Technique to obtain positron emission mammography images in registration with x-ray mammograms

Positron Emission Mammography (PEM) in the diagnosis of breast cancer: A systematic review and economic evaluation

Background: Positron Emission Mammography (PEM) is an imaging technique which is increasing focuses on imaging the chest instead of imaging the whole body. The aim of this study was to conduct a systematic review of the clinical efficacy and coste-ffectiveness of PEM technology, as compared with PET, as a diagnostic method used for breast cancer patients.

Methods: The present study was a Health Technology Assessment (HTA), which was conducted via a systematic review of clinical efficacy and cost-effectiveness of the methods based on domestic evidence. To evaluate the efficacy of the PEM diagnostic method, as compared with PET, we used efficacy indices, including Sensitivity, Specificity, Accuracy, PPV, and NPV. The required data were collected through a meta-analysis of studies published in electronic databases from 1990 to 2016. In addition, direct costs in both methods were estimated and finally, a cost-effectiveness analysis was performed using the results of the study. Also, a one-way sensitivity analysis was performed to examine the effects of parameters’ uncertainty in the model. In this study, we used STATA software to integrate the results of studies with similar parameters.

Results: A total of 722 cases (N) were obtained from the five final studies. The results of the meta-analysis performed on the collected data showed that the two methods were identical in terms of the Specificity and PPV parameters. However, as to Sensitivity, NPV, and Accuracy parameters, the PEM method was superior to the PET for diagnosis of primary breast cancer. The total cost of using PEM and PET was $1737385.7 and $1940903.5, respectively, and the cost of a one-time scan (cost per unit) using PEM and PET devices was $86.82 and $157.63, respectively. As compared with the PET method, the use of the PEM diagnostic method for diagnosis of breast cancer was cost-effective in terms of all the five studied parameters (it was definitely cost-effective for four parameters and was also considered as cost-effective for another index, since ICER was below the threshold).

Conclusion: The results showed that the use of PEM technology for the diagnosis of primary breast cancer is more cost-effective than PET technology; thus, due to the wide range of PET technology in different fields, it is recommended that this method should be used in other areas of priority.

Comparison of Diagnostic Performance of Three-Dimensional Positron Emission Mammography versus Whole Body Positron Emission Tomography in Breast Cancer

Objective

To compare the diagnostic performance of three-dimensional (3D) positron emission mammography (PEM) versus whole body positron emission tomography (WBPET) for breast cancer.

Methods

A total of 410 women with normal breast or benign or highly suspicious malignant tumors were randomized at 1 : 1 ratio to undergo 3D-PEM followed by WBPET or WBPET followed by 3D-PEM. Lumpectomy or mastectomy was performed on eligible participants after the scanning.

Results

The sensitivity and specificity of 3D-PEM were 92.8% and 54.5%, respectively. WBPET showed a sensitivity of 95.7% and specificity of 56.8%. After exclusion of the patients with lesions beyond the detecting range of the 3D-PEM instrument, 3D-PEM showed higher sensitivity than WBPET (97.0% versus 95.5%, P = 0.913), particularly for small lesions (<1 cm) (72.0% versus 60.0%, P = 0.685).

Conclusions

The 3D-PEM appears more sensitive to small lesions than WBPET but may fail to detect lesions that are beyond the detecting range. This study was approved by the Ethics Committee (E2012052) at the Tianjin Medical University Cancer Institute and Hospital (Tianjin, China). The instrument positron emission mammography (PEMi) was approved by China State Food and Drug Administration under the registration number 20153331166.

3D Breast Image Registration — A Review

Image registration is an important problem in breast imaging. It is used in a wide variety of applications that include better visualization of lesions on pre- and post-contrast breast MRI images, speckle tracking and image compounding in breast ultrasound images, alignment of positron emission, and standard mammography images on hybrid machines et cetera. It is a prerequisite to align images taken at different times to isolate small interval lesions. Image registration also has useful applications in monitoring cancer therapy. The field of breast image registration has gained considerable interest in recent years. While the primary focus of interest continues to be the registration of pre- and post-contrast breast MRI images, other areas like breast ultrasound registration have gained more attention in recent years. The focus of registration algorithms has also shifted from control point based semiautomated techniques, to more sophisticated voxel based automated techniques that use mutual information as a similarity measure. This paper visits the problem of breast image registration and provides an overview of the current state-of-the-art in this area.

