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Design and performance evaluation of high resolution small animal PET scanner based on monolithic crystal: a simulation study
摘要： Dedicated small-animal PET scanners functionality can be optimized by improving the sensitivity and spatial resolution of the scanner. Approximately most of the developed and commercially available small-animal PET scanners are equipped with pixelated scintillators; therefore, their spatial resolution is limited to the crystal pixel size. Complex fabrication, low-sensitivity, and disability in depth of interaction calculation (DOI) are the major disadvantages of pixelated crystals. However, monolithic scintillator crystals are known as one of the most commonly used substitutions, as they have higher sensitivity, DOI recognition, and lower cost. We already designed and implemented a dedicated small-animal PET scanner based on pixelated scintillator crystals and silicon photomultiplier (SiPM). In this study, we plan to present a new optimized design based on the monolithic crystal, with similar performance by the previous scanner. Then we would optimize the thickness of the monolithic crystals for animal PET scanners as a function of sensitivity and spatial resolution. All simulations were performed based on GEANT4, a validated Monte Carlo toolkit. We simulated a recently fabricated scanner with pixelated crystals and compared it with a simulated scanner based on an optimized monolithic crystal. The experimental setup used for comparison and validation is a small Animal PET consisting of ten pixelated modules. This study anticipates that by replacing a pixelated crystal (consist of 24 × 24 LYSO elements, and 2 × 2 × 10 mm3 crystal size) with a monolithic crystal (with 8 mm thickness and 50.2 × 50.2 entrance area), the average spatial resolution stays the same and sensitivity grows ～ 17% in the center of AFOV and also the fabrication cost dives remarkably. Simulation reveals that although the depth of interaction DOI was not taken into consideration, the crystals with 6 mm thickness have acceptable spatial resolution (～ 1.3 mm FWHM at the centre of the AFOV) and relatively good absolute sensitivity (～ 1.6%).
关键词： SPECT,coronary CT angiography (CTA),PET PET/CT,Gamma camera,Models and simulations
更新于2025-09-23 15:22:29
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Intraoperative indocyanine green angiography for the objective measurement of blood flow
摘要： Purpose: Intraoperative assessment of tissue perfusion is important to predict wound healing or improvement of symptoms in patients with peripheral arterial disease (PAD) or vascular trauma. There is no widely accepted standard for intraoperative measurement of tissue perfusion. Here, we report the use of indocyanine green (ICG)-based angiography to determine the blood flow in patients with PAD and vascular trauma. Methods: The SPY fluorescent imaging system was utilized. A dose of 3–5 mL of ICG (2.5 mg/mL) was injected intravenously followed by a 10-mL normal saline flush. The SPY imaging system was used to quantitatively assess perfusion. During the study period, the SPY imaging system was applied in 4 patients with PAD and one patient with vascular trauma. Results: In 3 patients with PAD associated with an ischemic wound, complete wound healing was achieved with the indication of viable tissue by the SPY system. In one patient with severe claudication in both lower extremities, the ICG angiography was used to determine the increased blood flow after revascularization. In the case of vascular trauma, this imaging system enabled the delineation of viability of the injured tissue. Conclusion: ICG angiography can determine the surface tissue viability in PAD patients. In cases of severe vascular trauma, the SPY system can be used to determine tissue perfusion. Further study is warranted to define the definite utility of this technology to assess perfusion, response to revascularization, and potentially, to predict the likelihood of wound healing.
关键词： Peripheral arterial disease,Perfusion,Angiography,Indocyanine green
更新于2025-09-23 15:22:29
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New Parametric Imaging Method with Fluorescein Angiograms for Detecting Areas of Capillary Nonperfusion
摘要： Fluorescein angiography (FAG) is currently the most useful diagnostic modality for examining retinal circulation, and it is frequently used for the evaluation of patients with diabetic retinopathy, occlusive diseases, such as retinal venous and arterial occlusions, and wet macular degeneration. This paper presents a method for objectively evaluating retinal circulation by quantifying circulation-related parameters. Methods: This method allows the semiautomatic preprocessing and registering of FAG images. The arterial input function is estimated from the registered set of FAG images using gamma-variate fitting. Then, the parameters can be computed by deconvolution on the basis of truncated singular value decomposition, and they can finally be presented as parametric color images in a combination of three colors, red, green, and blue. Results: After the estimation of arterial input function, the parameters of relative blood flow and mean transit time were computed using deconvolution analysis based on truncated singular value decomposition. Conclusions: The parametric color image is helpful to interpret the status of retinal blood circulation and provides quantitative data on retina ischemia without interobserver variability. This system easily provides the status of retinal blood circulation both qualitatively and quantitatively. It also helps to standardize FAG interpretation and may contribute to network-based telemedicine systems in the future.
