PEDIATRIC SPINE ULTRASOUND

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NEW ULTRASOUND SCORING SYSTEM for THYROID NODULES

Elastography can help evaluate carotid plaque

By Erik L. Ridley, AuntMinnie staff writer

June 19, 2017 -- A shear-wave ultrasound elastography method can be used to evaluate the stability of carotid plaques, helping to identify those that are most vulnerable to rupturing and causing a stroke, according to a study published in the June issue of the Journal of Ultrasound in Medicine.

Researchers from the First Affiliated Hospital of China Medical University in Shenyang, China, used shear-wave elastography to calculate the Young's modulus -- a measure of stiffness -- of carotid plaques in more than 60 patients. After retrospectively evaluating patient outcomes after six months, they found that patients who went on to have a stroke or transient ischemic attack within that time period had a lower mean Young's modulus score, indicating a more vulnerable plaque. In addition, the group found that the combination of the Young's modulus with the plaque's stenosis rate yielded the best diagnostic performance for identifying the plaques that became symptomatic.

"The [shear-wave elastography] technique is a noninvasive, vascular elastography technique that can provide information regarding carotid plaque vulnerability, and could be of clinical benefit to help identify symptomatic carotid plaques more comprehensively and to predict cardiovascular risk," wrote the team led by Dr. Zhe Lou.

Carotid plaque stability

The presence of carotid atherosclerotic plaques is a strong predictor of cerebrovascular events, and investigators are searching for noninvasive imaging and biochemical parameters that can accurately identify vulnerable plaques to prevent stroke. While the rigidity of a plaque can be calculated on shear-wave elastography via the Young's modulus stiffness measure, few studies have assessed its use for evaluating the stability of carotid atherosclerotic plaque. As a result, the researchers set out to evaluate the feasibility and clinical value of the technique in assessing the rigidity and vulnerability of carotid plaque (J Ultrasound Med, June 2017, Vol. 36:6, pp. 1213-1223).

Lou and colleagues retrospectively studied a total of 61 subjects with carotid plaques who had received carotid ultrasound from January to November 2015. Patients were excluded from the study if they showed disabilities caused by stroke, bilateral focal neurological symptoms, atrial fibrillation, vascular lesions, recent myocardial infarction, or severe congestive heart failure that could be the cardioembolic cause of cerebrovascular stroke.

To ensure that culprit plaques originated from the external cranial carotid artery, the researchers also excluded patients with moderate to severe stenosis of the intracranial artery, or with moderate to severe stenosis before the initial part of the carotid. Patients with radiation injury-associated stenosis, restenosis after endarterectomy, Takayasu arteritis, carotid artery dissection, or total carotid occlusion were also left out of the study.

The patients -- 45 men and 16 women -- were separated into two groups depending on whether they showed unilateral focal neurological symptoms within six months or if they were asymptomatic over that time frame. Of the 61 patients, 31 were in the symptomatic group; 16 had a nondisabling stroke and 15 had a transient ischemic attack. The remaining 30 were asymptomatic.

All patients received a clinical carotid ultrasound examination in conjunction with shear-wave elastography using an Aixplorer (SuperSonic Imagine) ultrasound scanner with a L10-2 MHz linear array transducer. Shear-wave elastography analysis was successfully carried out in 271 (92%) of the 295 plaques evaluated in the study, and the scanner's built-in Q-Box-Trace software tool was used to quantify the maximum, mean, and minimum Young's modulus values.

Finding vulnerable plaques

When confounding factors such as gender and smoking history were controlled, the researchers found a significant correlation between Gray-Weale plaque classification and mean Young's modulus (r = 50.728, p < 0.01). In addition, the mean Young's modulus of representative plaques in the symptomatic group was 81 kPa, compared with 115 kPa in the asymptomatic group. The difference was statistically significant (p < 0.01).

The researchers noted that the vulnerability of the whole plaque can be determined by calculating its Young's modulus measure on shear-wave elastography.

"The lower mean Young's modulus indicates a greater proportion of lipid cores, which could imply greater vulnerability than plaques with a higher fibrous content," they wrote.

(A, above) Carotid plaque classified as Gray-Weale Type II shown with a B-mode and shear-wave elastography image. (B, below) The Young's modulus value of the plaque located in the anterior of the internal carotid artery was obtained using the Q-Box-Trace software tool. All images courtesy of the Journal of Ultrasound in Medicine.

What's more, logistic regression and receiver operating characteristic (ROC) analysis suggested that the combination of the mean Young's modulus with stenosis rate could yield increased sensitivity and specificity for identifying symptomatic carotid plaques, according to the researchers.

