Outcomes in 74 patients with an appendicolith who did not undergo surgery: is follow-up imaging necessary?

The objective of this study was to report the clinical outcome of patients with an appendicolith on computed tomography (CT) who did not undergo appendectomy on initial presentation. Reports from 45,901 abdominal CT examinations performed between March 2000–March 2004 containing the words “appendicolith” or “fecalith” were identified. Patients with appendicoliths not initially undergoing appendectomy were followed to assess re-presentation with abdominal pain ultimately requiring appendectomy. Seventy-four patients had an appendicolith on CT report, were discharged without surgery, and had clinical follow-up. Fifty-two of 74 (70%) patients had no appendiceal symptoms, were given an alternate diagnosis, and did not return with appendicitis. Twenty-two of 74 (30%) patients were discharged without acute appendicitis but with possible appendiceal symptoms. Five of these 22 (23%) patients returned with pathologically proven acute appendicitis, and all had possible appendiceal symptoms at initial presentation. An appendicolith may be a marker of increased risk for appendicitis but is not an indication for appendectomy.     

Traumaradiologie beim Kind

The aim of this review article is to familiarize the reader with the specific paediatric conditions in trauma radiology. The article briefly describes the major pathophysiologic differences in childhood and the consecutive altered injury pattern. The standard radiological imaging protocol for various involved body regions and different trauma settings/varying queries is described, with suggestion for standardised diagnostic flow-charts in some typical settings. Special regard is given to radiation protection and the potential of newer imaging modalities such as ultrasound, multi-detector- and spiral CT as well as MRI in paediatric trauma patients. As such the paper hopefully provides some basic guidelines for general radiologists in peripheral hospitals who less often have to deal with paediatric queries.     

Evaluation of acute cervical spine imaging based on ACR Appropriateness Criteria?

The objectives of this study were to determine the rate of acute blunt cervical spine injury at an academic urban level 1 trauma center and to evaluate the utilization of cervical spine imaging based on the established American College of Radiology (ACR) Appropriateness Criteria?. We retrospectively reviewed all radiography and CT imaging of the cervical spine performed over a year period in adult patients presenting with acute blunt cervical spine trauma. Exclusion criteria were children ≤17 years, non-acute trauma of ≥72 h, and penetrating trauma. Any fracture, dislocation, or ligamentous instability demonstrated by diagnostic imaging and requiring stabilization or specialized follow-up was defined as clinically significant cervical spine injury. A total of 1,325 cervical spine studies were reviewed in 1,245 patients; 32.7% (433/1,325) were cervical spine radiographs and 67.3% (892/1,325) were CT examinations. Approximately 1.5% (19/1,245) of the patients demonstrated clinically significant acute cervical spine injury. There were 6.4% (80/1,245) patients who received both cervical spine radiographs and CT as imaging evaluation. Based on the ACR Appropriateness Criteria?, all of the cervical spine radiographs performed (433) were determined to be “inappropriate” imaging in the setting of acute cervical spine injury.     

Head trauma: comparison of MR and CT--experience in 100 patients

The results of CT and MR imaging were reviewed retrospectively and compared in 100 patients who experienced clinically significant head trauma. The findings were analyzed on the basis of several parameters in an attempt to establish objective clinical guidelines for the use of each diagnostic technique. CT remains the screening method of choice in evaluating acute severe head trauma; however, MR revealed additional clinically relevant findings in all four cases in which the patient's clinical symptoms were disproportionate to the CT findings. MR was equal or superior to CT in the evaluation of all patients with acute minor head trauma and in 94 of 95 patients examined in the subacute, chronic, or remote phase of injury, irrespective of the severity or pathologic nature of their injuries. All subacute contusions (21 lesions) and white-matter shearing lesions (18 cases) were demonstrated to particular advantage on MR compared with CT, as were all subdural hematomas (of 52 small subdural collections, 58% were detected only by MR). Although surgical management was not altered by the additional information provided by MR, the implications regarding the medical management and disposition of the patients with head trauma were significant.     

