Detection of fetal central nervous system anomalies: a practical level of effort for a routine sonogram

To evaluate the efficacy of examining the lateral ventricular atrium, cisterna magna, and cavum septi pellucidi as a means of ascertaining that the development of the fetal central nervous system (CNS) is normal, a retrospective evaluation of the sonograms of 112 fetuses (15-39 weeks gestational age) with sonographically diagnosed CNS anomalies was performed. Malformations included in the study were diverse. The lateral ventricular atrium was enlarged (greater than 10 mm) in 99 (88%) fetuses. Of the remaining 13 fetuses, seven had an abnormal-sized cisterna magna (less than 2 mm or greater than 11 mm). These two measurements alone could be used to identify the presence of a CNS abnormality in 95%. Three of the six remaining fetuses exhibited gross abnormalities easily seen on the standard axial images obtained for biparietal diameter measurement. Although the cavum septi pellucidi was absent in a number of cases, its absence did not enhance sensitivity in the cohort examined. Prospective examination of 130 consecutive normal fetuses (15-40 weeks gestational age) was also performed. When specifically sought, the ventricular atrium was identifiable and measurable 99% of the time; the cisterna magna, 90% of the time; and the cavum septi pellucidi, 95% of the time. Because major CNS anomalies are uncommon and these measurements afford high sensitivity, an extremely low probability (0.005%) of abnormal brain or spinal cord development can be predicted if a normal-sized lateral ventricular atrium and cisterna magna are present. These results should not be construed as a license to underexamine fetuses for malformations. Rather, these measurements should serve as simple positive steps to assist in a difficult task.     

The neonatal cisterna magna: ultrasonic evaluation

The normal topography of the region of the cisterna magna can be delineated by cranial ultrasound in neonates. Evaluation of this region requires ultrasonic imaging of the echodense occipital bone and the inferior vermis, as well as approximation of the plane of the foramen magnum. It also requires imaging of the anechoic cisterna magna and fastigium of the fourth ventricle. In order to appreciate subtle alterations in size and/or position of these structures, standardized measurements for the midsagittal height of the cisterna magna and the distance of the fastigium of the fourth ventricle from the plane of the foramen magnum were established. Normal values established by measurement in 59 patients were cisterna magna 4.52 +/- 1.29 mm and fastigium of the fourth ventricle 16.05 +/- 3.03 mm. These dimensions were demonstrated to be abnormally increased in posterior fossa arachnoid cysts, Dandy-Walker syndrome, and hydrocephalus.     

The fetal cisterna magna

Antenatal sonography routinely images the fetal cisterna magna. The identification of a prominent cisterna magna on a routine antenatal sonogram performed for obstetric indications may raise the question of a congenital posterior fossa lesion. To delineate the size of the fetal cisterna magna, standardized measurements for the midsagittal depth of the cisterna magna were prospectively obtained on 219 consecutive antenatal sonograms in fetuses of 15 menstrual weeks or more. The cisterna magna depth measured 5 +/- 3 mm; the largest cisterna magna measured 10 mm in depth. In the absence of other findings to suggest a posterior fossa lesion, a prominent cisterna magna is unlikely to be clinically significant.     

Normal thoracic aorta diameter on cardiac computed tomography in healthy asymptomatic adults: impact of age and gender