Diagnostic efficacy of ultrasound parameters for differentiating carotid plaque
	Area under the curve
Gray-Weale plaque classification	0.760
Mean Young's modulus	0.871
Stenosis rate	0.880
Gray-Weale classification and mean Young's modulus	0.872
Gray-Weale classification and stenosis rate	0.901
Stenosis rate and mean Young's modulus	0.933

"Further studies are required to prove our initial findings and to extend the study to the assessment of the different Young's modulus values against other noninvasive imaging techniques and pathological staining, which could further confirm the clinical potential and value of the carotid plaque evaluation via [shear-wave elastography]," the authors wrote.

Study questions use of FAST exam for kids with trauma

By Erik L. Ridley, AuntMinnie staff writer

June 14, 2017 -- Can a focused assessment with sonography for trauma (FAST) exam improve the clinical care of hemodynamically stable children who have blunt trauma to the torso? Apparently not, according to research published June 13 in the Journal of the American Medical Association.

In a randomized clinical trial involving nearly 1,000 hemodynamically stable pediatric patients being treated in the emergency department (ED) for blunt torso trauma, FAST failed to show any benefit over standard trauma evaluation in terms of reducing CT utilization, ED length of stay, missed intra-abdominal injuries, or hospital charges.

"These findings do not support the routine use of FAST in this setting," wrote the team led by Dr. James Holmes from University of California, Davis Medical Center.

Identifying hemoperitoneum

The FAST exam is used to evaluate injured patients with the goal of identifying hemoperitoneum associated with intra-abdominal injuries. Most research assessing the utility of FAST has involved adult patients, with randomized clinical trials finding that an initial FAST exam yielded lower utilization of abdominal CT, a shorter hospital length of stay, fewer complications, and fewer hospital charges.

The FAST exam isn't routinely used in the initial evaluation of injured children, however, perhaps reflecting the lack of randomized clinical trials involving children, according to the researchers.

To determine if pediatric patients would also benefit, the researchers set out to investigate whether a FAST exam performed during the initial evaluation of hemodynamically stable children with blunt torso trauma would lead to decreases in abdominal CT use, ED length of stay, and hospital charges without significantly increasing the number of missed intra-abdominal injuries (JAMA, June 13, 2017, Vol. 317:22, pp. 2290-2296).

"It was hypothesized that evaluating children with blunt torso trauma with the FAST examination would result in improved care and reduced costs," the authors wrote.

Randomized trial

The researchers performed a randomized, nonblinded trial at their large, urban, level I trauma center between April 2012 and May 2015, evaluating 925 hemodynamically stable children and adolescents younger than 18 years of age. The subjects had experienced blunt torso trauma and had presented to the ED within 24 hours of the traumatic event.

The children were placed into one of two cohorts: One group received standard trauma ED care, while another group received a FAST exam as an initial evaluation. The inclusion criteria aimed to select a study population with an approximate 5% risk of intra-abdominal injury. The baseline patient demographics were similar for each group.

All FAST exams were performed using a Zonare Z.One Ultra portable ultrasound scanner (Mindray Medical International) with 3.5-MHz and 5.0-MHz transducers. Patients received the standard FAST exam, including views of Morison's pouch, the splenorenal fossa, long and short axes of the pelvis, and subxiphoid.

The exams were performed and interpreted at the bedside by ED physicians who were certified in performing FAST exams based on guidelines from the American College of Emergency Physicians. The participating physicians -- 35 board-certified or eligible emergency physicians and five board-certified pediatric emergency physicians -- also recorded their suspicion of intra-abdominal injury, both before and after the FAST exam. In addition, they noted whether the FAST exam results had changed their decision to order an abdominal CT scan.

For the purposes of the study, all FAST exam results were also presented for later interpretation by one of two experienced ED ultrasonographers. These reviewers were blinded to all clinical data, according to the researchers.

No statistical benefit

Outcomes were similar for both groups of patients, the researchers found.

Effect of FAST exam on patient outcomes
	Control group	FAST group
No. of patients receiving abdominal CT exams	254 of 465 (54.6%)	241 of 460 (52.4%)
Mean length of ED stay	6.07 hours	6.03 hours
Median hospital charges	$47,759	$46,415

None of the differences were statistically significant. There was also one missed case of intra-abdominal injury in the FAST group, compared with no missed cases in the control group.

"Therefore, the study suggests that the routine use of the FAST examination in hemodynamically stable children with blunt torso trauma may not be useful," the authors wrote.

The group did find that the FAST examination was associated with a decrease in physician suspicion of intra-abdominal injury. However, this decrease was seen primarily in children initially suspected to have a 1% to 10% chance of intra-abdominal injury prior to the FAST exam.

"Changes in physician suspicion associated with the FAST examination, however, did not result in decreases in abdominal CT use," the authors wrote.

