Gamma Imaging Research Articles

Comparison of 99mTc-MIBI scintigraphy, ultrasound, and mammography for the diagnosis of BI-RADS 4 category lesions

BackgroundWe sought to determine the diagnostic efficacy of Breast-specific gamma imaging (BSGI) in Chinese women with BI-RADS 4 category lesions and to compare this efficacy to that of ultrasound/mammography.MethodsWe retrospectively analyzed data from 177 women that had undergone BSGI of BI-RADS 4 category lesions originally detected via ultrasound and/or mammography.ResultsOf these 177 cases, 117 (66.1%) were malignant lesions and 60 (33.9%) were benign. The sensitivity, specificity, positive predictive values, and negative predictive values of BSGI were 94.9% (111/117), 78.3% (47/60), 89.5% (111/124), and 88.7% (47/53), respectively. The specificity and positive predictive values for mammography were 48.3% (29/60) and 77.5% (107/138), while for ultrasound they were 53.3% (32/60) and 79.6% (109/137), respectively. The sensitivity and specificity of BSGI for the detection of lesions ≤1 cm in size were 90.9% (10/11) and 88.0% (22/25), respectively, while for breast lesions >1 cm in size these values were 94.3% (100/106) and 71.4% (25/35), respectively. In addition, BSGI sensitivity and specificity values for dense breast tissue were 94.0% (79/84) and 78.0% (39/50), respectively, whereas for non-dense breast tissue these vales were 97.0% (32/33) and 80.0% (8/10), respectively. The sensitivity of BSGI for invasive ductal carcinomas (IDC) and ductal carcinomas in situ (DCIS) was 98.9% (95/96) and 75.0% (9/12), respectively. The tumor to normal tissue ratio of BSGI for malignant lesions was significantly higher than for benign lesions (2.18 ± 1.17 vs 1.66 ± 0.40, t = 7.56, P<0.05).ConclusionsThese results indicate that BSGI is highly sensitive for the detection of such lesions, achieving good positive/negative predictive values. This suggests that for IDC in particular, BSGI is superior to ultrasound and mammography for the diagnosis of BI-RADS 4 category lesions, although this was less apparent for the diagnosis of DCIS lesions. BSGI exhibited excellent performance in dense breast tissue and for the detection of lesions ≤1 cm in size.

Development of integrated prompt gamma imaging and positron emission tomography system for in vivo 3-D dose verification: a Monte Carlo study

An accurate knowledge of in vivo proton dose distribution is key to fully utilizing the potential advantages of proton therapy. Two representative indirect methods for in vivo range verification, namely, prompt gamma (PG) imaging and positron emission tomography (PET), are available. This study proposes a PG-PET system that combines the advantages of these two methods and presents detector geometry and background reduction techniques optimized for the PG-PET system. The characteristics of the secondary radiations emitted by a water phantom by interaction with a 150 MeV proton beam were analysed using Geant4.10.00, and the 2-D PG distributions were obtained and assessed for different detector geometries. In addition, the energy window (EW), depth-of-interaction (DOI), and time-of-flight (TOF) techniques are proposed as the background reduction techniques. To evaluate the performance of the PG-PET system, the 3-D dose distribution in the water phantom caused by two proton beams of energies 80 MeV and 100 MeV was verified using 16 optimal detectors. The thickness of the parallel-hole tungsten collimator of pitch 8 mm and width 7 mm was determined as 200 mm, and that of the GAGG scintillator was determined as 30 mm, by an optimization study. Further, 3–7 MeV and 2–7 MeV were obtained as the optimal EWs when the DOI and both the DOI and TOF techniques were applied for data processing, respectively; the detector performances were improved by about 38% and 167%, respectively, compared with that when applying only the 3–5 MeV EW. In this study, we confirmed that the PG distribution can be obtained by simply combining the 2-D parallel hole collimator and the PET detector module. In the future, we will develop an accurate 3-D dose evaluation technique using deep learning algorithms based on the image sets of dose, PG, and PET distributions for various proton energies.

