Image Radiation Research Articles

Improving the Safety of Computed Tomography Through Automated Quality Measurement: A Radiologist Reader Study of Radiation Dose, Image Noise, and Image Quality.

The Centers for Medicare and Medicaid Services funded the development of a computed tomography (CT) quality measure for use in pay-for-performance programs, which balances automated assessments of radiation dose with image quality to incentivize dose reduction without compromising the diagnostic utility of the tests. However, no existing quantitative method for assessing CT image quality has been validated against radiologists' image quality assessments on a large number of CT examinations. Thus to develop an automated measure of image quality, we tested the relationship between radiologists' subjective ratings of image quality with measurements of radiation dose and image noise. Board-certified, posttraining, clinically active radiologists rated the image quality of 200 diagnostic CT examinations from a set of 734, representing 14 CT categories. Examinations with significant distractions, motion, or artifact were excluded. Radiologists rated diagnostic image quality as excellent, adequate, marginally acceptable, or poor; the latter 2 were considered unacceptable for rendering diagnoses. We quantified the relationship between ratings and image noise and radiation dose, by category, by analyzing the odds of an acceptable rating per standard deviation (SD) increase in noise or geometric SD (gSD) in dose. One hundred twenty-five radiologists contributed 24,800 ratings. Most (89%) were acceptable. The odds of an examination being rated acceptable statistically significantly increased per gSD increase in dose and decreased per SD increase in noise for most categories, including routine dose head, chest, and abdomen-pelvis, which together comprise 60% of examinations performed in routine practice. For routine dose abdomen-pelvis, the most common category, each gSD increase in dose raised the odds of an acceptable rating (2.33; 95% confidence interval, 1.98-3.24), whereas each SD increase in noise decreased the odds (0.90; 0.79-0.99). For only 2 CT categories, high-dose head and neck/cervical spine, neither dose nor noise was associated with ratings. Radiation dose and image noise correlate with radiologists' image quality assessments for most CT categories, making them suitable as automated metrics in quality programs incentivizing reduction of excessive radiation doses.

P352 Comparison of Radiation Dose, Image Quality, and Diagnostic Performance between Hybrid Iterative Reconstruction and Deep Learning Reconstruction for CT Enterography of IBD

Abstract Background CT enterography (CTE) is recommended as one of the preferred methods for patients with inflammatory bowel disease (IBD), especially in primary hospitals that lack MRI equipment. However, the potential risk of radiation derived from using CTE during the life-long follow-up is an important issue for these patients. This study aimed to compare the radiation dose, image quality, and diagnostic performance of CTE for IBD using hybrid iterative reconstruction (HIR) and deep learning reconstruction (DLR). Methods We prospectively collected data on low dose CTE reconstructed by HIR and DLR in patients with IBD between February 2023 and September 2023, and retrospectively enrolled IBD patients who underwent conventional dose CTE reconstructed by HIR between June 2019 and June 2022 as controls. The CTE examinations were performed within 2 weeks of bowel histologic evaluation (the reference standard of bowel inflammation). The objective and subjective image quality and the image features were evaluated by two IBD radiologists. The radiation dose, image quality, and diagnostic performance was compared between the two dose protocols. Results The preliminary study included 36 patients in the low dose group with HIR and DLR and 40 patients in the conventional dose group with HIR. There were no significant differences in demographic data of patients between the two groups (all P>0.05). The sensitivity, specificity, and diagnostic accuracy for detecting active inflammation were 71.4% (43.3%), 83.3% (80.0%), and 75.0% (52.5%) for the low dose group with DLR (HIR), respectively, and 84.4%, 62.5%, and 80% for the conventional dose HIR group. Low dose group with DLR resulted in significantly increased objective and subjective image quality and diagnostic confidence for active inflammation compared to low dose group with HIR (all P<0.05), with no inferiority to conventional dose group with HIR (all P>0.05). The dichotomous inter-reader reliability (k) for the entire group was 0.88. Low dose group resulted in a significant reduction in radiation exposure (mean [± SD], 2.20 ± 0.29 mSv) compared to conventional dose group (4.85 ± 1.96 mSv; P<0.001). Conclusion Low dose CTE with DLR significantly improved image quality compared to low dose CTE with HIR, and maintained similarly high diagnostic performance as conventional dose CTE with HIR. Importantly, the low dose CTE with DLR significantly reduced the radiation dose, improving the safety of CTE application in the life-long follow-up of patients with IBD.

