Observation Safely Reduces the Use of the Computerized Tomography in Medium-to-Low-Risk Patients with Suspected Acute Appendicitis: Results of a Randomized Controlled Trial.

Objectives-The objective was to compare the effectiveness of observation in standard-of-care computed tomography (CT) in adult patients with suspected acute appendicitis (AA). Methods-Patients with clinically suspected AA and inconclusive diagnosis after primary clinical examination, laboratory examination, and transabdominal ultrasound (TUS) were eligible for the study, and they were randomized (1:1) to parallel groups: observation-group patients were observed for 8-12 h and then, repeated clinical and laboratory examinations and TUS were performed; CT group (control group) patients underwent abdominopelvic CT scan. The study utilized Statistical Analysis System 9.2 for data analysis, including tests, logistic regression, ROC analysis, and significance evaluation. Patients were enrolled in the study at Vilnius University Hospital Santaros Klinikos in Lithuania between December 2018 and June 2021. Results-A total of 160 patients (59 men, 101 women), with a mean age of 33.7 ± 14.71, were included, with 80 patients in each group. Observation resulted in a reduced likelihood of a CT scan compared with the CT group (36.3% vs. 100% p < 0.05). One diagnostic laparoscopy was performed in the observation group; there were no cases of negative appendectomy (NA) in the CT group. Both conditional CT and observation pathways resulted in high sensitivity and specificity (97.7% and 94.6% vs. 96.7% and 95.8%). Conclusions-Observation including the repeated evaluation of laboratory results and TUS significantly reduces the number of CT scans without increasing NA numbers or the number of complicated cases.

Digital variance angiography in patients undergoing lower limb arterial recanalization: cost-effectiveness analysis within the English healthcare setting.

Aim: Digital variance angiography (DVA) is a recently developed image processing method capable of improving image quality compared with the traditionally used digital subtraction angiography (DSA), among patients undergoing lower limb x-ray angiography. This study aims to explore the potential cost-effectiveness of DVA from an English National Health Service perspective. Materials & methods: A two-part economic model, consisting of a decision tree and a Markov model, was developed to consider the costs and health outcomes associated with the use of DVA as part of current practice imaging, compared with x-ray angiography using standard DSA. The model explored the impact of DVA on the development of acute kidney injury (AKI), chronic kidney disease and radiation-induced cancer over a lifetime horizon. Both deterministic and probabilistic analyses were performed to assess the cost per quality-adjusted life-year (QALY). Results: Base-case results indicate that DVA results in cost savings of £309 per patient, with QALYs also improving (+0.025) over a lifetime. As shown in sensitivity analysis, a key driver of model results is the relative risk (RR) reduction of contrast-associated acute kidney injury associated with use of DVA. The intervention also decreases the risk of carcinoma over a lifetime. Scenario analyses show that cost savings range from £310 to £553, with QALY gains ranging from 0.048 to 0.109 per patient. Conclusion: The use of DVA could result in a decrease in costs and an increase in QALYs over a lifetime, compared with existing imaging practice. The potential for this technology to offer an economically viable alternative to existing image processing methods, through a reduction in contrast media volume and radiation exposure, has been demonstrated.

Radiation Exposure Reduction by Digital Variance Angiography in Lower Limb Angiography: A Randomized Controlled Trial.

BACKGROUND: digital variance angiography (DVA) provides higher image quality than digital subtraction angiography (DSA). This study investigates whether the quality reserve of DVA allows for radiation dose reduction during lower limb angiography (LLA), and compares the performance of two DVA algorithms. METHODS: this prospective block-randomized controlled study enrolled 114 peripheral arterial disease patients undergoing LLA into normal dose (ND, 1.2 µGy/frame, n = 57) or low-dose (LD, 0.36 µGy/frame, n = 57) groups. DSA images were generated in both groups, DVA1 and DVA2 images were generated in the LD group. Total and DSA-related radiation dose area product (DAP) were analyzed. Image quality was assessed on a 5-grade Likert scale by six readers. RESULTS: the total and DSA-related DAP were reduced by 38% and 61% in the LD group. The overall visual evaluation scores (median (IQR)) of LD-DSA (3.50 (1.17)) were significantly lower than the ND-DSA scores (3.83 (1.00), p < 0.001). There was no difference between ND-DSA and LD-DVA1 (3.83 (1.17)), but the LD-DVA2 scores were significantly higher (4.00 (0.83), p < 0.01). The difference between LD-DVA2 and LD-DVA1 was also significant (p < 0.001). CONCLUSIONS: DVA significantly reduced the total and DSA-related radiation dose in LLA, without affecting the image quality. LD-DVA2 images outperformed LD-DVA1, therefore DVA2 might be especially beneficial in lower limb interventions.

