Positron Emission Mammography Research Articles

Geospatial evaluation of radiologic access in Rwanda

BackgroundRwanda has aimed to rebuild its health care system since the Rwandan genocide against the Tutsis in 1994, though one of the challenges has been a scarcity of radiologic resources.ObjectiveTo assess the location and accessibility of radiologic facilities in Rwanda using geospatial mapping and population-based data.MethodsA cross-sectional study was conducted in May 2023 using location and radiologic modality data provided by the Department of Radiology at the University Teaching Hospital of Kigali and the WorldPop database, a publicly available database providing open-access geospatial population data. Radiologic equipment included magnetic resonance (MR), computed tomography (CT), positron emission tomography (PET), radiotherapy, X-ray, mammography, and fluoroscopy machines. Geospatial analysis was performed using ArcGIS Pro 2.8.6 software.ResultsFifty-six radiologic facilities were identified, including 5 MR, 7 CT, 1 radiotherapy, 52 X-ray, 5 mammography, 5 fluoroscopy, and 0 PET machines. There were 0.4 MR, 0.5 CT, 0 PET, 0.1 radiotherapy, 3.9 X-ray, 0.4 mammography, and 0.4 fluoroscopy units per 1 million people.ConclusionRwanda is one of the countries with the lowest radiologic access in East Africa; however, there is evidence of progress, particularly in more advanced diagnostic imaging techniques such as computed tomography and magnetic resonance imaging.Critical relevance statementThis study provides a 10-year update on current radiologic resources and access in Rwanda, identifying areas of progress and ongoing scarcity, serving as a guide for future direction of growth.Key points• As Rwanda works on rebuilding its health care system, this study provides an assessment of the current radiologic resources within the country.• There is less than one radiologic unit for every million of the Rwandan population for every imaging modality other than X-ray.• While radiologic access in Rwanda lags behind that of its neighbors, there has been growth focused on advanced imaging modalities and the training of human resources.Graphical

Image quality evaluation for a clinical organ-targeted PET camera.

A newly developed clinical organ-targeted Positron Emission Tomography (PET) system (also known as Radialis PET) is tested with a set of standardized and custom tests previously used to evaluate the performance of Positron Emission Mammography (PEM) systems. Imaging characteristics impacting standardized uptake value (SUV) and detectability of small lesions, namely spatial resolution, linearity, uniformity, and recovery coefficients, are evaluated. In-plane spatial resolution was measured as 2.3 mm ± 0.1 mm, spatial accuracy was 0.1 mm, and uniformity measured with flood field and NEMA NU-4 phantom was 11.7% and 8.3% respectively. Selected clinical images are provided as reference to the imaging capabilities under different clinical conditions such as reduced activity of 2-[fluorine-18]-fluoro-2-deoxy-D-glucose (18F-FDG) and time-delayed acquisitions. SUV measurements were performed for selected clinical acquisitions to demonstrate a capability for quantitative image assessment of different types of cancer including for invasive lobular carcinoma with comparatively low metabolic activity. Quantitative imaging performance assessment with phantoms demonstrates improved contrast recovery and spill-over ratio for this PET technology when compared to other commercial organ-dedicated PET systems with similar spatial resolution. Recovery coefficients were measured to be 0.21 for the 1 mm hot rod and up to 0.89 for the 5 mm hot rod of NEMA NU-4 Image Quality phantom. Demonstrated ability to accurately reconstruct activity in tumors as small as 5 mm suggests that the Radialis PET technology may be well suited for emerging clinical applications such as image guided assessment of response to neoadjuvant systemic treatment (NST) in lesions smaller than 2 cm. Also, our results suggest that, while spatial resolution greatly influences the partial volume effect which degrades contrast recovery, optimized count rate performance and image reconstruction workflow may improve recovery coefficients for systems with comparable spatial resolution. We emphasize that recovery coefficient should be considered as a primary performance metric when a PET system is used for accurate lesion size or radiotracer uptake assessments.

Crystal scatter effects in a large-area dual-panel Positron Emission Mammography system.