关键词： Fluorescein Angiography,Ophthalmology,Computer-Assisted Diagnosis,Eye Disease,Biomedical Engineering
更新于2025-09-23 15:22:29
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Radiation dose and image quality in intraoperative CT (iCT) angiography of the brain with stereotactic head frames
摘要： Objectives Intraoperative CT (iCT) angiography of the brain with stereotactic frames is an integral part of navigated neurosurgery. Validated data regarding radiation dose and image quality in these special examinations are not available. We therefore investigated two iCT protocols in this IRB-approved study. Methods Retrospective analysis of patients, who received a cerebral stereotactic iCT angiography on a 128 slice CT scanner between February 2016 and December 2017. In group A, automated tube current modulation (ATCM; reference value 410 mAs) and automated tube voltage selection (reference value 120 kV) were enabled, and only examinations with a selected voltage of 120 kV were included. In group B, fixed parameters were applied (300 mAs, 120 kV). Radiation dose was measured by assessing the volumetric CT dose index (CTDIvol), dose length product (DLP) and effective dose (ED). Signal-to-noise ratio (SNR) and image noise were assessed for objective image quality, visibility of arteries and grey-white differentiation for subjective image quality. Results Two hundred patients (n = 100 in each group) were included. In group A, median selected tube current was 643 mAs (group B, 300 mAs; p < 0.001). Median values of CTDIvol, DLP and ED were 91.54 mGy, 1561 mGy cm and 2.97 mSv in group A, and 43.15 mGy, 769 mGy cm and 1.46 mSv in group B (p < 0.001). Image quality did not significantly differ between groups (p > 0.05). Conclusions ATCM yielded disproportionally high radiation dose due to substantial tube current increase at the frame level, while image quality did not improve. Thus, ATCM should preferentially be disabled.
关键词： Neuronavigation,Brain,Computed tomography angiography,Radiation dosage
更新于2025-09-23 15:22:29
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Multimodal imaging based biomarkers predictive of early and late response to anti-VEGFs during the first year of treatment for neovascular age-related macular degeneration
摘要： Purpose. — To evaluate baseline predictive markers of early and late anatomical response to anti-vascular endothelial growth factor (anti-VEGF) treatment in patients with neovascular age-related macular degeneration (nAMD). Methods. — The records of the nAMD patients who underwent intravitreal ranibizumab or aflibercept treatment, received the 3 monthly loading doses, and completed a follow-up period of 12 months were included retrospectively. The anatomical treatment response at month 3 (early) and between month 3 and 12 (late) was classified as good, intermediate or poor. Baseline demographic, fluorescein angiography, and optical coherence tomography findings were compared among the three groups. Results. — One hundred and ten eyes (74.3%) showed good, 18 (12.2%) showed intermediate and 20 (13.5%) showed poor anatomical response at month 3, and 114 eyes (77.0%) showed good, 27 (18.2%) showed intermediate and 7 (4.7%) showed poor anatomical response between month 3 and month 12. Of the evaluated parameters, drug type (better in aflibercept), showed a statistically significant difference in regards to anatomical outcomes at both the early and late periods (P = 0.02 and P = 0.03). The greatest linear dimension of choroidal neovascularization (CNV) and presence of peaked pigment epithelial detachment (PED) were important factors for early anatomical anti-VEGF treatment response. Conclusion. — Larger CNV and the presence of a peaked PED appeared to be associated with a good early response, and the drug type seemed to be associated with both early and late poor anatomical response of anti-VEGF treatment in nAMD patients. Aflibercept appears to be more effective than ranibizumab in regards to the percentage of patients with better anatomical response in both the early and late treatment periods.
