二氧化碳用于多层螺旋CT诊断肺栓塞的初步实验研究

目的探讨二氧化碳(CO2)作为阴性对比剂在多层螺旋CT(MSCT)诊断肺栓塞(PE)中的可行性。材料与方法6只用明胶海绵建立了PE模型后的犬分别用CO2作为阴性对比剂、碘对比剂作为阳性对比剂行MSCT血管造影检查,对所得两组图像进行比较。结果60ml CO2可使肺动脉充分显影,CO2 CT血管成像和碘对比剂CT血管成像都显示了肺动脉内的栓子,栓子在前者图像上比后者更清晰。结论用CO2作为阴性对比剂行MSCT扫描对诊断PE是可行的。     

Susceptibility-weighted Imaging for Renal Iron Overload Assessment: A Pilot Study

Purpose: To explore the feasibility of susceptibility-weighted imaging (SWI) for evaluating renal iron overload.Methods: Twenty-eight rabbits were randomly assigned into control (n = 14) and iron (n = 14) group. In the 0th week, the study group was injected with iron dextran. Both groups underwent SWI examination at the 0th, 8th, and 12th week. The signal intensity (SI) of cortex and medulla was assessed. Angle radian value (ARV) calculated with phase image was taken as the quantitative value for cortical and medullary iron deposition. After the 12th week, the left kidneys of rabbits were removed for pathology. The difference in the ARV among three groups was analyzed using Kruskal–Wallis test. The difference of the iron content between two groups was analyzed through independent sample t-test.Results: In the iron group: at the 12th week, eight rabbits were found to have decreased SI of only cortex, and the other six rabbits had decreased SI of cortex and medulla by the same degree; the ARV of cortex at the 8th and 12th week was significantly higher than that of the 0th week (P < 0.05); the ARV of the six rabbits’ medulla at the 12th week was significantly higher than that of the 0th week, 8th week, and the other eight rabbits at the 12th week (P < 0.05); at the 12th week, eight rabbits (iron group) were found to have many irons only deposit in the cortex, and the others were found to have many irons deposit in both cortex and medulla; the iron content of cortex and six rabbits’ medulla in the iron group was significantly higher than that of the control (P < 0.05).Conclusion: The ARV of SWI can be used to quantitatively assess the excess iron deposition in the kidneys. Excessive iron deposition mainly occurs in the cortex or medulla and causes their SWI SI to decrease.     

香港儿童体力活动与住所周围建成环境:应用GIS的初步研究

目的:分析以地理信息系统(GIS)测量的住所周围建成环境与香港儿童体力活动的关系。方法:本研究的样本为香港一间小学的81名7~11岁儿童(男生44人)。本研究数据来自一项为期三年的追踪研究——儿童体力活动与营养调查(UCAN计划)。受试儿童体力活动分别以Acti Graph GT3X型加速度计和家长问卷进行测量。受试儿童住所周围道路总长度及住所至最近康乐设施的距离以GIS(Arc Map 10.0)测量。受试儿童被分为长道路组(住所周围道路总长度≥50百分位)与短道路组(住所周围道路总长度<50百分位),及近设施组(住所至最近康乐设施的距离≤50百分位)与远设施组(住所至最近康乐设施的距离>50百分位)。各组间(长道路组vs.短道路组;近设施组vs.远设施组)的体力活动时间差异以单因素协方差分析比较,同时控制受试儿童性别、年龄、身体质量指数(BMI)及母亲受教育水平。结果:加速度计测量的数据显示,男生无论在上学日还是周末日均比女生活跃。在控制受试儿童性别、年龄、BMI及母亲受教育水平后,单因素协方差分析显示相对于远设施组儿童,近设施组儿童参与中高强度体力活动时间较长(126.8±34.4 vs.113.6±27.1分钟/天,P<0.05);而两组间问卷报告的体力活动无差异。长道路组与短道路组间加速度计及问卷测量的体力活动均未见差异。结论:本研究初步证实,住所附近康乐设施对香港儿童的体力活动具有积极影响。今后的研究应纳入更具代表性的样本及更多的建成环境指标,以获得城市建成环境与儿童体力活动关系的更有力证据。     

Quantifying Intracranial Aneurysm Wall Permeability for Risk Assessment Using Dynamic Contrast-Enhanced MRI: A Pilot Study