HEX: a safe research framework for hybrid EMT X-ray navigation.

PURPOSE: Navigating with continuous X-ray provides visual guidance, but exposes both surgeon and patient to ionizing radiation, which is associated with serious health risks. Interleaving fluoro snapshots with electromagnetic tracking (EMT) potentially minimizes radiation. METHODS: We propose hybrid EMT + X-ray (HEX), a research framework for navigation with an emphasis on safe experimentation. HEX is based on several hardware and software components that are orchestrated to allow for safe and efficient data acquisition. RESULTS: In our study, hybrid navigation reduces radiation by [Formula: see text] with cubic, and by [Formula: see text] with linear error compensation while achieving submillimeter accuracy. Training points for compensation can be reduced by half while keeping a similar accuracy-radiation trade-off. CONCLUSION: The HEX framework allows to safely and efficiently evaluate the hybrid navigation approach in simulated procedures. Complementing intraoperative X-ray with EMT significantly reduces radiation in the OR, increasing the safety of patients and surgeons.

Stress-First Myocardial Perfusion Imaging.

Stress-first approaches to myocardial perfusion imaging provide diagnostically and prognostically accurate perfusion data equivalent to a full rest-stress study while saving time in the imaging laboratory and reducing the radiation exposure to patients and laboratory staff. Unfortunately, implementing a stress-first approach in a nuclear cardiology laboratory involves significant challenges such as the need for attenuation correction, triage of patients to an appropriate protocol, real-time review of stress images, and consideration of differential reimbursement. Despite it being best practice for both the patient and the laboratory, these impediments have kept the proportions of studies performed stress-first relatively unchanged in North America and world-wide in the last 10 years.

Oncology-specific radiation dose and image noise reference levels in adult abdominal-pelvic CT.

OBJECTIVES: To provide our oncology-specific adult abdominal-pelvic CT reference levels for image noise and radiation dose from a high-volume, oncologic, tertiary referral center. METHODS: The portal venous phase abdomen-pelvis acquisition was assessed for image noise and radiation dose in 13,320 contrast-enhanced CT examinations. Patient size (effective diameter) and radiation dose (CTDIvol) were recorded using a commercial software system, and image noise (Global Noise metric) was quantified using a custom processing system. The reference level and range for dose and noise were calculated for the full dataset, and for examinations grouped by CT scanner model. Dose and noise reference levels were also calculated for exams grouped by five different patient size categories. RESULTS: The noise reference level was 11.25 HU with a reference range of 10.25-12.25 HU. The dose reference level at a median effective diameter of 30.7 cm was 26.7 mGy with a reference range of 19.6-37.0 mGy. Dose increased with patient size; however, image noise remained approximately constant within the noise reference range. The doses were 2.1-2.5 times than the doses in the ACR DIR registry for corresponding patient sizes. The image noise was 0.63-0.75 times the previously published reference level in abdominal-pelvic CT examinations. CONCLUSIONS: Our oncology-specific abdominal-pelvic CT dose reference levels are higher than in the ACR dose index registry and our oncology-specific image noise reference levels are lower than previously proposed image noise reference levels. ADVANCES IN KNOWLEDGE: This study reports reference image noise and radiation dose levels appropriate for the indication of abdomen-pelvis CT examination for cancer diagnosis and staging. The difference in these reference levels from non-oncology-specific CT examinations highlight a need for indication-specific, dose index and image quality reference registries.

Radiation Dose Reduction Opportunities in Vascular Imaging.

Computed tomography angiography (CTA) has been the gold standard imaging modality for vascular imaging due to a variety of factors, including the widespread availability of computed tomography (CT) scanners, the ease and speed of image acquisition, and the high sensitivity of CTA for vascular pathology. However, the radiation dose experienced by the patient during imaging has long been a concern of this image acquisition method. Advancements in CT image acquisition techniques in combination with advancements in non-ionizing radiation imaging techniques including magnetic resonance angiography (MRA) and contrast-enhanced ultrasound (CEUS) present growing opportunities to reduce total radiation dose to patients. This review provides an overview of advancements in imaging technology and acquisition techniques that are helping to minimize radiation dose associated with vascular imaging.

