Linear Array Ultrasound Transducer Research Articles

Crohn's disease: Comparison of in vitro ultrasonographic images and histology

Objective. To examine some typical histological findings in Crohn's disease using high-frequency ultrasound and to define the echo properties of these findings. Material and methods. Bowel resection specimens from 14 patients operated on for Crohn's disease were examined with a 10 MHz linear array ultrasound transducer in a saline reservoir. Needles were placed in the specimen corresponding to the ultrasound plane. After formalin fixation, histological sections were taken according to these markings. Fifty-eight ultrasonographic images with 123 regions of interest were compared with corresponding histology. Results. A thickened muscularis mucosae (>0.3 mm) was found in 48 of 69 regions of interest on histology. Submucosa with slight to moderate fibrosis was imaged as an echo-rich layer with sporadic, echo-poor elements (36/56), while severe fibrosis was seen as an echo-rich layer with diffuse, echo-poor elements (40/55). Muscularis propria with slight to moderate fibrosis was seen as an echo-poor layer with sporadic, echo-rich elements (49/66) while severe fibrosis was seen as an echo-poor layer with diffuse, echo-rich elements (17/22). Crohn's rosary was seen as echo-poor extensions of the 4th echo layer (31/50). Conclusions. Typical histological findings in Crohn's disease such as a thickened muscularis mucosae and Crohn's rosary can be imaged with high-frequency ultrasound in vitro. Fibrosis in the submucosa and muscularis propria is associated with decreasing and increasing echogenicity, respectively.

Microchambers and macrochambers in heel pads: are they functionally different?

The heel pad consists of a superficial microchamber layer and a deep macrochamber layer. This study highlights the different biomechanical behaviors between the microchamber and macrochamber layers using ultrasonography. The heel pad in each left foot of six healthy volunteers aged approximately 25 yr old was measured with a device consisting of a 10-MHz linear-array ultrasound transducer and a load cell. The testing heels were loaded on the ultrasound transducer with a loading velocity of approximately 0.5 cm/s and were withdrawn when the specified maximum stress (158 kPa) was reached. Unloaded tissue thickness, end-loaded thickness, deformation proportion, average deformation, and rebound rates and elastic modulus of the microchamber and macrochamber layers were assessed. The unloaded thickness of the microchamber layer was approximately 30% of the macrochamber layer. The microchamber layer also had significantly less unloaded thickness, end-loaded thickness, mean deformation rate, mean rebound rate, and deformation proportion than the macrochamber layer. A significant difference between the unloaded and end-loaded thickness in the macrochamber layer was observed. The average soft tissue deformation rate was significantly different from the rebound rate in the microchamber layer. A similar trend was detected in the macrochamber layer. The elastic modulus of the microchamber layer was 450 kPa (SD 240), which was nearly 10 times of that in the macrochamber layer. In conclusion, ultrasound can identify the heterogeneous tissue properties of the heel pad. The macrochamber layer responds to loading with large deformation, and the microchamber layer has a high degree of tissue stiffness.

Altered energy dissipation ratio of the plantar soft tissues under the metatarsal heads in patients with type 2 diabetes mellitus: A pilot study

Foot ulceration occurs frequently on the plantar aspect of the metatarsal head region, in which the altered foot biomechanics has been mentioned as a contributor. This study attempted to compare the energy dissipation in the plantar soft tissue under the metatarsal head between type 2 diabetic patients and age-matched healthy subjects in vivo. The plantar soft tissues under the metatarsal heads in each left foot of 13 patients with type 2 diabetes mellitus and eight age-matched healthy subjects were measured with a loading-unloading device. The system comprised a 5-12 MHz linear-array ultrasound transducer and a load cell that operated at an impact velocity of about 5 cm/s. The stress-strain plot was derived by simultaneously recording the stress response and tissue deformation during a loading-unloading cycle. The energy dissipation ratio in all subjects could then be analyzed. Although only the plantar soft tissue under the fourth metatarsal head in the diabetic patients endured significantly greater energy (P=0.035) than the healthy subjects, a trend of an increased energy dissipation ratio for the metatarsals in the diabetic patients was observed. The plantar soft tissue under the metatarsal head in the diabetic patients endures high dissipated energy during a simulating walking status in the study. The increased dissipated energy in the tissue may be responsible for the tissue breakdown in the diabetic patients.

