Radionuclide methods and instrumentation for breast cancer detection and diagnosis

Attenuation correction and truncation completion for breast PET/MR imaging using deep learning

Objective. Simultaneous PET/MR scanners combine the high sensitivity of MR imaging with the functional imaging of PET. However, attenuation correction of breast PET/MR imaging is technically challenging. The purpose of this study is to establish a robust attenuation correction algorithm for breast PET/MR images that relies on deep learning (DL) to recreate the missing portions of the patient's anatomy (truncation completion), as well as to provide bone information for attenuation correction from only the PET data.Approach. Data acquired from 23 female subjects with invasive breast cancer scanned with18F-fluorodeoxyglucose PET/CT and PET/MR localized to the breast region were used for this study. Three DL models, U-Net with mean absolute error loss (DLMAE) model, U-Net with mean squared error loss (DLMSE) model, and U-Net with perceptual loss (DLPerceptual) model, were trained to predict synthetic CT images (sCT) for PET attenuation correction (AC) given non-attenuation corrected (NAC) PETPET/MRimages as inputs. The DL and Dixon-based sCT reconstructed PET images were compared against those reconstructed from CT images by calculating the percent error of the standardized uptake value (SUV) and conducting Wilcoxon signed rank statistical tests.Main results. sCT images from the DLMAEmodel, the DLMSEmodel, and the DLPerceptualmodel were similar in mean absolute error (MAE), peak-signal-to-noise ratio, and normalized cross-correlation. No significant difference in SUV was found between the PET images reconstructed using the DLMSEand DLPerceptualsCTs compared to the reference CT for AC in all tissue regions. All DL methods performed better than the Dixon-based method according to SUV analysis.Significance. A 3D U-Net with MSE or perceptual loss model can be implemented into a reconstruction workflow, and the derived sCT images allow successful truncation completion and attenuation correction for breast PET/MR images.

Clinical Applications of Dedicated Breast Positron Emission Tomography

Breast-specific positron imaging systems provide higher sensitivity than whole-body PET for breast cancer detection. The clinical applications for breast-specific positron imaging are similar to breast MRI including preoperative local staging and neoadjuvant therapy response assessment. Breast-specific positron imaging may be an alternative for patients who cannot undergo breast MRI. Further research is needed in expanding the field-of-view for posterior breast lesions, increasing biopsy capability, and reducing radiation dose. Efforts are also necessary for developing appropriate use criteria, increasing availability, and advancing insurance coverage.

Molecular Breast Imaging and Positron Emission Mammography

There is growing interest in application of functional imaging modalities for adjunct breast imaging due to their unique ability to evaluate molecular/pathophysiologic changes, not visible by standard anatomic breast imaging. This has led to increased use of nuclear medicine dedicated breast-specific single photon and coincidence imaging systems for multiple indications, such as supplemental screening, staging of newly diagnosed breast cancer, evaluation of response to neoadjuvant treatment, diagnosis of local disease recurrence in the breast, and problem solving. Studies show that these systems maybe especially useful for specific subsets of patients, not well served by available anatomic breast imaging modalities.

Breast Cancer Screening and Diagnosis: Recent Advances in Imaging and Current Limitations

Breast cancer detection has a significant impact on population health. Although there are many breast imaging modalities, mammography is the predominant tool for breast cancer screening. The introduction of digital breast tomosynthesis to mammography has contributed to increased cancer detection rates and decreased recall rates. In average-risk women, starting annual screening mammography at age 40 years has demonstrated the highest mortality reduction. In intermediate- and high-risk women as well as in those with dense breasts, additional modalities, including MRI, ultrasound, and molecular breast imaging, can also be considered for adjunct screening to improve the detection of mammographically occult malignancy.

The current role of nuclear medicine in breast cancer

Breast cancer is the most common cancer in females worldwide. Nuclear medicine plays an important role in patient management, not only in initial staging, but also during follow-up. Radiopharmaceuticals to study breast cancer have been used for over 50 years, and several of these are still used in clinical practice, according to the most recent guideline recommendations.In this critical review, an overview of nuclear medicine procedures used during the last decades is presented. Current clinical indications of each of the conventional nuclear medicine and PET/CT examinations are the focus of this review, and are objectively provided. Radionuclide therapies are also referred, mainly summarising the methods to palliate metastatic bone pain. Finally, recent developments and future perspectives in the field of nuclear medicine are discussed. In this context, the promising potential of new radiopharmaceuticals not only for diagnosis, but also for therapy, and the use of quantitative imaging features as potential biomarkers, are addressed.Despite the long way nuclear medicine has gone through, it looks like it will continue to benefit clinical practice, paving the way to improve healthcare provided to patients with breast cancer.