Positron Emission Mammography (PEM) is a valuable molecular imaging technique for breast studies using pharmaceuticals labeled with positron emitters and dual-panel detectors. PEM scanners normally use large scintillation crystals coupled to sensitive photodetectors. Multiple interactions of the 511 keV annihilation photons in the crystals can result in event mispositioning leading to a negative impact in radiopharmaceutical uptake quantification. In this work, we report the study of crystal scatter effects of a large-area dual-panel PEM system designed with either monolithic or pixelated lutetium yttrium orthosilicate (LYSO) crystals using the Monte Carlo simulation platform GATE. The results show that only a relatively small fraction of coincidences (~20%) arise from events where both coincidence photons undergo single interactions (mostly through photoelectric absorption) in the crystals. Most of the coincidences are events where at least one of the annihilation photons undergoes a chain of Compton scatterings: approximately 79% end up in photoelectric absorption while the rest (<1%) escape the detector. Mean positioning errors, calculated as the distance between first hit and energy weighted (assigned) positions of interaction, were 1.70 mm and 1.92 mm for the monolithic and pixelated crystals, respectively. Reconstructed spatial resolution quantification with a miniDerenzo phantom and a list mode iterative reconstruction algorithm shows that, for both crystal types, 2 mm diameter hot rods were resolved, indicating a relatively small effect in spatial resolution. A drastic reduction in peak-to-valley ratios for the same hot-rod diameters was observed, up to a factor of 14 for the monolithic crystals and 7.5 for the pixelated ones.

Low-Dose Positron Emission Mammography: A Novel, Promising Technique for Breast Cancer Detection.

Low-Dose Positron Emission Mammography: A Novel, Promising Technique for Breast Cancer Detection.

Optimization of the WLS design for positron emission mammography and Total-Body J-PET systems

Total-body positron emission tomography (PET) instruments are medical imaging devices that detect and visualize metabolic activity in the entire body. The PET scanner has a ring-shaped detector that surrounds the patient and detects the gamma rays emitted by the tracer as it decays. Usually these detectors are made up of scintillation crystals coupled to photodetectors that convert the light produced by the scintillation crystal into electrical signals. Jagiellonian Positron Emission Mammograph (J-PEM) is the first J-PET prototype module based on a novel idea with a plastic scintillator and wavelength shifter (WLS). At the same time, it is a prototype module for the TotalBody J-PET system. J-PEM can be an effective system for the detection and diagnosis of breast cancer in its early stage by improving sensitivity. This can be achieved using the superior timing properties of plastic scintillators combined with the WLS sheets readout. In this paper we present an application of the Geant4 program for simulating optical photon transport in the J-PEM module. We aim to study light transport within scintillator bars and WLS sheets to optimize gamma-ray hit position resolution. We simulated a pencil beam of 511 keV photons impinging the scintillator bar at different locations. For each condition we calculated the value of the pulse height centroid and the spread of the photon distribution. Some free parameters of the simulation, like reflectivity and the effective attenuation length in the sheet, were determined from a comparison to experimental data. Finally, we estimated the influence of the application of WLS layer in the Total-Body J-PET on the scatter fraction. To optimize the performance of the J-PEM module we compared geometry WLS strips 50 and 83. It was found that spatial resolution was 2.7 mm and 3.5 mm FWHM for 50 and 83 WLS strips, respectively. Despite the better granularity, the 83-strip WLS geometry exhibited poorer resolution due to fewer photons being transmitted to the strip, resulting in large fluctuations of signal.

