Computer-Aided Diagnosis of Hyperacute Stroke with Thrombolysis Decision Support Using a Contralateral Comparative Method of CT Image Analysis

New and improved techniques have been continuously introduced into CT and MR imaging modalities for the diagnosis and therapy planning of acute stroke. Nevertheless, non-contrast CT (NCCT) is almost always used by every institution as the front line diagnostic imaging modality due to its high affordability and availability. Consequently, the potential reward of extracting as much clinical information as possible from NCCT images can be very great. Intravenous tissue plasminogen activator (tPA) has become the gold standard for treating acute ischemic stroke because it is the only acute stroke intervention approved by the FDA. ASPECTS scoring based on NCCT images has been shown to be a reliable scoring method that helps physicians to make sound decisions regarding tPA administration. In order to further reduce inter-observer variation, we have developed the first end-to-end automatic ASPECTS scoring system using a novel method of contralateral comparison. Due to the self-adaptive nature of the method, our system is robust and has good generalizability. ROC analysis based on evaluation of 103 subjects who presented to the stroke center of Chang Gung Memorial Hospital with symptoms of acute stroke has shown that our system’s dichromatic classification of patients into thrombolysis indicated or thrombolysis contraindicated groups has achieved a high accuracy rate with AUC equal to 90.2 %. The average processing time for a single case is 170 s. In conclusion, our system has the potential of enhancing quality of care and providing clinical support in the setting of a busy stroke or emergency center.     

Time from hospital admission to CT brain in acute ischaemic stroke

A retrospective study of all acute ischaemic stroke patients admitted to Midland Regional Hospital Mullingar (MRHM) between January 2004 and September 2009 was undertaken in order to assess the median time from hospital admission to CT brain scan (n = 496). The median time to CT scan ranged from 19-24 hours between 2004-7. In 2008, coinciding with setting up a new Acute Stroke Service (ACSS), the median time to CT scan dropped to 15 hours (n = 130, p =0.03) and decreased further to 3 hours in 2009 (n = 125, p = 0.003). The proportion scanned within 1 hour of admission increased from 7 patients (4.6%) over 2004-7, to 28 patients (21.5%) in 2008 (p = 0) and 44 patients (35%) in 2009 (p = 0.018). This clinically and statistically significant reduction occurred following reorganisation of existing resources on a budget neutral basis at MRHM and was facilitated by the enthusiastic support of a range of disciplines bridging the community and acute hospital interface. Measurement of admission to CT brain scan time is one of several audit parameters which can assess hospitals responsiveness to acute stroke.     

原发性肝细胞癌的CT影像组学分析

目的:应用影像组学方法量化原发性肝细胞癌在CT增强扫描时“快进快出”的影像学表现。 方法:在平扫期、动脉期、门脉期上勾画肿瘤靶区（GTV）和部分正常肝脏组织,提取所勾画靶区的特征值,量化GTV以及正常肝脏组织在不同时相上影像组学特征值的差异。 结果:共提取55个特征,正常肝脏组织和GTV在平扫期与动脉期、平扫期与门脉期、动脉期与门脉期所提取的特征差异具有统计学意义的分别有7、8、22个和35、41、33个;GTV与正常肝脏组织在平扫期差异具有统计学意义的特征有49个,动脉期46个,门脉期38个;有6个特征与 “快进快出”现象有关。 结论:基于影像组学技术量化不同强化时机肝细胞癌和正常肝脏组织的特征,为追踪肝细胞癌肿瘤异质性及动态变化提供有效的手段。     

The relationship between intellectual impairment and mood disorder in the first year after stroke

In a community-based study of patients with a first-ever stroke, intellectual impairment (as defined by scores on a common screening test for dementia, the Mini-Mental State Examination) was found in 26% at 1 month post-stroke, and in 21% at 6 and 12 month follow-up. Low scores on the screening test were associated with greater age, physical disability before the stroke, larger stroke lesion volumes as measured on CT scan, and non-stroke changes such as atrophy and white matter low attenuation on the CT scan. There was a negative correlation between scores on the Mini-Mental State Examination and symptom levels on two measures of mood disorder. However, there was no evidence of a specific relationship between major depression and low scores on the Mini-Mental State. We examined various aspects of the relationship between mood symptoms and low scores on the Mini-Mental State, but found no evidence to support the suggestion that this relationship represented an example of depressive pseudodementia. We discuss the significance of our findings for clinical psychiatry and neuropsychology.     