The Clinical Value of Breast Specific Gamma Imaging and Positron Imaging: An Update

In the management of patients with breast cancer (BC), a mammography contributed to screen an early-stage patient, to plan a therapy strategy, to evaluate a therapy outcome, to detect a recurrence, and to reduce a mortality. Currently, various imaging modalities, such as CT, MR, Ultrasound (US), SPECT/CT, PET/CT, PET/MR have been utilized for the management of BC patients. In order to overcome a limited spatial resolution and sensitivity of whole-body systems in nuclear medicine imaging, dedicated breast imaging modalities were developed. One is a gamma imaging system with single/dual head scintillation detectors or semiconductor detectors associated with light compression device for breast parenchyma. Radiopharmaceutical for the gamma imaging is ^99mTc-sestamibi. Another is a positron imaging system with opposite-type panel detectors and ring-shaped type detectors. Radiopharmaceutical for positron imaging is ¹⁸F-fluorodeoxyglucose. The breast-specific gamma and positron imaging systems were utilized mainly to detect small lesions less than 1 cm in diameter especially in patients with dense breast, to evaluate an effect of preoperative neo-adjuvant therapy, to plan surgical procedures (conservative-surgery vs mastectomy), and to detect a recurrence. By combining higher sensitivity and spatial resolution scanners with new radiopharmaceuticals, an information on molecular-level pathology of BC is increasingly available in an individual patient. This article reviewed clinical impact and future perspective of this field.

Current State of Breast Cancer Diagnosis, Treatment, and Theranostics

Breast cancer is one of the leading causes of cancer-related morbidity and mortality in women worldwide. Early diagnosis and effective treatment of all types of cancers are crucial for a positive prognosis. Patients with small tumor sizes at the time of their diagnosis have a significantly higher survival rate and a significantly reduced probability of the cancer being fatal. Therefore, many novel technologies are being developed for early detection of primary tumors, as well as distant metastases and recurrent disease, for effective breast cancer management. Theranostics has emerged as a new paradigm for the simultaneous diagnosis, imaging, and treatment of cancers. It has the potential to provide timely and improved patient care via personalized therapy. In nanotheranostics, cell-specific targeting moieties, imaging agents, and therapeutic agents can be embedded within a single formulation for effective treatment. In this review, we will highlight the different diagnosis techniques and treatment strategies for breast cancer management and explore recent advances in breast cancer theranostics. Our main focus will be to summarize recent trends and technologies in breast cancer diagnosis and treatment as reported in recent research papers and patents and discuss future perspectives for effective breast cancer therapy.

Evaluating attenuation correction strategies in a dedicated, single-gantry breast PET-tomosynthesis scanner

We are developing a dedicated, combined breast positron emission tomography (PET)-tomosynthesis scanner. Both the PET and digital breast tomosynthesis (DBT) scanners are integrated in a single gantry to provide spatially co-registered 3D PET-tomosynthesis images. The DBT image will be used to identify the breast boundary and breast density to improve the quantitative accuracy of the PET image. This paper explores PET attenuation correction (AC) strategies that can be performed with the combined breast PET-DBT scanner to obtain more accurate, quantitative high-resolution 3D PET images. The PET detector is comprised of a 32 × 32 array of 1.5 × 1.5 × 15 mm3 LYSO crystals. The PET scanner utilizes two detector heads separated by either 9 or 11 cm, with each detector head having a 4 × 2 arrangement of PET detectors. GEANT4 Application for Tomographic Emission simulations were performed using an anthropomorphic breast phantom with heterogeneous attenuation under clinical DBT-compression. FDG-avid lesions, each 5 mm in diameter with 8:1 uptake, were simulated at four locations within the breast. Simulations were performed with a scan time of 2 min. PET AC was performed using the actual breast simulation model as well as DBT reconstructed volumetric images to derive the breast outline. In addition to using the known breast density as defined by the breast model, we also modeled it as uniform patient-independent soft-tissue, and as a uniform patient-specific material derived from breast tissue composition. Measured absolute lesion uptake was used to evaluate the quantitative accuracy of performing AC using the various strategies. This study demonstrates that AC is necessary to obtain a closer estimate of the true lesion uptake and background activity in the breast. The DBT image dataset assists in measuring lesion uptake with low bias by facilitating accurate breast delineation as well as providing accurate information related to the breast tissue composition. While both the uniform soft-tissue and patient-specific material approaches provides a close estimate to the ground truth, <5% bias can be achieved by using a uniform patient-specific material to define the attenuation map.