RATIONALE AND OBJECTIVES: To establish the normal criterion of ascending aortic diameter (AAOD) measured by 64 multidetector computed tomography (MDCT) and electron beam computed tomography (EBT) based on gender and age. MATERIALS AND METHODS: A total of 1442 consecutive subjects who were referred for evaluation of possible coronary artery disease underwent coronary computed tomographic (CT) angiography (CTA) and coronary artery calcium scanning (CACS) (55 + 11 years, 65% male) without known coronary heart disease, hypertension, chronic pulmonary and renal disease, diabetes, and severe aortic calcification. The AAOD aortic diameter, descending aortic diameter (DAOD), pulmonary artery (PAD), and chest anteroposterior diameter (CAPD), posterior border of the sternal bone to the anterior border of the spine, were measured at the slice level of mid-right pulmonary artery using end systolic trigger imaging. The volume of four chambers, ejection fraction of left ventricle, and cardiac output were measured in 56% of the patients. Patients' demographic information, age, gender, weight, height, and body surface area were recorded. The mean value and age-specific and gender-adjusted upper normal limits (mean +/- 2 standard deviation) were calculated. The linear correlation analysis was done between AAOD and all parameters. The reproducibility, wall thickness, and difference between end-systole and end-diastole were calculated. RESULTS: AAOD has significant linear association with age, gender, DAOD, and pulmonary artery diameter (P < .05). There is no significant correlation between AAOD and body surface area, four-chamber volume, left ventricular ejection fraction, cardiac output, and CAPD. The mean intraluminal AAOD was 31.1 +/- 3.9 and 33.6 +/- 4.1 mm in females and males, respectively. The upper normal limits (mean +/- 2 standard deviations) of intraluminal AAOD, were 35.6, 38.3, and 40 mm for females and 37.8, 40.5, and 42.6 mm for males in age groups 20-40, 41-60, and older than 60 years, respectively. Intraluminal aortic diameters should parallel echocardiography and invasive angiography. Traditional cross-sectional imaging (with CT and magnetic resonance imaging) includes the vessel wall. The mean total AAOD was 33.5 and 36.0 mm in females and males, respectively. The upper normal limits (mean +/- 2 standard deviations) of intraluminal AAOD were 38.0, 40.7 and 42.4 mm for females and 40.2, 42.9, and 45.0 mm for males in age group 20 to 40, 41 to 60, and older than 60 years, respectively. The inter- and intraobserver, scanner, and repeated measurement variabilities were low (r value >0.91, P < .001, coefficient variation <3.2%). AAOD was 1.7 mm smaller in end-diastole than end-systole (P < .001). CONCLUSIONS: The AAOD increases with age and male gender. Gender-specific and age-adjusted normal values for aortic diameters are necessary to differentiate pathologic atherosclerotic changes in the ascending aorta. Use of intraluminal or total aortic diameter values depends on the comparison study employed.     

后颅窝囊肿的CT－MR影像学

目的：本文目的是对后颅窝囊肿的ＣＴ－ＭＲ影像学的诊断作用进行评价。材料与方法：１２例后颅窝囊肿的ＣＴ和ＭＲ影像表现进行了分析，探讨了其与临床表现和类型的相关性。结果：本组病例包含Ｄａｎｄｙ－Ｗａｌｋｅｒ囊肿（５例）、蛛网膜囊肿（３例）和巨枕大池（４例），ＣＴ和ＭＲ都可提供无创性检测手段。结论：ＣＴ和ＭＲ二者对后颅窝囊肿的诊断均有效，但在显示病变的性状、大小和轮廓方面，ＭＲ比ＣＴ稍胜一筹     

DWI在胎儿后颅窝池扩张中的研究

目的 测量后颅窝池扩张胎儿脑部表观扩散系数(ADC),探讨DWI及ADC值在后颅窝池扩张胎儿的应用.方法 16例后颅窝池扩张胎儿及16例对照进行DWI扫描及ADC值测量,比较2组各脑区ADC值差异及后颅窝池扩张胎儿左右脑区ADC值差异.将ADC值、后颅窝池扩张程度分别与孕周进行相关分析.结果 后颅窝池扩张胎儿脑部ADC值在双侧额叶及顶叶白质、双侧丘脑及小脑下降;后颅窝池扩张胎儿左右脑区ADC值差异无统计学意义(P>0.05);双侧基底节区和丘脑ADC值与孕周呈负相关(P<0.05),后颅窝池扩张程度与孕周未见相关(P>0.05).结论 后颅窝池扩张胎儿多个脑区出现ADC值下降,提示ADC值对于检测潜在脑部损伤更为敏感,常规序列结合DWI及ADC值能更准确地检测胎儿异常.     