Comparison of Two Deformable Registration Algorithms in the Presence of Radiologic Change Between Serial Lung CT Scans

We evaluated the image registration accuracy achieved using two deformable registration algorithms when radiation-induced normal tissue changes were present between serial computed tomography (CT) scans. Two thoracic CT scans were collected for each of 24 patients who underwent radiation therapy (RT) treatment for lung cancer, eight of whom experienced radiologically evident normal tissue damage between pre- and post-RT scan acquisition. For each patient, 100 landmark point pairs were manually placed in anatomically corresponding locations between each pre- and post-RT scan. Each post-RT scan was then registered to the pre-RT scan using (1) the Plastimatch demons algorithm and (2) the Fraunhofer MEVIS algorithm. The registration accuracy for each scan pair was evaluated by comparing the distance between landmark points that were manually placed in the post-RT scans and points that were automatically mapped from pre- to post-RT scans using the displacement vector fields output by the two registration algorithms. For both algorithms, the registration accuracy was significantly decreased when normal tissue damage was present in the post-RT scan. Using the Plastimatch algorithm, registration accuracy was 2.4 mm, on average, in the absence of radiation-induced damage and 4.6 mm, on average, in the presence of damage. When the Fraunhofer MEVIS algorithm was instead used, registration errors decreased to 1.3 mm, on average, in the absence of damage and 2.5 mm, on average, when damage was present. This work demonstrated that the presence of lung tissue changes introduced following RT treatment for lung cancer can significantly decrease the registration accuracy achieved using deformable registration.     

'Ready-access' CT imaging for an orthopaedic trauma clinic

'Ready-Access' to CT imaging facilities in Orthopaedic Trauma Clinics is not a standard facility. This facility has been available at the regional trauma unit, in Merlin Park Hospital, Galway for the past four years. We reviewed the use of this facility over a 2-year period when 100 patients had CT scans as part of their trauma clinic assessment. The rate of CT scan per clinic was 0.6. The mean waiting time for a CT scan was 30 minutes. 20 (20%) new fractures were confirmed, 33 (33%) fractures were out-ruled, 25 (25%) fractures demonstrated additional information and 8 (8%) had additional fractures. 20 (20%) patients were discharged and 12 (12%) patients were admitted as a result of the CT scan. It adds little time and cost to CT scanning lists.     

影像增强剂对食管癌边缘靶区剂量的影响

目的:研究调强放射治疗中使用影像增强剂后靠近心脏及胸主动脉等血流丰富组织的食管癌边缘靶区的剂量是否会降低,是否会出现欠量照射的情况。方法:选取20例食管癌患者病例,在相同体位下进行平扫及增强CT扫描,在增强CT上完成靶区勾画及调强治疗计划设计。使用两种方法进行对比,方法（1）:在增强及平扫CT上确定PTV & 5 mm Aorta和PTV & 5 mm Heart两个边缘靶区,然后进行图像配准并将治疗计划移植到平扫CT上计算剂量,对比上述两个边缘靶区在增强及平扫CT中剂量的变化。方法（2）:因为增强和平扫CT是在不同时间点扫描的,配准时两幅图像之间会存在一定差异,为了避免体位偏差的影响,使用合成CT与增强CT对比。所谓合成CT,即在复制的增强CT中将心脏、胸主动脉等血流丰富组织的CT值人工修改为平扫CT的平均CT值,操作过程与方法（1）相同,仍然观察上述两个边缘靶区的剂量变化。实验中也对比了其它组织器官在平扫与增强CT中剂量的变化。结果:方法（1）和方法（2）均显示PTV & 5 mm Aorta和PTV & 5 mm Heart两个边缘靶区剂量有所增加,其中方法（1）中两个边缘靶区的剂量分别增加1.28%（P<0.01）和1.64%（P<0.01）,方法（2）中分别增加0.41%（P<0.01）和0.83%（P<0.01）;正常组织器官（心脏、肺、脊髓等）剂量也有所增加,但均在临床可接受范围以内。结论:使用影像增强剂后靠近心脏及胸主动脉等血流丰富组织的食管癌边缘靶区剂量有所增加,不会出现欠量照射情况。     