BACKGROUND AND PURPOSE:Pathological changes in the intracranial aneurysm wall may lead to increases in its permeability; however the clinical significance of such changes has not been explored. The purpose of this pilot study was to quantify intracranial aneurysm wall permeability (K^trans, V_L) to contrast agent as a measure of aneurysm rupture risk and compare these parameters against other established measures of rupture risk. We hypothesized K^trans would be associated with intracranial aneurysm rupture risk as defined by various anatomic, imaging, and clinical risk factors.MATERIALS AND METHODS:Twenty-seven unruptured intracranial aneurysms in 23 patients were imaged with dynamic contrast-enhanced MR imaging, and wall permeability parameters (K^trans, V_L) were measured in regions adjacent to the aneurysm wall and along the paired control MCA by 2 blinded observers. K^trans and V_L were evaluated as markers of rupture risk by comparing them against established clinical (symptomatic lesions) and anatomic (size, location, morphology, multiplicity) risk metrics.RESULTS:Interobserver agreement was strong as shown in regression analysis (R² > 0.84) and intraclass correlation (intraclass correlation coefficient >0.92), indicating that the K^trans can be reliably assessed clinically. All intracranial aneurysms had a pronounced increase in wall permeability compared with the paired healthy MCA (P < .001). Regression analysis demonstrated a significant trend toward an increased K^trans with increasing aneurysm size (P < .001). Logistic regression showed that K^trans also predicted risk in anatomic (P = .02) and combined anatomic/clinical (P = .03) groups independent of size.CONCLUSIONS:We report the first evidence of dynamic contrast-enhanced MR imaging–modeled contrast permeability in intracranial aneurysms. We found that contrast agent permeability across the aneurysm wall correlated significantly with both aneurysm size and size-independent anatomic risk factors. In addition, K^trans was a significant and size-independent predictor of morphologically and clinically defined high-risk aneurysms.

Intracranial aneurysms (IAs) affect 2%–6% of the population, with nearly 30,000 Americans having an aneurysm rupture each year.¹ Aneurysmal subarachnoid hemorrhage has an approximate 50% mortality, with survivors incurring a tremendous personal and financial burden due to permanent disabilities. Despite the potential devastating effects of IAs, the universal treatment of unruptured IAs still remains controversial. The largest prospective study to date on unruptured IAs, the International Study of Unruptured Intracranial Aneurysms (ISUIA), indicated lower rupture rates than previously suspected.² However, multiple subsequent reports challenged these findings,^3,4 thus further complicating management decisions. The exact pathogenesis and pathoevolution of IAs is largely unknown, with only a fraction of IAs progressing to rupture annually (<2%), suggesting potential differences in the pathobiology of ruptured-versus-unruptured IAs. Aneurysm risk stratification has been attempted by identifying specific characteristics of ruptured IAs, including size, location, and morphologic factors (eg, irregular contour⁵ and daughter sacs⁶), but also clinical factors, such as symptomatic lesions, hypertension, smoking, alcohol/drug abuse, and genetic predispositions to aneurysm formation/rupture. However, without absolute risk-stratification parameters for unruptured IAs, patients and physicians encounter difficult management decisions regarding the risk-benefit analysis for treatment. Aneurysm size measured by CTA, MRA, or DSA is the primary imaging marker of rupture risk and is used for clinical decisions to either treat with coil embolization/microsurgical clipping or offer conservative management with routine imaging follow-up evaluations and clinical risk-factor control.The pathobiology of IAs and alterations in the aneurysm wall have been shown to involve a multitude of histopathologic changes, such as disruption of the internal elastic lamina, smooth-muscle cell migration, and myointimal hyperplasia leading to irregular surfaces with variable thickness. In fact, direct inspection of the IA wall during surgery has demonstrated heterogeneous features, such as thin translucent regions,⁷ but these are not resolved with noninvasive imaging. Noninvasive CT or MR imaging of the morphologic phenotype of the aneurysm wall may be useful in assessing IA stability. It is plausible, given the aforementioned changes in IA wall histology, specifically apoptosis of endothelial cells, loss of collagen, and remodeling of the extracellular matrix, that contrast agents could extravasate or permeate these compromised areas into the surrounding CSF. This may be interpreted as a macroscopic manifestation of microscopic tracer permeability, which occurs through the capillary bed into tissue. The contrast agent permeability rate (K^trans) could then provide a surrogate measure of vessel wall integrity and focal degradation resulting from environmental factors such as hemodynamic stresses, typically assessed with advanced MR imaging acquisitions⁸ and postprocessing algorithms.⁹The purpose of this work was to determine the feasibility of quantifying aneurysm wall permeability by using widely available dynamic contrast-enhanced (DCE)–MR imaging. Our goal was to develop an adjunctive imaging metric to complement existing anatomic and developing flow-based imaging markers of aneurysm risk (size, location, morphology, computational/4D flow dynamics). We report the results of a prospective pilot study comparing aneurysm wall permeability by using DCE–MR imaging with anatomic and clinical metrics that predispose IAs to rupture. We hypothesized that increased IA wall permeability may be associated with IA size, location, morphology, and multiplicity and clinically defined high-risk or symptomatic lesions.     