Ultrasonographic Examination for Inversion Ankle Sprains Associated with Osseous Injuries

The study attempted to evaluate the value of ultrasonography in determining the therapeutic strategy for patients with osseous injuries caused by ankle sprains. A 10-MHz compact linear-array ultrasound transducer was used to assess patients with inversion ankle sprains. Eleven female and 12 male patients who had fractures detected by sonograms were included in the study. All 23 patients underwent radiographic examination for identification of fractures. Bone scintigraphy was performed for those who had negative x-ray findings. Eighteen patients had distal fibular tip fractures, three patients had the fifth metatarsal base fractures, one patient had a talar neck fracture, and one patient had a navicular fracture. These fractures were all detected by ultrasonography and then proved even by radiography or by bone scans. All the 23 patients had anterior talofibular ligament injuries. Among these patients, 11 had anterior ankle-joint recess effusion, and two had additional anterioinferior tibiofibular ligament injuries. Six weeks of immobilization with the ankle fracture brace was prescribed for all the patients after the identification of fractures. Their ankle pain symptoms soon improved. Ultrasonography is valuable in evaluating tiny foot and ankle fractures and coexistent soft tissue injuries. It can guide the treatment for patients with osseous injuries caused by ankle sprains.

Effects of aging on the plantar soft tissue properties under the metatarsal heads at different impact velocities

The plantar soft tissue properties under the metatarsal heads at different impact velocities in different age groups were measured. Each metatarsus of the left foot in healthy young adults ( n = 9, 19 to 35 years old) and in healthy older persons ( n = 10, 42 to 72 years old) was examined in vivo using a self-constructed loading-unloading device at low, medium and high impact status; the impact velocities of the device were about 2.5, 5 and 10 cm/s, respectively. The device comprised a 5- to 12-MHz linear-array ultrasound transducer, a miniature load cell and a fixation frame. From low to high impact status, the elastic modulus ( E) in young adults significantly increased from about 300 kPa to about 500 kPa. However, the E in the older group did not show this trend. From low to high impact status, the energy dissipation ratio ( EDR) of the metatarsus significantly increased from about 30% to about 60% in the young group and significantly increased from about 40% to about 70% in the older group. Most of the metatarsus in the older subjects had significantly greater E and EDR than those in the younger persons. (E-mail: chungli@ha.mc.ntu.edu.tw)

MUSCULARIS MUCOSAE, FIBROSIS AND NODULAR LYMPHOCYTE AGGREGATES IN CROHN'S DISEASE – NOVEL ULTRASONOGRAPHIC FINDINGS IN VITRO

Purpose: Transabdominal ultrasound (US) is applied in the examination of patients with Crohn's disease (CD). Advances in US technology enables detailed imaging of the gastrointestinal wall like evaluation of normal and abnormal wall layers and intramural structures. The aim of this study was to improve interpretation of US images of bowel wall changes in CD by comparing US images of bowel resection specimens with the corresponding histological sections. Materials and methods: Bowel resection specimens of 7 patients with CD were examined with a 10 MHZ linear array US transducer in a saline reservoir. Marking needles were placed in the specimen corresponding to the US plane. After formalin fixation, histological sections were taken according to these markings. 78 histological sections were examined with special emphasis on muscularis mucosae(MM) thickness, fibrosis and nodular lymphocyte aggregates. Results: A thickened MM was seen in 47/78 histological sections and MM could be identified on 31 US images. Significant fibrosis was seen as reduced echogenicity in the normally hyperechoic submucosa layer and as enhanced echogenicity in the normally hypoechoic muscularis propria layer. Nodular lymphocyte aggregates in close relation to the outer border of the proper muscle were seen in 43/78 histological sections. US images indicated hypoechoic areas corresponding to these aggregates on 37/43 images. Conclusions: High frequency ultrasound could visualise characteristic bowel wall changes in CD like thickened muscularis mucosa, fibrosis and nodular lymphocyte aggregates.