Diagnostic value of bilateral inferior petrosal sinus sampling in various modifications and methods of radiation and radionuclide imaging in the diagnosis and differential diagnosis of ACTH-dependent endogenous hypercortisolism

To analyze the diagnostic performance of bilateral inferior petrosal sinus sampling (BIPSS) with desmopressin as a stimulation agent and prolactin measurements to control catheter position with or without the ACTH/prolactin normalized ratio calculation in the differential diagnosis of ACTH-dependent endogenous hypercortisolism, and the diagnostics performance of ectopic ACTH-syndrome (EAS) visualization. A single-center diagnostic study with a retrospective analysis of the data was carried out. The study included patients with ACTH-dependent endogenous hypercorticism with no visualization of pituitary adenoma on MRI or adenoma sizes less than 6 mm. All patients underwent BIPSS with and without calculation of the ACTH/prolactin normalized ratio. Visualization of an EAS included pituitary MRI (to exclude EAS), whole-body CT scan with contrast, and somatostatin receptor scintigraphy with 99mTc-Tectrotide and CT (99mTc-Tectrotide SPECT). The final verification was based on immunohistochemical confirmation of the tumor or stable remission of Cushing's disease (CD) after surgical treatment. Statistical data processing was carried out by using IBM SPSS Statistics 23. Confidence intervals were calculated using the JavaStat online calculator. 230 BIPSS were performed in 228 patients (166 women, 62 men), of which 178 patients were verified as CD and 50cases were EAS of various localization. The effectiveness of catheterization of petrosal sinuses was 96.9%. The sensitivity of BIPSS without ACTH/prolactin ratio calculation (n=70) was 95.9% (95% CI 86.3-98.9), specificity was 92% (95% CI 75.0-97.8), for the BIPSS with additional determination of ACTH/prolactin-normalized ratio (n=51) - 97.3% (95% CI 86.2-99.5) and 93.8% (95% CI 71.7-98.9), respectively. The use of the MRI method for this sample of patients had a sensitivity of 60.2% (95% CI 52.6-67.5), specificity of 59.2% (95% CI 44.2-73.0), the total body CT with contrast has a sensitivity of 74% (95% CI 59.7-85.4), specificity of 100% (95% CI 97.95-100). The diagnostic accuracy for 99mTc-Tectrotide SPECT in NET visualization has a sensitivity of 73.3% (95% CI 44.9-92.2), specificity of 100% (95% CI 95.3-100). BIPSS with desmopressin stimulation and prolactin measurements to control catheter position, as well as the additional calculation of the ACTH/prolactin-normalized ratio, is an optimal method for the differential diagnosis of EAS. Patients who are identified an EAS on BIPSS may be further referred for 99mTc-Tectrotide SPECT and CT for tumor visualization.

Handheld Magnetometer-Assisted Localization andRemoval ofa Foreign Body From the Chest Wall.

Foreign bodies fully embedded in soft tissues present a unique challenge to surgeons attempting excision. Small fragments can be nonpalpable, and many prove difficult to visualize intra-operatively by means of classic radiologic techniques. A 35-year-old active duty soldier presented requesting excision of ballistic fragment embedded in his chest wall that had previously failed a previous attempt at removal. The metallic foreign body was successfully localized intra-operatively using a handheld magnetometer probe and removed without complication. This case demonstrates the utility and cost-effectiveness of the handheld magnetometry for intra-operative localization of metallic foreign bodies. Metallic foreign bodies may be localized intra-operatively using inexpensive and reusable equipment that does not require radiation or bulky radiographic imaging equipment.

Turning Nonemissive CsPb2Br5 Crystals into High-Performance Scintillators through Alkali Metal Doping.

