Reliability of Human Achilles Tendon Stiffness Measures Using Freehand 3-D Ultrasound

Achilles tendon (AT) stiffness is an important property of both human locomotor performance and injury mechanics. Freehand 3-D ultrasound (3-DUS) is a promising method for measuring stiffness of the Achilles tendon, particularly the free AT (2–6 cm proximal to calcaneus), which is commonly injured. The aim of this study was to investigate the test–retest reliability of freehand 3-DUS in measuring free AT stiffness in humans. The free Achilles tendon length of healthy participants (n = 10) was scanned on the same day on two consecutive occasions (1 h apart) during rest and isometric plantar flexion contractions at 20%, 40% and 60% of maximum force. The slope of the force–elongation curve over these force levels represented individual stiffness (N/mm). Relative reliability was assessed using the intra-class correlation coefficient (ICC), and absolute reliability was estimated with the standard error of measurement (SEM) and smallest detectable change. Systematic bias in stiffness measures was explored by comparing test and retest distributions and Bland–Altman plots. The test–retest reliability of free AT stiffness measured using freehand 3-DUS was excellent [ICC = 0.994, 95% confidence interval [CI]: 0.978–0.999)]. The mean stiffness values at test (361.83 N/mm [170.77]) and retest (364.98 N/mm [168.57]) did not significantly differ (p = 0.72), and the smallest detectable change was 52.14 N/mm. The Bland–Altman plot indicated the absence of systematic bias (95% CI: –22.18 to 15.88). Freehand 3-DUS provides reliable and precise measures of tendon stiffness and can be used to detect small changes in free AT stiffness in response to load or tendon pathology.     

In Vivo Measurement of Human Achilles Tendon Morphology Using Freehand 3-D Ultrasound

This study investigated the accuracy of phantom volume and length measurements and the reliability of in vivo Achilles tendon (AT) volume, length and cross-sectional area measurements obtained using freehand 3-D ultrasound. Participants (n = 13) were scanned on consecutive days under active and passive loading conditions. In vivo AT length was evaluated using a two-point method and an approach that accounted for AT curvature (centroid method). Three-dimensional ultrasound provided accurate measures of phantom volume and length (mean difference = 0.05 mL and 0.2 mm, respectively) and reliable in vivo measures of AT volume, length and average cross-sectional area, with all intra-class correlations coefficients greater than 0.98. The mean minimally detectable changes for in vivo AT volume, two-point length and centroid length were 0.2 mL, 1.5 mm and 2.0 mm, respectively. Two-point AT length underestimated centroid AT length by 0.7 mm, suggesting that the effect of curvature on in vivo AT length is negligible.     

Freehand 3-D Ultrasound Imaging: A Systematic Review

Two-dimensional ultrasound (US) imaging has been successfully used in clinical applications as a low-cost, portable and non-invasive image modality for more than three decades. Recent advances in computer science and technology illustrate the promise of the 3-D US modality as a medical imaging technique that is comparable to other prevalent modalities and that overcomes certain drawbacks of 2-D US. This systematic review covers freehand 3-D US imaging between 1970 and 2017, highlighting the current trends in research fields, the research methods, the main limitations, the leading researchers, standard assessment criteria and clinical applications. Freehand 3-D US systems are more prevalent in the academic environment, whereas in clinical applications and industrial research, most studies have focused on 3-D US transducers and improvement of hardware performance. This topic is still an interesting active area for researchers, and there remain many unsolved problems to be addressed.     

Reliability of Distal Hamstring Tendon Length and Cross-sectional Area Using 3-D Freehand Ultrasound

The objective of this study was to investigate the reliability of distal hamstring tendon morphology using freehand 3-D ultrasound (US). Freehand 3-D US scans were acquired for 16 young males and females, in two sessions, spaced a week apart. The length, volume, cross-sectional area (CSA) and echo intensity (EI) of the semitendinosus (ST), biceps femoris long and short head and semimembranosus (SM) tendons were acquired. Measurements of the CSA and EI were obtained from three sites along each tendon. The intra-class correlation coefficients ranged from 0.88–0.99 of the examined variables, indicating high test–retest reliability. In addition, the minimal detectable change (MDC) ranged from 0.255–3.766 mm (MDC% of the mean: 0.406%–12.558%) for hamstring tendon length, from 0.036–0.077 mL (MDC%: 1.548%–3.178%) for tendon volume, from 0.512–1.948 mm² (MDC%: 0.702%–3.586%) for CSA and from 0.898–2.586 au (MDC%: 1.145%–3.325%) for EI. Of the four hamstring tendons, ST had the greatest length (141.587 ± 10.701 mm) and EI (94.637 ± 5.536 au), while SM had the greatest volume (3.056 ± 0.421 mL) and CSA (115.277 ± 16.442 mm²) relative to other tendons. Freehand 3-D US appears to be a reliable tool for the evaluation of hamstring distal tendon morphology; hence, its use for in vivo evaluation of tendon properties is promising.     

