of urethral diverticula. We reviewed our experience with the use of endoluminal (endorectal or endovaginal) magnetic resonance imaging (eMRI) in these patients as an adjunctive study to VCUG to evaluate whether the MRI provided anatomically important information that was not apparent on VCUG.

METHODS

A retrospective analysis of all patients with a clinical diagnosis of urethral diverticula undergoing MRI at a single institution was performed. Patients were evaluated with history, physical examination, cystoscopy, VCUG, and eMRI. Endoluminal MRI was retrospectively compared to VCUG with respect to size, extent, and location found at operative exploration.

RESULTS

Twenty-seven consecutive patients underwent endorectal or endovaginal coil MRI in the evaluation of suspected urethral diverticula. Twenty patients subsequently had attempted transvaginal operative repair of the diverticulum. In 2 patients, eMRI demonstrated a urethral diverticulum, whereas VCUG did not. Operative exploration in these patients revealed a urethral diverticulum. In 14 of 27 patients, the VCUG underestimated the size and complexity of the urethral diverticulum as compared to eMRI and operative exploration. In 13 of 27 patients, the size, location, and extent of the urethral diverticulum on VCUG correlated well with the eMRI and/or operative findings.

CONCLUSIONS

We have found endorectal and endovaginal coil MRI to be extremely accurate in determining the size and extent of urethral diverticula as compared to VCUG. This information can be critical when planning the approach, dissection, and reconstruction of these sometimes complex cases.

Electrical stimulation of human muscle studied using 31P-nuclear magnetic resonance spectroscopy

This study used phosphorous nuclear magnetic resonance (31P-NMR) spectroscopy to examine the metabolic demand resulting from electrical muscle stimulation (EMS) applied to human skeletal muscle. For each of six subjects, the forearm flexor muscle group was monitored with 31P-NMR during both maximum voluntary and 6-s EMS-induced contractions. A simple protocol using a tourniquet was added in one subject to assess the role of blood flow in this model. Eight hertz (nontetanic) EMS showed less (p less than 0.025) depletion of phosphocreatine (36%) than did tetanic 70-Hz EMS (60%), voluntary isometric (66%), and voluntary isokinetic (68%). The results of the tourniquet studies suggested that the nontetanic EMS allowed relatively increased muscle blood flow and oxygen supply during contraction. Tetanic EMS provided a similar metabolic demand to that of conventional resistive exercise, as measured by 31P-NMR spectroscopy.

Application of magnetic resonance imaging to early detection of breast cancer

Since its introduction approximately 10 years ago, there has been extensive progress in the application of magnetic resonance imaging (MRI) to the detection and diagnosis of breast cancer. Contrast-enhanced MRI has been shown to have value in the diagnostic work-up of women who present with mammogram or clinical abnormalities. In addition, it has been demonstrated that MRI can detect mammogram occult multifocal cancer in patients who present with unifocal disease. Advances in risk stratification and limitations in mammography have stimulated interest in the use of MRI to screen high-risk women for cancer. Several studies of MRI high-risk screening are ongoing. Preliminary results are encouraging.

MR imaging: its current and potential utility in the diagnosis and management of breast cancer

The rapid evolution of the treatment of breast cancer has been paralleled by a similar rapid improvement in the imaging of breast cancer. High-resolution contrast-enhanced MR imaging of the breast has recently emerged as a sensitive instrument for the detection of breast cancer. The sensitivity of MR imaging makes it an excellent tool in specific clinical situations, such as the detection of local recurrence in patients who have received breast-conservation therapy. Furthermore, MR imaging of the breast has the potential to be a powerful aid in presurgical planning and to be a useful adjunct to mammography in selected patients. MR imaging, however, has a significant false-positive rate, is not readily available in all areas, and is more expensive than mammography and sonography. It also remains unclear if alterations of management plans based on MR imaging findings actually benefit affected patients. Therefore rigorous clinical trials are needed to define precisely the exact role that MR imaging should play in the diagnosis and management of breast cancer patients.