Rapid CT diagnosis of acute appendicitis with IV contrast material

The purpose of this study was to determine the sensitivity and specificity of computed tomography (CT) without administration of oral contrast in confirming suspected acute appendicitis. One hundred seventy-three patient studies were retrieved by a computer-generated search for the word “appendicitis” in radiology reports. Patients presenting to the emergency department over an 8-month period were examined for acute abdominal pain or suspected acute appendicitis. IV-contrast-enhanced CT scans of the abdomen and pelvis were obtained without oral or rectal contrast. Criteria for diagnosis of acute appendicitis included a dilated appendix (>6 mm), periappendiceal inflammation, or abscess. Final diagnoses were established with surgical/clinical follow-up, histopathological analysis or both. The standard time (1 h) for the administration of oral contrast prior to the CT scan was eliminated. Fifty-nine CT diagnoses were made of acute appendicitis, 56 of which were histologically verified and three of which resulted in another diagnosis. One hundred fourteen CT diagnoses were negative for appendicitis. This corresponds to a sensitivity of 100% and specificity of 97%, a positive predictive value of 95%, and a negative predictive value of 100%. CT with IV contrast is sensitive and specific for the confirmation or exclusion of acute appendicitis. By eliminating the time required to administer oral contrast, the diagnosis might be made more rapidly.     

Patients undergoing recurrent CT exams: assessment of patients with non-malignant diseases,reasons for imaging and imaging appropriateness

To determine percent of patients without malignancy and ≤ 40 years of age with high cumulative radiation doses through recurrent CT exams and assess imaging appropriateness. From the cohort of patients who received cumulative effective dose (CED) of ≥ 100 mSv over a 5-year period, a sub-set was identified with non-malignant disease. The top 50 clinical indications leading to multiple CTs were determined. Clinical decision support (CDS) system scores were analyzed using a widely adopted standard of 1–3 (red) as “not usually appropriate,” 4–6 (yellow) “may or may not be appropriate,” and 7–9 (green) “usually appropriate.” Clinicians reviewed patient records to assess compliance with appropriate use criteria (AUC). 9.6% of patients in our series were with non-malignant conditions and 1.4% with age ≤ 40 years. CDS scores (rounded) were 2% red, 38% yellow, 27% green, and 33% unscored CTs. Clinical society guidelines for CT exams, wherever available, were followed in 87.5 to 100% of cases. AUCs were not available for several clinical indications as also referral guidelines for serial CT imaging. More than half of CT exams were unrelated to follow-up of a primary chronic disease. We are faced with a situation wherein patients in age ≤ 40 years require or are thought to require many CT exams over the course of a few years but the radiation risk creates concern. There is a fair number of conditions for which AUC are not available. Suggested solutions include development of CT scanners with lesser radiation dose and further development of appropriateness criteria.     

Does the Addition of a “Black Bone” Sequence to a Fast Multisequence Trauma MR Protocol Allow MRI to Replace CT after Traumatic Brain Injury in Children?

BACKGROUND AND PURPOSE:Head CT is the current neuroimaging tool of choice in acute evaluation of pediatric head trauma. The potential cancer risks of CT-related ionizing radiation should limit its use in children. We evaluated the role of MR imaging, including a “black bone” sequence, compared with CT in detecting skull fractures and intracranial hemorrhages in children with acute head trauma.MATERIALS AND METHODS:We performed a retrospective evaluation of 2D head CT and brain MR imaging studies including the black bone sequence of children with head trauma. Two experienced pediatric neuroradiologists in consensus created the standard of reference. Another pediatric neuroradiologist blinded to the diagnosis evaluated brain MR images and head CT images in 2 separate sessions. The presence of skull fractures and intracranial posttraumatic hemorrhages was evaluated. We calculated the sensitivity and specificity of CT and MR imaging with the black bone sequence in the diagnosis of skull fractures and intracranial hemorrhages.RESULTS:Twenty-eight children (24 boys; mean age, 4.89 years; range, 0–15.5 years) with head trauma were included. MR imaging with the black bone sequence revealed lower sensitivity (66.7% versus 100%) and specificity (87.5% versus 100%) in identifying skull fractures. Four of 6 incorrectly interpreted black bone MR imaging studies showed cranial sutures being misinterpreted as skull fractures and vice versa.CONCLUSIONS:Our preliminary results show that brain MR imaging complemented by a black bone sequence is a promising nonionizing alternative to head CT for the assessment of skull fractures in children. However, accuracy in the detection of linear fractures in young children and fractures of aerated bone remains limited.