Acute stroke care in an Irish general hospital

A majority of in-patients with acute stroke in Ireland are cared for by general physicians. We studied the process of care and outcomes of stroke patients admitted to an acute general hospital in a rural setting. Ninety-five patients (55 males and 40 females) were admitted over 36 weeks. A majority of patients had a CT brain scan (97%) and were assessed by the multidisciplinary team (59-70%). The mean length of stay was 16.6 days. In patient mortality was 18.9%. The commonest discharge destination was to the Medical Rehabilitation Unit (44%). A high prevalence of cardiovascular risk factors was identified indicating significant potential for secondary prevention.     

鼻部外伤中X线侧位片与CT冠状和横断扫描的应用对比

目的通过三种影像学方法的研究,确定合理的鼻部外伤影像学检查方法。方法对106例鼻部外伤者同时作X线鼻骨侧位像、冠状和横断CT扫描。以冠状 横断CT扫描的结果为准,比较了各种检查方法之间对鼻部外伤影像学征象的检出率。结果两种CT扫描合用的诊断效果最好。X线鼻骨侧位片仅能检出70.76%的鼻骨骨折,对上颌骨骨折等其他鼻部外伤均不能诊断。在鼻骨或/和上颌骨额突骨折的诊断中冠状CT扫描均显著优于横断CT扫描,而在鼻泪管骨折、骨颌缝分离、鼻骨间缝增宽的诊断上则横断CT扫描均要显著优于冠状CT扫描。结论在鼻部外伤的影像学检查中仅作鼻骨X线侧位片是不够的;为了解有无鼻骨/或上颌骨突骨折应首先作鼻部冠状CT扫描,如经济条件许可,可加作鼻骨横断扫描。     

Radiation exposure in body computed tomography examinations of trauma patients

Multi-slice CT provides an efficient imaging modality for trauma imaging. The purpose of this study was to provide absorbed and effective dose data from CT taking into account the patient size and compare such doses with the standard CT dose quantities based on standard geometry. The CT examination data from abdominal and thoracic scan series were collected from 36 trauma patients. The CTDI(vol), DLP(w) and effective dose were determined, and the influence of patient size was applied as a correction factor to calculated doses. The patient size was estimated from the patient weight as the effective radius based on the analysis from the axial images of abdominal and thoracic regions. The calculated mean CTDI(vol), DLP(w) and effective dose were 15.2 mGy, 431 mGy cm and 6.5 mSv for the thorax scan, and 18.5 mGy, 893 mGy cm and 14.8 mSv for the abdomen scan, respectively. The doses in the thorax and abdomen scans taking the patient size into account were 34% and 9% larger than the standard dose quantities, respectively. The use of patient size in dose estimation is recommended in order to provide realistic data for evaluation of the radiation exposure in CT, especially for paediatric patients and smaller adults.     