Detection and localization of pulmonary air leaks using laser-polarized (3)He MRI

Pulmonary air leaks were created in the lungs of Yorkshire pigs. Dynamic, 3D MRI of laser-polarized (3)He gas was then performed using a gradient-echo pulse sequence. Coronal magnitude images of the helium distribution were acquired during gas inhalation with a voxel resolution of approximately 1.2 x 2.5 x 8 mm, and a time resolution of 5 sec. In each animal, the ventilation images reveal focal high-signal intensity within the pleural cavity at the site of the air leaks. In addition, a wedge-shaped region of increased parenchymal signal intensity was observed adjacent to the site of the air leak in one animal. (3)He MRI may prove helpful in the management of patients with pulmonary air leaks.

MR imaging in patients with nipple discharge: initial experience

PURPOSE

To investigate the potential of magnetic resonance (MR) imaging in patients with nipple discharge.

MATERIALS AND METHODS

Between February 1992 and December 1998, 23 patients with nipple discharge underwent contrast material-enhanced MR imaging at 1.5 T. Mammographic findings were negative in 22 of 23 patients and revealed asymmetry in one patient. Galactography was attempted in two patients, with negative findings in one patient and no success in the other. Fifteen of 23 patients underwent excisional biopsy-seven of 15 with MR imaging-guided localization, and one of 15 with mammographic localization. Eight of 23 patients were followed up clinically (range, 7-24 months; mean, 20 months).

RESULTS

In 11 of the 15 (73%) patients who underwent excisional biopsy, MR imaging findings correlated with histopathologic findings. MR imaging demonstrated four of six benign papillomas and one of two fibroadenomas as circumscribed, enhancing subareolar masses. Findings of one MR imaging examination were negative, and benign tissue was found at excisional biopsy. MR imaging findings were suspicious in six of the seven patients with excisional biopsy findings of malignancy (regional enhancement [n = 2], ductal enhancement [n = 2], peripherally enhancing mass [n = 1], and spiculated mass [n = 1]). In one of the seven patients, a benign-appearing intraductal mass was identified at MR imaging; excisional biopsy revealed a benign papilloma with an adjacent focus of DCIS.

CONCLUSION

MR imaging can help identify both benign and malignant causes of nipple discharge. It potentially offers a noninvasive alternative to galactography.

Intermolecular zero-quantum coherence imaging of the human brain

The first intermolecular zero-quantum coherence (iZQC) MR images of the human brain at 4T are presented. To generate iZQC images, a modified echo-planar imaging pulse sequence was used which included an additional 45 degrees RF pulse and a correlation gradient. The observability and nonconventional contrast of human brain iZQC images at 4T is demonstrated. Axial images are presented for various pulse sequence parameters, and a zero-quantum relaxation map is obtained.

Demonstration of a compact compressor for application of metastability-exchange optical pumping of 3He to human lung imaging

Hyperpolarized gas magnetic resonance imaging has recently emerged as a method to image lungs, sinuses, and the brain. The best lung images to date have been produced using hyperpolarized 3He, which is produced by either spin-exchange or metastability-exchange optical pumping. For hyperpolarized gas MRI, the metastable method has demonstrated higher polarization levels and higher polarizing rates, but it requires compression of the hyperpolarized gas. Prior to this work, compression of hyperpolarized gas had only been accomplished using a large, complex and expensive apparatus. Here, human lung ventilation images are presented that were obtained using a compact compressor that is relatively simple and inexpensive. For this test, 1.1 bar-L of 15% hyperpolarized 3He gas was produced at the National Institute of Standards and Technology using a modified commercial diaphragm pump. The hyperpolarized gas was transported to the University of Pennsylvania in a holding field provided by a portable solenoid.