CT is the initial neuroimaging technique of choice for the acute evaluation of pediatric head trauma due to its wider availability, lower cost, and short acquisition time. In addition, CT identifyies most traumatic injuries that require urgent treatment and correlates well with clinical scales and outcome.¹ However, CT-related ionizing radiation involves the potential risk of patients developing cancer and strongly argues in favor of alternative neuroimaging techniques such as MR imaging.² The lifetime cancer mortality risk attributable to the radiation from a single CT scan of the head in a 1-year-old child has been estimated as 0.07%. This small risk translates into a large population-level risk, especially because head trauma in children from 0 to 14 years of age accounts for nearly half a million emergency department visits in the United States annually.^3,4MR imaging is a nonionizing technique that provides superior contrast resolution and has a higher sensitivity and specificity for parenchymal lesions compared with CT.^3,4 Especially, advanced MR imaging techniques (DWI, SWI) provide additional information that correlates well with outcome.^5,6 Nonhemorrhagic shear injuries and subtle microhemorrhages are typically seen with higher sensitivity by MR imaging compared with CT. Nevertheless, the role of MR imaging in the acute diagnostic work-up of head trauma in children is still limited.^2,7,8 This limitation may be partially explained by longer acquisition times and the subsequent need for sedation as well as the low sensitivity of MR imaging for skull fractures.^2,8 Recently, black bone MR images have been introduced as a new sequence for the evaluation of structural bony abnormalities such as craniosynostosis.⁹On the basis of the inherent diagnostic quality of the black bone sequence, we aimed to determine whether a trauma brain MR imaging protocol with an included black bone MR image could be an alternative to head CT in the acute work-up of children with head trauma. To address our goal, we compared the diagnostic accuracy of brain MR imaging including the black bone sequence with CT for the detection of skull fractures after traumatic brain injury in children. Images were also studied for coexisting intracranial lesions.     

Subtle pathology detection with multidetector row coronal and sagittal CT reformations in acute head trauma

We sought to analyze retrospectively the advantages of coronal and sagittal reformations obtained with multidetector row computed tomography (CT) in patients with acute head trauma. Multidetector 16-section CT was performed in 200 patients (110 male and 90 female; age range, 3–87 years; mean age, 45 years) with acute head trauma. Scans were performed sequentially, and axial 5-mm-thick slices were obtained from base of skull to vertex. The source data set was reformatted in coronal and sagittal planes, with 2-mm-thick sections at 2-mm intervals. Images were analyzed retrospectively by two independent, blinded readers. The final diagnosis was determined by clinical follow-up. CT imaging abnormalities were detected in 55 out of 200 patients who were scanned for head trauma. Acute traumatic intracranial abnormality was detected on axial scans in 45 patients. Subtle findings were confirmed on coronal and sagittal CT reformations in ten cases, and these were undetected initially on axial CT. Coronal and sagittal reformations confirmed subtle findings in 18.2% (10/55) of the cases (P = 0.001). Indeterminate neuroimaging findings confirmed by coronal and sagittal CT head reformations include tentorial and interhemispheric fissure subdural hemorrhage, subarachnoid hemorrhage, and inferior frontal and temporal lobe contusions. Coronal and sagittal CT head reformations improve the sensitivity and diagnostic confidence in the clinical setting of acute trauma. Overall, coronal and sagittal reformations improved diagnostic confidence and interobserver agreement over axial images alone for visualization of normal structures and in the diagnosis of acute abnormality.     

Standardized CT examination of the multitraumatized patient

The aim of this study was to develop a standardized non-helical-CT protocol including head, body and proximal extremities in order to achieve a good time efficiency and diagnostic accuracy in the initial radiological evaluation of the multitraumatized patient. A total of 111 circulatory stable blunt trauma patients, brought in to a trauma level II–III hospital, were examined according to a standardized CT protocol. After examining the head with contiguous 10-mm slices without IV contrast medium injection, the trunk was examined with 10-mm slices every 30 mm through thorax–abdomen–pelvis with IV contrast medium enhancement (occasionally modified). All data in the medical reports were collected and used as “end-point”, and the outcome of the CT examination was compared with this final diagnosis. Mean examination time was 20 min (range 12–32 min). In total, 55 head injuries, 89 thoracic injuries, 27 abdominal/pelvic injuries and 62 fractures were found. Computed tomography correctly identified the injuries, except one brain stem injury, one contusion/rupture of the heart, one hepatic injury, two intestinal injuries, eight vertebral injuries and one joint dislocation. A standardized non-helical-CT examination of the head and body may be achieved in 20 min. Its diagnostic accuracy was high, except for vertebral column injuries, which is why we recommend it as the method of choice for initial radiological examination of multitraumatized patients. When available, helical scanning would improve both examination speed and accuracy. Received 28 April 1997; Revision received 27 February 1998; Accepted 3 March 1998     