Assessment of the attenuation of metal-infused filaments for 3D printing a gamma camera calibration phantom

The capability to produce customizable 3D printed imaging phantoms out of a growing number of materials has contributed to the increased use of such phantoms in clinical practice and research. Many of these materials have not been characterized at clinically relevant parameters for nuclear medicine imaging. In this work, we measured the attenuation of several 3D printing metal-infused filament materials with the potential for blocking 122 keV gamma photons using a scintillation detector. Understanding the ability of each material to attenuate gamma rays would allow modelling of varying levels of attenuation required for different body tissues at this energy. In addition, it allows for the determination of the thickness of the material needed to attenuate 122 keV photons, in order to build high-contrast spatial resolution phantoms. To achieve this goal, we performed attenuation experiments for three different 3D printing materials in this work (Tungsten infused Acrylonitrile Butadiene Styrene (ABS), Iron infused Polylactic Acid (PLA), and Stainless Steel (SS) infused PLA), by observing gamma transmission through blocks made of each material as a function of thickness. A Cobalt-57 (Co-57; 122 keV) source was chosen because of its relevance to nuclear medicine. Tungsten infused ABS showed the highest measured attenuation coefficient out of the three candidates at this energy (1.452 cm2/g). We further designed and 3D printed an imaging phantom to aid in characterizing the spatial resolution of novel gamma imaging systems at the above energy. The phantom design contains multiple line pairs (lp) located in four quadrants ranging from 1.2 mm – 8 mm. The 3D printed phantom was imaged by a molecular breast tomosynthesis (MBT) gamma camera. Assessment of the intrinsic spatial resolution of the MBT camera showed that our 3D printed phantom might be a viable option for routine spatial resolution quality control (QC) of gamma cameras used in clinical practice.

Memantine nanoemulsion: a new approach to treat Alzheimer’s disease

Aim: A nanoemulsion loaded with memantine for intranasal delivery to bypass the blood-brain barrier for the treatment of Alzheimer disease.Method: The nanoemulsion was prepared using homogenisation and ultrasonication methods. The developed nanoemulsion was characterised, in vitro release and antioxidant potential was analysed. The in vivo studies were carried out by radiolabelling the memantine with technetium pertechnetate.Results: The finalised NE showed particle-size of ∼11 nm and percentage transmittance of ∼99%. The in vitro release studies showed 80% drug release in simulated nasal fluid. The nanoemulsion showed 98% cell viability and antioxidative assays confirmed that the encapsulation of memantine in a nanoemulsion sustained its antioxidative potential. Gamma images and biodistribution results also confirmed higher uptake of formulation with %radioactivity of 3.6 ± 0.18%/g at 1.5 h in brains of rats administered intranasally.Conclusion: The developed nanoemulsion could be used as a potential carrier of memantine for a direct nose to brain delivery.

Characterization of monolithic GAGG:Ce coupled to both PMT and SiPM array for gamma imaging in Nuclear Medicine

GaGG:Ce scintillation crystal is very useful for nuclear imaging purposes, thanks to its several advantages (high density, short decay time, high light yield and good energy resolution, no self-activity, no hygroscopic). However, only the recent improvements in the growth processes make it available with large size, in order to use it in monolithic configuration. The main drawbacks of pixelated crystals, as non-uniform response, high production costs and optical light loss, could be therefore overcome. In this work the characterization of this promising crystal coupled both to a single channel PMT (spectrometric purpose) and to a new technology SiPM (50% PDE and 74% geometrical fill factor) has been performed. The detection efficiency results good both for SPECT (87% at 122 keV) and for PET (18% at 356 keV) applications. However, the unexpected result arises from the energy resolution: at 356 keV 8.9% and 8.0% for single channel PMT and SiPM configuration, respectively. In other terms, the used SiPM allows to achieve higher energy resolution than single channel PMT. Moreover, a high imaging performance has been observed, with a millimeter intrinsic spatial resolution.