Curvilinear areas in the perinephric fat seen on MR images

AIM

On magnetic resonance (MR) images, strands correspond to curvilinear areas running in the perinephric fat, and haloes to those lying on the renal surface. Our aim was to examine the diagnostic significance and histopathological basis of these areas.

PATIENTS AND METHODS

MR images obtained in 46 patients without renal disease and 96 patients with renal disease were assessed for the signal intensity and extent of strands and haloes, and their degree of right-left asymmetry.

RESULTS

Strands usually revealed low signal intensity on T1-weighted MR images and high signal intensity on fat-suppressed T2-weighted images and contrast-enhanced fat-suppressed T1-weighted images. Haloes revealed high signal intensity on fat-suppressed T2-weighted images, but most of haloes were not clearly depicted on T1-weighted images or contrast-enhanced fat-suppressed T1-weighted images. Strands and haloes were common and usually symmetrical or only mildly asymmetrical in both patient groups. However, in 11 of the 96 patients with renal disease, prominent strands and/or haloes appeared with remarkable asymmetry and likely represented definite changes in the perinephric fat. At histopathology, vascular loose fibrous tissue was found at the sites of strands and haloes.

CONCLUSION

Strands and haloes usually represent normal anatomical variations. However, the presence of prominent strands or haloes with remarkable right-left asymmetry implies abnormality and may provide additional information in the evaluation of renal disease.

Cost-effectiveness of MR imaging and core-needle biopsy in the preoperative work-up of suspicious breast lesions

PURPOSE

To assess the clinical and economic consequences of the use of preoperative breast magnetic resonance (MR) imaging and core-needle biopsy (CNB) to avert excisional biopsy (EXB).

MATERIALS AND METHODS

A decision-analytic Markov model was constructed to compare MR imaging, CNB, and EXB without preoperative testing in a woman with a suspicious breast lesion. Stage-specific cancer prevalence, tumor recurrence, progression rates, and MR imaging and CNB sensitivity and specificity were obtained from the literature. Cost estimates were obtained from the literature and from the Medicare fee schedule.

RESULTS

EXB without preoperative testing was associated with the greatest quality-adjusted life expectancy, followed by MR imaging and CNB; life expectancies were 17.409, 17.405, and 17.398 years, respectively. EXB resulted in the greatest lifetime treatment cost ($31,438), followed by MR imaging ($29,072) and CNB ($28,573). Results were robust over a wide range of cancer prevalence, stage distribution, tumor progression rates, and procedure and treatment costs. Incremental cost-effectiveness ratios showed that preoperative testing was cost-effective, but the choice between MR imaging and CNB was highly dependent on the accuracy of each test and to patient preferences.

CONCLUSION

Preoperative testing of most suspicious breast lesions was cost-effective. More precise estimates of MR imaging and CNB test performance characteristics are needed. Until those are available, patient preferences should inform individual decisions regarding preoperative testing.

Pulmonary perfusion: respiratory-triggered three-dimensional MR imaging with arterial spin tagging--preliminary results in healthy volunteers

The authors used a spin-tagging method of magnetic resonance perfusion imaging to measure pulmonary perfusion in eight healthy volunteers with use of a respiratory-triggered three-dimensional pulse sequence. The average signal intensity (SI) decrease upon arterial labeling was 24%. The perfusion SI increased by 21% after exercise (P = .02). Focal blood flow abnormalities were observed in a patient with chronic obstructive pulmonary disease.

Breast MR imaging in patients with axillary node metastases and unknown primary malignancy

PURPOSE

To assess the usefulness of magnetic resonance (MR) imaging of the breast in patients with malignant axillary adenopathy and unknown primary malignancy.

MATERIALS AND METHODS

Between October 1993 and December 1997, 38 women with malignant axillary adenopathy and negative mammographic and physical examination findings underwent contrast material-enhanced MR imaging. Sixteen patients were excluded due to axillary tail cancer (n = 7), lack of follow-up (n = 4), second primary malignancy (n = 3), or chemotherapy before MR imaging (n = 2). The study population comprised the remaining 22 patients. Histopathologic findings were available in 20 patients; follow-up MR imaging findings were available in two patients.