Disadvantages of Ultrasound Guidance in Caudal Epidural Needle Placement

Chang Gung Memorial Hospital, Tao-Yuan County, Taiwan. carlchendr@yahoo.com.twWe thank Dr. Edward for his comments. In this study,1we used the Philips S12 5–12 MHz real-time linear-array ultrasound transducer (Philips Medical Systems, Andover, MA). The contact surface area of the transducer head is 4.73 cm2.We tried both the linear-array and the curvilinear-array transducers. We found that the linear-array transducer was sufficient to depict the sacral cornua and the base of sacrum even in obese patients. The above-mentioned transducer is capable of penetrating to a depth of 8–10 cm. In patients weighing more than 100 kg, the distance from the skin to the base of the sacrum is far less than 8 cm. During the entire injection process, we adjusted the patient’s posture (such as flexing the hip more) to obtain the most suitable position for placement of the ultrasound probe and injection. The best sonogram can be obtained when full contact is made between the transducer head and the examined area. We found the curvilinear-array transducer inconvenient because full contact with the examined area cannot be achieved most of the time.I agree with Dr. Huang that ultrasound has the limitation of not being able to observe the inadvertent placement of the needle intravascularly. During the initial draft of the manuscript, the Discussion section contained more content. I even mentioned the possible sonogram findings for patients without sacral hiatus. One of our authors wanted to include in the Discussion section the fact that ultrasound cannot be used to observe the inadvertent needle placement into the vessels. The reviewers suggested that we shorten the manuscript and focus mainly on the application of ultrasound in locating the sacral hiatus. Therefore, after revision, the entire article focused mainly on the sonograms of the sacral hiatus, and how ultrasound can be used as an adjuvant tool in caudal needle placement. Content about the drugs used and complications of caudal injections was not included in the article.We were fortunate that the Christmas tree–like appearance (fig. 4 in the article) was observed under fluoroscope in all of our patients after locating the sacral hiatus accurately first by ultrasound. This symbolizes the fact that intravascular injection did not occur. Fluoroscopic guidance and contrast dye administration is still the standard in the assessment of the spread of the injected drugs into the desired target levels during caudal epidural injection.Chang Gung Memorial Hospital, Tao-Yuan County, Taiwan. carlchendr@yahoo.com.tw

Retrograde Air Embolization during Routine Radial Artery Catheter Flushing in Adult Cardiac Surgical Patients

Rapid flushing of radial artery catheters may result in retrograde embolization of air into the cerebral circulation. This study examined the incidence of central air embolization during and after flushing of an arterial pressure monitoring system. One hundred adult patients undergoing cardiac surgical procedures were enrolled in this study. Ten ml of saline and blood were withdrawn into a syringe in the arterial flushing-sampling pressure system and then readministered to the patient through a 20-gauge radial artery catheter over 3-12 s. The right carotid artery, left carotid artery, and aortic arch were visualized using ultrasound imaging techniques during three manual flushes of the system. The left and right common carotid arteries were examined for the presence of macrobubbles or microbubbles using a linear array ultrasound transducer. The aortic arch was imaged using transesophageal echocardiography to detect retrograde air emboli. The severity of air embolization was quantified using a modification of an established grading system. A total of 298 ultrasound studies in 100 patients were recorded and analyzed after radial artery catheter flushing. Two aortic arch images were not obtained because of an inability to place the probe. Most clinicians (54%) returned flush solution to patients at near-maximal injection rates (2-3 ml per second). No air emboli (macrobubbles or microbubbles) were detected in the carotid arteries or aortic arch of any subject. Retrograde air embolization is a rare event after routine radial artery catheter flushing in adult patients with stable hemodynamic conditions.

Measurement of vertical alignment of metatarsal heads using a novel ultrasonographic device

Although the vertical alignment of the metatarsal head (MTH) has been defined radiographically, data vary and are questionable. Recently, ultrasonography has been applied to measure the sole thickness of MTHs, but primarily in an unloading condition. This study designed a novel ultrasonographic device that incorporated a 10-MHz linear-array ultrasound (US) transducer on a platform to measure precisely the soft tissue thickness under the MTH on standing. A total of 25 healthy subjects with plantigrade feet were enrolled in this study. Each subject stood steadily on the platform, and the thickness of soft tissue of the MTH was measured based on the distance between the MTH and the plantar skin on the sonogram. The result showed that the MTHs were aligned linearly and inclined to the level surface with the first ray elevated. We concluded that there was neither transverse arch at the distal MTH on standing nor leveling alignment of the MTH, as speculated in conventional plantigrade foot studies.

In vivo real-time freehand palpation imaging

Previous experience with laboratory fixtures and off-line processing of elasticity data showed that problems occurring in data acquisition often resulted in poor elasticity image quality. A system for real-time estimation and display of tissue elastic properties using a clinical ultrasonic imaging system has been developed. A brief description of that system and the initial clinical tests of that system are reported. Experience with real-time freehand elasticity imaging shows that images with high contrast-to-noise ratios are consistently obtained. Images of breast lesions were acquired with freehand palpation using standard linear-array ultrasound (US) transducers. Results in volunteer patients show that high-quality elasticity images are easily obtained from in vivo breast studies. The key element to successful scanning is real-time visual feedback of B-mode and strain images that guide the patient positioning and compression direction. Results show that individual images of axial strain in tissues can be quite misleading, and that a “movie loop” of side-by-side B-mode and strain images provides significantly more information. Our preliminary data suggest that the strain image sequences for various breast pathologies are unique. For example, strain images of fibroadenomas lose contrast with increasing precompression, but those of invasive ductal carcinoma have high negative contrast (dark relative to “normal” tissue) for a wide range of precompression. In addition, a comparison of the lesion area measured in B-mode vs. strain images, for a representative image from the sequence, appears to be a sensitive criterion for separating invasive ductal carcinoma from cyst and fibroadenoma.