Positron emission mammography (PEM): a potentially promising one-stop shop for local staging of ILC

BackgroundInvasive lobular cancer (ILC) has a high propensity for multiplicity, along with a high probability of incomplete surgical excision. Due to its insidious proliferative pattern, it tends to be clinically silent and radiologically elusive. We assess the performance characteristics of PEM in the detection and local staging of ILC.MethodsA retrospective study evaluated a total of 193 patients who underwent PEM examination, including 44 patients with ILC. Image analysis of PEM examinations included morphological criteria, uptake pattern, lesion to background ratio (LTB) and maximum PEM uptake value (PUV max) assessment. The findings were correlated with the histopathological results.ResultsPEM showed high performance in surgical planning and detection of additional ILC lesions with sensitivity of 90.6% and specificity 82%. The mean PUV max and LTB of ILC lesions were significantly different from those of benign lesions and IDC lesions. The cutoff average LTB and PUVmax values to differentiate ILC from benign lesions were ≥ 3.3 & ≥ 2.2, respectively.ConclusionsThe inclusion of PEM provides a functional image that can improve the diagnostic accuracy of the conventional studies, decreasing the rates of false results and improving the detection of multicentric ILC lesions identification and their differentiation from other benign breast lesions.Advance in knowledgePEM is a promising new imaging technique that further improves the pretherapeutic assessment of ILC and facilitates the assessment of patients with renal impairment.

Early detection and Advanced Targeted Drug Therapies for HER2 positive breast cancer

HER 2 positive breast cancers are the aggressive subtype of breast cancer which can be treated completely if early detected. According to the National Cancer Institute, localized or stage 1 female breast cancer patients have a relative survival rate of 99% and they can survive for more than 5 years after diagnosis but only 63.1% cases are diagnosed at this stage. In later stages when it's diagnosed, the relative survival rate becomes 29%. The overexpression of HER2 proteins can be detected by early diagnosis and screening through advanced technologies like 3D mammography, Positron Emission Mammography, Molecular breast imaging, Contrast-enhanced mammography. The specific diagnosis can be done by Immunohistochemistry (IHC) and Fluorescence in situ hybridization (FISH) for confirmation of this type of breast cancer. Biomarkers such as Her2 heterogenicity, Her2 expression, Her2 mutations, Hormone receptor (ER positivity, PR positivity), PIK3CA mutation, PTEN, PD-L1, TIL, BRCA, miRNA can be used for detection of breast cancer. With successful early detection, which will be used to diagnose early and start the treatment as early as possible. Recently FDA has approved various individual and combination medications for treating the HER2 positive breast cancer and there are further research studies and clinical trials are going on to get more impactful treatment for providing complete cure of the deadly disease.

3D directional gradient L0 norm minimization guided limited-view reconstruction in a dual-panel positron emission mammography

BackgroundDual-panel PET is often used for local organ imaging, especially breast imaging, due to its simple structure, high sensitivity, good in-plane resolution, and straightforward fusion with other imaging modalities. Nevertheless, because of data loss caused by the dual-panel structure, using conventional image reconstruction methods results in limited-view artifacts and low image quality in dual-panel positron emission mammography (PEM), which may seriously affect the diagnosis. To mitigate the limited-view artifacts in the dual-panel PEM, we propose a 3D directional gradient L0 norm minimization (3D-DL0) guided reconstruction method. MethodsThe detailed derivation and reasonable simplification of the 3D-DL0 algorithm are given first. Using this algorithm, we then obtain a prior image with edge recovery but contrast loss. To limit the solution space, the 3D-DL0 prior is introduced into the Maximum a Posteriori reconstruction. Meanwhile, a space-invariant point spread function is also implemented to restore image contrast and boundaries. Finally, the reconstructed images with limited-view artifact suppression are obtained. The proposed method was evaluated using the data acquired from physical phantoms and patients with breast tumors on a commercial dual-panel PET system. ResultsThe qualitative and quantitative studies for phantom data and the blind reader study for clinical data show that the proposed method is more effective in reaching a balance between artifact elimination and image contrast improvement compared with various limited-view reconstruction methods. In addition, the iteration process of the method is proved convergent numerically. ConclusionsThe image quality improvement confirms the potential value of the proposed reconstruction algorithm to address the limited-view problem, and thus improve diagnostic accuracy in dual-panel PEM imaging.