RESULTS

MR imaging depicted a primary breast cancer in 19 patients (86%; identified at excisional biopsy or mastectomy in 17, resolved on follow-up MR images during treatment in two). MR imaging depicted 4-30-mm cancers (mean, 17 mm), which correlated closely with histopathologic size. Two patients (9%) had false-negative findings: (a) One had a 2-mm invasive ductal carcinoma, and (b) one had 17- and 20-mm invasive ductal carcinomas. Of the 19 patients, 11 underwent mastectomy, seven underwent breast-conservation therapy, and one did not undergo a surgical procedure.

CONCLUSION

MR imaging is very sensitive for the detection of mammographically and clinically occult breast cancer in patients with malignant axillary adenopathy. In these patients, MR imaging offers potential not only for cancer detection but also for staging the cancer within the breast, which may be useful for treatment planning.

Role of magnetic resonance imaging and magnetic resonance imaging--guided surgery in the evaluation of patients with early-stage breast cancer for breast conservation treatment

Magnetic resonance imaging (MRI) may be more sensitive than mammography for detecting breast cancer and may have an adjunctive role in assessing patients with early-stage disease for breast conservation treatment. This study was performed to analyze the impact of breast MRI on the clinical management of 83 patients being considered for breast conservation treatment. Eighty-three consecutive cases of patients undergoing breast MRI during standard workup and evaluation for breast conservation treatment from 1993 to 1996 were retrospectively reviewed. Records were reviewed for patient and tumor characteristics, mammographic findings, MRI findings, timing of MRI study, findings from MRI-guided surgery (when done), and whether the patient underwent breast conservation treatment. MRI definitely altered management in 15 patients (18%), may have affected management in 4 patients (5%), and did not change management in 64 patients (77%). Thirteen patients underwent additional surgery because of MRI findings; the positive predictive value for MRI-guided surgery was 38% (5 of 13). Ultimately, 82% of the patients received breast conservation treatment. No predictive factor was identified to characterize the patients most likely to have management affected by MRI findings. These findings suggest that breast MRI may be useful in the evaluation of patients with early-stage breast cancer for breast conservation treatment. A larger study population and outcome data will be required to confirm these findings and to define those patients most likely to benefit from breast MRI.

Discrimination of MR images of breast masses with fractal-interpolation function models

RATIONALE AND OBJECTIVES

The authors evaluated the feasibility of using statistical fractal-dimension features to improve discrimination between benign and malignant breast masses at magnetic resonance (MR) imaging.

MATERIALS AND METHODS

The study evaluated MR images of 32 malignant and 20 benign breast masses from archived data at the University of Pennsylvania Medical Center. The test set included four cases that were difficult to evaluate on the basis of border characteristics. All diagnoses had been confirmed at excisional biopsy. The fractal-dimension feature was computed as the mean of a sample space of fractal-dimension estimates derived from fractal interpolation function models. To evaluate the performance of the fractal-dimension feature, the classification effectiveness of five expert-observer architectural features was compared with that of the fractal dimension combined with four expert-observer features. Feature sets were evaluated with receiver operating characteristic analysis. Discrimination analysis used artificial neural networks and logistic regression. Robustness of the fractal-dimension feature was evaluated by determining changes in discrimination when the algorithm parameters were perturbed.

RESULTS

The combination of fractal-dimension and expert-observer features provided a statistically significant improvement in discrimination over that achieved with expert-observer features alone. Perturbing selected parameters in the fractal-dimension algorithm had little effect on discrimination.

CONCLUSION

A statistical fractal-dimension feature appears to be useful in distinguishing MR images of benign and malignant breast masses in cases where expert radiologists may have difficulty. The statistical approach to estimating the fractal dimension appears to be more robust than other fractal measurements on data-limited medical images.