Molecularly Targeted Therapy Using Bevacizumab for Non-Small Cell Lung Cancer: a Pilot Study for the New CT Response Criteria

Objective

We wanted to compare the efficacy of the new CT response evaluation criteria for predicting the tumor progression-free survival (PFS) with that of RECIST 1.1 in non-small cell lung cancer (NSCLC) patients who were treated with bevacizumab.

Materials and Methods

Sixteen patients (M:F = 11:5; median age, 57 years) treated with bevacizumab and combined cytotoxic chemotherapeutic agents were selected for a retrospective analysis. The tumor response was assessed by four different methods, namely, by using RECIST 1.1 (RECIST), RECIST but measuring only the solid component of tumor (RECISTsolid), the alternative method reflecting tumor cavitation (the alternative method) and the combined criteria (the combined criteria) that evaluated both the changes of tumor size and attenuation. To evaluate the capabilities of the different measurement methods to predict the patient prognosis, the PFS were compared, using the log rank test, among the responder groups (complete response [CR], partial response [PR], stable disease [SD] and progressive disease [PD]) in terms of the four different methods.

Results

The overall (CR, PR or SD) response rates according to RECIST, RECISTsolid, the alternative method and the combined criteria were 81%, 88%, 81% and 85%, respectively. The confirmed response rates (CR or PR) were 19%, 19%, 50% and 54%, respectively. Although statistically not significant, the alternative method showed the biggest difference for predicting PFS among the three response groups (PR, SD and PD) (p = 0.07). RECIST and the alternative method showed a significant difference for predicting the prognosis between the good (PR or SD) and poor overall responders (p = 0.02).

Conclusion

The response outcome evaluations using the three different CT response criteria that reflect tumor cavitation, the ground-glass opacity component and the attenuation changes in NSCLC patients treated with bevacizumab showed different results from that with using the traditional RECIST method.     

A New Porcine Sponge Material for Temporary Embolization: An Experimental Short-Term Pilot Study in Swine

Purpose To evaluate the safety and efficacy of a porcine-derived gelfoam, Curaspon, for the temporary occlusion of the visceral arteries. Methods Curaspon was used for the selective embolization of segmentary hepatic, unilateral polar renal, and single lumbar arteries of 10 pigs under general anesthesia. Sequential angiographic checks were carried out and the pigs killed between 3 days and 2 weeks later. Macroscopic and microscopic studies using standard techniques were used to evaluate the immediate efficacy of embolization, duration of and completeness of recanalization on angiography, macroscopic appearance of target-organ ischemia, and microscopic analysis of inflammatory reaction. Results Immediate arterial occlusion was obtained in all cases. Renal arteries showed a total recanalization in 63% of cases on day 7 and 100% on day 14. Total hepatic recanalization was obtained in 100% of animals on day 7. All lumbar arteries were recanalized on day 14. Microscopic analysis in the kidney revealed a mild inflammatory reaction and a progressive lysis of the Curaspon (87% of samples at day 3 showed a persistence of Curaspon and 5% at day 14). In some cases, localized and partial destruction of the arterial wall was visualized. In the liver the same patterns were observed but resolved more completely and more rapidly. Conclusions Curaspon is an efficient material for the temporary occlusion of visceral and parietal arteries in pigs. However, arterial aneurysms were observed and a relationship of these with the material cannot be excluded.     