Changes in CT orders

There were 25 cases in which physicians changed plans to order CT studies after performing the FAST exam. In 12 of these cases, a physician elected to order an abdominal CT study that had not been planned prior to the FAST exam; one of these patients was diagnosed with an intra-abdominal injury. The physician decided not to order a planned abdominal CT following the FAST exam in 13 cases, and none of these patients were later diagnosed with intra-abdominal injuries.

In other findings, agreement between the FAST exam interpretations by the treating physicians and the expert ultrasound viewer was only moderate.

"However, the aim of the study was not to assess agreement between physicians in the performance of the FAST examination but rather to evaluate the effect of the use of the FAST examination on clinical outcomes and resource use," the authors wrote.

They pointed out that the study excluded certain high-risk patients for whom the FAST exam may have the potential to be beneficial.

"The FAST examination is considered the standard of care at the study site in hypotensive injured adults and has a reported sensitivity of 100% for hemoperitoneum in hypotensive injured children," the authors wrote. "Including these high-risk patients in the current study may have improved the sensitivity of the FAST examination."

Unresolved questions

In an accompanying editorial (pp. 2283-2285), Dr. David Kessler of the Columbia University College of Physicians and Surgeons said that rather than removing FAST examinations from pediatric trauma algorithms, the pediatric emergency medicine and ultrasound communities should be encouraged by these study results to further investigate the many unresolved questions about integrating FAST examinations into pediatric blunt abdominal protocols. He noted that the FAST exam is increasingly being used in pediatric trauma despite the lack of robust evidence for best practice.

"Quality improvement or implementation studies may be better suited to studying the desired behavior changes resulting from FAST algorithms," he wrote. "This is worth pursuing considering the potential to reduce exposure to ionizing radiation, the evolving technological advances, and the minimal risks associated with point-of-care ultrasound.

Who should read point-of-care ED ultrasound exams

Who should read point-of-care ED ultrasound exams?

By Erik L. Ridley, AuntMinnie staff writer

May 26, 2017 -- When radiologists interpret initial ultrasound studies in the emergency department (ED), fewer follow-up imaging studies are needed, according to research presented this week at the American College of Radiology (ACR) meeting in Washington, DC.

After reviewing more than 200,000 ED ultrasound events in Medicare data files, researchers from the ACR's Harvey L. Neiman Health Policy Institute found that ED patients with ultrasound studies interpreted by nonradiologists had an average of 1.34 additional imaging procedures performed over the next month, compared with patients who had their exams read by a radiologist.

"While point-of-care ultrasound has the potential to reduce additional and often more costly imaging, studies demonstrating this potential have been limited to narrowly focused clinical scenarios," wrote a team led by Dr. Van Carroll, a radiology resident at Brookwood Baptist Health in Birmingham, AL. "Our data demonstrate in the aggregate that when radiologists interpret the initial ultrasound examination, subsequent use of imaging resources was significantly less than when the initial ED ultrasound examination was interpreted by nonradiologists."

The e-poster received an ACR 2017 Gold Merit Abstract Award in the advocacy, economics, and health policy category.

The rise of point-of-care ultrasound

Nonradiologists are increasingly using point-of-care ultrasound to evaluate patients in the ED, leveraging ultrasound's advantages such as lower cost, no radiation exposure, and increased throughput compared with other imaging modalities. However, evaluation of this diagnostic pathway requires consideration not only of the benefits of point-of-care ultrasound in the ED, but also the potential effect on healthcare resources, according to the researchers.

As the number of downstream imaging examinations required to make the final diagnosis can be one measure of resource use, the research team set out to assess how many follow-up imaging studies were performed in patients who had their initial ED ultrasound exams interpreted by radiologists versus nonradiologists.

After searching Medicare data files from 2009 to 2014 to identify all patients who had received an initial ultrasound exam in the ED setting, the researchers determined if the study had been interpreted by a radiologist or a nonradiologist. Next, they summed up all further imaging events that occurred for each of those patients within seven, 14, and 30 days after the initial ED ultrasound exam, and compared the numbers for radiologists and nonradiologists.

Of the 200,357 ED ultrasound events, 163,569 (81.6%) were interpreted by radiologists and 36,788 (18.4%) were read by nonradiologists.

Mean number of additional imaging studies after ED ultrasound
	Initial study interpreted by radiologist	Initial study interpreted by nonradiologist	Difference
7 days after initial ED ultrasound	3.17	4.25	1.08
14 days after initial ED ultrasound	3.60	4.83	1.26
30 days after initial ED ultrasound	4.30	5.65	1.34

The differences between radiologists and nonradiologists for subsequent imaging utilization were statistically significant (p < 0.01). After performing multivariate regression analysis, the researchers found no significant differences in comorbidities between the two groups.

They noted that the volume of subsequent imaging decreased over time, declining by 0.08 fewer imaging exams 14 days after the initial ED ultrasound study. That difference was statistically significant (p < 0.001). However, the differences in follow-up imaging between radiologists and nonradiologists persisted.