Abdominal confluence of lymph trunks: detectability and morphology on heavily T2-weighted images

OBJECTIVE: Our aims were to evaluate the detectability, configuration, location, and dimensions of the cisterna chyli on heavily T2-weighted images obtained with a single-shot fast spin-echo technique and to determine whether the disorders that have the potential to affect the abdominal lymphatic drainage could change the cisternal dimensions. MATERIALS AND METHODS: Thin-collimated axial and coronal images that were originally obtained for MR cholangiopancreatography in 125 patients were reviewed by three observers individually for the presence of abdominal lymphatic confluence. The configuration, location, and dimensions of hyperintense ductal or saccular structures immediately anterior to the vertebral bodies below the diaphragma were recorded. The differences between the mean values of the diameters of the cisterna chyli obtained in the control group and in groups in which lymphatic drainage was expected to be abnormally high were compared using a one-way analysis of variance test. RESULTS: Abdominal confluence of the lymphatics was shown in 96% of patients. The most common configuration of the cisterna chyli was tubular (42.5%). It was located at the level of L1-2 in 33% of cases and at the midline in 70%. Mean longitudinal, anteroposterior, and transverse diameters of the duct were 33.45 +/- 1.74 (SD) mm, 5.23 +/- 0.13 mm, and 5.23 +/- 0.15 mm, respectively. No significant difference was found in the mean values of antero-posterior, transverse, and longitudinal diameters of the cisterna chyli in the control group and in the groups expected to have an increased flow into the cisterna chyli. CONCLUSION: Abdominal confluence of lymphatics seems to be present on most of the heavily T2-weighted images. Its morphologic details and extensions can be visualized on images reconstructed with a maximum-intensity-projection algorithm. Any disorder does not necessarily lead to dilatation of these lymphatic structures.     

Diameter of the superior ophthalmic vein in relation to intracranial pressure

BACKGROUND AND PURPOSE: Bilateral engorged superior ophthalmic veins (SOV) have been reported in patients with diffuse brain swelling. We investigated the relationship between the diameter of the SOV on brain MR images and the intracranial pressure (ICP). METHODS: We reviewed the medical records of neurologic inpatients who had undergone both MR imaging of the brain and lumbar puncture. MR imaging had to have been performed before lumbar puncture, and the two studies had to have occurred within 2 days. The diameters of the SOV were measured on coronal contrast-enhanced fat-saturated T1-weighted MR images. For this, the image nearest the rear of the globe of the eye was chosen. RESULTS: Sixty-nine patients (32 male, 37 female; mean age, 46 years +/- 19) were included. The average diameters of the SOV and the ICP were positively correlated (r = 0.58, P <.001), if an SOV diameter of <1 mm was treated as 0.5 mm for calculations. In patients with increased ICP (CSF pressure >200 mm H(2)O), SOV diameters were larger than those of patients with a normal CSF pressure (3.0 vs 1.6 mm, P <.001). Frequencies of increased ICP were 3% among patients with an average SOV diameter of 0.5-1 mm, 15% for 1.5-2 mm, and 58% for 2.5-5 mm (P <.001). CONCLUSION: This study showed that the SOV diameter, determined on the basis on MR imaging, was positively correlated with ICP. Dilatation of the SOV should alert physicians to the possibility of increased ICP.     

Effacement of the fetal cisterna magna in association with myelomeningocele

The cisterna magna is effaced in association with myelomeningocele. The authors retrospectively investigated the size of the fetal cisterna magna as a predictor of fetal myelomeningocele in 67 pregnant women (17-38 menstrual weeks) referred for prenatal sonography because of an elevated serum alpha-fetoprotein level (n = 61) or a suspicion of fetal ventriculomegaly on previously obtained sonograms (n = 6). Twenty fetuses had myelomeningocele, 14 had isolated ventriculomegaly, and 33 were normal. A normal-sized cisterna magna (range, 4-9 mm in depth) was present in all normal fetuses. In 19 of 20 fetuses with myelomeningocele, the views of the posterior fossa were adequate, and in each of these the cisterna magna was effaced (n = 18) or very small (n = 1). The cisterna magna was effaced in five of 13 (38%) fetuses with isolated ventriculomegaly in whom the posterior fossa was adequately imaged. Although effacement of the cisterna magna is a nonspecific finding, the high negative predictive value of this sign is useful during routine screening of the fetal neural axis.     