A new treatment planning approach accounting for prompt gamma range verification and interfractional anatomical changes

Prompt gamma (PG) imaging is widely investigated for spot-by-spot in vivo range verification for proton therapy. Previous studies pointed out that the accuracy of prompt gamma imaging is affected by the statistics (number of protons delivered per pencil beam) of the proton beams and the conformity between prompt gamma and dose distribution (PG-dose correlation). Recently a novel approach to re-optimize conventional treatment plans by boosting a few pencil beams with good PG-dose correlation above the statistics limit for reliable PG detectability was proposed. However, up to now, only PG-dose correlation on the planning computed tomography (CT) was considered, not accounting for the fact that the robustness of the PG-dose correlation is not guaranteed in the cases of interfractional anatomical changes. In this work, this approach is further explored with respect to the robustness of the PG-dose correlation of each pencil beam in the case of interfractional anatomical changes. A research computational platform, combining Monte Carlo pre-calculated pencil beams with the analytical Matlab-based treatment planning system (TPS) CERR, is used for treatment planning. Geant4 is used for realistic simulation of the dose delivery and PG generation for all individual pencil beams in the heterogeneous patient anatomy using multiple CT images for representative patient cases (in this work, CTs of one prostate and one head and neck cancer patient are used). First, a Monte Carlo treatment plan is created using CERR. Thereby the PG emission and dose distribution for each individual spot is obtained. Second, PG-dose correlation is quantified using the originally proposed approach as well as a new indicator, which accounts for the sensitivity of individual spots to heterogeneities in the 3D dose distribution. This is accomplished by using a 2D distal surface (dose surface) derived from the 3D dose distribution for each spot. A few pencil beams are selected for each treatment field, based on their PG-dose correlation and dose surface, and then boosted in the new re-optimized treatment plan. All treatment plans are then fully re-calculated with Monte Carlo on the CT scans of the corresponding patient at three different time points. The result shows that all treatment plans are comparable in terms of dose distribution and dose averaged LET distributions. The spots recommended by our indicators maintain good PG-dose correlation in the cases of interfractional anatomical changes, thus ensuring that the proton range shift due to anatomical changes can be monitored. Compared to another proposed spots aggregation approach, our approach shows advantages in terms of the detectability and reliability of PG, especially in presence of heterogeneities.

Radiation Doses and Risks in Breast Screening.

This article describes radiation doses and cancer risks of digital breast imaging technologies used for breast cancer detection. These include digital mammography (DM), digital breast tomosynthesis (DBT), and newer technologies such as contrast-enhanced digital or spectral mammography (CEM), whole-breast computed tomography, breast-specific gamma imaging (BSGI), molecular breast imaging (MBI), and positron emission mammography (PEM). This article describes the basis for radiation risk estimates, compares radiation doses and risks, and provides benefit-to-radiation-risk ratios for different breast imaging modalities that use ionizing radiation. Current x-ray-based screening modalities such as DM and DBT have small to negligible risks of causing radiation-induced cancers in women of normal screening age. Possible new screening modalities such as CEM have similar small cancer risks. Potential screening modalities that involve radionuclide injection such as BSGI, MBI, and PEM have significantly higher cancer risks unless efficient detection systems and reduced administered doses are used. Benefit-to-radiation-risk estimates are highly favorable for screening with DM and other modalities having comparable (or higher) cancer detection rates and comparably low radiation doses.

PIBS: Proton and ion beam spectroscopy for in vivo measurements of oxygen, carbon, and calcium concentrations in the human body

Proton and ion beam therapy has proven to benefit tumour control with lower side-effects, mostly in paediatrics. Here we demonstrate a feasible technique for proton and ion beam spectroscopy (PIBS) capable of determining the elemental compositions of the irradiated tissues during particle therapy. This follows the developments in prompt gamma imaging for online range verification and the inheritance from prompt gamma neutron activation analysis. Samples of water solutions were prepared to emulate varying oxygen and carbon concentrations. The irradiation of those samples and other tissue surrogate inserts by protons and ion beams under clinical conditions clearly showed a logarithmic relationship between the target elemental composition and the prompt gamma production. This finding is in line with the known logarithmic dependence of the pH with the proton molar concentration. Elemental concentration changes of 1% for calcium and 2% for oxygen in adipose, brain, breast, liver, muscle and bone-related tissue surrogates were clearly identified. Real-time in vivo measurements of oxygen, carbon and calcium concentrations will be evaluated in a pre-clinical and clinical environment. This technique should have an important impact in the assessment of tumour hypoxia over the course of several treatment fractions and the tracking of calcifications in brain metastases.