Assessment of low-dose paranasal sinus CT imaging using a new deep learning image reconstruction technique in children compared to adaptive statistical iterative reconstruction V (ASiR-V).

PURPOSE: To compare the effects of deep learning image reconstruction (DLIR) and adaptive statistical iterative reconstruction V (ASiR-V) on image quality in low-dose computed tomography (CT) of paranasal sinuses in children. METHODS: Low-dose CT scans of the paranasal sinuses in 25 pediatric patients were retrospectively evaluated. The raw data were reconstructed with three levels of DLIR (high, H; medium, M; and low, L), filtered back projection (FBP), and ASiR-V (30% and 50%). Image noise was measured in both soft tissue and bone windows, and the signal-to-noise ratios (SNRs) and contrast-to-noise ratios (CNRs) of the images were calculated. Subjective image quality at the ethmoid sinus and nasal cavity levels of the six groups of reconstructed images was assessed by two doctors using a five-point Likert scale in a double-blind manner. RESULTS: The patients' mean dose-length product and effective dose were 36.65 ± 2.44 mGy·cm and 0.17 ± 0.03 mSv, respectively. (1) Objective evaluation: 1. Soft tissue window: The difference among groups in each parameter was significant (P < 0.05). Pairwise comparisons showed that the H group' s parameters were significantly better (P < 0.05) than those of the 50% post-ASiR-V group. 2. Bone window: No significant between-group differences were found in the noise of the petrous portion of the temporal bone or its SNR or in the noise of the pterygoid processes of the sphenoids or their SNRs (P > 0.05). Significant differences were observed in the background noise and CNR (P < 0.05). As the DLIR intensity increased, image noise decreased and the CNR improved. The H group exhibited the best image quality. (2) Subjective evaluation: Scores for images of the ethmoid sinuses were not significantly different among groups (P > 0.05). Scores for images of the nasal cavity were significantly different among groups (P < 0.05) and were ranked in descending order as follows: H, M, L, 50% post-ASiR-V, 30% post-ASiR-V, and FBP. CONCLUSION: DLIR was superior to FBP and post-ASiR-V in low-dose CT scans of pediatric paranasal sinuses. At high intensity (H), DLIR provided the best reconstruction effects.

Trends in Intraoperative Assessment of Spinal Alignment: A Survey of Spine Surgeons in the United States.

STUDY DESIGN: Survey. OBJECTIVES: To characterize national practices of and shortcomings surrounding intraoperative assessments of spinal alignment. METHODS: Spine surgeons in the US were surveyed to analyze their experience with assessing spinal alignment intraoperatively. RESULTS: 108 US spine surgeons from 77 surgical centers with an average of 19.2 + 8.8 years of surgical experience completed the survey. To assess alignment intraoperatively, 84% (91/108) use C-arm or spot radiographs, 40% (43/108) use full-length radiographs, and 20% utilize the T-bar (22/108). 88% of respondents' surgical centers (93/106) possessed a navigation camera and 63% of respondents (68/108) report using surgical navigation for 40% of their deformity cases on average. Reported deterrents for using current technology to assess alignment were workflow interruption (54%, 58/108), expense (33%, 36/108), and added radiation exposure (26%, 28/108). 87% of respondents (82/94) reported a need for improvement in current capabilities of making intraoperative assessments of spinal alignment. CONCLUSIONS: Corrective surgery for spinal deformity is a complex procedure that requires a high level of expertise to perform safely. The majority of surveyed surgeons primarily rely on radiographs for intraoperative assessments of alignment. Despite the majority of surveyed surgical practices possessing navigation cameras, they are utilized only for a minority of spinal deformity cases. With the majority of surveyed surgeons reporting a need for improvement in technology to assess spinal alignment intraoperatively, 3 of the top design considerations should include workflow interruption, expense, and radiation exposure.

A preliminary study on the radiation dose reduction during catheterization procedures using simple partial patient shielding.

Reduction in X-ray exposure during cardiac catheterization is important to reduce radiation risks to operators and personnel. Reducing scattered radiation from the patient can achieve this goal. The goal of this study was to evaluate the reduction in radiation using simple partial shielding of patients undergoing cardiac catheterization. By putting a lead-based apron on the lower extremities of patients undergoing cardiac catheterization, we analyzed the reduction in total radiation dose with and without this shielding. One hundred and twelve patients were divided into two groups. In one group, the protective lead-based apron was put on the lower extremities of patients. Another group did not have any shielding. Total duration of angiography was 332 minutes and 45 seconds in the first group and 269 minutes and 10 seconds in the second group. The total radiation exposure was 33 µGy in the first group vs 606 µGy in the second group. Despite higher exposure time, total radiation dose was 22 times lower in the simple shielded group. Our simple method without any additional cost can significantly reduce radiation exposure in the cardiac catheterization laboratory.