Cisterna chyli in patients with portal hypertension: evaluation with MR imaging

Purpose:

To evaluate the difference in the caliber of cisterna chyli between patients with and without portal hypertension on magnetic resonance imaging (MRI) and to assess the alteration of the caliber of cisterna chyli related to contraction waves during serial T2‐weighted MRI.

Materials and Methods:

This study included 177 patients with and without portal hypertension who underwent two sets of T2‐weighted MRI. MR images were evaluated for the visibility of cisterna chyli, the difference in the diameter of cisterna chyli between two patients groups, and the alteration in the diameter of cisterna chyli during serial T2‐weighted MRI.

Results:

The mean maximal diameter of cisterna chyli in patients with portal hypertension (4.97 ± 1.87 mm, range; 2.5–13.1 mm) was significantly larger (P < 0.001) than that in patients without portal hypertension (3.37 ± 1.25 mm, range; 1.5–6.8 mm). In 132 patients with visible cisterna chyli and portal hypertension, 25 (19%) patients had a positive caliber change of cisterna chyli of more than 2 mm between two sets of T2‐weighted MR images.

Conclusion:

The dilatation of cisterna chyli can be demonstrated at MRI in patients with portal hypertension. Additionally, the positive caliber change of cisterna chyli related to contraction waves was observed in subsets of patients during serial T2‐weighted MRI. J. Magn. Reson. Imaging 2012;35:624‐628. © 2011 Wiley Periodicals, Inc.     

Preoperative detection of hepatocellular carcinoma: ferumoxides-enhanced versus mangafodipir trisodium-enhanced MR imaging

OBJECTIVE: The purpose of our study was to compare the diagnostic accuracy and lesion conspicuity of ferumoxides-enhanced MR imaging with those of mangafodipir trisodium-enhanced MR imaging for the preoperative detection of hepatocellular carcinoma. SUBJECTS AND METHODS: Twenty-one patients with 39 hepatocellular carcinomas underwent ferumoxides-enhanced and mangafodipir trisodium-enhanced MR imaging. The diagnosis was established by pathologic examination after surgical resection in all patients. Five MR sequences were obtained 30 min after ferumoxides administration, and two MR sequences were obtained before and 15 min after mangafodipir trisodium administration. Three observers independently interpreted both MR images of all sequences on a segment-by-segment basis. The diagnostic accuracy of MR imaging was assessed using receiver operating characterizing analysis. Lesion (hepatocellular carcinoma > 10 mm in diameter)-to-liver contrast-to-noise ratio was calculated on MR images. RESULTS: Ferumoxides-enhanced MR imaging (A(z) = 0.971) was significantly more accurate (p < 0.05) than mangafodipir trisodium-enhanced MR imaging (A(z) = 0.950). The mean sensitivity of ferumoxides-enhanced MR imaging (86%) was significantly greater (p < 0.05) than that of mangafodipir trisodium-enhanced MR imaging (44%) in lesions smaller than 10 mm. The mean lesion-to-liver contrast-to-noise ratio of hepatocellular carcinoma on ferumoxides-enhanced MR imaging (13.7 +/- 8.8) was significantly greater than on mangafodipir trisodium-enhanced MR imaging (5.4 +/- 5.1) (p < 0.01). CONCLUSION: Ferumoxides-enhanced MR imaging has superior diagnostic accuracy in lesions smaller than 10 mm and superior lesion conspicuity compared with mangafodipir trisodium-enhanced MR imaging for the preoperative detection of hepatocellular carcinoma.     