The mechanism of edge effect in CdZnTe pixel detector and an improved design of pixel sizes of anode

In this paper, the mechanism of the edge effect in Cadmium Zinc Telluride (CZT) pixel detectors is studied, and the energy spectrum performance and the charge collection efficiency of peripheral pixels with reduced sizes are analysed by computer-aided simulation and measurement. The results show that the distribution of the weighting potential, which is determined by the electrode structure, has significant influence on the edge effect. Reducing the sizes of peripheral pixels can optimize the weighting potential and improve the detection performance. A detector with reduced peripheral pixel sizes is prepared. We build a gamma imaging system using this kind of detector, test the spectrum response to 137Cs@662 keV and image a M10 nut under the collimated 241Am@59.5 keV . The measured spectrum of the edge/corner/intermediate pixels is consistent with the simulated spectrum and the obtained countingtype gray-scale image of the nut clearly shows its shape and sizes. These results prove that reducing peripheral pixel sizes has practical value in gamma imaging technology.

Search method for weld area in water-cooled wall pipe based on YOLO detection network

Focused on the defects that the traditional target detection algorithm has low detection precision and is greatly affected by the industrial imaging environment, YOLO algorithm of computer vision is proposed, the features of the image through the deep convolutional neural network are extracted, and the automatic detection function of the weld area is realized. Firstly, the detected image is preprocessed, and the image inversion, k-nearest median filtering, CLAHE image enhancement, gamma image correction and other algorithms are used to improve the contrast of the weld area in the whole picture. Secondly, the data enhancement algorithm is used to increase the number of training samples and diversity. Finally, the YOLO target detection network is trained by using the training samples obtained from the data enhancement, and the performance of the network is evaluated through test samples. In experiments, 500 images of 50 ray-detected image data are used to train the YOLO target detection network, and the test results are tested in a test set consisting of 50 additional images. The experimental results demonstrate that the accuracy of weld inspection is 96%, it is much better than the accuracy of traditional target detection algorithms, and has guiding value for industrial application.

End-to-end delivery quality assurance of computed tomography–based high-dose-rate brachytherapy using a gel dosimeter

PurposeThe purpose of this study was to develop a novel quality assurance (QA) program to check the entire treatment chain of image-guided brachytherapy with dose distribution evaluation in a single setup and irradiation using a gel dosimeter. Methods and MaterialsA polymer gel was used, and the readout was performed by magnetic resonance scanning. A CT-based treatment plan was generated using the Oncentra planning system (Elekta, Sweden), and irradiation was performed three times using an afterloading device with an Ir-192 source. The dose-response curve of the gel was created using 6-MV X-ray, which is independent of the source beams. Planar gamma images on a coronal plane along the source transport axis were calculated using the measured dose as a reference, and the calculated doses were used in several error simulations (no error; 2.0 or 2.5 mm systematic and random source dwell mispositioning; and dose error of 2%, 5%, 10%, and 20%). ResultsThe dose-R2 (spin-spin relaxation rate) conversion table revealed that the uncertainty and dose resolution of 6-MV X-ray were better than those of Ir-192 and also constant between the three measurements. With the 3%/1 mm criteria, there were statistically significant differences between each pair of settings except dose error of 2% and 5%. ConclusionThis work depicts a simple and efficient end-to-end test that can provide a clinically useful tool for QA of image-guided brachytherapy. In this QA program, air kerma strength and dwell position setting could also be verified. This test can also distinguish between different types of error.

Breast-Specific Gamma Imaging with [99mTc]Tc-Sestamibi: An In Vivo Analysis for Early Identification of Breast Cancer Lesions Expressing Bone Biomarkers.