Validity of Freehand 3-D Ultrasound System in Measurement of the 3-D Surface Shape of Shoulder Muscles

Freehand 3-D ultrasound (3DUS) system is a promising technique for accurately assessing muscle morphology. However, its accuracy has been validated mainly in terms of volume by examining lower limb muscles. This study was aimed at validating 3DUS in the measurements of 3-D surface shape and volume by comparing them with magnetic resonance imaging (MRI) measurements while ensuring the reproducibility of participant posture by focusing on the shoulder muscles. The supraspinatus, infraspinatus and posterior deltoid muscles of 10 healthy men were scanned using 3DUS and MRI while secured by an immobilization support customized for each participant. A 3-D surface model of each muscle was created from the 3DUS and MRI methods, and the agreement between them was assessed. For the muscle volume, the mean difference between the two models was within –0.51 cm³. For the 3-D surface shape, the distances between the closest points of the two models and the Dice similarity coefficient were calculated. The results indicated that the median surface distance was less than 1.12 mm and the Dice similarity coefficient was larger than 0.85. These results suggest that, given the aforementioned error is permitted, 3DUS can be used as an alternative to MRI in measuring volume and surface shape, even for the shoulder muscles.     

Automated Registration of Freehand B-Mode Ultrasound and Magnetic Resonance Imaging of the Carotid Arteries Based on Geometric Features

An automated method for registering B-mode ultrasound (US) and magnetic resonance imaging (MRI) of the carotid arteries is proposed. The registration uses geometric features, namely, lumen centerlines and lumen segmentations, which are extracted fully automatically from the images after manual annotation of three seed points in US and MRI. The registration procedure starts with alignment of the lumen centerlines using a point-based registration algorithm. The resulting rigid transformation is used to initialize a rigid and subsequent non-rigid registration procedure that jointly aligns centerlines and segmentations by minimizing a weighted sum of the Euclidean distance between centerlines and the dissimilarity between segmentations. The method was evaluated in 28 carotid arteries from eight patients and six healthy volunteers. First, the automated US lumen segmentation method was validated and optimized in a cross-validation experiment. Next, the effect of the weighting parameter of the proposed registration dissimilarity metric and the control point spacing in the non-rigid registration was evaluated. Finally, the proposed registration method was evaluated in comparison to an existing intensity-and-point-based method, a registration using only the centerlines and a registration using manual US lumen segmentations. Registration accuracy was measured in terms of the mean surface distance between manual US segmentations and the registered MRI segmentations. The average mean surface distance was 0.78 ± 0.34 mm for all subjects, 0.65 ± 0.09 mm for healthy volunteers and 0.87 ± 0.42 mm for patients. The results for the complete set were significantly better (Wilcoxon test, p < 0.01) than the results for the intensity-and-point-based method and the centerline-based registration method. We conclude that the proposed method can robustly and accurately register US and MR images of the carotid artery, allowing multimodal analysis of the carotid plaque to improve plaque assessment.     

Prenatal Imaging of Fetal Lung Lesions: Magnetic Resonance Imaging Complements Ultrasound

Prenatal ultrasound has been used for 30 to 40 years in the evaluation of the fetus. In the 1980s, magnetic resonance imaging (MRI), given its high soft tissue detail, was introduced as an alternative method for fetal evaluation. Initially, MRI of pregnancy was limited to assessing maternal complications, as the fetal detail was poor because of motion on long acquisition times. However, in the 1990s, with the advent of short imaging sequences, fetal MRI rapidly established itself as a technique of diagnostic value. In this article, the authors present a case review of a fetus with a lung lesion, demonstrating the value of this modality.     

Common Carotid Artery Flow Measured by 3-D Ultrasonic Vector Flow Imaging and Validated with Magnetic Resonance Imaging

Ultrasound (US) examination of the common carotid artery was compared with a through-plane magnetic resonance imaging (MRI) sequence to validate a recently proposed technique for 3-D US vector flow imaging. Data from the first volunteer examined were used as the training set, before volume flow and peak velocities were calculated for the remaining eight volunteers. Peak systolic velocities (PSVs) and volume flow obtained with 3-D US were, on average, 34% higher and 24% lower than those obtained with MRI, respectively. A high correlation was observed for PSV (r = 0.79), whereas a lower correlation was observed for volume flow (r = 0.43). The overall standard deviations were ±5.7% and ±5.7% for volume flow and PSV with 3-D US, compared with ±2.7% and ±3.2% for MRI. Finally, the data were re-processed with a change in the parameter settings for the echo-canceling filter to investigate its influence on overall performance. PSV was less affected by the re-processing, whereas the difference in volume flow between 3-D vector flow imaging and MRI was reduced to ?9%, and with an improved overall standard deviation of ±4.7%. The results illustrate the feasibility of using 3-D US for precise and angle-independent volume flow and PSV estimation in vivo.     

