Recent Advances in Breast-Specific Imaging

Efficacy and safety of breast radiothermometry in the differential diagnosis of breast lesions

Aim of the study

The aim of this study is to research the contribution of radiothermometry (RTM) to the characterization of breast masses, the differentiation of malignant-benign masses and diagnosis of early stage breast cancer.

Material and methods

This prospective study comprised 182 cases of patients diagnosed with a breast mass and a control group of 55 cases: a total of 237.

Results

When histopathology is accepted as the gold standard among diagnostic methods, the sensitivity, specificity, and positive-negative predictive value for RTM were 90.9%, 20.8%, 61.2% and 62.5%, respectively. Consistency was 0.129. When compared with mammography the same values for RTM examination are 87%, 81.4%, 58% and 95.5%. Consistency was 0.582. Evaluating with respect to size of the mass accepting mammography as the gold standard, RTM examination had sensitivity, specificity, positive and negative predictive values for masses 2 cm and above of 88.9%, 83.3%, 88.9% and 83.3%. Consistency was 0.722. The consistency of RTM for lesion diagnosis in BI-RADS II breast structure is higher than the consistency of mammography.

Conclusions

Identification of lesions in the breast and presence of microcalcification by RTM shows that it is more trustworthy compared to mammography. When compared with mammography the validity results for RTM show there is a good level of conformity between the two methods. When evaluated based on the area below the ROC cure and compared to mammography, RTM is sufficiently successful at evaluating positive and negative cases.

Assessing health care use and cost consequences of a new screening modality: the case of digital mammography

BACKGROUND

Full-field digital mammography (FFDM) has largely replaced screen-film mammography (SFM) for breast cancer screening, but how this affects downstream breast-related use and costs is unknown.

OBJECTIVES

To compare breast-related health care use and costs among Medicare beneficiaries undergoing SFM versus FFDM from 1999 to 2005.

DESIGN

Retrospective cohort study.

SUBJECTS

Medicare-enrolled women aged 66 and older with mammograms in Breast Cancer Surveillance Consortium registries.

MEASURES

Subsequent follow-up with additional imaging or breast biopsy within 12 months was ascertained through Medicare claims. Associated mean costs were estimated by screening modality and year, adjusting for confounding factors, and clustering within mammography facilities using Generalized Estimating Equations.

RESULTS

Among 138,199 women, 332,324 SFM and 22,407 FFDM mammograms were analyzed. Approximately 6.5% of SFM and 9.0% of FFDM had positive findings. In 2001, subsequent imaging was higher among FFDM versus SFM (127.5 vs. 97.4 follow-up mammography claims per 1000 index mammograms), whereas subsequent biopsy was lower among FFDM versus SFM (19.2 vs. 24.9 per 1000 index mammograms) with differences decreasing over time. From 2001 to 2004, mammography subsequent to FFDM had higher mean costs than SFM ($82.60 vs. $64.31 in 2001). The only cost differences between SFM and FFDM for ultrasound or biopsy were in 2001.

CONCLUSIONS

Subsequent breast-related health care use differed early in FFDM introduction, but diminished over time with differences attributable to higher recall rates for additional imaging and lower rates of biopsy in those undergoing FFDM versus SFM. Remaining cost differences are because of higher reimbursement rates for FFDM versus SFM.

Digital mammography: more microcalcifications, more columnar cell lesions without atypia

The incidence of columnar cell lesions in breast core needle biopsies since full-field digital mammography in comparison with screen-filmed mammography was analyzed. As tiny microcalcifications characterize columnar cell lesions at mammography, we hypothesized that more columnar cell lesions are diagnosed since full-field digital mammography due to its higher sensitivity for microcalcifications. In all, 3437 breast core needle biopsies performed in three hospitals and resulting from in total 55 159 mammographies were revised: 1424 taken in the screen-filmed mammography and 2013 in the full-field digital mammography period. Between the screen-filmed mammography and full-field digital mammography periods, we compared the proportion of mammographies that led to core needle biopsies, the mammographic indication for core needle biopsies (density, microcalcifications, or both) and the proportion of columnar cell lesions with or without atypia. The columnar cell lesions were graded according to Schnitt, and we included atypical ductal hyperplasia arising in the context of columnar cell lesions. Proportions were compared using χ(2) tests and prevalence ratios were adjusted for age and hospital. We found that more core needle biopsies per mammogram were taken in the full-field digital mammography period (7.6%) compared with the screen-filmed mammography period (5.0%, P<0.0001). Microcalcifications were more often diagnosed with full-field digital mammography than with screen-filmed mammography (adjusted prevalence ratio: 1.14, confidence interval 95%: 1.01-1.28). Core needle biopsies from the full-field digital mammography era showed more columnar cell lesions (10.8%) than those from the screen-filmed mammography era (4.9%; adjusted prevalence ratio: 1.93, confidence interval 95%: 1.48-2.51), particularly due to more columnar cell lesions without atypia (8.2% respectively 2.8%) while the proportion of columnar cell lesions with atypia remained nearly constant (2.0 vs 2.6%). In conclusion, since the implementation of full-field digital mammography, more microcalcifications are seen at mammography, more often resulting in core needle biopsies, which especially yields more columnar cell lesions without atypia.