The main purpose of this pilot investigation was to evaluate the possible relationship among [99mTc]Tc-Sestamibi uptake, the presence of breast osteoblast-like cells, and the expression of molecules involved in bone metabolism, such as estrogen receptor, bone morphogenetic proteins-2, and PTX3. To this end, forty consecutive breast cancer patients who underwent both breast-specific gamma imaging with [99mTc]Tc-Sestamibi and breast bioptic procedure were retrospectively enrolled. From each diagnostic paraffin block collected in the study, histological diagnosis, immunohistochemical investigations, and energy dispersive X-ray microanalysis were performed. Our data highlight the possible use of breast-specific gamma imaging with [99mTc]Tc-Sestamibi for the early detection of breast cancer lesions expressing bone biomarkers in the presence of breast osteoblast-like cells. Specifically, we show a linear association among sestamibi uptake, the presence of breast osteoblast-like cells, and the expression of estrogen receptor, bone morphogenetics proteins-2, and PTX3. Notably, we also observed an increase of [99mTc]Tc-Sestamibi in breast cancer lesions with magnesium-substituted hydroxyapatite. In conclusion, in this pilot study we evaluated data from the nuclear medicine unit and anatomic pathology department on breast cancer osteotropism, identifying a new possible interpretation of Breast Specific Gamma Imaging with [99mTc]Tc-Sestamibi analysis.

Design and Performance Evaluation of a BGO + SiPM Detector for High-Energy Prompt Gamma Imaging in Proton Therapy Monitoring

Proton therapy is attracting increasing attention nowadays owing to its accurate dose delivery to the target tumor. However, this advanced treatment modality is subject to proton beam range uncertainty, which could lead to overdose in healthy tissues. In the past decades, prompt gamma imaging (PGI) has gained increasing interest and been proved promising for realtime proton beam monitoring. The detection of 2-8 MeV high energy prompt gamma, however, poses a serious challenge for PGI system design, especially, for the detector design. In this article, we propose a prompt gamma detector design for a PGI system under development in our lab. The detector was composed of a 12 x 12 BGO block coupled to an 8 x 8 SiPM array with a crystal pixel size of 3.5 mm x 3.5 mm x 30 mm. A numerical simulation model was developed to evaluate the SiPM saturation effect caused by the finite number of microcells in each SiPM pixel while a huge number of optical photons might impinge the SiPM pixel under high energy gamma ray irradiation. Experiments under high energy gamma isotopes ( <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">22</sup> Na - 511 keV, 1.275 MeV, <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">88</sup> Y - 898 keV, 1.836 MeV, and <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">232</sup> Th - 2.6 MeV) irradiation were conducted to evaluate positioning performance, energy response linearity, and energy resolution (ER) of the detector. Root mean squared (RMS) metric was defined to assess the detector's positioning performance quantitatively. The numerical simulation results demonstrated that the SiPM saturation effect of the proposed detector design is negligible up to 10-MeV gamma photon detection. In the experimental studies, the obtained energy response linearity was 0.9997±0.0005, indicating almost no SiPM saturation effect for up to 2.6-MeV gamma photon detection with the proposed detector design. ER of 31.96% (511 keV), 26.67% (898 keV), 20.19% (1.275 MeV), 17.38% (1.836 MeV), and 15.88% (2.6 MeV) were achieved. With increased gamma photon energy, the crystal elements in the flood maps became clearer with reduced RMS value of the flood maps, indicating improved positioning performance. Based on the simulation and experimental results, we conclude that the proposed detector design is feasible for the PGI system with good energy and positioning performance as well as excellent anti-saturation capability for high energy gamma ray detection.

Efficacy of dual use of Tc-99m-pertechnetate and Tc-99m-tetrofosmin scintigraphy for the assessment of thyroid nodules.

Radioisotope methods have shown to be useful in the non-invasive diagnosis of thyroid nodules over the past years. The present prospective study aims to evaluate the efficacy of gamma imaging using single and dual tracer using Tc-99m pertechnetate and Tc-99m tetrofosmin for evaluation and management of thyroid nodules. Dynamic (perfusion) imaging was performed after injecting 148-185MBq (4-5mCi) of Tc-99m pertechnetate followed by static imaging. A second, dynamic (perfusion) imaging study within same week was performed with 296-370MBq (8-10mCi) of Tc-99m tetrofosmin on same group of patients followed by early and delayed images. Results of radionuclide perfusion scan from both studies were compared qualitatively with postsurgical histopathology or fine needle aspiration cytology (FNAC). Total 65 nodules in 50 patients were included in the study. With single tracer, the specificity and accuracy of Tc-99m pertechnetate was 23% and 45% and for Tc-99m tetrofosmin scan was 40% and 49%. When dual tracers were evaluated for the same group of patients, the specificity was 56% and accuracy was 55%. Dual Tracer technique with Tc-99m pertechnetate and Tc-99m tetrofosmin could be helpful in selecting nodules need surgical intervention. This technique can be used for convenient and rapid diagnostic evaluation of thyroid nodules non-invasively. We suggest a combination of fine needle aspiration biopsy and dual use of Tc-99m-pertechnetate and Tc-99m-tetrofosmin as a routine diagnostic approach to thyroid nodules.