The researchers acknowledged a number of limitations in their study, including its reliance on billed fee-for-service encounters in the Medicare population, the lack of differentiation between community and academic institutions, and the lack of differentiation between exams that were performed and interpreted versus exams that were only interpreted by the provider billing Medicare. The study also didn't assess the situations in which a "limited" ultrasound exam performed by a nonradiologist led to more downstream imaging. The authors noted that some limited ultrasound exams may be performed in the ED without being billed to Medicare.

Possible explanations

While the causes of this difference in downstream imaging utilization aren't clear, potential explanations could range from a previously documented higher use of limited ultrasound examinations by nonradiologists to a lack of confidence in the interpretations of nonradiologists, according to Dr. Bibb Allen Jr., a co-author and chair of the Neiman Institute advisory board.

As resource use will be a critical metric in federal health reform efforts, further analysis is needed to elucidate the causes of this discrepancy, he said.

"Since emerging federal health reform includes cost and resource use as part of the Medicare Quality Payment Program, emerging patterns of care such as point-of-care ultrasound should include resource use in outcomes evaluation," Allen said in a statement. "Efforts toward improving documentation of findings and archiving of images as well as development of more robust quality assurance programs could all be beneficial."

THUẬT NGỮ SIÊU ÂM ĐÀN HỒI

GLOSSARY for US Elasto Terminology 

BẢNG TỪ VỰNG CHUYÊN NGÀNH VỚI CÁC ĐỊNH NGHĨA  MỘT SỐ THUẬT NGỮ ĐÀN HỒI

acoustic radiation force

lực bức  xạ  âm=hiện tượng vật lý do tương tác sóng âm với môi trường truyền qua tạo bởi chuyển đổi động lượng từ sóng âm với môi trường, khởi lên từ hấp phụ và/hoặc tán xạ/phản hồi của năng lượng âm; thuật ngữ ‘bức xạ âm’ dùng cho sự truyền năng lượng âm, là một dạng bức xạ không ion-hóa.

- A physical phenomenon resulting from the interaction of an acoustic wave with the medium through which it is propagating, generated by a transfer of momentum from the wave to the medium, arising from the absorption and/or scattering/reflection of acoustic energy; the term ‘acoustic radiation’ refers to the propagation of acoustic energy, which is a form of non-ionizing radiation.

acoustic radiation force impulse (ARFI)

xung lực bức xạ âm (ARFI)=như xung tạm thời [rất ngắn, 1miligiây] của lực bức xạ âm, tạo bởi một chùm âm tập trung. Trong sách báo kỹ thuật, thuật ngữ này thường dùng thay đổi cho ‘tạo hình ARFI’, tuy nhiên, trong sách báo thương mại và lâm sàng, thuật ngữ này được dùng cho cả tạo hình ARFI lẫn định lượng ARFI.

- A temporally impulse-like (i.e., very short duration, 1 msec) acoustic radiation force, typically generated with a focused acoustic beam. In the technical literature, this term has been used interchangeably with ‘ARFI imaging’, however, in the clinical and commercial product literature, this term has been used to refer to both ARFI imaging and quantitative ARFI.

acoustic radiation pressure

áp suất bức xạ âm= lực bức xạ âm tác động trên bề mặt một vật trong đường truyền sóng âm

- The acoustic radiation force exerted on the surface of an object placed in the path of a propagating acoustic wave.

ARFI imaging

tạo hình ARFI= dạng tạo hình đàn hồi dùng tác động xung lực bức xạ âm, và tạo ra hình ảnh dời chỗ mô trong chùm ARFI kích thích. Kích thích ARFI được dùng để khảo sát những vị trí bên lân cận theo chuỗi trong vùng quan tâm, với những hình ảnh tương đương với dời chỗ mô tương đối. Thông tin tương tự như từ các hình ảnh căng tạo ra do lực đè từ ngoài.

- A form of elasticity imaging that uses acoustic radiation force impulse (ARFI) excitation, and generates images related to the corresponding tissue displacement within the ARFI excitation beam. ARFI excitations are used to sequentially interrogate adjacent lateral positions within a specified field of view, with the corresponding images reflecting relative tissue displacement. The information in these images is similar to that from strain images generated with external compression

ARFI quantification

định lượng ARFI=thuật ngữ dùng nhiều trong y văn nhằm mô tả kỹ thuật đàn hồi sóng biến dạng từng điểm  của Siemens VTTMQ.  Xem thêm point shear wave elastography.

- A term widely used in the clinical literature to describe the point shear wave elastography method employed by the Siemens VTTMQ feature. See also point shear wave elastography

axial strain

căng theo trục=căng theo hướng lực tác động. Trong đàn hồi, nói chung là theo hướng chùm âm, hay hướng vào chiều sâu.