Renal artery stenosis: evaluation with conventional angiography versus gadolinium-enhanced MR angiography

PURPOSE

To evaluate the interobserver and intermodality variability of conventional angiography and gadolinium-enhanced magnetic resonance (MR) angiography in the assessment of renal artery stenosis.

MATERIALS AND METHODS

Fifty-four patients underwent conventional angiography and gadolinium-enhanced three-dimensional gradient-echo MR angiography. Three angiographers blinded to each other's interpretations and the MR angiographic findings assessed the conventional angiograms for renal artery stenosis. Similarly, three blinded MR imagers evaluated the MR angiograms.

RESULTS

Interobserver variability for the degree of renal artery stenosis in the 107 kidneys evaluated was not significantly different between the two modalities. The mean SD of the degree of stenosis was 6.9% at MR angiography versus 7.5% at conventional angiography (alpha < or = .05, P > .05). In 70 kidneys (65%), the average degree of stenosis reported by the readers for the two modalities differed by 10% or less. In 22 cases (21%), the degree of stenosis was overestimated with MR angiography by more than 10% relative to the results of conventional angiography. In 15 cases (14%), the degree of stenosis was underestimated with MR angiography by more than 10%.

CONCLUSION

Gadolinium-enhanced MR angiography permits evaluation of renal artery stenosis with an interobserver variability comparable with that of conventional angiography.

Correlation of lesion appearance and histologic findings for the nodes of a breast MR imaging interpretation model

An interpretation model for evaluating magnetic resonance (MR) images of the breast was constructed that allowed differentiation of benign from malignant palpable or mammographically visible abnormalities. Architectural features define each node of the model. Investigation was subsequently made of the histologic findings in individuals within each node and of the frequency with which each histologic finding manifested as a particular architectural feature to determine whether nodal location and specific histologic findings are mutually predictive. The strongest associations were found between fibrocystic change and smooth masses, fibroadenoma and lobulated masses with nonenhancing internal septations, invasive ductal carcinoma (with or without ductal carcinoma in situ [DCIS]) and enhancing irregular or spiculated masses, invasive tubular carcinoma or radial scar and spiculated masses, medullary or colloid carcinoma and enhancing lobulated masses, invasive lobular carcinoma and the absence of a focal mass, DCIS and ductal enhancement, and DCIS (with or without invasive ductal carcinoma) and regional enhancement. Nodal location and histologic findings proved to be mutually predictive within the model; that is, the nodal location of MR imaging features within the model can be used to predict histologic findings and vice versa.

Solitary intraductal papilloma: findings at MR imaging and MR galactography

OBJECTIVE

The purpose of this article is to describe MR findings in surgically proven solitary intraductal papillomas of the breast, including findings on MR galactography.

CONCLUSION

Women with spontaneous nipple discharge and solitary intraductal papilloma show, on MR imaging, dilated ducts with an associated enhancing, well-circumscribed mass.

Use of endorectal MR imaging to predict prostate carcinoma recurrence after radical prostatectomy

PURPOSE

To determine the ability of endorectal magnetic resonance (MR) imaging to help predict postprostatectomy disease recurrence and, thereby, patient outcome.

MATERIALS AND METHODS

The authors evaluated 116 patients referred for prostate MR imaging during 1991 and 1992 who subsequently underwent radical prostatectomy and for whom follow-up data through 1996 could be obtained. The MR reports, clinic charts, and pathology reports were reviewed. Disease recurrence was established by means of detectable levels of serum prostate-specific antigen (PSA) after surgery.

RESULTS

Thirty-four patients (29%) had postoperative disease recurrence. Patients with recurrence had higher preoperative PSA values (P < .0001). These patients also more frequently had positive surgical margins (P = .0005), transcapsular tumor spread (P < .0001), seminal vesicle involvement (P = .0012), and tumors of advanced stage (P < .0001) and high grade (P = .0058). Of 13 patients whose MR examinations showed definite extracapsular disease, eight (62%) had disease recurrence. The recurrence rate when MR imaging indicated limited disease (24%) was similar to that when MR imaging showed possible microscopic extension (27%). An MR finding of definite extracapsular disease was 24% sensitive and 94% specific for the prediction of disease recurrence.