Dynamic Angiography and Perfusion Imaging Using Flat Detector CT in the Angiography Suite: A Pilot Study in Patients with Acute Middle Cerebral Artery Occlusions

BACKGROUND AND PURPOSE:Perfusion and angiographic imaging using intravenous contrast application to evaluate stroke patients is now technically feasible by flat detector CT performed by the angiographic system. The aim of this pilot study was to show the feasibility and qualitative comparability of a novel flat detector CT dynamic perfusion and angiographic imaging protocol in comparison with a multimodal stroke MR imaging protocol.MATERIALS AND METHODS:In 12 patients with acute stroke, MR imaging and the novel flat detector CT protocol were performed before endovascular treatment. Perfusion parameter maps (MTT, TTP, CBV, CBF) and MIP/volume-rendering technique images obtained by using both modalities (MR imaging and flat detector CT) were compared.RESULTS:Comparison of MIP/volume-rendering technique images demonstrated equivalent visibility of the occlusion site. Qualitative comparison of perfusion parameter maps by using ASPECTS revealed high Pearson correlation coefficients for parameters CBF, MTT, and TTP (0.95–0.98), while for CBV, the coefficient was lower (0.49).CONCLUSIONS:We have shown the feasibility of a novel dynamic flat detector CT perfusion and angiographic protocol for the diagnosis and triage of patients with acute ischemic stroke. In a qualitative comparison, the parameter maps and MIP/volume-rendering technique images compared well with MR imaging. In our opinion, this flat detector CT application may substitute for multisection CT imaging in selected patients with acute stroke so that in the future, patients with acute stroke may be directly referred to the angiography suite, thereby avoiding transportation and saving time.

Flat detector CT (FD-CT) equipped angiographic systems are now widely used in neurointerventional institutions. Recently, an application to perform imaging of the brain parenchyma (FD-CT), cerebral vasculature (flat detector CT dynamic perfusion and angiographic imaging [FD-CTA]), and cerebral blood volume has been described and was evaluated in patients with acute middle cerebral artery occlusions.^1–3 However, this application was limited due to the inferior FD-CT soft-tissue resolution of the brain parenchyma in comparison with multisection CT (MS-CT) or MR imaging. Additionally, there was a lack of temporal resolution so that calculation of dynamic (time-dependent) perfusion parameters was not possible.Assessment of the impact of an ischemic stroke is best performed with physiologic criteria because especially in the acute phase, morphologic changes are only minimal and may be difficult to recognize by using MS-CT imaging.⁴ The use of perfusion and angiographic imaging increases the sensitivity of MS-CT and MR imaging in the acute phase of ischemic stroke. Thus, MS-CT angiography and MS-CT perfusion imaging are used to assess patients within a 0- to 4.5-hour time window of ischemic stroke. On the basis of the mismatch concept beyond 4.5 hours, multimodal MR imaging by using FLAIR, MR angiography, diffusion-weighted, and MR perfusion imaging (MRP) is used in many centers to identify patients eligible for recanalization therapies.⁵ MS-CT and MR imaging applications allow visualization of brain parenchyma and vessel occlusion (MS-CT angiography, MRA); and calculation of the dynamic perfusion parameter maps (time-to-peak, mean transit time, cerebral blood flow, and cerebral blood volume) to assess the viability of the brain.^6–9 The ability to obtain dynamic perfusion maps (FD-CTP) and angiographic images by using an intravenous contrast application within the angiography suite would seem to create a single ideal venue for both diagnosis and treatment of patients with an acute ischemic stroke. A FD-CT application replacing MS-CT or MR imaging would optimize the work flow, avoid transportation of the patient from one imaging location to the other, save time, and may allow periodic monitoring of brain viability during the endovascular treatment.To date, dynamic perfusion imaging with the C-arm angiographic system has been limited by the slow gantry rotation time. However, recent studies in canines and swine models have now demonstrated the feasibility of dynamic perfusion imaging with the use of a flat detector angiographic system.^10–12 The aim of this pilot study was to test the feasibility of this novel application by comparing FD-CTP and FD-CTA with a multimodal MR imaging protocol in patients with acute ischemic stroke. Additionally, the effective patient dose was evaluated.     