Effect of projections number on the image quality of industrial parallel beam gamma tomography

Gamma tomography technique can provide cross-sectional visualization of an object that needed for investigating pipe scale in geothermal power plants. Parallel beam tomography has advantages such as a simple system so that it is easier to apply in the field, but the scanning duration is relatively long. This paper discusses the effect of projections number on the reconstructed images quality and proposes the number of most effective projections for pipe scale investigation. Geothermal pipe sample (OD = 275 mm, t = 10 mm) with scale has been scanned with a parallel beam gamma tomography system. The system consists of a gamma radiation source (137Cs, 80 mCi), scintillation detector, motorized gantry, control module, data acquisition, and computer. The images were reconstructed with six different projections: 128, 64, 32, 16, 8, and 4 projections and the scanning duration: 530.8, 258.9, 127.9, 63.5, 31.7, and 15.8 minutes, respectively. Visually, the 128 projections data produces the smoothest image, whereas 64 and 32 projections images look almost the same. The 16 and 8 projections images are still able to distinguish between the pipe wall, scale, and void even though the 8 projections image looks very blurry. Then, the 4 projections image is not able to visualize the shape of the object. The gaps between the average pipe wall and void gray-scale pixels value of 128, 64, 32, 16, 8 and 8 projections images are 175, 174, 167, 153, 106, and 45, respectively. Based on the scanning duration, visualization, and the gray contrast, then the number of most effective projections is 32.

An Improved LWD Azimuth Gamma Imaging Model Based on HSI Space

In recent years, in the process of oil and gas exploration and development, the situation of drilling tools drilling out of the reservoir often occurs. Due to the lack of directional indication, the traditional LWD(Logging While Drilling) natural gamma measurement technology cannot guide drilling tools to return to the reservoir efficiently. In order to solve this problem, this paper improves the traditional radiometric gamma measurement technology and establishes a set of azimuth gamma imaging model. Firstly, the basic imaging model is established based on HSI (Hue, Saturation, Intensity) color space. Then, the study focuses on the design of the gamma data quality control algorithm, which can effectively suppress the original gamma data noise. In addition, the cubic spline interpolation algorithm is selected to support the model to obtain 360° omni-directional gamma data. Finally, the image processing technology based on fast grayscale grouping is applied in this study, which greatly improves the imaging effect. Field application shows that the model runs stably on site, and the azimuth gamma image is well indicative. It can monitor the relative position relationship between the borehole trajectory and the formation, which effectively improves the reservoir encounter rate, and has high application and promotion value.

A deep learning approach for converting prompt gamma images to proton dose distributions: A Monte Carlo simulation study

PurposeIn proton therapy, imaging prompt gamma (PG) rays has the potential to verify proton dose (PD) distribution. Despite the fact that there is a strong correlation between the gamma-ray emission and PD, they are still different in terms of the distribution and the Bragg peak (BP) position. In this work, we investigated the feasibility of using a deep learning approach to convert PG images to PD distributions. MethodsWe designed the Monte Carlo simulations using 20 digital brain phantoms irradiated with a 100-MeV proton pencil beam. Each phantom was used to simulate 200 pairs of PG images and PD distributions. A convolutional neural network based on the U-net architecture was trained to predict PD distributions from PG images. ResultsOur simulation results show that the pseudo PD distributions derived from the corresponding PG images agree well with the simulated ground truths. The mean of the BP position errors from each phantom was less than 0.4 mm. We also found that 2000 pairs of PG images and dose distributions would be sufficient to train the U-net. Moreover, the trained network could be deployed on the unseen data (i.e. different beam sizes, proton energies and real patient CT data). ConclusionsOur simulation study has shown the feasibility of predicting PD distributions from PG images using a deep learning approach, but the reliable prediction of PD distributions requires high-quality PG images. Image-degrading factors such as low counts and limited spatial resolution need to be considered in order to obtain high-quality PG images.