CONCLUSION

MR imaging findings of definite extracapsular spread of disease helped predict prostate tumor recurrence with high specificity, although with low sensitivity.

Human breast lesions: characterization with proton MR spectroscopy

PURPOSE

To assess the clinical usefulness of spatially localized hydrogen-1 magnetic resonance (MR) spectroscopy in distinguishing benign from malignant lesions on the basis of total choline levels.

MATERIALS AND METHODS

These studies were performed at 1.5 T with a four-channel multicoil that compresses the breast sagittally. Contrast material-enhanced MR imaging and single-voxel H-1 MR spectroscopy were performed in 17 patients (age range, 25-68 years) who had nonspecific mammographic findings. Histopathologic correlations were made from biopsy or surgical specimens. Ten patients had various malignant breast lesions 1-4 cm in diameter, and seven patients had benign processes.

RESULTS

Most studies were performed with nominal voxel sizes (< 2 cm3). Spectra obtained with an echo time of 31 msec showed resonances from water and mobile fatty acids and, in some cases, the N-trimethyl resonance of choline-containing compounds (Cho) at 3.2 ppm. The absolute concentration of Cho in each lesion was determined with a phantom containing 1 mmol/L Cho as an external reference. On the basis of reference measurements, the least detectable level of Cho was 0.2 mmol/L. With this threshold, seven of 10 malignant lesions showed detectable levels of Cho. In contrast, Cho was seen in only one patient with an extremely rare benign process, a tubular adenoma. The remaining six patients with benign processes demonstrated no detectable Cho levels.

CONCLUSION

Spatially localized H-1 MR spectroscopy can provide sufficient sensitivity and spectral resolution at 1.5 T to demonstrate Cho in human breast lesions with a spectroscopic protocol that provides up to 1-cm3 resolution. Determining the presence of Cho may provide a useful test for malignancy.

Proton T1rho-dispersion imaging of rodent brain at 1.9 T

Detection of H2(17)O with proton T1rho-dispersion imaging holds promise as a means of quantifying metabolism and blood flow with MRI. However, this technique requires a priori knowledge of the intrinsic T1rho dispersion of tissue. To investigate these properties, we implemented a T1rho imaging sequence on a 1.9-T Signa GE scanner. A series of T1rho images for different locking frequencies and locking durations were obtained from rat brain in vivo and compared with 5% (wt/vol) gelatin phantoms containing different concentrations of (17)O ranging from .037% (natural abundance) to 2.0 atom%. Results revealed that, although there is considerable T1rho-dispersion in phantoms doped with H2(17)O, the T1rho of rat brain undergoes minimal dispersion for spin-locking frequencies between .2 and 1.5 kHz. A small degree of T1rho dispersion is present below .2 kHz, which we postulate arises from natural-abundance H2(17)O. Moreover, the signal-to-noise ratios of T1rho-weighted images are significantly better than comparable T2-weighted images, allowing for improved visualization of tissue contrast. We have also demonstrated the feasibility of proton T1rho-dispersion imaging for detecting intravenous H2(17)O on a live mouse brain. The potential application of this technique to study brain perfusion is discussed.

MRI of hyperpolarized 3He gas in human paranasal sinuses

In this study, MRI of hyperpolarized 3He gas in human paranasal sinuses is presented. Helium images were obtained at 1.5 T, using a surface coil and a 2D, fast gradient-echo sequence with a nominal constant flip angle of 12 degrees. Coronal images of 20-mm thick slices were generated and compared with proton images of the corresponding sections. The images enable visualization of the paranasal sinuses and the nasal cavity, suggesting a potential use of this method not only in identifying the anatomical configuration of these pneumatic spaces, but also in assessing sinus ventilation.