关键词： Optical coherence tomography,Ranibizumab,Age-related macular degeneration,Aflibercept,Fluorescein angiography
更新于2025-09-23 15:22:29
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The role of indocyanine green fluoroscopy for intraoperative bile duct visualization during laparoscopic cholecystectomy: an observational cohort study in 70 patients
摘要： Background: Bile duct injury is the most feared complication during laparoscopic cholecystectomy. Real-time intraoperative imaging using indocyanine green (ICG) might reduce the risk of bile duct injury by improving visualization of the biliary tree during laparoscopic cholecystectomy. We compared the outcomes of laparoscopic cholecystectomy in patients with and without real-time ICG. Methods: A retrospective analysis of the data of patients undergoing laparoscopic cholecystectomy with and without ICG in a referral centre for minimally invasive surgery was performed. We hypothesized that laparoscopic cholecystectomy with real-time ICG enables a better identification of the biliary tree and thus increases surgical safety. The outcomes of laparoscopic cholecystectomy with and without ICG were compared using the duration of surgery, the rate of bile duct injury, the rate of conversion, complications and the length of stay. Results: Seventy patients including 29 with and 41 without ICG underwent laparoscopic cholecystectomy within the period of investigation. The median duration of surgery was 53.0 vs. 54.0 min while the median length of stay was 2.0 d in the group with and without ICG respectively. The rate of conversion was 2.4% in the group without ICG, while no conversion was performed in the group with ICG. NO bile duct injury occurred in both groups. These differences were not statistically significant. Conclusion: Laparoscopic cholecystectomy with real-time indocyanine green fluorescence cholangiography enables a better visualization and identification of biliary tree and therefore should be considered as a means of increasing the safety of laparoscopic cholecystectomy.
关键词： Bile duct injury,Laparoscopic cholecystectomy,Intraoperative fluorescence angiography,Indocyanine green
更新于2025-09-23 15:22:29
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How to Utilize Coronary Computed Tomography Angiography in the Treatment of Coronary Artery Disease
摘要： Coronary computed tomography angiography (CCTA) has high negative predictive power for detecting coronary artery disease. However CCTA is limited by moderate positive predictive power in the detection of myocardial ischemia. This is not unexpected because the diameter of a stenosis is a poor indicator of myocardial ischemia and discrepancy between the severity of stenosis and noninvasive tests is not uncommon. The value of stenosis for predicting future development of acute coronary syndrome represented by plaque rupture has been questioned. CCTA identifies the characteristics of high-risk plaque including positive remodeling, low density plaque and spotty or micro-calcification. Also, additional evaluation of myocardial ischemia using computational flow dynamics, and luminal attenuation gradient are expected to increase both diagnostic performance for hemodynamically significant stenosis and the predictive power for future cardiovascular risk. Technical advances in CCTA would enable evaluation of both coronary artery stenosis and myocardial ischemia simultaneously with high predictive performance, and would improve vastly the clinical value of CCTA.
关键词： Functional ischemia,Coronary artery disease,Atherosclerosis,Prognosis,Coronary CT angiography,Myocardial mass
更新于2025-09-23 15:22:29
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Autofluorescence and spectral-domain optical coherence tomography of optic disk melanocytoma
摘要： The authors report fundus autofluorescence (FAF) and spectral-domain optical coherence tomography (OCT ) findings of two consecutive patients who presented with optic disk melanocytoma (ODM). A retrospective study was performed by reviewing medical records and ophthalmic imaging examinations. Optical coherence tomography findings were sloped and brightly reflective anterior tumor surface, adjacent retinal desorganization and abrupt posterior optical shadowing. Vitreous seeds were found in one patient. Fundus autofluorescence revealed outstanding hypoautofluorescence at the tumor area and isoautofluorescence at the remaining retina. Optical coherence tomography findings of the reported cases are consistent with those reported in the reviewed literature. Fundus autofluorescence has been used in the assessment of choroidal melanocytic tumors, but not yet in melanocytomas. We assume that this is the first report of these findings and believe that when its pattern has become clearly defined, fundus autofluorescence will be a useful tool to avoid misdiagnosis in suspicious cases and for follow-up.