- Strain in the direction of the applied force. In elastography, this is generally in the direction of the acoustic beam, or the depth direction.

bulk modulus

mô đun đàn hồi  khối,  mô đun biến dạng thể tích=đặc trưng vật chất căn bản của sự chống đối của thay đổi khối lượng do áp suất tăng.  Tương đương với chống đối với tăng tỷ trọng khi áp suất tăng. Đàn hồi khối là phản nghĩa với sự đè ép.

- A fundamental material property that quantifies the resistance to volume change with increasing pressure. It is equivalent to the resistance to increase density with increasing pressure. The bulk modulus is the inverse of compressibility.

compressibility

đè ép=đo thay đổi khối lượng tương đối khi đáp ứng với thay đổi áp suất. Đè ép là phản nghĩa của đàn hồi khối. Ghi nhận rằng có khác biệt giữa đoạn nhiệt (đẳng entropy), đè ép  và đẳng nhiệt (nhiệt độ không đổi), nhưng sự khác biệt không đủ cho hầu hết nhu cầu trong đàn hồi.

- A measure of the relative volume change in response to a pressure change. Compressibility is the inverse of the bulk modulus. Note that there is a distinction between adiabatic (constant entropy) compressibility and isothermal (constant temperature) compressibility, but the distinction is beyond the scope of most needs in elastography.

compressional wave

sóng ép= sóng cơ học truyền theo hướng phần tử dời chỗ. Sóng ép tăng truyền (và kế tiếp giảm truyền) trong áp suất tại chỗ hay tỷ trọng. Cũng là sóng âm, sóng âm thanh, sóng áp lực, sóng p hay sóng dọc.

- A mechanical wave that propagates in the direction of the particle displacement. A compressional wave is a propagating increase (and then decrease) in the local pressure or density. These are also known as acoustic waves, sound waves, pressure waves, p-waves or longitudinal waves.

dispersion (acoustics)

tán âm=hiện tượng sóng phân cách theo thành phần tần số khi truyền. Tán âm gây ra bởi vận tốc pha trong vật chất tùy thuộc tần số (nói chung, thành phần tần số sóng cao hơn truyền đi nhanh hơn các thành phần tần số sóng thấp hơn).

- The phenomena of a wave separating into its frequency components as it propagates. Dispersion is caused by the phase velocity in the material being frequency-dependent (generally, higher frequency component of the wave traveling faster than lower frequency components).

dispersive medium

môi trường tán âm=vật chất có tán âm.

- A material that exhibits dispersion.

elastic modulus

mô đun đàn hồi=định lượng khả năng vật chất biến dạng chống lại lực tác động. Có nhiều loại mô đun đàn hồi chuyên biệt cho các loại lực (hay ứng suất, stress) và các loại biến dạng (hoặc căng); thí dụ như mô đun biến dạng khối, mô đun ngang, mô đun biến dạng dọc, và hệ số biến dạng ngang Poisson.

- A quantity relating the ability of a material to resist deformation when a force is applied. There are many elastic moduli that are specific to the type of force (or stress) and the type of deformation (or strain); see, for example, bulk modulus, shear modulus, Young’s modulus, and Poisson’s ratio.

elastic nonlinearity

đàn hồi phi tuyến=tăng độ dốc đường cong ứng suất-biến dạng với gia tăng căng. Đo tăng độ cứng của vật chất khi gia tăng biến dạng vật chất.

- The increase in the slope of the stress-strain curve with increasing strain. It is a measure of the increased  stiffness of a material as the deformation of that material increases.

elastogram

bản đồ đàn hồi= hình ảnh các đặc điểm (nhày-) đàn hồi mô

- An image of the (visco-) elastic properties of tissue.

elastography

đo đàn hồi=phương pháp tạo hình cung cấp thông tin liên quan đến độ cứng mô (hay đặc điểm đàn hồi khác).

 Any imaging method that provides information related to the stiffness (or another elastic property) of tissue.

group velocity

vận tốc nhóm=vận tốc ở dạng toàn thể của truyền sóng (sự điều biến, đường bao). Là tốc độ sóng kết hợp với tổng trọng số các vận tốc pha lẽ cấu tạo nên sóng.

- The velocity at which the overall shape (modulation, envelope) of a wave propagates. It is the wave speed associated with the weighted sum of the individual phase velocities comprising the wave.

indentation test

test làm lõm, test đánh giá đặc điểm cơ học vật chất=test thiết kế đo độ cứng vật chất (nói chung có khả năng chống lại biến dạng dẻo hay gãy). Đôi khi cách này dùng đánh giá mô đun biến dạng dọc của vật chất.

- A method for estimating the mechanical properties of a material. Specifically, indentation tests are designed to measure the ‘‘hardness’’ of a material (generally, its ability to resist plastic deformation or fracture). This approach is sometimes used to estimate the Young’s modulus of a material.