In vivo measurement of the apparent diffusion coefficient in normal and malignant prostatic tissue using thin-slice echo-planar imaging

PURPOSE: Diffusion is a physical process based on the random movement of water molecules, known as Brownian movement. Diffusion-weighted imaging (DWI) is a magnetic resonance imaging (MRI) technique that provides information on such biophysical properties of tissues as density, cell organisation and microstructure, which influence the diffusion of water molecules. The aim of this study was to evaluate the ability of MRI to obtain information on the diffusion of water molecules in normal and malignant prostate tissues. MATERIALS AND METHODS: Ten volunteers and 19 patients with prostate lesions diagnosed by transrectal ultrasound (TRUS) were enrolled in our study. Morphological imaging was obtained with T2-weighted turbo spin-echo (TSE) sequences with and without fat suppression [spectral presaturation with inversion recovery (SPIR)] and an axial dynamic T1-weighted SPIR fast-field echo (FFE) sequence during intravenous administration of contrast material. DWI was obtained with a high-spatial-resolution single-shot spin-echo echo planar imaging (EPI) inversion recovery (IR) sequence. The apparent diffusion coefficient (ADC) maps were analysed by positioning an 8-pixel region of interest (ROI) over different zones of the prostate, and the focal lesion when present. The tumour was confirmed by a TRUS-guided needle biopsy taken within 1 month of the MRI examination. RESULTS: The mean ADC value of the central zones (1,512.07+/-124.85x10(-3) mm2/s) was significantly lower than the mean ADC of the peripheral zones (1,984.11+/-226.23x10(-3) mm2/s) (p<0.01). The mean ADC value of tumours (958.97+/-168.98x10(-3) mm2/s) was significantly lower than the mean values of normal peripheral zones (p<0.01). CONCLUSIONS: Our preliminary results indicate that DWI is useful for characterising tissue in the different regions of the prostate gland and in distinguishing normal from cancerous tissues, given its ability to detect early changes in the structural organisation of prostate tissue.     

中国汉族正常成人垂体的高分辨率MRI研究

目的 研究中国汉族正常成人垂体MRI形态学特征,为建立国人正常标准脑提供垂体形态学数据.方法 采用全国多中心临床研究形式,选取18～70岁978名健康志愿者,并按18～30、31～40、41～50、51～60、61～70岁5个年龄段分为A、B、C、D、E组,行3D磁化强度预备梯度回波序列T1WI,利用3D后处理软件进行MPR,测量垂体体积及各方向径线,以及垂体柄与大脑中线、视交叉及垂体表面夹角.相同性别不同年龄分组的垂体测量值比较采用方差分析,相同组别不同性别垂体测量值的比较采用独立样本t检验分析,垂体分型数据采用x2分析.结果 (1)垂体体积:男性5组垂体体积分别为(1142±290)、(996±223)、(979±178)、(971±174)、(930±189)mm3,女性分别为(1247±210)、(1199±216)、(1108±196)、(1059±212)、(984±177)mm3,在不同年龄组间差异有统计学意义(F值分别为13.811、27.091,P值均<0.01),在男性30岁以后,女性40岁以后垂体体积变小;同年龄组女性垂体体积大于男性(P<0.05);垂体体积与性别、年龄、分型、正中高径、前后径和宽径相关(r=0.646,P<0.01).(2)垂体径线测量统计:垂体正中高径男性各组分别为(6.6±1.5)、(6.0±1.4)、(5.6±1.1)、(5.0±1.2)、(4.9±1.4)mm,女性分别为(7.9±1.6)、(6.4±2.0)、(5.6±1.7)、(5.1±1.7)、(4.4±1.4)姗,不同年龄组间差异有统计学意义(F值分别为24.582、62.978,P值均<0.01),30岁之前女性正中矢状高径大于男性,30岁之后男女垂体正中矢状高径逐渐减小,男性50岁后,女性60岁后降至最低;垂体正中矢状高径与性别、年龄相关(r=0.570,P<0.01).垂体宽径男性各组分别为(14.8±1.8)、(14.7±1.4)、(14.2±1.9)、(14.3±2.1)、(13.8±2.4)mm,女性各组分别为(14.9±1.8)、(15.8±1.7)、(15.5±2.1)、(15.6±2.2)、(14.9±2.1)mm,不同年龄组间差异有统计学意义(F值分别为4.566、4.233,P值均<0.05);垂体宽径与性别、体重、年龄相关(r=0.300,P<0.01).垂体前后径男性各组分别为(11.2±1.2)、(11.8±1.3)、(11.8±1.5)、(12.3±1.8)、(12.2±2.0)mm,女性分别为(11.9±1.3)、(12.5±1.5)、(12.4±1.5)、(12.9±1.6)、(12.7±1.6)mm,不同年龄组间差异有统计学意义(F值分别为7.270、5.903,P值均<0.01),60岁之前男性垂体前后径小于女性(P<0.05),且随后逐渐减小,女性前后径随年龄逐渐减小;垂体正中矢状前后径与性别、年龄相关(r=0.276,P<0.01).(3)垂体柄夹角统计:冠状面重组上垂体柄与垂体表面、视交叉及脑中线之间并无明显偏移,且男女之间差异无统计学意义(P>0.05).(4)垂体分型统计:不同性别年龄组间分型差异有统计学意义(x2值分别为44.212、107.518,P值均<0.01).随年龄增加,隆起型逐渐减少,凹陷型逐渐增加.结论 3D高分辨率MRI能够清晰显示垂体形态,结合3D后处理软件能够准确测量垂体体积及各方向径线以及垂体柄的夹角,为建立标准脑提供科学数据.     