关键词： Melanoma/diagnosis,Female,Adult,Male,Case reports,Optic nerve neoplasms/diagnosis,Fluorescein angiography,Humans,Tomography, optical coherence
更新于2025-09-23 15:22:29
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Choroidal imaging biomarkers
摘要： The choroid is the vascular coat of the eye,and its role has been studied in multiple chorioretinal disorders. The recent advancements in choroidal imaging techniques including enhanced depth imaging optical coherence tomography (EDI-OCT), swept source (SS-OCT), enface OCT and OCT angiography have facilitated an in-depth analysis of choroid. The gradual shift from manual to automated segmentation and binarization methods have led to precise and reproducible measurements of choroidal parameters. These qualitative and quantitative parameters, called choroidal imaging biomarkers, have evolved over the past decade from a simple linear subfoveal choroidal thickness to more complex 3 dimensional (3-D) choroidal reconstruction thus widening the spectrum encompassing multiple parameters. These biomarkers have provided a better understanding of the pathogenesis, are helpful in diagnostic dilemmas, and in future may also help to devise treatment options. The lack of normative data, absence of standardized parameters and limitations of the imaging techniques, however, have led to ambiguity and difficulty in the interpretation of these variables. We attempt to address these lacunae in the literature and provide a basic understanding of the choroid in both health and disease using these choroidal biomarkers.
关键词： Optical coherence tomography angiography (OCTA),En-face OCT,Swept source optical coherence tomography (SS-OCT),Choroidal thickness,Choroidal vascularity index (CVI),Choroidal imaging biomarkers,Choroidal volume
更新于2025-09-23 15:21:21
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256-Slice Coronary Computed Tomography Angiography Using Low Tube Voltage of 100 KV
摘要： Purpose: To evaluate the image quality and radiation dose of 100 kV with 1000 mAs retrospective electrocardiography (ECG)-gated CCTA protocol, compared to the standard protocol of 120 kV with 800 mAs retrospective ECG-gated CCTA. Material and Methods: We divided 70 patients into two, a reduced dose group with 35 patients (18 M, 17 F; Mean age 56.94 ± 11.51 years) were examined by 100-kV with 1000 mAs retrospective ECG-gated CCTA, and another as a standard group of 35 patients (21, 14 F; Mean age 54.03 ± 9.81 years) were examined by 120-kV with 800 mAs retrospective ECG-gated CCTA. The two blinded radiologists analyzed the image quality of the coronary arteries independently and they accessed subjective and objective image quality. The radiation dose was also measured as effective radiation dose [ED] and was calculated using CT dose volume index [CTDIvol.], dose-length product [DLP] and conversion coefficient for chest (conversion factor k=0.014 mSv mGy-1cm-1). Results: Although the objective image quality of the 100-kV with 1000 mAs was significantly better than the 120-kV with 800 mAs (mean SNR, 36.65 ± 2.95 vs. 33.47 ± 3.86, P<0.0001; mean CNR, 34.27 ± 2.92 vs. 30.62 ± 3.90, P<0.0001). There was no significant variation in the subjective image quality between two groups (mean image score, 4.54 ± 0.37 vs. 4.56 ± 0.25 for radiologist 1, P = 0.781; 4.52 ± 0.25 vs. 4.56 ± 0.25 for radiologist 2, P=0.486). The radiation dose was found to be reduced by 28% with the 100-kV/1000 mAs protocol than with the 120-kV/800 mAs retrospective ECG-gated CCTA (7.87 ± 0.59 vs. 10.95 ± 1.67 mSv, P<0.0001). Conclusion: The protocol of low tube voltage CCTA using 100 kV/1000 mAs retrospective ECG-gated shows significant reduction of the radiation dose without disturbing the subjective image quality of CCTA.
关键词： Coronary CT angiography,Image quality,Radiation dose
更新于2025-09-23 15:21:21