Kilopascal

Kilopascal=một ngàn Pascals (kPa)

- One thousand Pascals (kPa).

loss modulus

loss modulus [mô đun mất] = mô tả lượng không đàn hồi (hoặc nhày) của vật chất nhày-đàn hồi đáp ứng lực tác động (ứng xuất, stress). Loss modudus kết hợp với storage modulus (đáp ứng đàn hồi hay năng lượng hàm trữ) diển tả mô đun phức động [complex modulus] (dynamic modulus).

- The quantity describing inelastic (or viscous) response of a viscoelastic material to an applied force (stress). The loss modulus combines with the storage modulus (the elastic response or stored energy) to express the complex modulus.

magnetic resonance elastography (MRE)

cộng hưởng từ đàn hồi (MRE)=phương pháp tạo hình đàn hồi dùng máy rung ngoài tạo nên sóng biến dạng, và tạo hình cộng hưởng từ theo dỏi đáp ứng mô tạo ra hình mô đun ngang (liên quan đến mô đun biến dạng dọc bằng một yếu tố 1/3 theo một số giả định đơn giản hóa nhất định)

- An elasticity imaging method that uses an external vibration device to generate shear waves, and Magnetic Resonance Imaging to monitor the tissue response to generate images of shear modulus (which is related to Young’s modulus by a factor of 1/3 under certain simplifying assumptions).

modulus of rigidity

mô đun độ cứng= xem mô đun ngang

- See shear modulus.

pascal

pascal=đơn vị đo áp suất, ứng xuất, mô đun độ cứng, mô đun biến dạng dọc hay độ bền kéo. Đặt tên theo nhà toán học và vật lý Pháp Blaise Pascal, một pascal (Pa) tương đương với một newton trên mét vuông, và 1 kPascal ứng với 0,01 atmotphe [đơn vị đo áp suất]

- A unit measure of pressure, stress, shear modulus, Young’s modulus or tensile strength. Named for the French mathematician and physicist Blaise Pascal, one pascal (Pa) is equivalent to one newton per square meter, and 1 kPa is approximately 0.01 atmospheres.

phase velocity

vận tốc pha=tốc độ khi phase của sóng, hay bất kỳ thành phần tần số đơn của sóng, truyền trong không gian. Là chỉ số của độ dài sóng với chu kỳ sóng.

- The rate at which the phase of a wave, or any single frequency component of the wave, travels in space. The phase velocity is the ratio of the wavelength to the period of the wave.

point shear wave elastography

đàn hồi đo theo điểm sóng biến dạng= phương pháp  đánh giá độ đàn hồi bằng cách tạo ra sóng biến dạng với lực bức xạ âm và ghi lại số đo định lượng độ cứng (cả tốc độ sóng biến dạng hoặc mô đun biến dạng dọc), số đo này diễn tả bình quân số đo một khu vực giả định đồng dạng trong vùng quan tâm.

- An elasticity estimation method that generates a shear wave with acoustic radiation force, and reports a quantitative stiffness metric (either shear wave speed or Young’s modulus) that represents the average of that metric within a local region of interest that is assumed to be homogeneous.

Poisson’s ratio

hệ số biến dạng ngang Poisson=đặc tính vật chất cơ bản định lượng hệ số âm của căng ngang với căng dọc trong vật chất đàn hồi. Với vật chất đẳng hướng, hệ số Poisson nằm giữa -1 và 0,5. Vật chất không đè ép được có hệ số Poisson là 0,5. Đặt tên theo nhà toán học và vật lý Pháp Simeon Denis Poisson, hệ số Poisson, như mô đun ngang, mô tả sự chống đối của vật chất khi thay đổi dạng, nhưng hệ số Poisson liên quan với thay đổi kích thước theo hướng tải tác động lên thay đổi dạng của vật chất theo hướng thẳng góc .

- A fundamental material property that quantifies the negative ratio of transverse strain to longitudinal strain in an elastic material. For isotropic materials, Poisson’s ratio lies between -1 and 0.5. Incompress -ible materials have a Poisson’s ratio of 0.5. Named after the French mathematician and physicist Sim- eon Denis Poisson, Poisson’s ratio, like the shear modulus, describes the resistance of a material to changes in shape, but Poisson’s ratio relates a change in dimension in the direction of the applied load to the change in shape of the material in the perpendicular direction.

quasi-static loading

tải chuẩn-tĩnh=ngược lại với tải động. Ứng dụng của ứng xuất xảy ra đủ chậm như là hiệu ứng quán tính không đáng kể (độc lập thời gian của tải và khối quán tính có thể không biết)

- The application of stress that happens sufficiently slowly such that the inertial effects are negligible (time dependence of the load and inertial mass can be ignored). This is in contrast to dynamic loading.

radiation force

lực bức xạ= xem lực bức xạ âm

- See acoustic radiation force.

shear modulus

mô đun ngang=đặc tính vật chất định lượng sự chống đối của vật chất để thay đổi dạng trong hệ số shear stress với  shear strain, và cũng là modulus of rigidity. Đơn vị là Pascals.