Abstract P2-09-01: An Emerging Technology for Breast Cancer Detection - Preliminary Data of Breast Cancer Detection using Novel Low Dose Positron Emission Mammography

Abstract Purpose: To investigate the feasibility of low-dose Positron Emission Mammography (PEM) to identify breast cancer. Materials and Methods: In an REB-approved ongoing clinical trial, which started in December 2019, all newly diagnosed women with breast cancer who had not undergone neoadjuvant chemotherapy and consented to the study were randomly assigned independently of their mammographic breast density, tumor size, and histopathology cancer subtype to perform PEM using a novel organ-targeted PET system(Radialis PET Imager, Radialis Inc., FDA cleared to image and measure the distribution of injected positron-emitting radiopharmaceuticals) with either 1mCi, 2mCi or 5 mCi of 18F-FDG. The PEM images acquired 1 and 4 hours after 18F-FDG administration were reviewed in consensus by two fellowship-trained breast radiologists blinded to cancer location. PEM imaging features of known malignancies and additional PEM findings were recorded and correlated with histopathology as the ground truth. Results: Our cohort comprised 22 women with a median age of 51 years (range 32-85) with 88 completed bilateral sets of images where 23 cancers (18 invasives, and 5 in situ) were present. The median invasive cancer size on surgical pathology was 28 mm (range: 3-120). Out of 18 invasive cancers, the only PEM images that did not visualize cancer (2 invasive lobular cancers and 2 in-situ cancers) were acquired with the lowest dose of 18F-FDG (1 mCi). A total of 6 (27.3%) subjects received 1mCi 18F-FDG with 5 invasive cancers, 7 (31.8%) of patients received 5 mCi 18F-FDG with 7 invasive cancers, and 9 (40.9%) of patients received 5 mCi 18F-FDG with 6 invasive cancers. A total of 3 false-positive images of benign findings were also present. No additional cancers were identified exclusively by PEM. The PEM performance was similar following an additional 3-hour interval for radiotracer uptake. Conclusion: This preliminary data results show the feasibility of invasive breast cancer detection with a decreased 18F-FDG dose, possibly due to the novel PEM system detectors increasing the sensitivity to radiotracer and the perceived spatial resolution by the visual assessment. Larger-scale clinical trials are required to consolidate our preliminary findings. Clinical Relevance: A novel organ-targeted PET system enables the detection of invasive breast cancer using low-dose PEM, potentially emerging as a promising novel imaging tool. Citation Format: Vivianne Freitas, Michael L. Waterston, Ken O. Olsen, Oleksandr Bubon, Shayna Parker, Brandon Baldassi, Borys Komarov, Samira Taeb, Alla Reznik. An Emerging Technology for Breast Cancer Detection - Preliminary Data of Breast Cancer Detection using Novel Low Dose Positron Emission Mammography [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P2-09-01.

Dedicated phantom tools using traceable 68Ge/68Ga point-like sources for dedicated-breast PET and positron emission mammography scanners.

Since the early 2000s, many types of positron emission tomography (PET) scanners dedicated to breast imaging for the diagnosis of breast cancer have been introduced. However, conventional performance evaluation methods developed for whole-body PET scanners cannot be used for such devices. In this study, we developed phantom tools for evaluating the quantitative accuracy of positron emission mammography (PEM) and dedicated-breast PET (dbPET) scanners using novel traceable point-like 68Ge/68Ga sources. The PEM phantom consisted of an acrylic cube (100 × 100 × 40mm) and three point-like sources. The dbPET phantom comprised an acrylic cylinder (ø100 × 100mm) and five point-like sources. These phantoms were used for evaluating the fundamental responses of clinical PEM and dbPET scanners to point-like inputs in a medium. The results showed that reasonable recovery values were obtained based on region-of-interest analyses of the reconstructed images. The developed phantoms using traceable 68Ge/68Ga point-like sources were useful for evaluating the physical characteristics of PEM and dbPET scanners. Thus, they offer a practical, reliable, and universal measurement scheme for evaluating various types of PET scanners using common sets of sealed sources.

A New Method for Optimizing the Size of Axial FOV in TOF-PEM to Improve Performance of the Scanner.