Fast imaging of phosphocreatine using a RARE pulse sequence

A technique is described for acquiring phosphocreatine (PCr) images of skeletal muscle using a rapid acquisition with relaxation enhancement (RARE) pulse sequence. All of the phosphorus metabolites other than PCr are forced to dephase within the first few echoes, whereas the Carr-Purcell Meiboom-Gill (CPMG) pulse sequence maintains a high PCr signal long enough to acquire 64 echoes in a single shot. Axial PCr images of a human forearm with a signal-to-noise ratio of 9 were acquired in 2 min. The effect of the refocusing pulse section profile on the ratio of desired to undesired metabolite signal is demonstrated.

Extracranial atherosclerotic carotid artery disease: evaluation of non-breath-hold three-dimensional gadolinium-enhanced MR angiography

OBJECTIVE

The purpose of this study was to compare the diagnostic information provided by a combination of two-dimensional and three-dimensional (3D) time-of-flight (TOF) techniques with that provided by non-breath-hold 3D spoiled gradient-echo gadolinium-enhanced MR angiography.

MATERIALS AND METHODS

Fifty patients suspected of having extracranial atherosclerotic carotid artery disease were examined with all three imaging techniques using a 1.5-T MR imaging system. Three observers independently and retrospectively measured the degree of stenosis according to the North American Symptomatic Carotid Endarterectomy trial criteria. The observers were unaware of the results of other MR imaging pulse sequences and digital subtraction angiography. The standard of reference was established by digital subtraction angiography. Results were evaluated with receiver operating characteristic curve analysis. The degree of interobserver agreement was determined using pairwise kappa statistics.

RESULTS

The grading of carotid artery stenosis as measured by the area under the receiver operating characteristic curve was less accurate with non-breath-hold 3D gadolinium-enhanced MR angiography than with TOF imaging. Interobserver variability was greater for non-breath-hold 3D gadolinium-enhanced MR angiography than for TOF techniques.

CONCLUSION

Routine evaluation of carotid artery stenosis at the level of the bifurcation using non-breath-hold 3D gadolinium-enhanced MR angiography is less accurate than is TOF imaging and is therefore not recommended. The weakness of this technique may be due to problems in timing the injection of gadolinium and the masking of the carotid bifurcation by the venous jugular system.

Future directions in imaging of breast diseases

In the near future, investigation and refinement of emerging anatomic and functional breast imaging techniques will enable clinical trials that will evaluate their utility and potential for improving the survival and quality of life for patients with breast cancer. In the longer term, strategic research collaborations among investigators in the fields of functional imaging, molecular biology, and pathology are needed to merge existing science and advance the development of biomarker and genetic techniques focused on detecting and characterizing disease at the cellular and molecular levels. This research could create clinical tools for (a) detecting breast cancer earlier, (b) more accurately quantifying the extent of disease, (c) noninvasively evaluating lymph node involvement, (d) identifying micrometastases and residual microscopic disease, and (e) enhancing therapy by means of imaging-guided biomarker or tumor-specific delivery of pharmacologic, chemosensitizing, or radiosensitizing agents to tumors.

Bilateral imaging using separate interleaved 3D volumes and dynamically switched multiple receive coil arrays

Multiple receive coil arrays are often designed for unilateral imaging of anatomy having bilateral symmetry. A technique is described for extending the utility of such arrays to simultaneously image both bilaterally symmetric anatomical features. A separate, complete multiple receive coil array is placed at each location. Two separate, noncontiguous 3D volumes are then acquired, one at each location, in an interleaved fashion. High-impedance blocking networks are alternately activated and deactivated to minimize coupling between the arrays. It is demonstrated that there is no degradation in image quality when compared to a unilateral exam. A general method for analyzing the interactions between separate multiple coil arrays is presented.