- A material property that quantifies the resistance of a material to change its shape in shear ratio of the shear stress to the shear strain and is also known as the modulus of rigidity. The units of the shear modulus are Pascals.

shear strain

biến dạng căng, biến dạng trượt=biến dạng vật thể trong đó một  mặt phẳng cắt ngang qua vật thể dời chỗ song song với chính nó.Biến dạng như vậy là kết quả của biến dạng căng.

- The deformation of a body in which a cross sectional plane through the body is displaced parallel to itself. Such a deformation is the result of a shear stress.

shear stress

ứng xuất biến dạng= thành phần của ứng xuất trên một bề mặt tiếp tuyến với bề mặt. Đối với mặt phẳng, vectơ lực trong mặt phẳng bề mặt. Đơn vị của ứng xuất biến dạng là Pascals.

- The component of stress on a surface that is tangential to the surface. For flat surfaces, the force vector is in the plane of the surface. The units of shear stress are Pascals.

shear viscosity

độ nhày biến dạng=chống đối của  chất dịch với biến dạng (dòng chảy). Chất dịch không có độ nhớt gọi là ‘chất dịch lý tưởng’. Các chất dịch chảy dễ dàng, như nước, có độ  nhớt thấp. Các dịch kháng chảy có độ nhớt cao, như rỉ mật. Đơn vị của độ nhày nhớt là Pascal-giây.

- The resistance of a fluid to deformation (flow). A fluid with no viscosity is called an ‘ideal fluid’. Fluids that flow readily, such as water, are low viscosity. Fluids that resist flow, such as molasses, are high viscosity. The units of viscosity are Pascal – second.

shear wave

sóng biến dạng=

- A mechanical wave that propagates in the direction perpendicular to the particle displacement in an infinite material. These are a special type of transverse waves and are also known as s-waves.

shear wave elastography

đàn hồi sóng biến dạng=phương pháp tạo hình đàn hồi dùng  lực bức xạ âm tạo ra sóng biến dạng  và tạo ra hình ảnh định lượng của việc đo độ cứng (nơi đó color bar trình bày cả mô đun Young hoặc tốc độ sóng biến dạng)

- An elasticity imaging method that uses acoustic radiation force to generate shear waves and generates quantitative images of a stiffness metric (where the color bar represents either Young’s modulus or shear wave speed).

shear wave imaging

tạo hình sóng biến dạng=phương pháp đàn hồi kích thích và theo dỏi truyền sóng biến dạng trong mô và ghi lại giá trị định lượngnliên quan đến độ cứng (thí dụ, tốc độ sóng biến dạng, mô đun biến dạng dọc, mô đun ngang).

- An elastography method that induces and monitors shear wave propagation in tissue and reports a quantitative value related to the stiffness (i.e., shear wave speed, Young’s modulus, shear modulus).

SNR (signal to noise ratio)

- The ratio of the amount of signal divided by the amount of noise present in data.

Stiffness

độ cứng

- The extent to which an object resists deformation in response to an applied force.

strain

căng=

- A measure of relative deformation. The most commonly used form is referred to as ‘‘infinitesimal strain’’ or ‘‘engineering strain,’’ which is the ratio of the total deformation (DL) divided by the initial dimension of the material (L), so that strain 5 DL/L.

strain imaging

tạo hình căng=phương pháp đàn hồi tạo nên hình ảnh căng mô, liên quan cả độ cứng cấu trúc của đối tượng và mô đun ngang của mô.

- An elastography method that generates images of tissue strain, which is related to both the structural stiffness of the object and the shear modulus of tissue.

stress

ứng xuất=ứng xuất=lực trên mỗi đơn vị vùng tác động trên vật thể. Ứng xuất có thể từ lực trên bề mặt vật thể hoặc do phần tử nội tại (thành phần thể tích) tácđộng trên phần tử lân cận (thành phần thể tích). Đơn vị của ứng xuất  là Pascal. Xem các loại ứng xuất cá biệt như compressive stress, shear stress và  uniaxial stress.

- The force per unit area acting on a body. Stresses can result from forces on the surface of the body or can be due to an internal particle (volume element) acting on an adjacent particle (volume element). The units of stress are the Pascal. See also particular types of stress such as compressive stress, shear stress and uniaxial stress.

stress concentration

tập trung ứng suất= ứng xuất khu trú cao đáng kể hơn bình quân ứng xuất xung quanh. Thường được tạo ra từ dạng bề mặt không đều  hoặc được vùi khu trú các đặc điểm nhày đàn hồi khác nhau.