Effect of motion on tracer activity determination in CT attenuation corrected PET images: a lung phantom study

Respiratory motion is known to affect the quantitation of 18FDG uptake in lung lesions. The aim of the study was to investigate the magnitude of errors in tracer activity determination due to motion, and its dependence upon CT attenuation at different phases of the motion cycle. To estimate these errors we have compared maximum activity concentrations determined from PET/CT images of a lung phantom at rest and under simulated respiratory motion. The NEMA 2001 IEC body phantom, containing six hollow spheres with diameters 37, 28, 22, 17, 13, and 10 mm, was used in this study. To mimic lung tissue density, the phantom (excluding spheres) was filled with low density polystyrene beads and water. The phantom spheres were filled with 18FDG solution setting the target-to-background activity concentration ratio at 8:1. PET/CT data were acquired with the phantom at rest, and while it was undergoing periodic motion along the longitudinal axis of the scanner with a range of displacement being 2 cm, and a period of 5 s. The phantom at rest and in motion was scanned using manufacturer provided standard helical/clinical protocol, a helical CT scan followed by a PET emission scan. The moving phantom was also scanned using a 4D-CT protocol that provides volume image sets at different phases of the motion cycle. To estimate the effect of motion on quantitation of activities in six spheres, we have examined the activity concentration data for (a) the stationary phantom, (b) the phantom undergoing simulated respiratory motion, and (c) a moving phantom acquired with PET/4D-CT protocol in which attenuation correction was performed with CT images acquired at different phases of motion cycle. The data for the phantom at rest and in motion acquired with the standard helical/clinical protocol showed that the activity concentration in the spheres can be underestimated by as much as 75%, depending on the sphere diameter. We have also demonstrated that fluctuations in sphere's activity concentration from one PET/CT scan to another acquired with standard helical/clinical protocol can arise as a consequence of spatial mismatch between the sphere's location in PET emission and the CT data.     

Shading correction algorithm for improvement of cone-beam CT images in radiotherapy

Cone-beam CT (CBCT) images have recently become an established modality for treatment verification in radiotherapy. However, identification of soft-tissue structures and the calculation of dose distributions based on CBCT images is often obstructed by image artefacts and poor consistency of density calibration. A robust method for voxel-by-voxel enhancement of CBCT images using a priori knowledge from the planning CT scan has been developed and implemented. CBCT scans were enhanced using a low spatial frequency grey scale shading function generated with the aid of a planning CT scan from the same patient. This circumvents the need for exact correspondence between CBCT and CT and the process is robust to the appearance of unshared features such as gas pockets. Enhancement was validated using patient CBCT images. CT numbers in regions of fat and muscle tissue in the processed CBCT were both within 1% of the values in the planning CT, as opposed to 10-20% different for the original CBCT. Visual assessment of processed CBCT images showed improvement in soft-tissue visibility, although some cases of artefact introduction were observed.     

肺癌侵犯肺动脉干19例

目的 观察肺癌侵犯肺动脉干的病理解剖,ＣＴ征象,为手术提供参考。方法 对１９例肺癌侵犯肺动脉干的切除标本进行病理解剖。与术前ＣＴ比较。结果 肿瘤包绕肺动脉全周８例,部分包绕１１例。肿瘤侵犯以管壁外膜和中膜为主,尤其局限在中膜的外弹性膜周围,内膜未受侵。管壁炎性浸润,水肿或肉芽及结缔组织增生突出。ＣＴ表现管周脂肪异常１０例,肿块与肺动脉干肾密相贴或包绕１６例,压迫及移位２例,低肺血流灌注３例。     

Mood disorders in long-term survivors of stroke: associations with brain lesion location and volume

Sixty surviving patients from a community-based stroke register who had CT scan evidence of a single brain lesion and neurological signs appropriate to it were interviewed three to five years following their first-ever stroke. Mood disorder (anxiety and depression), physical disability, and intellectual impairment were assessed using standardized measures. The position and volume of the brain lesion was determined from CT scans performed soon after the stroke. The prevalence of depressive disorder was lower in this sample than that reported in previous studies (DSM-IIIR major depression 8.3%; all DSM-IIIR depressive disorders 18.3%). Reports by other workers for an association of depressive disorder either with left-sided brain lesions, or with anteriorly placed lesions in the left cerebral hemisphere, were not supported. Neither was there evidence of a correlation between symptom score and proximity of the lesion to the anterior pole of the left cerebral hemisphere. Psychiatric symptom scores were however greater with larger volume brain lesions. Anxiety disorders, especially agoraphobia, were relatively common (20% if diagnosed in the presence of depressive disorder), but were not related to lesion location or volume.     