Variation in Anisotropy and Diffusivity along the Medulla Oblongata and the Whole Spinal Cord in Adolescent Idiopathic Scoliosis: A Pilot Study Using Diffusion Tensor Imaging

BACKGROUND AND PURPOSE:Disturbed somatosensory evoked potentials have been demonstrated in patients with adolescent idiopathic scoliosis (but this functional delay was found to originate above the C5–6 level, while the lower cord level was unaffected). Together with MR imaging observation of tonsillar ectopia and a relatively tethered cord, we hypothesized that there is disturbed mean diffusivity integrity along the spinal cord. In this study, advanced DTI was used to evaluate whether there was underlying decreased WM integrity within the brain stem and spinal cord in adolescent idiopathic scoliosis and any relationship to cerebellar tonsillar ectopia. Clinical impact on balance testing was also correlated.MATERIALS AND METHODS:Thirteen girls with adolescent idiopathic scoliosis with right thoracic curves were compared with 13 age-matched healthy girls. DTI of the brain and whole spinal cord was performed. ROIs were manually defined for the medulla oblongata and along each intervertebral segment of the cord. Mean values of fractional anisotropy and mean diffusivity were computed at the defined regions. Between-group comparisons were performed by 1-way ANOVA.RESULTS:Significantly decreased fractional anisotropy values and increased mean diffusivity values were found at the medulla oblongata and C1–2, C2–3, C3–4, and C4–5 segments in patients with adolescent idiopathic scoliosis compared with healthy subjects. No significant difference was found in the lower cord levels. Significant correlation was found between the tonsillar level and fractional anisotropy value at the C4–5 level in patients with adolescent idiopathic scoliosis only.CONCLUSIONS:The findings from this study are in agreement with previous findings showing abnormal somatosensory evoked potential readings occurring only above the C5–6 level in patients with adolescent idiopathic scoliosis; these findings might partially explain the pathophysiology of the neural pathway involved.

Adolescent idiopathic scoliosis (AIS) is a complex 3D deformity of the spine that affects approximately 4% of school children worldwide.¹ Despite intensive research in the past decades, the pathophysiology of AIS remains uncertain.² There is, however, growing evidence suggesting that an underlying neurologic disorder may be a causative factor of AIS.³ Previous studies have reported changes in central nervous system structures in patients with AIS based on advanced medical imaging modalities.^4–6 Furthermore in a number of MR imaging studies, the observable changes in morphologic shape and position of the cord,⁷ mismatch in lengthening between the cord and vertebral column,⁸ and increased incidence of low-lying cerebellar tonsils⁹ have led to the postulation of the presence of subclinical tethering of the spinal cord in AIS.¹⁰The proposed disturbed spinal cord function in AIS was further supported by the clinical observation of abnormal somatosensory function, which has been widely reported in this group. Prolonged latency or absent waveforms in posterior tibial nerve somatosensory evoked potentials (SEPs) were reported in 12%–61% of patients with scoliosis in different series.^8,11–13 A previous study also suggested that balance control was affected by somatosensory input.¹⁴ In the study by Cheng et al,¹⁵ 14.6% of patients with AIS had abnormal SEPs with either prolonged latency or decreased amplitude, while tonsillar ectopia was found in 33.3% of those with abnormal SEPs. A subsequent study with detailed analysis of SEPs recorded at 3 different levels (popliteal fossa, cervical level C4–6, and the scalp) showed that in patients with AIS with abnormal SEPs, the readings were only abnormal at the scalp level, while the readings at the popliteal and cervical regions were normal, indicating that the level of abnormality along the somatosensory pathway was superior to that at the cervical C5–6 level.¹⁶DTI is a recent advanced imaging technique to evaluate WM architecture within the brain and spinal cord in vivo.¹⁷ This technique can detect the microstructural changes of the WM and is presently a promising tool to study WM fiber bundles in vivo. In recent years, the advanced technique has been increasingly used to examine the spinal cord parenchyma for multiple diseases, including myelitis, spinal cord injury,¹⁸ multiple sclerosis,¹⁹ and intramedullary spinal cord neoplasms.²⁰ On the basis of the observation of tonsillar ectopia, relatively tethered cord, and abnormal SEP, we hypothesized that there is disturbed WM integrity within the brain stem and the spinal cord, most likely at the more cranial level as indicated by the level of SEP abnormality in the previous study.¹⁶ The disturbed WM integrity is likely reflecting underlying cord abnormality in patients with AIS in addition to their skeletal abnormality. We sought to prove the above hypothesis by evaluating the fractional anisotropy (FA) and mean diffusivity (MD) values of the spinal cord and correlating them with the position of cerebellar tonsils and balance testing.     