Reversal of delayed vasospasm by TS-011 in the dual hemorrhage dog model of subarachnoid hemorrhage

PURPOSE: Arachidonic acid is avidly metabolized to a potent vasoconstrictor, 20-hydroxyeicosatetraenoic acid (20-HETE), in the cerebral circulation. 20-HETE has been reported to contribute to the acute fall in cerebral blood flow following subarachnoid hemorrhage (SAH), but its role in the development of delayed vasospasm is unknown. The present study examined whether delayed vasospasm is associated with elevations in 20-HETE in CSF in the dual hemorrhage model of SAH in dogs and if blockade of the synthesis of 20-HETE with N-(3-chloro-4-morpholin-4-yl)phenyl-N'-hydroxyimido formamide (TS-011) can reverse delayed vasospasm in this model. MATERIALS AND METHODS: Delayed vasospasm was induced in 22 adult beagle dogs by dual injection of blood (0.5 mL/kg) into the cisterna magna on days 1 and 4. Sequential samples of CSF were collected before intracisternal injections of blood on days 1 and 4 and after the development of delayed vasospasm on day 7. Sequential angiograms were obtained before and after intracisternal injection of blood on days 1 and 4 and before and 1 hour after administration of TS-011 (1 mg/kg IV) on day 7. RESULTS: The dogs consistently developed delayed vasospasm, and the diameter of the basilar artery fell to 68 +/- 3% (n = 15), 3 days after the second intracisternal injection of blood. The levels of 20-HETE in CSF increased from 4 +/- 2 to 39 +/- 16 pg/mL. In 9 dogs with delayed vasospasm, acute blockade of the synthesis of 20-HETE with TS011 (1 mg/kg IV) significantly increased the diameter of the basilar artery by 39%. Chronic administration of TS-011 (1 mg/kg per day) attenuated the development of delayed vasospasm, and the diameter of the basilar artery fell by 17 +/- 1% versus the 33 +/- 3% decrease in diameter seen in control animals 3 days following the second injection of blood into the cisterna magna. CONCLUSIONS: These results indicate that the development of delayed vasospasm in dogs is associated with an increase in 20-HETE levels in CSF, and acute blockade of the synthesis of 20-HETE with TS-011 reverses delayed vasospasm in this model.     

The value of in-utero magnetic resonance imaging in ultrasound diagnosed foetal isolated cerebral ventriculomegaly