宁夏儿童头颅、胸部CT辐射剂量状况分析

目的 评估宁夏地区儿童头颅、胸部CT检查的辐射剂量水平,为不同年龄段儿童的CT辐射剂量优化提供基础。方法 采用分层整群抽样的方法,实地采集宁夏地区不同市、县、区不同规模医院1~2周内儿童（≤15岁）头颅、胸部CT的扫描参数、容积CT剂量指数（CTDI_vol）及剂量长度乘积（DLP）,计算患者有效剂量（E）值;并将CTDI_vol、DLP的第75百分位数（P₇₅）与其他国家推荐的DRL值进行比较;所有儿童分4个年龄组：<1岁、1~5岁、6~10岁、11~15岁。结果 走访调查39家医院,调查CT设备47台,采集头颅断层扫描1 134例,胸部平扫636例。头颅CTDI_vol、DLP的P₇₅分别为：<1岁：44.2 mGy、456.2 mGy·cm;1~5岁：57.2 mGy、659.6 mGy·cm;6~10岁：61.1 mGy、668.7 mGy·cm;11~15岁：63.6 mGy、849.3 mGy·cm。胸部CTDI_vol、DLP的P₇₅分别为：<1岁：5.0 mGy、89.2 mGy·cm;1~5岁：5.9 mGy、124.8 mGy·cm;6~10岁：6.0 mGy、167.9 mGy·cm;11~15岁：7.1 mGy、235.0 mGy·cm。结论 宁夏地区儿童胸部CT的辐射剂量与其他报道相近,但头颅CT的辐射剂量相对偏高,且各年龄段均存在偏高现象,尤以婴儿患者较著;应加强宁夏地区儿童头颅CT的辐射剂量优化与监管,增强儿科医生、放射科医生的剂量控制意识,提高对辐射相关风险的认识。     

小儿急性阑尾炎CT诊断

目的　提高小儿急性阑尾炎CT诊断水平。方法　回顾性分析 35例经临床病理证实的 9岁以下急性阑尾炎的CT表现。结果　35例中阑尾肿大增粗,直径>6mm25例,阑尾腔内结石钙化 5例,盲肠周围炎并盲肠壁增厚 27例,肠淤张 22例。结论　CT对急性阑尾炎的诊断有较高的准确性和临床实用性。     

An evaluation of the effect that the implementation of the NICE rules may have on a diagnostic imaging department for the early management of head injuries

IntroductionGuidelines by the National Institute of Clinical Excellence (NICE) for the early management of minor head injuries initiate the use of computed tomography (CT) for patients who may be at risk of developing intracranial haematoma. This retrospective study was designed to evaluate the effect the implementation of the NICE guidelines would have on the diagnostic imaging department of a local district general hospital. The main objective was to establish if there would be an increase in the number of CT head referrals for patients with minor head injuries. Secondly to assess how the implementation of these guidelines would affect the workload to the diagnostic imaging department in terms of cost and time, and to discuss the issue of radiation dose to patients.MethodA sample of 100 patients who were referred from the Accident and Emergency department (A&E) for plain skull radiographs, over a 4-month period were selected. The clinical information on each of these patients' was then extracted and a data collection sheet was to assess each patient according to the NICE criteria.Results and conclusionThe study found an 18% (n = 100) increase in the referral rate for CT heads for patients presenting with minor head injuries. It was also found that the use of these guidelines would mean a decrease in cost to the diagnostic imaging department of £324. Furthermore a saving of 10 h of radiographers' time was established, although the effective radiation dose to patients would be increased by 29 mSv.The NICE guidelines have proved efficient in identifying patients with intracranial damage although this coincides with an 18% (n = 100) increase in referral rates for CT and increased radiation dose to patients. However, the use of these guidelines would reduce workload to the diagnostic imaging department in terms of cost and time.     