A Novel Hybrid Precoding-Companding Technique for Peak-to-Average Power Ratio Reduction in 5G and beyond.

Several high-speed wireless systems use Orthogonal Frequency Division Multiplexing (OFDM) due to its advantages. 5G has adopted OFDM and is expected to be considered beyond 5G (B5G). Meanwhile, OFDM has a high Peak-to-Average Power Ratio (PAPR) problem. Hybridization between two PAPR reduction techniques gains the two techniques' advantages. Hybrid precoding-companding techniques are attractive as they require small computational complexity to achieve high PAPR reduction gain. Many precoding-companding techniques were introduced to increasing the PAPR reduction gain. However, reducing Bit Error Rate (BER) and out-of-band (OOB) radiation are more significant than increasing PAPR reduction gain. This paper proposes a new precoding-companding technique to better reduce the BER and OOB radiation than previous precoding-companding techniques. Results showed that the proposed technique outperforms all previous precoding-companding techniques in BER enhancement and OOB radiation reduction. The proposed technique reduces the Error Vector Magnitude (EVM) by 15 dB compared with 10 dB for the best previous technique. Additionally, the proposed technique increases high power amplifier efficiency (HPA) by 11.4%, while the best previous technique increased HPA efficiency by 9.8%. Moreover, our proposal achieves PAPR reduction gain better than the most known powerful PAPR reduction technique with a 99% reduction in required computational complexity.

Novel Minimal Radiation Approach for Percutaneous Pulmonary Valve Implantation.

The aim of the study is to evaluate the impact of multimodality imaging technology during percutaneous pulmonary valve implantation (PPVI). Among percutaneous procedures, PPVI traditionally has one of the highest patient radiation exposures. Different protocol modifications have been implemented to address this problem (i.e., improvements in guidance systems, delivery systems, valve design, post-implantation evaluation). Although the effectiveness of individual modifications has been proven, the effect of an approach which combines these changes has not been reported. We performed a retrospective chart review of 76 patients who underwent PPVI between January 2018 and December 2019. Patients were classified in "Traditional protocol," using routine biplane angiography and/or 3D rotational angiography (3DRA); and "Multimodality protocol" that included the use of VesselNavigator for guidance, selective 3DRA for coronary evaluation, Long DrySeal Sheath for valve delivery, and Intracardiac Echocardiography for valve evaluation after implantation. Radiation metrics, procedural time, and clinical outcomes were compared between groups. When the traditional protocol group was compared with the multimodality protocol group, a significant reduction was described for total fluoroscopy time (31.6 min vs. 26.2 min), dose of contrast per kilogram (1.8 mL/Kg vs. 0.9 mL/Kg), DAP/kg (26.6 µGy·m2/kg vs. 19.9 µGy·m2/kg), and Air Kerma (194 mGy vs. 99.9 mGy). A reduction for procedure time was noted (140 min vs. 116.5 min), but this was not statistically significant. There was no difference in clinical outcomes or the presence of complications between groups. The combination of novel technology in PPVI caused a significant reduction in radiation metrics without increasing the complication rate in our population.

Review, monitor, educate: A quality improvement initiative for sustained chest radiation reduction in pediatric trauma patients.

BACKGROUND: We hypothesize that in pediatric trauma patients, CT scans after normal chest x-rays do not add information that alters clinical decision making. METHODS: A retrospective review of trauma patients < 15 years with chest imaging evaluated at a pediatric trauma center between 1/2013 and 6/2019 was performed. Imaging was reviewed for significant findings that could affect care. A guideline was established in January 2017 which emphasized x-rays prior to CTs and no CTs after normal x-rays. A prospective review was performed from 1/2017-6/2019. Pre and post guideline groups were compared. RESULTS: From 2013 to 2016, 246 patients met inclusion. 29.5% had a chest CT after a normal x-ray, only 1.8% (1/57) had a significant result. From 2017 to 2019, 188 patients were reviewed post guideline; only 9.4% received a CT after normal x-ray, of which 6.3% (1/16) were significant. Neither changed clinical management. CONCLUSIONS: Chest CT following normal chest x-ray does not change clinical management in pediatric trauma patients. Monitoring and education following guideline implementation improves long term outcomes.