AIM: To assess whether magnetic resonance imaging (MRI) is a useful adjunct to ultrasound (US) when imaging cases of foetal isolated cerebral ventriculomegaly. To assess whether, in such cases, ventricular morphology is a useful indicator for the underlying pathology, as has recently been suggested. MATERIALS AND METHODS: A retrospective analysis was undertaken of 30 cases of isolated ventriculomegaly diagnosed using US and referred for in utero MRI. The gestational age of each case was noted and the MRI report. Both ventricles were measured and each case was categorized according to severity and morphology. The MRI report was compared to the final diagnosis. RESULTS: Of the 30 cases evaluated 18 had mild ventriculomegaly (<15 mm; gestational age range 20-31 weeks, mean 22.8, median 22) and 12 had severe ventriculomegaly (>15 mm; gestational age range 21-37 weeks, mean 28, median 28.5). Additional abnormalities were found in 50% of cases overall (44% mild, 58% severe) using MRI. CONCLUSIONS: Using MRI additional abnormalities were identified in 50% of the foetuses. The morphology of the cases did not suggest underlying pathology in this group. In utero MRI is a useful adjunct to US in cases of foetal cerebral ventriculomegaly referred after initial diagnosis using US.     

Sonography during early pregnancy: dependence of threshold and discriminatory values on transvaginal transducer frequency

OBJECTIVE: Our goal was to determine if normal and abnormal pregnancies could be distinguished at smaller sac sizes with a higher frequency transvaginal transducer than with a 5-MHz transducer. SUBJECTS AND MATERIALS: Thirty-nine patients with potentially abnormal pregnancies identified with a 5-MHz transvaginal transducer were immediately reimaged with a 9-5-MHz transducer. We compared our ability to visualize the yolk sac, embryo, and cardiac activity relative to mean sac diameter on imaging at both frequencies in women with normal and abnormal pregnancies. RESULTS: Of the 39 pregnancies, 22 (56%) were normal or probably normal. Using the 5-MHz transducer, a yolk sac was first seen in a 6.4-mm gestational sac but was not definitively seen in 12 gestational sacs measuring 5-13 mm. Using the 9-5-MHz transducer, yolk sacs were identified in all gestational sacs measuring 4.6-13 mm, and live embryos were seen in five of eight sacs measuring 8.1-13 mm. The largest normal gestational sac without a live embryo measured 11 mm. When we compared these pregnancies with 17 (44%) abnormal pregnancies, we found that all pregnancies that had no yolk sac by the time the gestational sac measured 5.0 mm or no live embryo by 13 mm had abnormal findings on higher frequency imaging. CONCLUSION: The ability to visualize the yolk sac and embryo in early pregnancy is critically dependent on transvaginal transducer frequency. Threshold values and discriminatory sizes used to distinguish normal and abnormal pregnancies are smaller on higher frequency than on lower frequency imaging and, therefore, should be redetermined for specific transducer frequencies.     

三维超声容积对比成像-C平面在胎儿小脑蚓部发育诊断中的应用研究

目的探讨三维超声容积对比成像（VCI）-C平面对胎儿小脑蚓部的诊断价值。方法随机选取本院接受产前超声检查的孕妇260名,胎儿的超声系统检查无异常。分别采用经腹二维超声检查和三维超声容积对比成像技术,在胎头的正中矢状面观察发育状况,测量小脑蚓部的前后径、上下径和面积。采用配对t检验和线性回归方法,分析胎儿小脑蚓部的发育规律。结果三维超声与二维超声在胎儿小脑蚓部的观察数据的差异无统计学意义,但前者的显示成功率要大于后者;胎儿小脑蚓部的前后径、上下径和面积与孕周均呈正相关;上下径的发育速度要快于前后径和面积。结论三维超声在胎儿小脑蚓部发育诊断中具有重要的应用价值。     

Preoperative sizing of meniscal allografts in meniscus transplantation

The purpose of this study was to determine the accuracy of radiographic and magnetic resonance imaging techniques in preoperative sizing for allograft meniscus transplantation. Twelve cadaveric knee specimens underwent sequential radiographs, magnetic resonance imaging scans, and arthrotomy. Meniscus dimensions were measured in multiple planes for the purpose of determining accuracy of imaging studies in comparison with actual meniscus dimensions. Overall, magnetic resonance imaging proved only slightly more accurate than conventional radiography. The mean difference between magnetic resonance imaging measurements and actual meniscus dimensions was 2.25 +/- 2.04 mm. The mean difference between radiographic measurements and actual meniscus dimensions was 2.35 +/- 1.79 mm. Neither imaging technique was accurate for measuring individual meniscus dimensions, with only 35% of images measuring within 2 mm of actual meniscus dimensions. Using less stringent criteria for accuracy (within 5 mm), radiography and magnetic resonance imaging were 79% and 83% reliable, respectively. Failure to obtain true anteroposterior or lateral images (15 degrees of external and internal rotation) increased measurement inaccuracy. Intraobserver agreement was significantly higher for magnetic resonance imaging than for radiography. Further research into the development of alternative techniques for more reliable meniscus sizing and better understanding of the tolerance for meniscus size mismatch is necessary.     