The use of advanced imaging for appendicitis in children

Improved resolution of late-generation CT and US technology has fostered an increased reliance on imaging for the preoperative diagnosis or exclusion of appendicitis. Both modalities have been shown to have a high accuracy rate, but certain diagnostic challenges persist. CT has largely replaced US for the diagnosis of appendicitis in adults, but the modality of choice is less clear in children. US is usually more easily and rapidly performed in young patients, obviating the need for contrast administration and sedation. Ionizing radiation exposure is avoided with US. Assessment of physical signs and symptoms can be achieved while performing US, an advantage over CT. However, US is best interpreted during performance of the examination, and thus CT is often favored when the interpreter is in a remote location. Strategies using limited CT to follow an indeterminate US show high diagnostic accuracy. This article discusses the controversy surrounding the optimal imaging approach to acute abdominal pain in children and illustrates some of the challenges encountered with US and CT for the evaluation of appendicitis.     

Local cortical hypoperfusion imaged with CT perfusion during postictal Todd’s paresis

Introduction Postictal (“Todd’s”) paralysis, or “epileptic hemiplegia,” is a well-known complication of focal or generalized epileptic seizures. However, it is unclear whether the pathophysiology of Todd’s paralysis is related to alterations in cerebral perfusion. We report CT perfusion findings in a patient presenting with postictal aphasia and right hemiparesis. Methods A 62-year-old woman with a history of alcohol abuse, closed head injury and posttraumatic epilepsy, presented with acute onset aphasia and right hemiparesis. A non-contrast head CT scan demonstrated no acute hemorrhage. Left hemispheric ischemia was suspected, and the patient was considered for acute thrombolytic therapy. MRI revealed a subtle increase in signal intensity involving the left medial temporal, hippocampal and parahippocampal regions on both T2-weighted FLAIR and diffusion-weighted sequences. CT angiography and CT perfusion study were performed. The CT perfusion study and CT angiography demonstrated a dramatic reduction in cerebral blood flow and blood volume involving the entire left hemisphere, but with relative symmetry of mean transit time, ruling out a large vessel occlusion. Results Clinical resolution of the aphasia and hemiparesis occurred within a few hours, and correlated with normalization of perfusion to the left hemisphere (detected by MR perfusion). Conclusion This unique case is the first in which clinical evidence of Todd’s paralysis has been correlated with reversible postictal hemispheric changes on CT and MR perfusion studies. This is important because CT perfusion study is being used more and more in the diagnosis of acute stroke, and one needs to be careful to not misinterpret the data.     

Controversies in emergency radiology: acute appendicitis in children—the case for CT

Acute appendicitis is the most common condition requiring surgical intervention in childhood. The clinical diagnosis of acute appendicitis is often not straightforward and can be challenging. Approximately one-third of children with the condition have atypical clinical findings and are initially managed nonoperatively. There is currently great variability in the utilization of imaging for the assessment of suspected acute appendicitis in children. The principal imaging modalities utilized are graded-compression sonography and CT. Sonography has important diagnostic limitations that are addressed by CT. The principal advantages of CT include its operator independency, with resultant higher diagnostic accuracy, enhanced delineation of disease extent in perforated appendicitis, and improved patient outcomes including decreased negative laparotomy and perforation rates.     

Akutes Schädel-Hirn-Trauma im Kindesalter – frühzeitiger Einsatz der MRT

The purpose of the study was to evaluate the present diagnostic potential of MRI in early stage head trauma und possibly to replace CT studies in children. FLAIR-techniques consequently applied as "scout sequences" provided reliable identification of traumatic intra- and extracranial lesions yet during the first measurement in all 24 cases. Follow-up scan confirmed the initial results. The reliability of MRI in acute pediatric head trauma is underlined by the fact that CT scans were no longer necessary within in the last three years. Therefore the imaging algorithm of acute head trauma in children has changed in our institution: medium and high risk patients undergo MRI, in young infants we do US first. HR-CT is reserved for lesions of the visceral cranium. X rays are out.     