A dedicated phantom design for positron emission mammography performance evaluation

A standard protocol for performance evaluation of positron emission mammography (PEM) systems has not yet been established. In this work we propose a methodology based on the design of specific phantoms for this imaging modality with component dimensions in accordance with typical breast lesion sizes together with the adaptation of current international protocols designed for clinical and preclinical positron emission tomographs (PET) systems. This methodology was used to evaluate the performance of the Flex Solo II PEM scanner in terms of spatial resolution, uniformity and contrast lesion detectability, recovery coefficients and spill-over ratios. Positron range effects were studied with ¹⁸F and ⁶⁸Ga, which have very different energy spectra. Our results indicate that in-plane spatial resolution of the system is around 3.0 mm and 4.4 mm for ¹⁸F and ⁶⁸Ga, respectively. Lesion detectability tests with sphere diameters between 4 and 10 mm confirmed that the PEM system can resolve all the spheres (hot or cold). Percent contrast values for ¹⁸F lie between 6%-38% and 34%-51% for hot- and cold- spheres, respectively; the corresponding intervals for ⁶⁸Ga are lower, 4%-25% and 32%-44%. Regarding uniformity quantification, the system shows percentage standard deviations within 4.9%-5.7%, while the percent background variability measurements ranged between 6.7% and 10.9% for both radionuclides. Recovery coefficients measured with hot rod diameters between 1.5 and 9 mm, have values between 0.2-1.05 and 0.17-0.69 for ¹⁸F and ⁶⁸Ga, respectively. Spill-over ratios have large values (0.22 in average) for both radionuclides. Our results indicate that the phantoms and the methodology developed in this work can serve as the basis for establishing an image quality protocol for the systematic evaluation of PEM systems, with a potential extension for performance evaluation of dedicated breastPET scanners.

Advanced and futuristic approaches for breast cancer diagnosis

Background

Breast cancer is the most frequent cancer and one of the most common causes of death in women, impacting almost 2 million women each year. Tenacity or perseverance of breast cancer in women is very high these days with an extensive increasing rate of 3 to 5% every year. Along with hurdles faced during treatment of breast tumor, one of the crucial causes of delay in treatment is invasive and poor diagnostic techniques for breast cancer hence the early diagnosis of breast tumors will help us to improve its management and treatment in the initial stage.

Main body

Present review aims to explore diagnostic techniques for breast cancer that are currently being used, recent advancements that aids in prior detection and evaluation and are extensively focused on techniques that are going to be future of breast cancer detection with better efficiency and lesser pain to patients so that it helps to a physician to prevent delay in treatment of cancer. Here, we have discussed mammography and its advanced forms that are the need of current era, techniques involving radiation such as radionuclide methods, the potential of nanotechnology by using nanoparticle in breast cancer, and how the new inventions such as breath biopsy, and X-ray diffraction of hair can simply use as a prominent method in breast cancer early and easy detection tool.

Conclusion

It is observed significantly that advancement in detection techniques is helping in early diagnosis of breast cancer; however, we have to also focus on techniques that will improve the future of cancer diagnosis in like optical imaging and HER2 testing.

Augmented Whole-Body Scanning via Magnifying PET

A novel technique, called augmented whole-body scanning via magnifying PET (AWSM-PET), that improves the sensitivity and lesion detectability of a PET scanner for whole-body imaging is proposed and evaluated. A Siemens Biograph Vision PET/CT scanner equipped with one or two high-resolution panel-detectors was simulated to study the effectiveness of AWSM-PET technology. The detector panels are located immediately outside the scanner's axial field-of-view (FOV). A detector panel contains 2 ×8 detector modules each consisting of 32 ×64 LSO crystals ( 1.0 ×1.0 ×10.0 mm3 each). A 22Na point source was stepped across the scanner's FOV axially to measure sensitivity profiles at different locations. An elliptical torso phantom containing 7×9 spherical lesions was imaged at different axial locations to mimic a multi-bed-position whole-body imaging protocol. Receiver operating characteristic (ROC) curves were analyzed to evaluate the improvement in lesion detectability by the AWSM-PET technology. Experimental validation was conducted using an existing flat-panel detector integrated with a Siemens Biograph 40 PET/CT scanner to image a torso phantom containing spherical lesions with diameters ranging from 3.3 to 11.4 mm. The contrast-recovery-coefficient (CRC) of the lesions was evaluated for the scanner with or without the AWSM-PET technology. Monte Carlo simulation shows 36%-42% improvement in system sensitivity by a dual-panel AWSM-PET device. The area under the ROC curve is 0.962 by a native scanner for the detection of 4 mm diameter lesions with 5:1 tumor-to-background activity concentration. It was improved to 0.977 and 0.991 with a single- and dual-panel AWSM-PET system, respectively. Experimental studies showed that the average CRC of 3.3 mm and 4.3 mm diameter tumors were improved from 2.8% and 4.2% to 7.9% and 11.0%, respectively, by a single-panel AWSM-PET device. With a high-sensitivity dual-panel device, the corresponding CRC can be further improved to 11.0% and 15.9%, respectively. The principle of the AWSM-PET technology has been developed and validated. Enhanced system sensitivity, CRC and tumor detectability were demonstrated by Monte Carlo simulations and imaging experiments. This technology may offer a cost-effective path to realize high-resolution whole-body PET imaging clinically.