The Effect of Faster Reporting Speed for Imaging Studies on the Number of Misses and Interpretation Errors: A Pilot Study

PurposeThe purpose of the study was to determine if increasing radiologist reading speed results in more misses and interpretation errors.MethodsWe selected a sample set of 53 abdomen-pelvis CT scans of variable complexity performed at a teaching hospital during the study period. We classified the CT scans into 4 categories based on their level of difficulty, with level 4 representing the most-complex cases. Five attending radiologists participated in the study. We initially established an average baseline reporting time for each radiologist. Radiologists were randomly assigned a set of 12 studies, of varying complexity, to dictate at their normal speed, and a separate set of 12 studies, of similar complexity, to read at a speed that was twice as fast as their normal speed. The major and minor misses were recorded and analyzed. A χ² analysis was used to compare the results.ResultsReading at the faster speed resulted in more major misses for 4 of the 5 radiologists. The total number of major misses for the 5 radiologists, when they reported at the faster speed, was 16 of 60 reported cases, versus 6 of 60 reported cases at normal speed; P = .032. The average interpretation error rate of major misses among the 5 radiologists reporting at the faster speed was 26.6%, compared with 10% at normal speed.ConclusionsOur pilot study found a significant positive correlation between faster reading speed and the number of major misses and interpretation errors.     

Comparison of Simulation-based Treatment Planning with Imaging and Pathology Outcomes for Percutaneous CT-guided Irreversible Electroporation of the Porcine Pancreas: A Pilot Study

PurposeTo investigate the reliability of simulations for planning pancreatic irreversible electroporation (IRE) ablations compared with computed tomography (CT) and pathology outcomes in an animal model.Materials and MethodsSimulations were performed varying treatment parameters, including field strength (1.5–2.5 kV/cm), pulse number (70–90 pulses), and pulse length (70–100 µs). Pancreatic IRE was performed in six pigs under CT guidance. Two animals each were sacrificed for histology after 1 day, 14 days, and 28 days. Follow-up CT scans were performed on day 0, day 1, day 14, and day 28. Biochemical markers were collected before the procedure, 1 day after the procedure, and 14 days after the procedure.ResultsAll ablation zones could be visualized on CT scan immediately after the procedure and on day 1 follow-up CT scan, and all animals survived until the designated endpoints. Histopathology revealed necrosis and edema on day 1 and fibrosis and glandular atrophy after 28 days. Blood vessels close to the ablation zone appeared normal. Laboratory analysis indicated mild to moderate amylasemia and lipasemia with normalization after 14 days. The ablation size on CT scan measured a mean (± SD) 146% ± 18 (day 0, P < .126) and 168% ± 18 (day 1, P < .026) of the simulation and on pathology measured 119% ± 10 (day 1, not significant) of the simulation.ConclusionsResults from simulations for planning IRE ablations, CT, and pathology may differ from each other. Ablation zones on CT and pathology appear larger than simulated, suggesting that clinically used treatment planning may underestimate the ablation size in the pancreas.     

A New Device for Vascular Embolization: Report on Case of Two Pulmonary Arteriovenous Fistulas Embolization Using the Amplatzer Vascular Plug

A pulmonary arteriovenous fistula (PAVF) is a rare vascular malformation commonly treated by embolization with coils or balloons to prevent the risk of several serious complications such as cerebral embolism and brain abscess. A 32-year-old female with two PAVFs and neurological ischemic manifestations has been successfully treated by transcatheter embolization of both fistulas using a new device (Amplatzer Vascular Plug). This self-expanding cylindrical nitinol mesh cage with high radial strength allows a chance of relocation until properly positioned. It is preferred to coils or balloons because a large caliber of feeding artery implied high risk of uncontrollable distal embolization. There appear to be no reports in the literature concerning use of this device, which could represent a useful innovative tool in embolotherapies, especially in large vascular areas.     