Evolution and Developments in Instrumentation for Positron Emission Mammography

Molecular imaging using high-resolution PET instrumentation is now playing a pivotal role in basic and clinical research. The development of optimized detection geometries combined with high-performance detector technologies and compact designs of PET tomographs have become the goal of active research groups in academic and corporate settings. Significant progress has been achieved in the design of commercial PET instrumentation in the last decade allowing a spatial resolution of about 4 to 6 mm to be reached for whole-body imaging, about 2.4 mm for PET cameras dedicated for brain imaging, and submillimeter resolution for female breast, prostate, and small-animal imaging. In particular, significant progress has been made in the design of dedicated positron emission mammography (PEM) units. The initial concept suggested in 1993 consisted of placing 2 planar detectors capable of detecting the 511-keV annihilation photons in a conventional mammography unit. Since that time, many different design paths have been pursued and it will be interesting to see which technologies become the most successful in the future. This paper discusses recent advances in PEM instrumentation and the advantages and challenges of dedicated standalone and dual-modality imaging systems. Future opportunities and the challenges facing the adoption of PEM imaging instrumentation and its role in clinical and research settings are also addressed.

A review of biomechanically informed breast image registration

Breast radiology encompasses the full range of imaging modalities from routine imaging via x-ray mammography, magnetic resonance imaging and ultrasound (both two- and three-dimensional), to more recent technologies such as digital breast tomosynthesis, and dedicated breast imaging systems for positron emission mammography and ultrasound tomography. In addition new and experimental modalities, such as Photoacoustics, Near Infrared Spectroscopy and Electrical Impedance Tomography etc, are emerging. The breast is a highly deformable structure however, and this greatly complicates visual comparison of imaging modalities for the purposes of breast screening, cancer diagnosis (including image guided biopsy), tumour staging, treatment monitoring, surgical planning and simulation of the effects of surgery and wound healing etc. Due primarily to the challenges posed by these gross, non-rigid deformations, development of automated methods which enable registration, and hence fusion, of information within and across breast imaging modalities, and between the images and the physical space of the breast during interventions, remains an active research field which has yet to translate suitable methods into clinical practice. This review describes current research in the field of breast biomechanical modelling and identifies relevant publications where the resulting models have been incorporated into breast image registration and simulation algorithms. Despite these developments there remain a number of issues that limit clinical application of biomechanical modelling. These include the accuracy of constitutive modelling, implementation of representative boundary conditions, failure to meet clinically acceptable levels of computational cost, challenges associated with automating patient-specific model generation (i.e. robust image segmentation and mesh generation) and the complexity of applying biomechanical modelling methods in routine clinical practice.

Nuclear imaging of the breast: translating achievements in instrumentation into clinical use

Approaches to imaging the breast with nuclear medicine and∕or molecular imaging methods have been under investigation since the late 1980s when a technique called scintimammography was first introduced. This review charts the progress of nuclear imaging of the breast over the last 20 years, covering the development of newer techniques such as breast specific gamma imaging, molecular breast imaging, and positron emission mammography. Key issues critical to the adoption of these technologies in the clinical environment are discussed, including the current status of clinical studies, the efforts at reducing the radiation dose from procedures associated with these technologies, and the relevant radiopharmaceuticals that are available or under development. The necessary steps required to move these technologies from bench to bedside are also discussed.

F-18 Fluorodeoxyglucose-Positron Emission Tomography Imaging for Primary Breast Cancer and Loco-Regional Staging

Breast cancer is the most common female malignancy in Western countries. The limitations of mammography, ultrasound and MRI do not allow reliable identification of primary breast cancer at early stages. Functional breast imaging with positron emission tomography (PET) and F-18 fluorodeoxyglucose (FDG) enables the visualization of increased glucose metabolism of breast cancer. However, despite the successful identification of primary breast cancer, FDG-PET provides a low sensitivity to detect small tumors. Therefore, FDG-PET does not allow screening of asymptomatic women and cannot be used to exclude breast cancer in patients with suspicious breast masses or abnormal mammography. FDG-PET is a powerful tool for staging of breast cancer patients, but does not detect micrometastases and small tumor infiltrated lymph nodes. Nevertheless, in patients with locally advanced breast cancer, PET accurately determines the extent of disease, particularly the loco-regional lymph node status. Advances in technology, for example the development of dedicated breast imaging devices such as positron emission mammography, hold promise to improve the detection of primary tumors in the future.

Fast 3D-EM reconstruction using Planograms for stationary planar positron emission mammography camera