Imaging and biodistribution of radiolabeled SP90 peptide in BT-483 tumor bearing mice

The objective of this study was to evaluate radiolabeled DOTA-SP90 as a radiotracer for breast cancer. The in vitro competition assay showed that radiolabeled DOTA-SP90 had significant binding affinity to BT-483 cancer cells. Biodistribution, nanoSPECT/CT and nanoPET/CT imaging results indicated that radiolabeled DOTA-SP90 can accumulate in tumors. In addition, radiolabeled DOTA-SP90 peptides can also detect metastatic tumors. Therefore, radiolabeled SP90 peptide may provide the potential capability as diagnostic agent for breast cancer patients.

A second-generation virtual-pinhole PET device for enhancing contrast recovery and improving lesion detectability of a whole-body PET/CT scanner

PURPOSE

We have developed a second-generation virtual-pinhole (VP) positron emission tomography (PET) device that can position a flat-panel PET detector around a patient's body using a robotic arm to enhance the contrast recovery coefficient (CRC) and detectability of lesions in any region-of-interest using a whole-body PET/computed tomography (CT) scanner.

METHODS

We constructed a flat-panel VP-PET device using 32 high-resolution detectors, each containing a 4  ×  4 MPPC array and 16  ×  16 LYSO crystals of 1.0  ×  1.0  ×  3.0 mm³ each. The flat-panel detectors can be positioned around a patient's body anywhere in the imaging field-of-view (FOV) of a Siemens Biograph 40 PET/CT scanner by a robotic arm. New hardware, firmware and software have been developed to support the additional detector signals without compromising a scanner's native functions. We stepped a ²² Na point source across the axial FOV of the scanner to measure the sensitivity profile of the VP-PET device. We also recorded the coincidence events measured by the scanner detectors and by the VP-PET detectors when imaging phantoms of different sizes. To assess the improvement in the CRC of small lesions, we imaged an elliptical torso phantom measuring 316  ×  228  ×  162 mm³ that contains spherical tumors with diameters ranging from 3.3 to 11.4 mm with and without the VP-PET device. Images were reconstructed using a list mode Maximum-Likelihood Estimation-Maximization algorithm implemented on multiple graphics processing units (GPUs) to support the unconventional geometries enabled by a VP-PET system. The mean and standard deviation of the CRC were calculated for tumors of different sizes. Monte Carlo simulation was also conducted to image clusters of lesions in a torso phantom using a PET/CT scanner alone or the same scanner equipped with VP-PET devices. Receiver operating characteristic (ROC) curves were analyzed for three system configurations to evaluate the improvement in lesion detectability by the VP-PET device over the native PET/CT scanner.

RESULTS

The repeatability in positioning the flat-panel detectors using a robotic arm is better than 0.15 mm in all three directions. Experimental results show that the average CRC of 3.3, 4.3, and 6.0 mm diameter tumors was 0.82%, 2.90%, and 5.25%, respectively, when measured by the native scanner. The corresponding CRC was 2.73%, 6.21% and 10.13% when imaged by the VP-PET insert device with the flat-panel detector under the torso phantom. These values may be further improved to 4.31%, 9.65% and 18.01% by a future dual-panel VP-PET insert device if DOI detectors are employed to triple its detector efficiency. Monte Carlo simulation results show that the tumor detectability can be improved by a VP-PET device that has a single flat-panel detector. The improvement is greater if the VP-PET device employs a dual-panel design.

CONCLUSIONS

We have developed a prototype flat-panel VP-PET device and integrated it with a clinical PET/CT scanner. It significantly enhances the contrast of lesions, especially for those that are borderline detectable by the native scanner, within regions-of-interest specified by users. Simulation demonstrated the enhancement in lesion detectability with the VP-PET device. This technology may become a cost-effective solution for organ-specific imaging tasks.