Digital radiographic evaluation of medial joint space narrowing after partial meniscectomy of bucket-handle medial meniscus tears in anterior cruciate ligament-intact knees

BACKGROUND: Few studies exist that evaluate the effect of partial medial meniscectomy in knees with intact anterior cruciate ligaments. HYPOTHESIS: Partial meniscectomy of bucket-handle medial meniscus tears will cause joint space narrowing. STUDY DESIGN: Case series; Level of evidence, 4. METHODS: Between 1982 and 2001, 135 patients met the study criteria of a partial medial meniscectomy, intact ligaments, no surgery to the contralateral knee, and no chondromalacia greater than grade II. Seventy-nine patients living within 150 miles of the clinic were asked to return for physical examination. Joint space narrowing was measured from the middle of the femoral condyle to the middle of the tibial plateau using digitally magnified weightbearing 45 degrees flexed posteroanterior and full-extension anteroposterior radiographs. Measurements were performed twice with the observer blinded to the previous measurements. Subjective follow-up was obtained prospectively on an annual basis with International Knee Documentation Committee and modified Noyes knee questionnaires. RESULTS: Forty-nine patients were examined at a mean of 11.8 years postoperatively. Mean medial joint space narrowing was 1.2 +/- 0.5 mm on 45 degrees flexed posteroanterior radiograph and 0.2 +/- 0.9 mm on full-extension anteroposterior radiographs (P < .001). Four patients had 2 mm or more of joint space narrowing. Subjective surveys obtained from 95 patients showed a mean subjective score of 89.9 points. Subjective scores did not decrease through time, and there was no correlation of joint space narrowing to lower subjective scores. CONCLUSION: Partial medial meniscectomy in stable knees causes only mild joint space narrowing (mean, 1.2 mm) at a mean 12-year follow-up. Digitally magnified 45 degrees flexed posteroanterior radiographs are more likely to demonstrate joint space narrowing than are full-extension anteroposterior radiographs.     

The deep infrapatellar bursa: prevalence and morphology on routine magnetic resonance imaging of the knee

OBJECTIVE: To evaluate the presence, location, and dimensions of the deep infrapatellar bursa on routine magnetic resonance (MR) imaging of the knee. METHODS: The study group consisted of 213 knees in 204 consecutive individuals who had undergone routine MR imaging examination of the knee within a 365-day period. Magnetic resonance examinations consisted of T1-, proton-density-, and T2-weighted sagittal; spectral presaturation inversion recovery coronal; and T2*-weighted transverse sequences. Exclusion criteria were previous knee arthroscopy or surgery or the presence of a mass lesion infiltrating the infrapatellar fat pad. The presence, location, and dimensions of the deep infrapatellar bursa were studied. The bursa was also analyzed with regard to knee joint synovial effusion (absent, mild, or marked). RESULTS: The deep infrapatellar bursa was detected in 68% of the knees, most commonly on the lateral paramedian sagittal MR images. There was no statistically significant difference between male and female subjects or between the knee sides with regard to the detection of the deep infrapatellar bursa (P > 0.05). No correlation was found between synovial effusion and the presence of the deep infrapatellar bursa. The mean anteroposterior and craniocaudal dimensions of the deep infrapatellar bursa on sagittal T2-weighted MR images were 2.1-2.7 mm and 7.3-9.1 mm, respectively, on its lateral, central, or medial location within the sagittal MR image stack. CONCLUSION: An awareness of the dimensions and location of the deep infrapatellar bursa is important in distinguishing it from pathologic lesions (eg, bursitis).