X-ray scintillators have utility in radiation detection, therapy, and imaging. Various materials, such as halide perovskites, organic illuminators, and metal clusters, have been developed to replace conventional scintillators due to their ease of fabrication, improved performance, and adaptability. However, they suffer from self-absorption, chemical instability, and weak X-ray stopping power. Addressing these limitations, we employ alkali metal doping to turn nonemissive CsPb2Br5 into scintillators. Introducing alkali metal dopants causes lattice distortion and enhances electron-phonon coupling, which creates transient potential energy wells capable of trapping photogenerated or X-ray-generated electrons and holes to form self-trapped excitons. These self-trapped excitons undergo radiative recombination, resulting in a photoluminescence quantum yield of 55.92%. The CsPb2Br5-based X-ray scintillator offers strong X-ray stopping power, high resistance to self-absorption, and enhanced stability when exposed to the atmosphere, chemical solvents, and intense irradiation. It exhibits a detection limit of 162.3 nGyair s-1 and an imaging resolution of 21 lp mm-1.

PAE planning: Radiation exposure and image quality of CT and CBCT

PurposeTo determine accurate organ doses, effective doses, and image quality of computed tomography (CT) compared with cone beam CT (CBCT) for correct identification of prostatic arteries. MethodA dual-energy CT scanner and a flat-panel angiography system were used. Dose measurements (gallbladder (g), intestine (i), bladder (b), prostate (p), testes (t), active bone marrow of pelvis (bmp) and femura (bmf)) were performed using an anthropomorphic phantom with 65 thermoluminescent dosimeters in the pelvis and abdomen region. For the calculation of the contrast-to-noise ratio (CNR) of the pelvic arteries, a patient whose weight and height were almost identical to those of the phantom was selected for each examination type. ResultsThe effective dose of CT was 2.7 mSv and that of CBCT was 21.8 mSv. Phantom organ doses were lower for CT than for CBCT in all organs except the testes (g: 1.2 mGy vs. 3.3 mGy, i: 5.8 mGy vs. 23.9 mGy, b: 6.9 mGy vs. 19.4 mGy, p: 6.4 mGy vs. 13.2 mGy, t: 4.7 mGy vs. 2.4 mGy, bmp: 5.1 mGy vs. 18.2 mGy, bmf: 3.3 mGy vs. 6.6 mGy). For human pelvic arteries, the CNR of CT was better than that of CBCT, with the exception of one prostate artery that showed stenosis on CT. Evaluation by experienced radiologists also confirmed the better detectability of prostate arteries on CT examination. ConclusionsIn our study preprocedural CT had lower organ doses and better image quality comparedd with CBCT and should be considered for the correct identification of prostatic arteries.

Pulsed radiation image restoration based on unsupervised deep learning

The process of pulsed X-ray imaging generates noise and blurring that significantly degrade image quality, lead to loss of image information, and interfere with accurate diagnosis of X-ray spot size and objects. Traditional radiation image restoration methods lack flexibility and generalization. Furthermore, neural network methods based on supervised learning require many actual image data sets to be obtained in advance, which limits network training. In this paper, we propose an unsupervised radiation image restoration method based on a deep image prior. The classical DeepRED framework is extended by adding weight-adaptive variational regularization. Automatic strategies are employed to estimate local regularization parameters, resulting in better noise removal and preservation of image edges and texture structures. The proposed method is evaluated through numerical simulations and experimental studies of X-ray source images and flash radiographic images. The results indicate that the proposed method is effective in restoring pulsed radiation images, removing noise, and preserving boundary region information. Additionally, this method produces satisfactory results for the restoration of real neutron images, demonstrating its applicability in the field of radiation imaging.

Alterations in white matter fiber tracts and their correlation with flying cadet behavior.

An increasing number of studies have shown that flight training alters the human brain structure; however, most studies have focused on gray matter, and the exploration of white matter structure has been largely neglected. This study aimed to investigate the changes in white matter structure induced by flight training and estimate the correlation between such changes and psychomotor and flight performance. Diffusion tensor imaging data were obtained from 25 flying cadets and 24 general college students. Data were collected in 2019 and 2022 and analyzed using automated fiber quantification. This study found no significant changes in the flight group in 2019. However, in 2022, the flight group exhibited significant alterations in the diffusion tensor imaging of the right anterior thalamic radiation, left cingulum cingulate, bilateral superior longitudinal fasciculus, and left arcuate fasciculus. These changes occurred within local nodes of the fiber tracts. In addition, we found that changes in fiber tracts in the 2022 flight group were correlated with the reaction time of the psychomotor test task and flight duration. These findings may help improve flight training programs and provide new ideas for the selection of excellent pilots.