The sub-millisievert era in CTCA: the technical basis of the new radiation dose approach.

Computed tomography coronary angiography (CTCA) has become a cornerstone in the diagnostic process of the heart disease. Although the cardiac imaging with interventional procedures is responsible for approximately 40% of the cumulative effective dose in medical imaging, a relevant radiation dose reduction over the last decade was obtained, with the beginning of the sub-mSv era in CTCA. The main technical basis to obtain a radiation dose reduction in CTCA is the use of a low tube voltage, the adoption of a prospective electrocardiogram-triggering spiral protocol and the application of the tube current modulation with the iterative reconstruction technique. Nevertheless, CTCA examinations are characterized by a wide range of radiation doses between different radiology departments. Moreover, the dose exposure in CTCA is extremely important because the benefit-risk calculus in comparison with other modalities also depends on it. Finally, because anatomical evaluation not adequately predicts the hemodynamic relevance of coronary stenosis, a low radiation dose in routine CTCA would allow the greatest use of the myocardial CT perfusion, fractional flow reserve-CT, dual-energy CT and artificial intelligence, to shift focus from morphological assessment to a comprehensive morphological and functional evaluation of the stenosis. Therefore, the aim of this work is to summarize the correct use of the technical basis in order that CTCA becomes an established examination for assessment of the coronary artery disease with low radiation dose.

Image Quality Assessment of Abdominal CT by Use of New Deep Learning Image Reconstruction: Initial Experience.

OBJECTIVE. The purpose of this study was to perform quantitative and qualitative evaluation of a deep learning image reconstruction (DLIR) algorithm in contrast-enhanced oncologic CT of the abdomen. MATERIALS AND METHODS. Retrospective review (April-May 2019) of the cases of adults undergoing oncologic staging with portal venous phase abdominal CT was conducted for evaluation of standard 30% adaptive statistical iterative reconstruction V (30% ASIR-V) reconstruction compared with DLIR at low, medium, and high strengths. Attenuation and noise measurements were performed. Two radiologists, blinded to examination details, scored six categories while comparing reconstructions for overall image quality, lesion diagnostic confidence, artifacts, image noise and texture, lesion conspicuity, and resolution. RESULTS. DLIR had a better contrast-to-noise ratio than 30% ASIR-V did; high-strength DLIR performed the best. High-strength DLIR was associated with 47% reduction in noise, resulting in a 92-94% increase in contrast-to-noise ratio compared with that of 30% ASIR-V. For overall image quality and image noise and texture, DLIR scored significantly higher than 30% ASIR-V with significantly higher scores as DLIR strength increased. A total of 193 lesions were identified. The lesion diagnostic confidence, conspicuity, and artifact scores were significantly higher for all DLIR levels than for 30% ASIR-V. There was no significant difference in perceived resolution between the reconstruction methods. CONCLUSION. Compared with 30% ASIR-V, DLIR improved CT evaluation of the abdomen in the portal venous phase. DLIR strength should be chosen to balance the degree of desired denoising for a clinical task relative to mild blurring, which increases with progressively higher DLIR strengths.

Gain-Enhanced Metamaterial Absorber-Loaded Monopole Antenna for Reduced Radar Cross-Section and Back Radiation.

This paper proposes a gain-enhanced metamaterial (MM) absorber-loaded monopole antenna that reduces both radar cross-section and back radiation. To demonstrate the proposed idea, we designed a wire monopole antenna and an MM absorber. The MM absorber comprised lumped elements of subwavelength unit cells and achieved 90% absorbance bandwidth from 2.42-2.65 GHz. For low-profile configurations, the MM absorber was loaded parallel to and 10 mm from the monopole antenna, corresponding to 0.09 λ0 at 2.7 GHz. The monopole antenna resonated at 2.7 GHz with a 3.71 dBi peak gain and 2.65 GHz and 6.46 dBi peak gain, before and after loading the MM absorber, respectively. Therefore, including the MM absorber increased peak gain by 2.7 dB and reduced back radiation by 15 dB. The proposed antenna radar cross-section was reduced by 2 dB compared with a monopole antenna with an artificial magnetic conductor.

Clinical pediatric positron emission tomography/magnetic resonance program: a guide to successful implementation.