Positron Emission Mammography (PEM) is a nuclear medicine imaging tool, playing a significant role in the diagnosis of patients with breast cancer. These days, many research has been done in order to improve the performance of this system. This study aims to propose a new method for optimizing the size of axial Field of View (FOV) in PEMs and improving the performance of the systems. In this analytical study, a conventional Inveon PET is simulated using GATE in order to validate the simulation. For this simulation, the mean relative difference is 2.91%, showing the precision and correction of simulation and consequently it is benchmarked. In the next step, for design of the new optimized detector, several validated simulations are performed in order to find the best geometry. The best result is obtained with the axial FOV of 101.7 mm. It has 1.6×1.6×15 mm3 lutetium yttrium orthosilicate (LYSO) crystals. The detector consists of 6 block rings with 30 detector blocks in each ring. In this paper, the performance of the scanner is improved and the geometry is optimized. Sensitivity and scatter fraction of the designed scanner are 4.65% and 21.2%, respectively, also noise equivalent count rate (NECR) is 105.442 kcps. The results showed 1 up to 3% improvement in the sensitivity of this new detector compared with different PEMs.

Detection of Axillary Lymph Node Involvement in Early-Stage Breast Cancer: Comparison between Staging 18F-2-Fluoro-2-Deoxy-D-Glucose Positron Emission Tomography-Computed Tomography Scans, Mammography, and Sentinel Lymph Node Biopsy.

The aim of this study was to evaluate the role of 18F-2-fluoro-2-deoxy-D-glucose (18F-FDG) positron emission tomography-computed tomography (PET-CT) scan in the detection of axillary lymph node (ALN) involvement and comparison with sentinel lymph node biopsy (SLNB) in operable early-stage breast cancer (EBC). It is a retrospective analysis of staging PET-CT scan of EBC. A total of 128 patients with histopathologically proven breast cancer (BC) were included in the study. Preoperative mammography supplemented with ultrasonography and staging 18F-FDG PET-CT scan was done for all patients. Surgery was done within 30 (mean ± standard deviation = 13.8 ± 10.5) days of staging. SLNB was performed in patients without PET-positive ALNs. All patients with positive sentinel nodes and PET-positive ALNs underwent axillary lymph node dissection (ALND). The comparison between categorical variables was made by Chi-square/Fisher's exact test as applicable. For continuous variables comparisons, Student's t-test and one-way analysis of variance tests were used. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of PET-CT scan for detection of ALN involvement were 41.7%, 93.2%, 92.1%, and 45.6%, respectively. Sensitivity, specificity, PPV, and NPV of mammography were 84.5%, 54.5%, 78.0%, and 68.6%, respectively. Sixteen out of 46 (34.7%) patients with negative ALNs in PET-CT scan finally showed involvement in histopathology report after SLNB resulting in upstage of the disease. The size of tumor deposits in sentinel nodes was significantly smaller than PET-positive ALNs (P = 0.01). Our observations correlate with the results of earlier studies published in the literature. 18F-FDG PET-CT scan cannot substitute SLNB for ALN screening in EBC. The limitations are most marked in smaller and micrometastatic tumor deposits in ALNs and may be attributed to limitations of PET resolution. However, PET-positive nodes showed good specificity for disease involvement in our study. Therefore, ALND can safely be performed by omitting SLNB in such cases.

A detector block-pairwise dead time correction method for improved quantitation with a dedicated BrainPET scanner