At the University of Pisa we are building a PEM prototype, the YAP-PEM camera, consisting of two opposite 6 x 6 x 3 cm3 detector heads of 30 x 30 YAP:Ce finger crystals, 2 x 2 x 30 mm3 each. The camera will be equipped with breast compressors. The acquisition will be stationary. Compared with a whole body PET scanner, a planar Positron Emission Mammography (PEM) camera allows a better, easier and more flexible positioning around the breast in the vicinity of the tumor: this increases the sensitivity and solid angle coverage, and reduces cost. To avoid software rejection of data during the reconstruction, resulting in a reduced sensitivity, we adopted a 3D-EM reconstruction which uses all of the collected Lines Of Response (LORs). This skips the PSF distortion given by data rebinning procedures and/or Fourier methods. The traditional 3D-EM reconstruction requires several times the computation of the LOR-voxel correlation matrix, or probability matrix {p(ij)}; therefore is highly time-consuming. We use the sparse and symmetry properties of the matrix {p(ij)} to perform fast 3D-EM reconstruction. Geometrically, a 3D grid of cubic voxels (FOV) is crossed by several divergent 3D line sets (LORs). The symmetries occur when tracing different LORs produces the same p(ij) value. Parallel LORs of different sets cross the FOV in the same way, and the repetition of p(ij) values depends on the ratio between the tube and voxel sizes. By optimizing this ratio, the occurrence of symmetries is increased. We identify a nucleus of symmetry of LORs: for each set of symmetrical LORs we choose just one LOR to be put in the nucleus, while the others lie outside. All of the possible p(ij) values are obtainable by tracking only the LORs of this nucleus. The coordinates of the voxels of all of the other LORs are given by means of simple translation rules. Before making the reconstruction, we trace the LORs of the nucleus to find the intersecting voxels, whose p(ij) values are computed and stored with their voxel coordinates on a hard disk. Only the non-zero p(ij) are considered and their computation is performed just once. During the reconstruction, the stored values are loaded and are available in the random access memory for all of the operations of normalization, backprojection and projection: these are now performed rapidly, because the application of the translation rules is much faster than the probability computations. We tested the algorithm on Monte Carlo data fully simulating the typical YAP-PEM clinical condition. The adopted algorithm gives an excellent positioning capability for hot spots in the camera FOV. To use all of the possible skew LORs in the FOV avoids the software rejection of collected data. Reconstructed images indicate that a 5mm diameter tumor of 37 kBq/cm3, in an active breast with a 10:1 Tissue to Background ratio (T/B), with a 10 min acquisition, for a head distance of 5 cm, can be detected by the YAP-PEM with a SNR of 8.7+/-1.0. The obtained SNR values depend linearly on the tumor volume. The algorithm allows one to discriminate between two hot sources of 5.0 mm diameter if they do not lie on the same axis. The YAP-PEM is now in the assembly stage.

Pilot clinical trial of 18F-fluorodeoxyglucose positron-emission mammography in the surgical management of breast cancer

BACKGROUND

High-resolution positron-emission mammography (PEM) is a new device, which allows the imaging of breast tissue. A prospective study was performed to assess the accuracy of PEM in newly diagnosed breast cancer patients.

METHODS

In a prospective multicenter study, 44 women with confirmed breast cancers were imaged with a high-resolution PEM scanner (Naviscan PET Systems, Rockville, MD) with 18F-fluorodeoxyglucose. The images were blindly evaluated and were compared with final pathology.

RESULTS

The majority of the index lesions were seen on PEM (89%, 39/44). PEM detected 4 of 5 incidental breast cancers, 3 of which were not seen by any other imaging modalities. Of 19 patients undergoing breast-conserving surgery, PEM correctly predicted 6 of 8 (75%) patients with positive margins and 100% (11/11) with negative margins.

CONCLUSION

The current PEM device shows promise in detecting breast malignancies and may assist in the planning of adequate partial mastectomy procedures to better ensure negative margins.

[(18F)-fluoro-2-deoxyglucose PET in imaging of gynecologic cancers]

Although gynaecological cancers are not currently part of the clinical indications in the French registration for [18F]-fluoro-2-deoxyglucose (FDG), various studies indicate in this context a potential clinical benefit of imaging with this radiopharmaceutical and PET, a new imaging modality that can be performed either with a dedicated machine or with a "hybrid" gamma-camera (CDET). The potential indications of FDG-PET in mammary, ovarian or cervical cancers are reviewed according to the diagnostic phase: screening, tumour characterisation, staging, therapeutic follow-up and search for recurrence. By pooling the published results, the accuracy of FDG-PET could be estimated with a reasonable precision in various clinical settings: characterisation of a breast tumour (598/696 = 86%), lymph node invasion in breast cancer (525/602 = 87%), recurrence of breast cancer (114/127 = 90%), characterisation of adnexal masses (130/176 = 78%), recurrence of ovarian cancer (152/172 = 88%), lymph node invasion in cervical cancer (98/103 = 95%). Authors also present original data concerning their experience of recurrence detection with CDET in breast or ovarian cancers. In 44 patients suspicious of recurrence of breast cancer, FDG-CDET sensitivity was 94%, specificity 82% and accuracy 91%; in 18 patients suspicious of recurrence of ovarian cancer, specificity, sensitivity and accuracy were 100%. The impact of dedicated PET and CDET examinations performed by our team during year 2000, led, according to 63 forms returned to us, to a modification of stage in 48% of breast cancers, 36% of ovarian cancers, 43% of cervical cancers and above all induced a modification in patients' management in respectively 69%, 64% and 60% of cases, more than the average rate in cancer patients which was 50%. No significant difference was observed between clinical impact of dedicated PET and CDET examinations.