- Localized stress that is considerably higher than the average surrounding stress. This is usually caused by an irregular surface shape or a local inclusion with different viscoelastic properties.

stress decay

phân rã ứng xuất=mất ứng xuất trong đối tượng cũng như với thời gian (như trong thực nghiệm xã stress) hoặc trong  không gian (như do hiệu ứng nhiễu xạ từ bề mặt làm lõm)

- A loss in stress in an object either with time (such as in a stress relaxation experiment) or in space (such as due to diffraction effects from a surface indenter).

structural stiffness

độ cứng cấu trúc=độ cứng khởi phát từ cấu trúc vật chất; độ cứng một đối tượng khởi phát từ cả mô đun ngang và hiệu ứng của cấu trúc. Ví dụ, một màng mỏng sẽ có độ cứng cấu trúc thấp hơn và, do vậy, độ cứng thấp hơn, so với màng dày hơn của cùng mô đun ngang, hoặc một ống tạo bởi một tờ giấy thì cứng hơn một tờ giấy do những khác biệt về độ cứng cấu trúc.

- Stiffness arising from the structure of an object; an object’s stiffness arises from both its shear modulus and the effect of its structure. For example, a thin membrane will have a lower structural stiffness and, hence, lower stiffness, than a thicker membrane of the same shear modulus, or a tube formed from a sheet of paper is stiffer than the sheet of paper due to the differences in structural stiffness.

transient elastography

đàn hồi thoáng qua=phương pháp đánh gía đàn hồi bằng cách tạo ra sóng biến dạng với máy rung ngoài và ghi lại số đo độ cứng định lượng (mô đun Young), số đo này là bình quân của việc đo trong một vùng giả định đồng dạng khu trú.

- An elasticity estimation method that generates a shear wave with an external vibration and reports a quantitative stiffness metric (Young’s modulus) that represents the average of that metric within a local region that is assumed to be homogeneous.

transverse strain
căng ngang =thành phần của căng thẳng góc với trục vật chất thích hợp

- That component of strain perpendicular to some relevant axis of the material.

transverse wave

sóng ngang=sóng truyền theo hướng thẳng góc với dời chỗ của vật chất

- A wave that propagates in a direction that is perpendicular to the particle displacement.

uniaxial strain

căng không theo trục=

- An idealized condition in which a planar surface (or cross section through a material) has uniform

displacement perpendicular to the plane of the surface (or cross section).

uniaxial stress

ứng xuất  không theo trục=

- An idealized condition in which a planar surface (or cross section through a material) has uniformly distributed force over the entire surface and that force is perpendicular to the plane of the surface (or cross section).

viscoelastic material

vật chất nhày đàn hồi=vật chất như polymer hay mô không đàn hồi hoàn toàn. Vật chất đàn hồi hoàn toàn trữ toàn bộ năng lượng từ sự biến dạng và phóng thích năng lượng này [như khi trở lại trạng thái ban đầu] khi lực tác động bị gỡ bỏ. Khi có tải động tác động vào vật chất đàn hồi hoàn toàn, căng cùng phase với ứng xuất. Đối với dịch nhớt thuần nhất, căng sẽ chậm so với ứng xuất 90 độ. Vật chất nhày đàn hồi đáp ứng bất kỳ lúc nào giữa 2 trường hơp trên.

- A material, such as a polymer or tissue, that is not perfectly elastic. A perfectly elastic material stores all energy from a deformation and releases that energy (such as to return to its initial state) when the applied force is removed. When a dynamic load is applied to a perfectly elastic material, the strain is in phase with the stress. For a purely viscous fluid, the strain will lag the stress by 90 degrees. A viscoelastic material will respond somewhere between these ideal cases.

viscosity

độ nhày=Xem độ nhày biến dạng

- See shear viscosity.

wave

sóng=là sự nhiễu loạn hay dao động truyền qua môi trường.

- A disturbance or oscillation that travels through a medium.

Young’s modulus

mô đun đàn hồi dọc=đặc điểm vật chất cho thấy khó làm biến dạng vật chất bằng cách làm giãn hay đè ép. Là tỷ số của ứng xuất không theo trục và căng không theo trục (cả với đè nén hoặc tải trọng kéo đứt)

- A material property that indicates how difficult it is to deform a material by stretching or compression. It is the ratio of the uniaxial stress to the uniaxial strain (either compressive or tensile loading).

WFUMB GUIDELINES ELASTOGRAPHY 2015-2016

WFUMB GUIDELINES ELASTOGRAPHY 2015-2016
Download theo link

- Part 1 Basic Shiina 2015.

- Part 2 Breast_Barr   2015.

- Part 3 Liver_Ferraioli   2015.

- Part 4 Thyroid_Cosgrove   2016.

- Part 5 Prostate_Barr   2016.