Comparison of two techniques for measurement of visceral adipose tissue cross‐sectional areas by computed tomography

Most computed tomography (CT) scanners used today are able to accurately measure adipose tissue (AT) areas at any site of the body. However, first generation CT scanners used by some medical centers are not equipped with appropriate software allowing the measurements of AT areas. The aim of this study was to validate a technique of AT area measurements independent from CT scanner software. Abdominal AT areas were recorded with CT in a sample of 30 men. Areas were thereafter calculated using the standard CT software technique. Total and visceral AT areas were then remeasured using another technique for which X‐ray film of each subject's scan was analysed by a system completely independent from the CT scanner (imaging densitometer and NIH image analysis software). Correlations between measurements obtained with the two techniques were very strong for both total (n = 0.99; SEE = 11.7 cm²) and visceral AT areas (r = 0.99; SEE = 5.3 cm²). Values obtained with the image analysis method were generally higher than with the conventional CT software technique (cross‐sectional areas of AT were overestimated by 4.7% for total abdominal and 8.5% for visceral AT respectively). In conclusion, the results indicate that measurements obtained with this image analysis technique would be adequate to correctly rank subjects according to levels of total or visceral AT areas. However, since this method appears to slightly overestimate AT areas, a standardized correction should be performed before comparing subjects with AT areas measured with this technique to subjects whose AT areas have been obtained with the conventional CT software technique. Am. J. Hum. Biol. 11:61–68, 1999. © 1999 Wiley‐Liss, Inc.     

Brain lesions in eclampsia: A series of 39 cases admitted in an Intensive Care Unit

The aim of this study was to identify the encephalic lesions in the eclampsia occurrences. Within a period of 18 months, computed tomography (CT) of the brain was performed in all patients admitted in intensive care for eclampsia. These CTs were analyzed and intracerebral lesions were identified. Thirty-nine patients were included. We noted 10 cases of ischemic stroke, 9 cases of cerebral edema, and 3 cases of hemorrhagic stroke and subarachnoid hemorrhage. The CT scan came back to normal in 20 eclamptic patients. Overall, delays in obstetric and intensive care and time of completion of the CT were long. CT has allowed highlighting in patients with eclampsia varied intracerebral lesions. The early performance of the CT is therefore essential for a better support of patients.     

Life events and social support in prediction of stroke outcome

A prospective study of 252 patients (average age 73, range 26-95) admitted to a regional general hospital over a 12-month period was carried out. 241 patients had stroke verified by the initial neurological examination and CT scan, and of these baseline data were not available on 27%. 34% died before or were not willing or able to provide data at follow-up. 39% survived and completed the study. Prestroke life events and social support could not predict the outcome of stroke rehabilitation measured as survival, length of stay, functional recovery (Barthel's Index) or placement at the follow-up 12 months after the onset of stroke. Age and arteriosclerotic heart disease predicted poor survival at follow-up. Premorbid hypertension, stroke, diabetes, obesity, tobacco smoking, and alcohol consumption did not significantly influence the outcome. Problems in stroke rehabilitation research are discussed.     