儿童急性阑尾炎的CT表现及其评价

目的：探讨儿童急性阑尾炎的CT表现及其诊断价值。方法：回顾性分析本院2007年1月～2008年12月经手术和病理证实的55例小儿急性阑尾炎的临床和CT资料,总结其CT表现特点和临床应用价值。结果：55例急性阑尾炎中,卡他型12例,化脓型25例,坏疽型18例。CT表现为阑尾肿胀增粗（37/55）;阑尾腔内肠石（35/55）;阑尾腔内积气（17/55）;阑尾穿孔并周围脓肿形成（18/55）;阑尾周围组织密度不均匀升高（19/55）;相邻盲肠壁增厚（24/55）;腹水（11/55）;肠梗阻（5/55）;其它还有肝脓肿、NEC等并发症形成。结论：儿童急性阑尾炎的CT表现具有一定特点,CT检查可显示阑尾及其周围组织结构的病理改变,为临床明确诊断提供客观依据,尤其适用于儿童。     

A strategy to optimize CT use in children with mild blunt head trauma utilizing clinical risk stratification; Could we improve CT use in children with mild head injury?

AimThe purpose of our study was to investigate the impact of clinical risk classification on optimization of the rationale of CT scanning in children with mild blunt head trauma. Exposed effective radiation dose values of CT scanning were also evaluated.MethodsChildren with isolated pediatric mild head trauma admitted in a single center over a 5-year period (n=3102, > 2 years and < 16 years of age) were retrospectively reviewed. The study group comprised 806 patients with a mean age of 7.4±2.1 years (range, 2–15 years). The patients were categorized into low and high risk groups with regard to presence of predefined signs and symptoms. Effective radiation dose values were calculated.ResultsIncidences of the pathologic CT findings related to trauma were significantly different between low (n=10) 1.9% and high (n=90) 29.8% risk groups. Certain predefined signs and symptoms (e.g., vomiting, suspected skull fracture and loss of consciousness) were related significantly with pathologic CT findings attributed to trauma. Estimated mean effective dose values were 3.91±0.38mSv for 2-6 year old (n=557), and 3.33±0.12mSv for 7-16 year old patients (n=349).ConclusionThe pediatric victims of mild head trauma patients within high risk group and those with vomiting, suspected skull fracture and loss of consciousness should undergo head CT scanning. The manufacturer settings on the CT scanners for children should be revised to alleviate untoward radiation exposure.     

A dose comparison survey in CT departments of dedicated paediatric hospitals in Australia and Saudi Arabia

AIM: To measure and compare computed tomography (CT) radiation doses delivered to patients in public paediatric hospitals in Australia and Saudi Arabia. METHODS: Doses were measured for routine CT scans of the head, chest and abdomen/pelvis for children aged 3-6 years in all dedicated public paediatric hospitals in Australia and Saudi Arabia using a CT phantom measurement cylinder.RESULTS: CT doses, using the departments’ protocols for 3-6 year old, varied considerably between hospitals. Measured head doses varied from 137.6 to 528.0 mGy·cm, chest doses from 21.9 to 92.5 mGy·cm, and abdomen/pelvis doses from 24.9 to 118.0 mGy·cm. Mean head and abdomen/pelvis doses delivered in Saudi Arabian paediatric CT departments were significantly higher than those in their Australian equivalents. CONCLUSION: CT dose varies substantially across Australian and Saudi Arabian paediatric hospitals. Therefore, diagnostic reference levels should be established for major anatomical regions to standardise dose.     

儿童颅脑外伤CT扫描参数的优化设置

目的研究儿童头颅外伤患者CT扫描参数的设置。在不影响影像诊断的前提下,尽可能降低辐射剂量。方法用不同的CT扫描参数对随机分组的小儿进行扫描,有3个变量电压分为120、140kV;毫安状态分为normal、low;层厚分为7、10mm。分别组合成8组不同的扫描参数组。记录各组的辐射计量(权重CT剂量学指数,CTDIW);用CT值的标准差和诊断阳性率作为图像质量的主客观标准进行分析。结果①在自动mA状态下,140KV比120KV剂量平均降低22.7%;降低毫安状态从normal到low可使剂量降低18.1%;选择较大层厚10mm比7mm辐射剂量平均降低19.7%;若同时同向改变参数,辐射剂量最大可减少近50%。②各组之间图像质量的CT值标准差(CTsd)和CT诊断阳性率的差异无显著性意义。结论用高KV、低毫安状态(low)、较大层厚均可以降低辐射剂量,且图像质量对诊断没有影响。因此对于外伤患者建议用140KV、自动mAs的低毫安状态(low)和10mm层厚为最佳扫描方式。