‘Objective. Dead time correction (DTC) is an important factor in ensuring accurate quantification in PET measurements. This is currently often achieved using a global DTC method, i.e., an average DTC factor is computed. For PET scanners designed to image dedicated organs, e.g., those used in brain imaging or positron emission mammography (PEM), a substantial amount of the administered radioactivity is located outside of the PET field-of-view (FOV). This activity contributes to the dead time (DT) of the scintillation detectors. Moreover, the count rates of the individual scintillation detectors are potentially very inhomogeneous due to the specific irradiation of each detector, especially for combined MR/PET systems, where radiation shields cannot be applied. Approach: We have developed a block-pairwise DTC method for our Siemens 3T MR BrainPET insert by extending a previously published method that uses the delayed random coincidence count rate to estimate the DT in the individual scans and planes (i.e., scintillation pixel rings). The method was validated in decay experiments using phantoms with a homogenous activity concentration and with and without out-of-FOV activity. Based on a three-compartment phantom, we compared the accuracy and noise properties of the block-pairwise DTC and the global DTC method. Main results. The currently used global DTC led to a substantial positive bias in regions with high activity; the block-pairwise DTC resulted in substantially less bias. The noise level for the block-pairwise DTC was comparable to the global DTC and image reconstructions without any DTC. Finally, we tested the block-pairwise DTC with a data set obtained from volunteer measurements using the mGluR5 (metabotropic glutamate receptor subtype 5) antagonist [11C]ABP688. When the relative differences in activity concentrations obtained with global DTC and block-pairwise DTC for the ACC and the cerebellum GM were compared, the ratios differed by a factor of up to 1.4 at the beginning—when the first injection is administered as a bolus with high radioactivity. Significance. In this work, global DTC was shown to have the potential to introduce quantification bias, while better quantitation accuracy was achieved with the presented block-pairwise DTC method. The method can be implemented in all systems that use the delayed window technique and is particulary expected to improve the quantiation accuracy of dedicated brain PET scanners due to their geometry.’

DH-Mammo PET: a dual-head positron emission mammography system for breast imaging

Objective. To develop a simultaneous positron emission tomography-Optical (OPET) breast imaging dual-head PET subsystem, called DH-Mammo PET, for accurate, early diagnosis and efficacy assessment of breast cancer with high resolution and sensitivity. Approach. We developed a breast-dedicated PET based on LYSO crystal, silicon photomultiplier array and multi-voltage threshold sampling technique. It consists of two detector heads, each with a detection area of 216 mm × 145.5 mm. The distance between the detector heads is fixed at 120 mm. In order to extract coincidences and correct data, GPU-based software coincidence processing, random, scatter, normalization, gap-filling and attenuation corrections were applied in turn. The images were reconstructed using maximum likelihood expectation maximization with depth of interaction (DOI) modeling. The performance of DH-Mammo PET was evaluated referring to NEMA NU 4–2008, NU 2–2007 and Chinese industry recommended standard YY/T 1835–2022. Besides, several clinical patient images of DH-Mammo PET were compared with those of a whole-body PET/CT. Main results. The energy resolution was 14.5%, and time resolution was < 1.31 ns. Indicated by the 22Na point source imaging, its spatial resolution was 2.60 mm (5.40 mm), 1.00 mm (1.04 mm), and 0.96 mm (0.93 mm) in the X, Y and Z directions, respectively, using the system response matrix with (without) DOI modeling. Indicated by the Derenzo phantom imaging, the spatial resolution was ∼3.0 mm, <1.2 mm, and <1.2 mm in the X, Y and Z directions. The system sensitivity was 6.87%, 4.89% and 3.37% with an energy window of 100–800, 250–750 and 350–650 keV, respectively. The scatter fraction was 26.43%, and the peak NECR was 162.6 kcps at 24.1 MBq for the modified rat-like phantom. As for the recovery coefficients, they ranged from 0.15 to 1.04 for rods between 1 and 5 mm obtained with a NEMA image quality phantom. The spill-over ratio for the air-filled and water-filled chamber was 0.05 and 0.11, respectively. DH-Mammo PET can provide more image details in clinical experiments and fulfil a fast scan with 60–120 s acquisition time. Significance. Good spatial resolution and high sensitivity of DH-Mammo PET would enable fast and accurate PET imaging of the breast. Besides, combining the DH-Mammo PET with the diffuse optical tomography would make full use of tumor metabolic imaging and tissue endogenous optical imaging, which would improve the accuracy of early clinical diagnosis of small lesions of breast cancers.