Influence of z overscanning on normalized effective doses calculated for pediatric patients undergoing multidetector CT examinations

The purpose of this study was to evaluate the effect of z overscanning on normalized effective dose for pediatric patients undergoing multidetector-computed tomography (CT) examinations. Five commercially available mathematical anthropomorphic phantoms representing newborn, 1-, 5-, 10-, and 15-year-old patients and the Monte Carlo N-Particle (MCNP, version 4C2) radiation transport code were employed in the current study to simulate pediatric CT exposures. For all phantoms, axial and helical examinations at 120 kV tube voltage were simulated. Scans performed at 80 kV were also simulated. Sex-specific normalized effective doses were estimated for four standard CT examinations i.e., head-neck, chest, abdomen-pelvis, and trunk, for all pediatric phantoms. Data for both axial and helical mode acquisition were obtained. In the helical mode, z overscanning was taken into account. The validity of the Monte Carlo results was verified by comparison with dose data obtained using thermoluminescence dosimetry and a physical pediatric anthropomorphic phantom simulating a 10-year-old child. In all cases normalized effective dose values were found to increase with increasing z overscanning. The percentage differences in normalized data between axial and helical scans may reach 43%, 70%, 36%, and 26% for head-neck, chest, abdomen-pelvis, and trunk studies, respectively. Normalized data for female pediatric patients was in general higher compared to male patients for all ages, examined regions, and z overscanning values. For both male and female children, the normalized effective dose values were reduced as the age was increased. For the same typical exposure conditions, dose values decreased when lower tube voltage was used; for a 1-year-old child, for example, the effective dose was 3.8 times lower when 80 kV instead of 120 kV was used. Normalized data for the estimation of effective dose to pediatric patients undergoing standard axial and helical CT examinations on an multidetector CT system were calculated. This data was found to depend strongly on CT acquisition mode and exposure parameters as well as patient age and sex. The effective dose from a pediatric CT scan performed in axial mode was always considerably lower compared to the corresponding scan performed in helical mode, due to the additional tissue regions exposed to the primary beam in helical examinations as a result of z overscanning.     

Phased attenuation correction in respiration correlated computed tomography/positron emitted tomography

The motion of lung tumors with respiration causes difficulties in the imaging with computed tomography (CT) and positronemitted tomography (PET). Since an accurate knowledge of the position of the tumor and the surrounding tissues is needed for radiation treatment planning, it is important to improve CT/PET image acquisition. The purpose of this study was to evaluate the potential to improve image acquisition using phased attenuation correction in respiration correlated CT/PET, where data of both modalities were binned retrospectively. Respiration correlated scans were made on a Siemens Biograph Sensation 16 CT/PET scanner which was modified to make a low pitch CT scan and list mode PET scan possible. A lollipop phantom was used in the experiments. The sphere with a diameter of 3.1 cm was filled with approximately 20 MBq 18F-FDG. Three longitudinal movement amplitudes were tested: 2.5, 3.9, and 4.8 cm. After collection of the raw CT data, list mode PET data, and the respiratory signal CT/PET images were binned to ten phases with the help of in-house-built software. Each PET phase was corrected for attenuation with CT data of the corresponding phase. For comparison, the attenuation correction was also performed with nonrespiration correlated (non-RC) CT data. The volume and the amplitude of the movement were calculated for every phaseof both the CT and PET data (with phased attenuation correction). Maximum and average activity concentrations were compared between the phased and nonphased attenuation corrected PET. With a standard non-RC CT/PET scan, the volume was underestimated by as much as 46% in CT and the PET volume was overestimated to 370%. The volumes found with RC-CT/PET scanning had average deviations of 1.9% (+/- 4.8%) and 1.5% (+/- 3.4%) from the actual volume, for the CT and PET volumes, respectively. Evaluation of the maximum activity concentration showed a clear displacement in the images with non-RC attenuation correction, and activity values were on average14% (+/- 12%) lower than with phased attenuation correction. The standard deviation of the maximum activity values found in the different phases was a factor of 10 smaller when phased attenuation correction was applied. In this phantom study, we have shown that a combination of respiration correlated CT/PET scanning with application of phased attenuation correction can improve the imaging of moving objects and can lead to improved volume estimation and a more precise localization and quantification of the activity.