Treatment of proximal plantar fasciitis with ultrasound-guided steroid injection

Tsai W-C, Wang C-L, Tang F-T, Hsu T-C, Hsu K-H, Wong M-K. Treatment of proximal plantar fasciitis with ultrasound-guided steroid injection. Arch Phys Med Rehabil 2000;81:1416-21. Objective: To investigate the efficacy of ultrasound-guided steroid injection for the treatment of proximal plantar fasciitis and to evaluate mechanical properties of the heel pad after steroid injection. Design: Proximal plantar fascia and heel pad were assessed with a 10-MHz linear array ultrasound transducer. Pain intensity was quantified with a tenderness threshold (TT) and visual analog scale (VAS). The transducer was incorporated into a specially designed device to measure mechanical properties of the heel pad. Evaluations were performed before injection and at 2 weeks and 3 months after injection. Setting: An outpatient clinic of a tertiary care center. Patients: Fourteen consecutive patients with unilateral proximal plantar fasciitis. Intervention: Ultrasound-guided injection of 7mg betamethasone and 0.5mL of 1% lidocaine into the inflamed proximal plantar fascia. Main Outcome Measures: VAS, TT, heel pad and plantar fascia thickness, and echogenicity of the proximal plantar fascia on sonogram were assessed. Mechanical properties included unloaded heel pad thickness, compressibility index, and energy dissipation ratio. Results: Both VAS score ± standard deviation (SD; 5.43 ± 2.03, 1.39 ± 2.19, 0.57 ± 1.40 at the 3 measurements, respectively) and TT ± SD (5.05 ± 1.42, 9.34 ± 1.84, 9.93 ± 1.98kg/cm2 at the 3 measurements, respectively) improved significantly (p <.001) after steroid injection. The mean thickness of the plantar fascia was greater in the symptomatic side than in the asymptomatic side before treatment (0.58 ± 0.13cm vs 0.40 ± 0.11cm, p <.001). The thickness had decreased significantly 3 months after injection (0.46 ± 0.12cm at 2 weeks, 0.42 ± 0.10cm at 3 months,p <.001). The hypoechogenicity at the proximal plantar fascia disappeared after steroid injection (p <.001). Mechanical properties of the heel pad did not change 3 months after steroid injection (p >.05). Conclusion: Ultrasound offers an objective measurement of the therapeutic effect on proximal plantar fasciitis. Accurate steroid injection under ultrasound guidance can effectively treat proximal plantar fasciitis without significant deterioration of the mechanical properties of the heel pads. © 2000 by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation

Hochauflösende Sonographic des Nervus medianus - neue sonomorphologische Untersuchungstechnik peripherer Nerven

Introduction: In contrast to the standardized methods of clinical neurophysiology, neurosonography of the peripheral nerves has not yet been well established. The development of a new generation of high-resolution ultrasound transducers, however, allows detailed imaging of peripheral nerves including their internal structure, with a high spatial resolution up to 500 μm. Normal age-correlated values for the morphological parameters of peripheral nerves do not exist to date. Methods: Ultrasound examinations of the median nerve including a.p.-diameter, radioulnar diameter, area and circumference were performed at the levels of the wrist, the distal forearm and the cubital fossa in 28 healthy volunteers (range 20-73 years, median 49 years). A 13 MHz linear array ultrasound transducer (Acuson) was employed. Results: Imaging of the median nerve could be achieved in all volunteers, without significant age-dependant variation, at each of the three above-mentioned anatomical levels. Normal values (mean values ± standard deviation) are presented. The internal fascicular structure of the median nerve could be demonstrated in 23 out of 28 volunteers. Interestingly, the median nerve shows physiological flattening at the level of the entrance into the carpal tunnel in healthy volunteers. Discussion: Using high-resolution sonography the median nerve can be clearly depicted at three different anatomical levels of the forearm. Hence, neurosonography is a feasible diagnostic tool to provide realtime information on peripheral nerve morphology. Ultrasound examinations are well tolerated by patients, can be easily performed at bedside at a lower cost than MRI. Thus, neurosonography may provide new and relevant structural information on peripheral nerves and be complementary to conventional neurophysiological examinations.