Self-supporting design of a time-encoded aperture, gamma-neutron imaging system

A self-supporting, 2-D, time-encoded aperture system was developed for both gamma and neutron imaging. The system achieved high sensitivity for imaging due to the use of an M–P array which has flat sidelobes of cross-correlation reconstruction and is self-supporting. It is demonstrated that a 24.4 μCi 137 Cs radiological point source could be detected within 10 min when the source-to-background ratio is 1:1. Several radiation scenes support that the system has an imaging capability of multipoint, extended, and gamma/neutron discrimination sources. The features of good cross-correlation decoding properties, panoramic imaging, and rapid reconstruction make such a system design attractive and prospective for the localization of radioactive hot spots.

Characterization and validation of multimodal annihilation-gamma/near-infrared/visible laparoscopic system.

.Minimally invasive robotic surgery using fluorescence-guided images with a video laparoscope has been widely used because of its advantages of small incision, fast recovery time, and efficiency. However, the penetration depth limitation of fluorescence is a disadvantage caused by the absorption and scattering in tissues and blood cells. If this limitation can be overcome by additional imaging modalities, the surgical procedure can be quite efficient and precise. High-energy annihilation-gamma photons have a stronger penetration capability than visible and fluorescence photons. To characterize and validate a multimodal annihilation-gamma/near-infrared (NIR)/visible laparoscopic imaging system, an internal detector composed of an annihilation-gamma detector and an optical system was assembled inside a surgical stainless pipe with an outer diameter of 15.8 mm and an external detector with a dimension of placed at the opposite side of the internal detector. Integrated images of 511-keV gamma rays, NIR fluorescence, and visible light were obtained simultaneously. The 511-keV gamma image could be clearly seen with the acquisition of 5 s, while NIR and visible images could be presented in real time. This multimodal system has the potential for improving the surgery time and the quality of patient care.

Advanced approaches to imaging primary breast cancer: an update

Breast cancer (BC) is the most common cancer in women. Early detection of BC plays an important role in preventing advanced disease and improving survival. In this article, we aim to describe both advantages and limitations of conventional and new BC-imaging modalities. A literature search was performed for the period of January 2013 through October 2018, using search engines such as PubMed, PMC, and Google scholar. Search topics included: “breast cancer”, “breast lesion”, and “breast tumor imaging, diagnosis, and detection”. A total of 143 papers which primarily addressed imaging efficacy issues are included in the review. Mammography is the oldest and most commonly utilized screening modality for BC. Ultrasonography (US), computed tomography (CT), magnetic resonance imaging (MRI), positron emission mammography (PEM), and positron emission tomography/computed tomography (PET/CT) are the other conventional BC-imaging modalities. To overcome certain weaknesses of these modalities, new imaging tools including contrast-enhanced spectral mammography (CSEM), digital breast tomosynthesis (DBT), multiparametric (MP)-MRI, microwave imaging, and PET/MRI have been investigated. Conventional BC-imaging modalities have both advantages and limitations. When utilized in combination, they are often complementary. For example, a limitation of mammography is low sensitivity in dense breasts. The addition of DBT lessens this limitation by providing three-dimensional (3D) images of the breast that minimizes the effect of overlying breast tissue. Additionally, US added to mammography in dense breasts increases screening sensitivity and has the advantages of accessibility and lack of ionizing radiation. MRI is currently the most sensitive method used for detecting BC. When MRI is not suitable for patients, such as those with prosthesis, dedicated breast CT can be used. Scintimammography is another alternative method, although not commonly performed due to low sensitivity in < 1 cm tumors. Breast-specific gamma imaging (BSGI), on the other hand, can detect breast tumor < 1 cm; however, effective radiation dose is higher than mammography. PEM, with its high resolution, has been developed to image small breast tumors. PET/CT and PET/MRI have also been used to detect BC. Despite complementary roles of conventional imaging techniques, none of them have addressed all issues in BC diagnosis. Research studies developing novel target-specific molecular imaging agents are in progress with hopes to fill gaps in currently available imaging technologies.