Significance of nuclear medicine methods for diagnosis and predicting the course of renal transplantation complications

Renal transplantation is a replacement-based therapeutic method in end-stage kidney failure.It is based on the interdisciplinary collaboration between scientists and clinicians, which match together the achievements of surgery, immunology, and radiation diagnostics. After transplantation the complications appear, which can be associated with status of the graft, the immunological factors of compatibility between the donor and the recipient, the surgical intervention. Early diagnosis and forehanded treatment of such complications is important, as it helps to evaluate and predict the functionality of the graft. In this article we discuss the complications after kidney transplantation: the reasons of their occurrence, pathogenesis, clinical features, and radiation imaging signs. The opportunities of the radiology methods for the differential diagnostics of complications which appear before, during or after the surgery, are shown. We pay the main attention to the nuclear medicine methods, especially the dynamic renal scintigraphy (DRSG) as a method for the evaluation of graft functionality. This is a safe, accessible and non-invasive method for evaluation the quantitative and qualitative parameters of kidney function. DRSG consequently characterizes the perfusion, the extraction and the excretion in the studied organ. We display the standard DRSG protocols using [99mTc] Tc-MAG3 and [99mTc] Tc-DTPA radiopharmaceuticals. We analyze investigations of kinetic perfusion and parenchymal DRSG parameters and their importance for differential diagnosis of complications, prognosis on delayed and slow graft function, short-term and long-term graft functionality assessment. We make an accent on the prognostic importance of the dynamic changes visible on DRSG. We discuss the perspectives of further development of scintigraphic methods for the assessment of kidney grafts. It is related to the implementation of high-quality 3-dimentional visualization, newest radiopharmaceuticals. We conclude the importance of the nuclear medicine as an element of multidisciplinary approach in transplantology.

Radiation oncology department policy development for patients who may become pregnant.

In the context of radiation oncology, radiation exposure from radiation therapy simulation, image guidance, and radiation therapy procedures can have severe adverse biological effects on a developing embryo or fetus. Patients who may be pregnant are screened for the possibility of pregnancy to prevent unnecessary or excessive exposure of radiation in utero. Some radiation therapy patients for whom a pregnancy test is indicated may elect to decline the test. In addition, some patients who are found upon screening to be pregnant may decide, with their attending radiation oncologist, to continue with treatment. A radiation oncology department policy was developed to provide guidelines regarding screening and consent. The policy was designed to prevent unnecessary exposure to patients who may be pregnant, and to limit dose to the embryo or fetus in patients for whom treatment is medically indicated. The policy is presented as an example for physicists intending to develop or revise their own practice's policy regarding patients who may become pregnant.

Optimizing cone-beam computed tomography exposure for an effective radiation dose and image quality balance.

The aim of this study was to evaluate the influence of different cone-beam computed tomography (CBCT) acquisition protocols on reducing the effective radiation dose while maintaining image quality. The effective dose emitted by a CBCT device was calculated using thermoluminescent dosimeters placed in a Rando Alderson phantom. Image quality was assessed by 3 experienced evaluators. The relationship between image quality and confidence was evaluated using the Fisher exact test, and the agreement among raters was assessed using the kappa test. Multiple linear regression analysis was performed to investigate whether the technical parameters could predict the effective dose. P-values<0.05 were considered to indicate statistical significance. The optimized protocol (3 mA, 99 kVp, and 450 projection images) demonstrated good image quality and a lower effective dose for radiation-sensitive organs. Image quality and confidence had consistent values for all structures (P<0.05). Multiple linear regression analysis resulted in a statistically significant model. The milliamperage (b=0.504; t=3.406; P=0.027), kilovoltage peak (b=0.589; t=3.979; P=0.016) and number of projection images (b=0.557; t=3.762; P=0.020) were predictors of the effective dose. Optimized CBCT acquisition protocols can significantly reduce the effective radiation dose while maintaining acceptable image quality by adjusting the milliamperage and projection images.