Performance evaluation of a high resolution dedicated breast PET scanner

PURPOSE

Early stage breast cancers may not be visible on a whole-body PET scan. To overcome whole-body PET limitations, several dedicated breast positron emission tomography (DbPET) systems have emerged nowadays aiming to improve spatial resolution. In this work the authors evaluate the performance of a high resolution dedicated breast PET scanner (Mammi-PET, Oncovision).

METHODS

Global status, uniformity, sensitivity, energy, and spatial resolution were measured. Spheres of different sizes (2.5, 4, 5, and 6 mm diameter) and various 18 fluorodeoxyglucose ((18)F-FDG) activity concentrations were randomly inserted in a gelatine breast phantom developed at our institution. Several lesion-to-background ratios (LBR) were simulated, 5:1, 10:1, 20:1, 30:1, and 50:1. Images were reconstructed using different voxel sizes. The ability of experienced reporters to detect spheres was tested as a function of acquisition time, LBR, sphere size, and matrix reconstruction voxel size. For comparison, phantoms were scanned in the DbPET camera and in a whole body PET (WB-PET). Two patients who just underwent WB-PET/CT exams were imaged with the DbPET system and the images were compared.

RESULTS

The measured absolute peak sensitivity was 2.0%. The energy resolution was 24.0% ± 1%. The integral and differential uniformity were 10% and 6% in the total field of view (FOV) and 9% and 5% in the central FOV, respectively. The measured spatial resolution was 2.0, 1.9, and 1.7 mm in the radial, tangential, and axial directions. The system exhibited very good detectability for spheres ≥4 mm and LBR ≥10 with a sphere detection of 100% when acquisition time was set >3 min/bed. For LBR = 5 and acquisition time of 7 min the detectability was 100% for spheres of 6 mm and 75% for spheres of 5, 4, and 2.5 mm. Lesion WB-PET detectability was only comparable to the DbPET camera for lesion sizes ≥5 mm when acquisition time was >3 min and LBR > 10.

CONCLUSIONS

The DbPET has a good performance for its clinical use and shows an improved resolution and lesion detectability of small lesions compared to WB-PET.

Breast Imaging Utilizing Dedicated Gamma Camera and (99m)Tc-MIBI: Experience at the Tel Aviv Medical Center and Review of the Literature Breast Imaging

The scope of the current article is the clinical role of gamma cameras dedicated for breast imaging and (99m)Tc-MIBI tumor-seeking tracer, as both a screening modality among a healthy population and as a diagnostic modality in patients with breast cancer. Such cameras are now commercially available. The technology utilizing a camera composed of a NaI (Tl) detector is termed breast-specific gamma imaging. The technology of dual-headed camera composed of semiconductor cadmium zinc telluride detectors that directly converts gamma-ray energy into electronic signals is termed molecular breast imaging. Molecular breast imaging system has been installed at the Department of Nuclear medicine at the Tel Aviv Sourasky Medical Center, Tel Aviv in 2009. The article reviews the literature well as our own experience.

In vitro detection of human breast cancer cells (SK-BR3) using herceptin-conjugated liquid crystal microdroplets as a sensing platform

Polarized light micrographs showing bipolar orientation of 5CB molecules in herceptin-conjugated LC microdroplets on selective interactions with SK-BR3 cancer cells.

Alternative screening for women with dense breasts: breast-specific gamma imaging (molecular breast imaging)

OBJECTIVE. Given mammography's limitations in evaluating dense breasts, examination with breast-specific gamma imaging (BSGI)-also called molecular breast imaging (MBI)-has been proposed. We review the literature pertinent to the performance of BSGI in patients with dense breasts. CONCLUSION. Many studies have reported the sensitivity of BSGI in finding cancers even in dense breasts. However, BSGI has not yet been validated as an effective screening tool in large prospective studies. In addition, whole-body dose remains a significant concern.

The role of general nuclear medicine in breast cancer

The rising incidence of breast cancer worldwide has prompted many improvements to current care. Routine nuclear medicine is a major contributor to a full gamut of clinical studies such as early lesion detection and stratification; guiding, monitoring, and predicting response to therapy; and monitoring progression, recurrence or metastases. Developments in instrumentation such as the high-resolution dedicated breast device coupled with the diagnostic versatility of conventional cameras have reinserted nuclear medicine as a valuable tool in the broader clinical setting. This review outlines the role of general nuclear medicine, concluding that targeted radiopharmaceuticals and versatile instrumentation position nuclear medicine as a powerful modality for patients with breast cancer.