Combined DCE-MRI and single-voxel 2D MRS for differentiation between benign and malignant breast lesions

Dynamic contrast-enhanced (DCE) magnetic resonance imaging (MRI) and proton (1H) magnetic resonance spectroscopy (MRS) provide structural and biochemical information, including vascular volume, vascular permeability and tissue metabolism. In this study, we performed analysis of the enhancement characteristic from DCE-MRI and the biochemical information provided by two-dimensional (2D) Localized Correlated Spectroscopy (L-COSY) MRS to determine the sensitivity and specificity of using DCE-MRI alone compared to the combination with 2D MRS. The metabolite ratios from the 2D MRS spectra were analyzed using multivariate statistical analyses to determine a method capable of automatic separation of the patient cohort into malignant and benign lesions. A total of 24 lesions were studied with 21 diagnosed accurately using the enhancement characteristics alone resulting in sensitivity and specificity of 100% and 73%, respectively. Analysis of the 2D MRS data demonstrated a significant difference (p < 0.05) in 12 of 18 metabolite ratios analyzed for malignant compared to benign lesions. Previous research focused on utilizing the choline signal to noise ratio (SNR) as a marker for malignancy has been verified using 2D MRS in this study. Using Fisher's linear discriminant test using water (WAT)/olefinic fat diagonal (UFD), choline (CHO)/fat (FAT), CHO/UFD, and FAT/methyl fat (FMETD) as predictors the sensitivity and specificity increased to 92% and 100%, respectively. Using the Classification and Regression Tree (CART) statistical analysis the resulting sensitivity and specificity were 100% and 91%, respectively, with the most accurate predictor for differentiating malignant and benign determined to be FAT/FMETD. The cases within the study that presented a indeterminate diagnosis using DCE-MRI alone were able to be accurately diagnosed when the metabolic information from 2D MRS was incorporated. The results suggest improved breast cancer detection through the combination of morphological and enhancement information from DCE-MRI and metabolic information from 2D MRS.

Performance characterization of a new high resolution PET scintillation detector

Performance of a new high resolution PET detection concept is presented. In this new concept, annihilation radiation enters the scintillator detectors edge-on. Each detector module comprises two 8 × 8 LYSO scintillator arrays of 0.91 × 0.91 × 1 mm(3) crystals coupled to two position-sensitive avalanche photodiodes (PSAPDs) mounted on a flex circuit. Appropriate crystal segmentation allows the recording of all three spatial coordinates of the interaction(s) simultaneously with submillimeter resolution. We report an average energy resolution of 14.6 ± 1.7% for 511 keV photons at FWHM. Coincident time resolution was determined to be 2.98 ± 0.13 ns FWHM on average. The coincidence point spread function (PSF) has an average FWHM of 0.837 ± 0.049 mm (using a 500 μm spherical source) and is uniform across the arrays. Both PSF and coincident time resolution degrade when Compton interactions are included in the data. Different blurring factors were evaluated theoretically, resulting in a calculated PSF of 0.793 mm, in good agreement with the measured value.

Molecular and Functional Imaging of Breast Cancer

Background

Significant efforts have been directed toward developing and enhancing imaging methods for the early detection, diagnosis, and characterization of small breast tumors. Molecular and functional imaging sets the stage for enhancement of current methodology.

Methods

Current imaging modalities are described based on the molecular characteristics of normal and malignant tissue. New molecular imaging methods that have the potential for clinical use are also discussed.

Results:

Dynamic contrast-enhanced magnetic resonance imaging is more sensitive than mammography in BRCA1 carriers. It is used in screening and in the early evaluation of neoadjuvant therapy. Positron emission mammography is 91% sensitive and 93% specific in detecting primary breast cancers. Sentinel node scintigraphy is a key component of axillary lymph node evaluation. Other imaging modalities being studied include Tc99m sestamibi, radiolabeled thymidine or uridine, estrogen receptor imaging, magnetic resonance spectroscopy, and diffusion magnetic resonance imaging.