Research on the Protection and Dissemination of Cultural Heritage in Rural Landscapes Based on Image Processing

Abstract The countryside is an important part of the social development process, but with the acceleration of urbanization, the protection of rural landscapes as cultural heritage is facing an increasingly severe situation. In this study, image radiation correction, image fusion, cropping and mosaicing, geometric correction, band selection, and image enhancement are applied to rural landscapes using remote sensing image processing technology. A digital protection system for rural landscape cultural heritage is created using the processed rural landscapes. By comparing the accuracy of this paper’s method to other classification methods, we can explore the classification performance of this paper’s PCA method. By comparing the changes in rural landscape types before and after landscape protection, the effect of landscape protection is explored. Finally, the communication effect of rural landscapes on social media is explored by utilizing the evaluation index system. The PCA method employed in this paper achieves a landscape classification accuracy of 83%, which is significantly superior to the IHS transformation method (73.5%) and the Brovey transformation method (76%). After the rural landscape protection, the degree of landscape fragmentation in Village A was significantly improved compared to before the protection, and the effect of protection was remarkable. The scores of social media users on each dimension of the rural landscape communication effect in Village A were greater than 4, and rural landscape communication achieved a positive effect.

Ultra-stable CsPbBr3-embedded polymer films for spectrally tunable X-ray nuclear batteries and flexible radiation imaging applications

CsPbBr3-embedded polystyrene films exhibit excellent luminescence stability in various environments and have the special advantages of achieving spectral regulation of radioluminescent nuclear batteries and X-ray imaging of irregular objects.

Mass attenuation Coefficient and Total cross-section Area of Platinum Group Composition

Radiation shielding is a critical practice involving the utilization of materials or barriers to safeguard against ionizing radiation by absorbing, scattering, or blocking the radiation. Its primary objective is to curtail exposure and mitigate potential health risks associated with radiation. In diverse fields like medicine, industry, and nuclear applications, radiation shielding materials play a pivotal role in ensuring the safety of individuals and equipment, contributing significantly to the maintenance of secure environments. This study focuses on characterizing materials for radiation shielding, particularly of Platinum group alloys in varying compositions with hydrogen. Using the Klein-Nishina (KN) formula, the investigation calculates electronic cross-sections (ECS), total mixture cross-section (TMCS), and mass attenuation coefficient (MAC) for different weight percentages of Platinum group alloys (0.1 to 0.6) when exposed to γ-ray photons of various energies. The outcomes emphasize the strong dependence of these cross-sections and MAC on photon energy and the charge number of the material, revealing a decrease with increasing photon energy and an increase with the charge number to mass number ratio (Z/A). The research underscores that fundamental parameters such as charge number, photon energy, and Z/A can be manipulated to enhance the utility of these elements in radiation shielding, protection, dose measurements, and imaging. The study's implications extend to the optimization of Platinum Group alloy compositions, offering insights for the development of tailored materials with enhanced shielding effectiveness in radiation protection and safety applications.

Material Discrimination Using X-Ray and Neutron

Background: A nondestructive test is commonly used to inspect the surface defects and internal structure of an object without any physical damage. X-rays generated from an electron accelerator or a tube are one of the methods used for nondestructive testing. The high penetration of X-rays through materials with low atomic numbers makes it difficult to discriminate between these materials using X-ray imaging. The interaction characteristics of neutrons with materials can supplement the limitations of X-ray imaging in material discrimination.Materials and Methods: The radiation image acquisition process for air-cargo security inspection equipment using X-rays and neutrons was simulated using a GEometry ANd Tracking (Geant4) simulation toolkit. Radiation images of phantoms composed of 13 materials were obtained, and the R-value, representing the attenuation ratio of neutrons and gamma rays in a material, was calculated from these images.Results and Discussion: The R-values were calculated from the simulated X-ray and neutron images for each phantom and compared with those obtained in the experiments. The R-values obtained from the experiments were higher than those obtained from the simulations. The difference can be due to the following two causes. The first reason is that there are various facilities or equipment in the experimental environment that scatter neutrons, unlike the simulation. The other is the difference in the neutron signal processing. In the simulation, the neutron signal is the sum of the number of neutrons entering the detector. However, in the experiment, the neutron signal was obtained by superimposing the intensities of the neutron signals. Neutron detectors also detect gamma rays, and the neutron signal cannot be clearly distinguished in the process of separating the two types of radiation. Despite these differences, the two results showed similar trends and the viability of using simulation-based radiation images, particularly in the field of security screening. With further research, the simulation-based radiation images can replace ones from experiments and be used in the related fields.Conclusion: The Korea Atomic Energy Research Institute has developed air-cargo security inspection equipment using neutrons and X-rays. Using this equipment, radiation images and R-values for various materials were obtained. The equipment was reconstructed, and the R-values were obtained for 13 materials using the Geant4 simulation toolkit. The R-values calculated by experiment and simulation show similar trends. Therefore, we confirmed the feasibility of using the simulation-based radiation image.