Simulation of the Positron Emission Mammography system based on the Monte Carlo method by considering the effects of Time Of Flight (TOF) and Depth Of Interaction (DOI)

PEM (Positron Emission Mammography) imaging is a molecular imaging technique for early diagnosis and staging of breast cancer. So, it is very important to check the performance of the PAM device in order to improve the image quality. The aim of this work was to investigate the effects of Time Of Flight (TOF) and Depth Of Interaction (DOI) corrections in the PEM system's performance. For this purpose, the commercially available clinical PEM scanner (PEM Flex Solo II, Naviscan) was simulated using GATE software. This system consists of two non-rotating detector heads that are positioned in an opposing fashion on each side of the body part. Each detector head contains 12 sensitive PMTs with a 6 × 2 array. Also, each PMT is coupled by a light guide to 169 crystals with a 13 × 13 array of 2 mm × 2 mm × 13 mm LYSO crystals. The sensitivity parameter and the scattering fraction of the system were investigated according to the NEMA NU4-2008 standard's manual. Then to assessment the effect of TOF, the coincidence time resolution was changed from 900ps to 100ps. The maximum of NECR curve increases by 42.3% for considering the TOF in the simulation. Also, the Phoswich detector with BGO and LYSO crystals was used to investigate the effect of DOI. The results also show that in Phoswich detector with LYSO crystal with a thickness of 5 mm and BGO crystal with a thickness of 9 mm, the maximum NECR curve increases by 54%. The spatial resolution of the system improves from 2.4 mm to 1 mm by considering TOF and DOI. According to these results, considering the TOF and DOI have a significant role in improving the performance of the PEM system.

Benefits and limitations for the use of radiation dose management systems in medical imaging. Practical experience in a university hospital.

Radiation dose management systems (DMS) are currently used to help improve radiation protection in medical imaging and interventions. This study presents our experience using a homemade DMS called DOLQA (Dose On-Line for Quality Assurance). Our DMS is connected to 14 X-ray systems in a university hospital linked to the central data repository of a large network of 16 public hospitals in the Autonomous Community of Madrid, with 6.7 million inhabitants. The system allows us to manage individual patient dose data and groups of procedures with the same clinical indications, and compare them with diagnostic reference levels (DRLs). The system can also help to prioritise optimisation actions. This study includes results of imaging examinations from 2020, with 37,601 procedures and 286,471 radiation events included in the radiation dose structured reports (RDSR), for computed tomography (CT), interventional procedures, positron emission tomography-CT (PET-CT) and mammography. The benefits of the system include: automatic registration and management of patient doses, creation of dose reports for patients, information on recurrent examinations, high dose alerts, and help to define optimisation actions.The system requires the support of medical physicists and implication of radiologists and radiographers. DMSs must undergo periodic quality controls and audit reports must be drawn up and submitted to the hospital's quality committee.The drawbacks of DMSs include the need for continuous external support (medical physics experts, radiologists, radiographers, technical services of imaging equipment and hospital informatics services) and the need to include data on clinical indication for the imaging procedures. DMS perform automatic management of radiation doses, produces patient dose reports, and registers high dose alerts to suggest optimisation actions. Benefits and limitations are derived from the practical experience in a large university hospital.

An Analysis Scheme for 3D Visualization of Positron Emitting Radioisotopes Using Positron Emission Mammography System

Proton range monitoring and verification is important to enhance the effectiveness of treatment by ensuring that the correct dose is delivered to the correct location. Upon proton irradiation, different positron emitting radioisotopes are produced by the inelastic nuclear interactions of protons with the target elements. Recently, it was reported that the 16O(p,2p2n)13N reaction has a relatively low threshold energy, and it could be potentially used for proton range verification. In the present work, we have proposed an analysis scheme (i.e., algorithm) for the extraction and three-dimensional visualization of positron emitting radioisotopes. The proposed step-by-step analysis scheme was tested using our own experimentally obtained dynamic data from a positron emission mammography (PEM) system (our developed PEMGRAPH system). The experimental irradiation was performed using an azimuthally varying field (AVF) cyclotron with a 80 MeV monoenergetic pencil-like beam. The 3D visualization showed promising results for proton-induced radioisotope distribution. The proposed scheme and developed tools would be useful for the extraction and 3D visualization of positron emitting radioisotopes and in turn for proton range monitoring and verification.