Ultrasonographic imaging of canine mammary tumours

The efficiency and reliability of an ultrasonographic technique for evaluating mammary neoplasms was tested in 19 female dogs with palpable tumours. A 7.5 MHz linear-array ultrasound transducer was used, with...

Comparison of the mechanical properties of the heel pad between young and elderly adults

Objective: To compare the mechanical properties of the human heel pad between young and aged adults. Design: A 7.5-MHz linear-array ultrasound transducer was incorporated into a specially designed device to measure the thickness of the heel pad under different loads. The heel pad was compressed with serial increments of 0.5kg to a maximum of 3kg and then relaxed sequentially. Then the load-displacement curve of the heel pad during a loading-unloading cycle was plotted. Participants: Convenience sample of 33 volunteers without heel problems, aged 18 to 78 years, were divided into young (less than 40 years) and elderly (older than 60 years) groups. Main Outcome Measures: Unloaded heel-pad thickness, compressibility index, stiffness, and energy dissipation ratio were calculated from the load-displacement curves. Student's t-test was used to compare the mechanical properties of the heel between these two groups. Results: The average unloaded heel-pad thickness was 1.76 ± .20cm in the young group and 2.01 ± .24cm in the elderly group ( p < .001). The average compressibility index was 53.3% ±7.7% in the young group and 61.3% ± 5.5% in the elderly group ( p < .001). Energy dissipation ratio representing shock absorbency of the heel pad, was 23.7% ± 6.9% in the young group and 35.3% ± 10% in the elderly group ( p < .001). Conclusion: Unloaded heel-pad thickness, compressibility index, and energy dissipation ratio of the heel pad were significantly increased in the elderly group, indicating loss of the elasticity of the heel pad. The loss of elasticity may be responsible for the higher incidence of heel injury in elderly individuals.

Changes in pennation with joint angle and muscle torque: in vivo measurements in human brachialis muscle.

1. Estimates of pennation in human muscles are usually obtained from cadavers. In this study, pennation of human brachialis was measured in vivo using sonography. Effects of static and dynamic changes in elbow angle and torque were investigated. 2. Pennation was measured in eight subjects using an 80 mm, 5 MHz, linear-array ultrasound transducer to generate sagittal images of the brachialis during maximal and submaximal isometric contractions at various elbow angles. It was shown that estimates of pennation were reproducible, representative of measurements made throughout the belly of the muscle and not distorted by compression of the muscle with the transducer or rotation of the muscle out of the plane of the transducer. 3. Mean resting pennation was 9.0 +/- 2.0 deg (S.D., range 6.5-12.9 deg). When the muscle was relaxed there was no effect of elbow angle on pennation. However, during a maximal isometric contraction (MVC), with the elbow flexed to 90 deg, pennation increased non-linearly with elbow torque to between 22 and 30 deg (mean 24.7 +/- 2.4 deg). The effect of increasing torque was small when the elbow was fully extended. The relationship between elbow angle, elbow torque and brachialis pennation suggests that the relaxed brachialis muscle is slack over much of its physiological range of lengths. 4. There was no hysteresis in the relationship between torque and pennation during slow isometric contractions (0.2 MVC s-1), and the relationship between elbow angle and pennation was similar during slow shortening and lengthening contractions. 5. Two consequences follow from these findings. Firstly, intramuscular mechanics are complex and simple planar models of muscles underestimate the increases in pennation which occur during muscle contraction. Second, spindle afferents from relaxed muscles may not encode joint angle over the full range of movement.

Collection, in vitro fertilisation and culture of bovine oocytes intravaginally or in a conventional incubator

The aim of this study was to test the feasibility of intravaginal culture for in vitro fertilisation and production of bovine embryos. Oocytes were collected from five cows, superovulated with ovine follicle stimulatory hormone (oFSH), by using a 7.5 MHz rectal linear array ultrasound transducer. From 124 follicles punctured, the oocyte recovery rate was 48 per cent. Fifty-one oocytes were placed in capsules either in the vagina or in an incubator, and cocultured with sperm for 24 hours followed by coculture with oviductal cells for 48 hours. There was no significant difference between the fertilisation rates or the cleavage rates achieved by the two systems and the mean fertilisation rate was 44 per cent. However, the fertilised oocytes did not develop beyond the eight-cell stage.

A simple device to couple linear array transducers to neonate heads for ultrasonic scanning of the brain.

A plastisol coupler has been designed that improves acoustical coupling for linear array ultrasound transducers. This device improves both ease in scanning and image quality in real-time scanning of the infant brain.