Conclusions

Molecular and functional imaging of the breast will likely alter clinical practice in diagnosing and staging primary breast cancer and assessing response to therapy since it will provide earlier information regarding the underlying biology of individual breast cancers, tumor stage, potential treatment strategies, and biomarkers for early evaluation of treatment effects.

A technique optimization protocol and the potential for dose reduction in digital mammography

Digital mammography requires revisiting techniques that have been optimized for prior screen/film mammography systems. The objective of the study was to determine optimized radiographic technique for a digital mammography system and demonstrate the potential for dose reduction in comparison to the clinically established techniques based on screen- film. An objective figure of merit (FOM) was employed to evaluate a direct-conversion amorphous selenium (a-Se) FFDM system (Siemens Mammomat Novation(DR), Siemens AG Medical Solutions, Erlangen, Germany) and was derived from the quotient of the squared signal-difference-to-noise ratio to mean glandular dose, for various combinations of technique factors and breast phantom configurations including kilovoltage settings (23-35 kVp), target/filter combinations (Mo-Mo and W-Rh), breast-equivalent plastic in various thicknesses (2-8 cm) and densities (100% adipose, 50% adipose/50% glandular, and 100% glandular), and simulated mass and calcification lesions. When using a W-Rh spectrum, the optimized FOM results for the simulated mass and calcification lesions showed highly consistent trends with kVp for each combination of breast density and thickness. The optimized kVp ranged from 26 kVp for 2 cm 100% adipose breasts to 30 kVp for 8 cm 100% glandular breasts. The use of the optimized W-Rh technique compared to standard Mo-Mo techniques provided dose savings ranging from 9% for 2 cm thick, 100% adipose breasts, to 63% for 6 cm thick, 100% glandular breasts, and for breasts with a 50% adipose/50% glandular composition, from 12% for 2 cm thick breasts up to 57% for 8 cm thick breasts.

Mode of detection and secular time for ductal carcinoma in situ

In this article, the published literature on the role of screening mammography in the detection of ductal carcinoma in situ (DCIS) is reviewed. This includes what is known about the detection of DCIS in different demographic groups. Finally the author describes her views on how the field might be advanced.

Investigation of breast cancer using two-dimensional MRS

Proton (1H) MRS enables non-invasive biochemical assay with the potential to characterize malignant, benign and healthy breast tissues. In vitro studies using perchloric acid extracts and ex vivo magic angle spinning spectroscopy of intact biopsy tissues have been used to identify detectable metabolic alterations in breast cancer. The challenges of 1H MRS in vivo include low sensitivity and significant overlap of resonances due to limited chemical shift dispersion and significant inhomogeneous broadening at most clinical magnetic field strengths. Improvement in spectral resolution can be achieved in vivo and in vitro by recording the MR spectra spread over more than one dimension, thus facilitating unambiguous assignment of metabolite and lipid resonances in breast cancer. This article reviews the recent progress with two-dimensional MRS of breast cancer in vitro, ex vivo and in vivo. The discussion includes unambiguous detection of saturated and unsaturated fatty acids, as well as choline-containing groups such as free choline, phosphocholine, glycerophosphocholine and ethanolamines using two-dimensional MRS. In addition, characterization of invasive ductal carcinomas and healthy fatty/glandular breast tissues non-invasively using the classification and regression tree (CART) analysis of two-dimensional MRS data is reviewed.

Is a short-interval postradiation mammogram necessary after conservative surgery and radiation in breast cancer?

PURPOSE

To examine, in a retrospective study, whether the initial posttreatment mammogram offers any benefit to patients.

METHODS AND MATERIALS

Patients were selected who had radiation after breast-conservation therapy from 1995 through 2005 and had follow-up mammography at the University of California-Los Angeles (UCLA) within 1 year of completing radiotherapy. Results of the initial follow-up mammogram were analyzed to determine the yield of this initial mammogram.

RESULTS

Between 1995 and 2005, 408 patients treated with breast-conserving therapy and radiation had follow-up mammograms at UCLA within 1 year of completion of radiation. Median age at radiation completion was 56.9 years. Median interval between radiation and the initial mammogram was 3.1 months. Ten patients were found to have suspicious findings on the initial postradiation mammogram, prompting biopsy, but only 2 were found to have recurrent cancer. None of those lesions were palpable. In both cases the recurrences were ductal carcinoma in situ. Thus, the yield of the initial postoperative mammogram as compared with physical examination findings is estimated at 0.49 recurrences detected per 100 mammograms performed (95% confidence interval 0.059-1.759).

CONCLUSIONS

The yield of the initial postradiation mammography at UCLA seems to be low, and only noninvasive carcinomas were found. Our data support the rationale to avoid the initial short-interval postradiation mammography and evaluate patients at 12 months.