Deep Learning Algorithm for Simultaneous Noise Reduction and Edge Sharpening in Low-Dose CT Images: A Pilot Study Using Lumbar Spine CT

ObjectiveThe purpose of this study was to assess whether a deep learning (DL) algorithm could enable simultaneous noise reduction and edge sharpening in low-dose lumbar spine CT.Materials and MethodsThis retrospective study included 52 patients (26 male and 26 female; median age, 60.5 years) who had undergone CT-guided lumbar bone biopsy between October 2015 and April 2020. Initial 100-mAs survey images and 50-mAs intraprocedural images were reconstructed by filtered back projection. Denoising was performed using a vendor-agnostic DL model (ClariCT.AI™, ClariPI) for the 50-mAS images, and the 50-mAs, denoised 50-mAs, and 100-mAs CT images were compared. Noise, signal-to-noise ratio (SNR), and edge rise distance (ERD) for image sharpness were measured. The data were summarized as the mean ± standard deviation for these parameters. Two musculoskeletal radiologists assessed the visibility of the normal anatomical structures.ResultsNoise was lower in the denoised 50-mAs images (36.38 ± 7.03 Hounsfield unit [HU]) than the 50-mAs (93.33 ± 25.36 HU) and 100-mAs (63.33 ± 16.09 HU) images (p < 0.001). The SNRs for the images in descending order were as follows: denoised 50-mAs (1.46 ± 0.54), 100-mAs (0.99 ± 0.34), and 50-mAs (0.58 ± 0.18) images (p < 0.001). The denoised 50-mAs images had better edge sharpness than the 100-mAs images at the vertebral body (ERD; 0.94 ± 0.2 mm vs. 1.05 ± 0.24 mm, p = 0.036) and the psoas (ERD; 0.42 ± 0.09 mm vs. 0.50 ± 0.12 mm, p = 0.002). The denoised 50-mAs images significantly improved the visualization of the normal anatomical structures (p < 0.001).ConclusionDL-based reconstruction may enable simultaneous noise reduction and improvement in image quality with the preservation of edge sharpness on low-dose lumbar spine CT. Investigations on further radiation dose reduction and the clinical applicability of this technique are warranted.     

Optimal Pulse Sequence for Ferumoxides-Enhanced MR Imaging Used in the Detection of Hepatocellular Carcinoma: A Comparative Study Using Seven Pulse Sequences

Objective

To identify the optimal pulse sequence for ferumoxides-enhanced magnetic resonance (MR) imaging in the detection of hepatocelluar carcinomas (HCCs).

Materials and Methods

Sixteen patients with 25 HCCs underwent MR imaging following intravenous infusion of ferumoxides. All MR studies were performed on a 1.5-T MR system, using a phased-array coil. Ferumoxides (Feridex IV) at a dose of 15 µmol/Kg was slowly infused intravenously, and axial images of seven sequences were obtained 30 minutes after the end of infusion. The MR protocol included fast spin-echo (FSE) with two echo times (TR3333 8571/TE18 and 90-117), singleshot FSE (SSFSE) with two echo times (TR∞/TE39 and 98), T2*-weighted gradient-recalled acquisition in the steady state (GRASS) (TR216/TE20), T2*-weighted fast multiplanar GRASS (FMPGR) (TR130/TE8.4-9.5), and T2*-weighted fast multiplanar spoiled GRASS (FMPSPGR) (TR130/TE8.4-9.5). Contrast-to-noise ratios (CNRs) of HCCs determined during the imaging sequences formed the basis of quantitative analysis, and images were qualitatively assessed in terms of lesion conspicuity and image artifacts. The diagnostic accuracy of all sequences was assessed using receiver operating characteristic (ROC) analysis.

Results

Quantitative analysis revealed that the CNRs of T2*-weighted FMPGR and T2*-weighted FMPSPGR were significantly higher than those of the other sequences, while qualitative analysis showed that image artifacts were prominent at T2*-weighted GRASS imaging. Lesion conspicuity was statistically significantly less clear at SSFSE imaging. In term of lesion detection, T2*-weighted FMPGR, T2*-weighted FMPSPGR, and proton density FSE imaging were statistically superior to the others.

Conclusion

T2*-weighted FMPGR, T2*-weighted FMPSPGR, and proton density FSE appear to be the optimal pulse sequences for ferumoxides-enhanced MR imaging in the detection of HCCs.     