PET imagining in Alzheimer’s disease

Purpose. The purpose of this article is to explore the potential of positron emission tomography (PET) in early diagnosis of Alzheimer's disease (AD), monitoring of disease progression and assessment of treatment effectiveness. And also, to become familiar with advantages and disadvantages of application of various radiopharmaceuticals.&#x0D; Materials and methods. The material for the study was the scientific results of publications in professional scientific journals of the leading countries of the world of scientific and clinical activity over the past 10 years on the clinical significance of hybrid radiation imaging methods in the diagnosis and treatment of patients with AD. The study involved the use of PET radiation imaging methods in Alzheimer's disease.&#x0D; Results. The efficacy of PET at different stages of AD has been demonstrated. The advantages and disadvantages of using different PET techniques and different radiopharmaceuticals are discussed. PET, unlike other biomarkers, is able to assess the prevalence of lesions, evaluate progression and make a prediction of the further course of the disease.&#x0D; Conclusions. Positron emission tomography in patients with AD is an effective diagnostic technique that can be used at different stages from the prodromal period in the form of mild cognitive impairment to assessing the progression or effectiveness of treatment in numerous clinical trials.

Radiation dose assessment: Establishment of local diagnostic reference levels for selected radiography examinations across three prominent hospitals in Sudan

Due to variation among radiographers’ practice, and the importance of unifying practice during radiography for optimizing radiation level and image quality, the current manuscript aims to assess the radiation dose level and propose local diagnostic reference levels (LDRL) for posterior-anterior (PA) chest, antero-posterior (AP) abdomen, and pelvis examinations in two hospitals in Khartoum (‘K’) and one hospital in Wad-Medani (‘M’) cities, Sudan. Along with patient demographics like height and weight, the radiation exposure parameters including tube potential, current, and radiation duration were documented. This included 732 patients whose tests were conducted at one of three departments located in two different cities. The entrane surface air kerma (ESAK) was calculated using DosCal software and an Unfors -Xi-meter. The average ESAK for an X-ray of the chest was 0.18 mGy in M, 0.19 mGy in K (averaged over two hospitals in the K), for the abdomen it was 1.1 and 1.23 mGy, and for the pelvis it was 1.8 and 01.9 mGy respectively. The proposed DRL was achieved from the third quartile of radiation dosage of data, and it was 0.21, 1.7 and 1.9 mGy for the chest, abdomen and pelvis respectively. There was a wide variation in dosage levels among the three hospitals. The current proposed DRL was lower than most literature for the chest, abdomen and pelvis. More studies are recommended for other examinations such as skull and contrast media studies.

Gridless adult cervical spine radiography and its' effect on image quality and radiation dose: A phantom study

IntroductionImaging of the cervical spine in general radiography is most frequently performed using an anti-scatter grid. The purpose of this study was to investigate the effects of a gridless setting on image quality and radiation dose during digital radiography of the anteroposterior (AP) and lateral (LAT) cervical spine. MethodsA phantom study was performed with a variety of tube voltages (63–75 kV) with and without an anti-scatter grid. The tube current time product (mAs) and dose area product (DAP) were recorded and used to calculate effective dose (ED) and individual organ dose using PCXMC 2.0 software, as well as entrance surface dose (ESD) and objective image quality: signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR). Subjective visual image quality grading characteristics (VGC) was performed by five qualified radiographers. ResultsIn a gridless setting, the AP and LAT positions showed significantly lower DAP (1.6 μGym2; 61.3 % and 1.6 μGym2; 51.2%), ESD (27.6 μGy; 57.3% and 77.2 μGy; 47.2%) and ED (4.2 μSv; 61.3% and 2.3 μSv; 48.9%). In a gridless setting in the AP position, there is a slight significant deterioration in image quality. In the lateral projection, on the other hand, the image quality without the use of grid was only significantly reduced in three of six criteria and there was no difference in the objective image quality between the two settings examined. ConclusionThe results of this study show that gridless setting significantly decreases radiation dose and image quality, but the quality in the lateral projection is still acceptable for diagnostic purpose. Implications for practiceThe protocol without the use of the anti-scatter grid in cervical spine radiography leads to a reduction in the radiation dose in both projections, but the image quality in the AP is significantly reduced for all criteria examined, with a slight deterioration in image quality in the lateral projection.