Multimodal Evaluation of 2-D and 3-D Ultrasound,Computed Tomography and Magnetic Resonance Imaging in Measurements of the Thyroid Volume Using Universally Applicable Cross-Sectional Imaging Software: A Phantom Study

A precise estimate of thyroid volume is necessary for making adequate therapeutic decisions and planning, as well as for monitoring therapy response. The goal of this study was to compare the precision of different volumetry methods. Thyroid-shaped phantoms were subjected to volumetry via 2-D and 3-D ultrasonography (US), computed tomography (CT) and magnetic resonance imaging (MRI). The 3-D US scans were performed using sensor navigation and mechanical sweeping methods. Volumetry calculation ensued with the conventional ellipsoid model and the manual tracing method. The study confirmed the superiority of manual tracing with CT and MRI volumetry of the thyroid, but extended this knowledge also to the superiority of the 3-D US method, regardless of whether sensor navigation or mechanical sweeping is used. A novel aspect was successful use of the same universally applicable cross-imaging software for all modalities.     

Imaging Features of Fetal Chest Lesions With a Focus on Ultrasound and Magnetic Resonance Imaging

Congenital lung anomalies vary in origin with numerous theories about overall formation. While many of these lesions may be asymptomatic or incidentally detected, on occasion these can have potentially life-threatening effects such as mass effect on adjacent structures and pulmonary hypoplasia. Prenatal diagnosis is advantageous to help direct prenatal counseling and perinatal care. Ultrasound and magnetic resonance imaging (MRI) are the most widely used modalities for fetal imaging and provide complementary information. This review describes congenital fetal chest lesions with a focus on differentiating imaging features.     

胰腺实性假乳头肿瘤超声和核磁共振表现

目的:探讨胰腺实性假乳头肿瘤超声和核磁共振(MRI)特点,以提高诊断水平。方法:回顾分析8例经病理证实为胰腺实性假乳头肿瘤图像资料。结果:8例均女性.平均年龄29±11岁,肿瘤大小平均74±37 mm。超声影像上5例呈囊实性,界清,有包膜,内部回声不均。1例呈均匀低回声,2例呈混合回声。4例行MRI检查,均为囊实性,边界清,有包膜,T1 WI与T2WI均为高低混杂信号。结论:胰腺实性假乳头肿瘤年轻女性多见,典型表现为肿瘤较大、边界清晰、有包膜、囊实性。     

Chronic Pancreatitis: Ultrasound, Computed Tomography, and Magnetic Resonance Imaging Features

Chronic pancreatitis is a progressive, irreversible inflammatory and fibrosing disease of the pancreas with clinical manifestations of chronic abdominal pain, weight loss, and permanent pancreatic exocrine and endocrine insufficiency. In the United States, a long history of heavy alcohol consumption is the most common cause of chronic pancreatitis. This review discusses the different modalities such as computed tomography, transabdominal and endoscopic ultrasound, magnetic resonance imaging/magnetic resonance cholangiopancreatography, and endoscopic retrograde cholangiopancreatography available to image chronic pancreatitis, along with their advantages and limitations. In addition, topics such as groove pancreatitis and autoimmune pancreatitis are examined, along with a discussion of distinguishing chronic pancreatitis from pancreatic adenocarcinoma.     

彩超、MRI及两种方法联合试验对胎盘植入的诊断价值

目的 评价彩超、MRI及2种方法联合3种试验方法在胎盘植入(PIA)诊断中的价值.方法 对131例怀疑胎盘植入的患者进行彩超及MRI检查,将检查结果与手术及病理结果(金标准)进行比较,并对彩超、MRI及两法联合方法的诊断价值进行分析.结果 彩超、MRI及两法联合组的Youden指数、Kappa值均大于或等于0.70.但3组中两法联合组的灵敏度最高,漏诊率最低.与非PIA组相比,彩超检查PIA组在基底宫壁肌层血流速度方面均明显增大(P＜0.01);S/D和RI却显著减少(P＜0.05).结论 彩超、MRI及两法联合组都是诊断PIA的适宜方法,但以彩超和MRI联合应用的灵敏度最高,漏诊率最低.