ElastPQ and LIVER FIBROSIS, [PQ=point quantification]

Liver stiffness values obtained by Elast PQ technique are significantly lower than those obtained by ARFI elastography and future studies are needed to establish the best LS cut-offs assessed by ElastPQ for predicting different liver fibrosis stages.

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ElastPQ (Philips)

from JSUM Ultrasound Elastography Practice Guideline Liver

 Masatoshi Kudo1*, Tsuyoshi Shiina2, Fuminori Moriyasu3, Hiroko Iijima4, Ryosuke Tateishi5, Norihisa Yada1, Kenji Fujimoto6, 7, Hiroyasu Morikawa8, Masashi Hirooka9, Yasukiyo Sumino10, Takashi Kumada11

 A) Introduction

  Name: ElastPQ (PQ: point quantification)

  Equipment: The iU22 xMATRIX ultrasound system (iU: Intelligent Ultrasound)

 ElastPQ is a non-invasive diagnostic tool to measure tissue stiffness using an ARFI-based technology. Immediately after image acquisition, the screen displays the image and measurement results, including the mean and median values and the deviations in kPa or m/s (Fig. 33).

＊If measurement reliability is low, 0.00 kPa will be displayed as the result.

    Elastic value E [kPa] is calculated using the equation E = 3ρVsଶ where Vs [m/s] is defined as the       shear wave propagation velocity and ρ as tissue density (whose approximated value in the human       body is 1). 

    An ROI can be placed anywhere but at a depth of uder  8 cm.

B) Indication

 1. Quantitative assessment of liver fibrosis in diffuse liver diseases

 2. Neoplastic lesions of the liver

C) Procedures (including Tips and Tricks)

 1. Perform right intercostal scanning to visualize the liver

 2. Steadily place the probe with minimum compression

 3. Set the ROI with a depth of under 8 cm.

 4. Ask the patient to breath hold (if not possible, ask the patient to breathe as shallowly as possible).
 5. Push the” Update” button for quantification 

 6. The use of a mean value from more than 10 measurements is recommended.

 Approach the right hepatic lobe from the right intercostal space. Avoid the left hepatic lobe because the measurement is affected by cardiac movement. Breath hold without exerting abdominal pressure. The most appropriate ROI is the center of the image, namely, immediately below the probe, and 3–5 cm from the probe surface. Avoid blood vessels, any necrotic areas, the boundary between organs, and areas influenced by cardiac movement (ex. left hepatic lobe). Three frequencies (R1/RP/P1) are available. The measurement sensitivity of areas deep inside the body can be improved by using a lower frequency. 

 D) Results (What does the value mean?)

 ・Healthy liver: 4 kPa (2.5–4.7 kPa, 1–1.5 m/s) 

 ・Mild fibrosis: 7 kPa (4.7–12.0 kPa, 1.5–2.0 m/s) 

 ・Moderate–severe fibrosis: 12 kPa (12.0–21.0 kPa, 2.0–2.5 m/s) 

 ・Severe fibrosis: over 21 kPa (over 2.5 m/s)

E) Limitations

・There is a limit to measurable depth.

・ElastPQ is affected by respiratory and body movement.

・Cardiac movement also affects the system.

・Accuracy of measurement depends on the skills of the examiner.

・Measurement accuracy is generally low at the sides of an image.

・Ribs may cast lateral acoustic shadows.

F) Recommendations

At present, the number of studies using ElastPQ is not large enough to reach a definitive conclusion. We look forward to having more study results in the near future.