Molecular and cellular imaging of the eye.

The application of molecular and cellular imaging in ophthalmology has numerous benefits. It can enable the early detection and diagnosis of ocular diseases, facilitating timely intervention and improved patient outcomes. Molecular imaging techniques can help identify disease biomarkers, monitor disease progression, and evaluate treatment responses. Furthermore, these techniques allow researchers to gain insights into the pathogenesis of ocular diseases and develop novel therapeutic strategies. Molecular and cellular imaging can also allow basic research to elucidate the normal physiological processes occurring within the eye, such as cell signaling, tissue remodeling, and immune responses. By providing detailed visualization at the molecular and cellular level, these imaging techniques contribute to a comprehensive understanding of ocular biology. Current clinically available imaging often relies on confocal microscopy, multi-photon microscopy, PET (positron emission tomography) or SPECT (single-photon emission computed tomography) techniques, optical coherence tomography (OCT), and fluorescence imaging. Preclinical research focuses on the identification of novel molecular targets for various diseases. The aim is to discover specific biomarkers or molecular pathways associated with diseases, allowing for targeted imaging and precise disease characterization. In parallel, efforts are being made to develop sophisticated and multifunctional contrast agents that can selectively bind to these identified molecular targets. These contrast agents can enhance the imaging signal and improve the sensitivity and specificity of molecular imaging by carrying various imaging labels, including radionuclides for PET or SPECT, fluorescent dyes for optical imaging, or nanoparticles for multimodal imaging. Furthermore, advancements in technology and instrumentation are being pursued to enable multimodality molecular imaging. Integrating different imaging modalities, such as PET/MRI (magnetic resonance imaging) or PET/CT (computed tomography), allows for the complementary strengths of each modality to be combined, providing comprehensive molecular and anatomical information in a single examination. Recently, photoacoustic microscopy (PAM) has been explored as a novel imaging technology for visualization of different retinal diseases. PAM is a non-invasive, non-ionizing radiation, and hybrid imaging modality that combines the optical excitation of contrast agents with ultrasound detection. It offers a unique approach to imaging by providing both anatomical and functional information. Its ability to utilize molecularly targeted contrast agents holds great promise for molecular imaging applications in ophthalmology. In this review, we will summarize the application of multimodality molecular imaging for tracking chorioretinal angiogenesis along with the migration of stem cells after subretinal transplantation in vivo.

Quantitative functional imaging with CT perfusion: technical considerations, kinetic modeling, and applications

CT perfusion (CTP)-derived quantitative maps of hemodynamic parameters have found important clinical applications in stroke, cancer, and cardiovascular disease. Blood flow, blood volume, transit time, and other perfusion parameters are sensitive markers of pathophysiology with impaired perfusion. This review summarizes the basic principles of CTP including image acquisition, tracer kinetic modeling, deconvolution algorithms, and diagnostic interpretation. The focus is on practical and theoretical considerations for accurate quantitative parametric imaging. Recommended CTP scan parameters to maintain CT number accuracy and optimize radiation dose versus image noise are first reviewed. Tracer kinetic models, which describe how injected contrast material is distributed between blood and the tissue microenvironment by perfusion and bidirectional passive exchange, are then derived. Deconvolution algorithms to solve for hemodynamic parameters of kinetic models are discussed and their quantitative accuracy benchmarked. The applications and diagnostic interpretation of CTP in stroke, cancer, and cardiovascular disease are summarized. Finally, we conclude with a discussion of future directions for CTP research, including radiation dose reduction, new opportunities with novel CT hardware, and emerging diagnostic applications.