Development of a mechatronic guidance system for targeted ultrasound-guided biopsy under high-resolution positron emission mammography localization.

Image-guided needle biopsy of small, detectable lesions is crucial for early-stage diagnosis, treatment planning, and management of breast cancer. High-resolution positron emission mammography (PEM) is a dedicated functional imaging modality that can detect breast cancer independent of breast tissue density, but anatomical context and real-time needle visualization are not yet available to guide biopsy. We propose a mechatronic guidance system integrating an ultrasound (US)-guided core-needle biopsy (CNB) with high-resolution PEM localization to improve the spatial sampling of breast lesions. This paper presents the benchtop testing and phantom studies to evaluate the accuracy of the system and its constituent components for targeted PEM-US-guided biopsy under simulated high-resolution PEM localization. A mechatronic guidance system was developed to operate with the Radialis PEM system and a conventional US system. The system includes a user-operated guidance arm and end-effector biopsy device, integrating a US transducer and CNB gun, with its needle focused on a remote center of motion (RCM). Custom software modules were developed to track, display, and guide the end-effector biopsy device. Registration of the mechatronic guidance system to a simulated PEM detector plate was performed using a landmark-based method. Testing was performed with fiducials positioned in the peripheral and central regions of the simulated detector plate and registration error was quantified. Breast phantom experiments were performed under ideal detection and localization to evaluate for bias in the end-effector biopsy device. The accuracy of the complete mechatronic guidance system to perform targeted breast biopsy was assessed using breast phantoms with simulated lesions. Three-dimensional positioning error was quantified, and principal component analysis assessed for directional trends in 3D space within 95% prediction intervals. Targeted breast biopsies with test phantoms were performed and an overall in-plane needle targeting error was quantified. The mean registration errors were 0.63mm (N=44) and 0.73mm (N=72) in the peripheral and central regions of the simulated PEM detector plate, respectively. A 3D 95% prediction ellipsoid shows an error volume <2.0mm in diameter, centered on the mean registration error. Under ideal detection and localization, targets <1.0mm in diameter can be sampled with 95% confidence. The complete mechatronic guidance system was able to successfully spatially sample simulated breast lesions, 4mm and 6mm in diameter and height (N=20) in known 3D positions in the PEM image coordinate space. The 3D positioning error was 0.85mm (N=20) with 0.64mm in-plane and 0.44mm cross-plane component errors. Targeted breast biopsies resulted in a mean in-plane needle targeting error of 1.08mm (N=15) allowing for targets 1.32mm in radius to be sampled with 95% confidence. We demonstrated the utility of our mechatronic guidance system for targeted breast biopsy under high-resolution PEM localization. Breast phantom studies showed the ability to accurately guide, position, and target breast lesions with the accuracy to spatially sample targets <3.0mm in diameter with 95% confidence. Future work will integrate the developed system with the Radialis PEM system toward combined PEM-US-guided breast biopsy.

Clinical practice guidelines for high-resolution breast PET, 2019 edition

Breast positron emission tomography (PET) has had insurance coverage when performed with conventional whole-body PET in Japan since 2013. Together with whole-body PET, accurate examination of breast cancer and diagnosis of metastatic disease are possible, and are expected to contribute significantly to its treatment planning. To facilitate a safer, smoother, and more appropriate examination, the Japanese Society of Nuclear Medicine published the first edition of practice guidelines for high-resolution breast PET in 2013. Subsequently, new types of breast PET have been developed and their clinical usefulness clarified. Therefore, the guidelines for breast PET were revised in 2019. This article updates readers as to what is new in the second edition. This edition supports two different types of breast PET depending on the placement of the detector: the opposite-type (positron emission mammography; PEM) and the ring-shaped type (dedicated breast PET; dbPET), providing an overview of these scanners and appropriate imaging methods, their clinical applications, and future prospects. The name “dedicated breast PET” from the first edition is widely used to refer to ring-shaped type breast PET. In this edition, “breast PET” has been defined as a term that refers to both opposite- and ring-shaped devices. Up-to-date breast PET practice guidelines would help provide useful information for evidence-based breast imaging.

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.