Current status of PET in breast cancer imaging, staging, and therapy

The exact roles of PET in the imaging management of patients with known or suspected breast cancer are still in evolution. For assessing primary lesions, it is sometimes possible with PET to detect cancers occult on standard methods. This could be useful in high-risk patient populations, but in dense breasts, background FDG uptake is often higher than in women with fatty breasts, making identification of lesions < 1 cm in size improbable with current technologies. Distinguishing malignant from benign primary breast disease would seem better addressed by biopsy. With a positive predictive value of FDG PET for cancer over 96%, any FDG-avid breast lesion is highly suspicious and merits biopsy. Although PET in theory should be useful for depicting multifocal disease before surgery, the limitations in detecting small lesions in the breast limit the contribution of PET at present. It is most likely that PET will have a greater role in depicting primary breast lesions as dedicated PET imaging devices for the breast evolve. For axillary and internal mammary nodal staging, results with FDG PET are variable. Small nodal metastases < or = 5 mm will be missed by PET, whereas larger ones are more likely to be detected. PET can depict internal mammary nodes, but the accuracy of the method in this setting is not known, nor is there consensus on how identifying internal mammary node metastases will change treatment. Based on the available data, for pT1 breast lesions, PET, if negative, is not an adequate replacement for sentinel node surgery or axillary dissection. Results from the multicenter trial will be of great interest. Clearly PET can stage metastatic disease well. Bone scans with 18F- are exquisitely sensitive for metastases, and FDG is also very good. However, FDG PET can miss some blastic metastases to bone so at present FDG is not capable of excluding the presence of bone metastases. PET seems very well suited to detecting recurrences in soft tissues and the brachial plexus region in particular. The utility of PET in planning the treatment of individual patients appears promising. Although results must be confirmed in larger studies, it appears safe to conclude that failure of a chemotherapy regimen to decrease FDG uptake promptly in a breast cancer portends poor response. This does not hold true for hormonal therapy. At present, labeled estrogens are not widely available and cannot be recommended for clinical use. Thus, PET has shown considerable promise in breast cancer imaging, but in the author's experience is best applied to solve difficult imaging questions in specific patients and is not recommended for routine evaluation of the breast cancer patient. However, in larger primary tumors, the ability to use PET for staging and to plan treatment response suggest it will be more widely used. Additional studies with newer PET imaging devices and FDG and other tracers will help us better determine the role of PET in routine clinical care of the patient with known or suspected breast cancer. Certainly, this represent a fertile area for translational research studies over the next several years with the potential to significantly alter the way breast cancer is imaged and managed.

Design and evaluation of an LSO PET detector for breast cancer imaging

Functional imaging with positron emission tomography (PET) may be a promising technique in conjunction with x-ray mammography for breast cancer patient management. Conventional whole body PET scanners provide metabolic images of breast cancer patients with several shortcomings related to the general-purpose nature of these systems. In whole body scanners, the detectors are typically 20-30 cm away from the breast or axilla, reducing sensitivity, and these scanners have relatively large detector elements (> 4 mm), limiting spatial resolution. Dedicated PET systems for breast imaging aim to overcome these limitations and improve the overall diagnostic quality of the images by bringing the detectors closer to the area to be imaged, thereby improving sensitivity, and by using smaller detector elements to improve the spatial resolution. We have designed and developed a modular PET detector that is composed of a 9x9 array of 3x3x20 mm3 lutetium oxyorthosilicate (LSO) scintillator crystals coupled to an optical fiber taper, which in turn is coupled to a Hamamatsu R5900-C8 position-sensitive photomultiplier tube. These detectors can be tiled together without gaps to construct large area detector arrays to form a dedicated PET breast cancer imaging system. Two complete detector modules have been built and tested. All detector elements are clearly visualized upon flood irradiation of the module. The intrinsic spatial resolution (full-width at half-maximum) was measured to be 2.26 mm (range 1.8-2.6 mm). The average energy resolution was 19.5% (range 17%-24%) at 511 keV. The coincidence time resolution was measured to be 2.4 ns. The detector efficiency for 511 keV gamma rays was 53% using a 350 keV energy threshold. These promising results support the feasibility of developing a high resolution, high sensitivity dedicated PET scanner for breast cancer applications.

Positron emission mammographic instrument: initial results

Performance characteristics of a positron emission mammographic (PEM) instrument were studied. This dedicated metabolic breast imaging system has spatial resolution of 2.8-mm full width at half maximum (FWHM), coincidence resolving time of 12-nsec FWHM, and absolute efficiency of 3%. Hot spots with diameter of 16 mm in a phantom with signal-to-background activity ratio of 6:1 were distinguishable with a scanning time of 5 minutes.