CT Fractional Flow Reserve for the Diagnosis of Myocardial Bridging-Related Ischemia: A Study Using Dynamic CT Myocardial Perfusion Imaging as a Reference Standard

ObjectiveTo investigate the diagnostic performance of CT fractional flow reserve (CT-FFR) for myocardial bridging-related ischemia using dynamic CT myocardial perfusion imaging (CT-MPI) as a reference standard.Materials and MethodsDynamic CT-MPI and coronary CT angiography (CCTA) data obtained from 498 symptomatic patients were retrospectively reviewed. Seventy-five patients (mean age ± standard deviation, 62.7 ± 13.2 years; 48 males) who showed myocardial bridging in the left anterior descending artery without concomitant obstructive stenosis on the imaging were included. The change in CT-FFR across myocardial bridging (ΔCT-FFR, defined as the difference in CT-FFR values between the proximal and distal ends of the myocardial bridging) in different cardiac phases, as well as other anatomical parameters, were measured to evaluate their performance for diagnosing myocardial bridging-related myocardial ischemia using dynamic CT-MPI as the reference standard (myocardial blood flow < 100 mL/100 mL/min or myocardial blood flow ratio ≤ 0.8).ResultsΔCT-FFR_systolic (ΔCT-FFR calculated in the best systolic phase) was higher in patients with vs. without myocardial bridging-related myocardial ischemia (median [interquartile range], 0.12 [0.08–0.17] vs. 0.04 [0.01–0.07], p < 0.001), while CT-FFR_systolic (CT-FFR distal to the myocardial bridging calculated in the best systolic phase) was lower (0.85 [0.81–0.89] vs. 0.91 [0.88–0.96], p = 0.043). In contrast, ΔCT-FFR_diastolic (ΔCT-FFR calculated in the best diastolic phase) and CT-FFR_diastolic (CT-FFR distal to the myocardial bridging calculated in the best diastolic phase) did not differ significantly. Receiver operating characteristic curve analysis showed that ΔCT-FFR_systolic had largest area under the curve (0.822; 95% confidence interval, 0.717–0.901) for identifying myocardial bridging-related ischemia. ΔCT-FFR_systolic had the highest sensitivity (91.7%) and negative predictive value (NPV) (97.8%). ΔCT-FFR_diastolic had the highest specificity (85.7%) for diagnosing myocardial bridging-related ischemia. The positive predictive values of all CT-related parameters were low.ConclusionΔCT-FFR_systolic reliably excluded myocardial bridging-related ischemia with high sensitivity and NPV. Myocardial bridging showing positive CT-FFR results requires further evaluation.     

Ultrasound-Guided Radiofrequency Ablation Using a New Electrode with an Electromagnetic Position Sensor for Hepatic Tumors Difficult to Place an Electrode: A Preliminary Clinical Study

Purpose

To evaluate whether a new electrode embedded with an electromagnetic position sensor (EMPS) improves the technical feasibility of percutaneous radiofrequency ablation (RFA) in patients with hepatic tumors difficult to place an electrode under ultrasonography (US) guidance and to assess short-term therapeutic efficacy and safety.

Materials and Methods

This prospective study was approved by the institutional review board, and written informed consent was obtained from all patients. Between January 2015 and December 2016, 10 patients (7 men and 3 women; age range 52–75 years) with a single hepatic tumor (median 1.4 cm; range 1.1–1.8 cm) difficult to place an electrode under US guidance were enrolled. The technical feasibility of targeting and overlapping ablation during the RFA procedure was graded using a four-point scale and analyzed using the Wilcoxon signed rank test according to the use of EMPS. In addition, the rates of technical success, local tumor progression (LTP), and major complications were assessed.

Results

The use of the new RF electrode with EMPS significantly improved the technical feasibility of targeting and overlapping ablation (p = 0.002 and p = 0.003, respectively). After treatment, the technical success rate was 100%. LTP was not found in any patient during the follow-up period (median 8 months; range 4–22 months). No major procedure-related complications occurred.

Conclusions

The technical feasibility of percutaneous RFA improves with the use of this RF electrode embedded with an EMPS. Short-term therapeutic efficacy and safety after RFA using the electrode were promising in patients with hepatic tumors difficult to place an electrode under US guidance.