Children with malignancies undergo recurrent imaging as part of tumor diagnosis, staging and therapy response assessment. Simultaneous positron emission tomography (PET) and magnetic resonance (MR) allows for decreased radiation exposure and acts as a one-stop shop for disease in which MR imaging is required. Nevertheless, PET/MR is still less readily available than PET/CT across institutions. This article serves as a guide to successful implementation of a clinical pediatric PET/MR program based on our extensive clinical experience. Challenges include making scanners more affordable and increasing patient throughput by decreasing total scan time. With improvements in workflow and robust acquisition protocols, PET/MR imaging is expected to play an increasingly important role in pediatric oncology.

The Role of Generative Adversarial Networks in Radiation Reduction and Artifact Correction in Medical Imaging.

Adversarial networks were developed to complete powerful image-processing tasks on the basis of example images provided to train the networks. These networks are relatively new in the field of deep learning and have proved to have unique strengths that can potentially benefit radiology. Specifically, adversarial networks have the potential to decrease radiation exposure to patients through minimizing repeat imaging due to artifact, decreasing acquisition time, and generating higher quality images from low-dose or no-dose studies. The authors provide an overview of a specific type of adversarial network called a "generalized adversarial network" and review its uses in current medical imaging research.

Protecting Surgeons' Fingers from Radiation Exposure during Lumbosacral Selective Nerve Root Block.

INTRODUCTION: Fluoroscopy-guided selective nerve root block (SNRB) is useful for the diagnosis and treatment of nerve root pain. However, the procedure exposes the surgeon's hands to radiation. Therefore, the purpose of this randomized prospective study was to assess the radiation exposure per unit time of the surgeon's fingers during performance of a lumbosacral SNRB and to calculate the annual exposure time limits for four hand-protection methods. METHODS: We prospectively recruited patients scheduled for an SNRB and measured the radiation exposure using a ring-type passive radiation dosimetry device attached to the distal phalanx of the index finger of the hand performing the needle placement. Patients were randomly divided into the following four groups: a) the direct exposure group, b) the 0.03-mmPb glove group, c) the 0.25-mmPb glove group, and d) the forceps group (in which the needle was held using forceps such that the fingers did not enter the irradiation field). RESULTS: We recruited 40 consecutive patients (16 men and 24 women), with a mean age of 69 years. In all cases, SNRB was successfully performed without complications. The average exposure per hour for each of the four groups was as follows: 0.67 ± 0.56 mSv/s in the direct exposure group, 0.12 ± 0.07 mSv/s in the 0.03-mmPb glove group, 0.019 ± 0.02 mSv/s in the 0.25-mmPb glove group, and 0.001 ± 0.004 mSv/s in the forceps group (p < 0.01). The average annual exposure time limit was 12.4 min in the direct exposure group, 67.9 min in the 0.03-mmPb glove group, 7.5 h in the 0.25-mmPb glove group, and 5.0 days in the forceps group. CONCLUSIONS: Using a radiation reduction glove or forceps greatly decreased the radiation exposure and increased the annual exposure time limit for SNRB.

STIR-Net: Deep Spatial-Temporal Image Restoration Net for Radiation Reduction in CT Perfusion.

Computed Tomography Perfusion (CTP) imaging is a cost-effective and fast approach to provide diagnostic images for acute stroke treatment. Its cine scanning mode allows the visualization of anatomic brain structures and blood flow; however, it requires contrast agent injection and continuous CT scanning over an extended time. In fact, the accumulative radiation dose to patients will increase health risks such as skin irritation, hair loss, cataract formation, and even cancer. Solutions for reducing radiation exposure include reducing the tube current and/or shortening the X-ray radiation exposure time. However, images scanned at lower tube currents are usually accompanied by higher levels of noise and artifacts. On the other hand, shorter X-ray radiation exposure time with longer scanning intervals will lead to image information that is insufficient to capture the blood flow dynamics between frames. Thus, it is critical for us to seek a solution that can preserve the image quality when the tube current and the temporal frequency are both low. We propose STIR-Net in this paper, an end-to-end spatial-temporal convolutional neural network structure, which exploits multi-directional automatic feature extraction and image reconstruction schema to recover high-quality CT slices effectively. With the inputs of low-dose and low-resolution patches at different cross-sections of the spatio-temporal data, STIR-Net blends the features from both spatial and temporal domains to reconstruct high-quality CT volumes. In this study, we finalize extensive experiments to appraise the image restoration performance at different levels of tube current and spatial and temporal resolution scales.The results demonstrate the capability of our STIR-Net to restore high-quality scans at as low as 11% of absorbed radiation dose of the current imaging protocol, yielding an average of 10% improvement for perfusion maps compared to the patch-based log likelihood method.