Virtual Touch™ Quantification

Virtual Touch™Quantification This web-based training provides ultrasound technologists and physicians with relevant information to enhance and improve their clinical knowledge of Virtual Touch Quantification, also referred to as VTq on the ACUSON S2000 HELX Evolution and the ACUSON S3000 HELX Evolution ultrasound systems. This module explains  the technology and the clinical background and identifies what is required to successfully utilize and optimize VTq on the ACUSON S2000 HELX and the ACUSON S3000 HELX ultrasound systems. Course Objectives Describe the steps required to perform Virtual Touch quantification Describe the Virtual Touch Quantification technology Identify the VTq reporting capabilities Identify types of chronic liver disease Scan with VTq Upon completion of this course, you will be able to: You should now be able to: Describe Virtual Touch Quantification Identify chronic liver disease Perform scanning techniques Identify the steps required to perform a workflow Identify the VTq reporting capabilities Image Mode Characteristics Historically, palpation has been widely used as a method to assess the stiffness and elasticity of tissue Changes in tissue stiffness are known to generally correlate with pathological changes Fingertips provide the pressure, sense and interpretation Detect size, location, mobility in an area of interest Palpation has limitations: Deeper depths, smaller lesion sizes Subtle differences in tissue composition Thus it can be difficult to make a diagnosis Now, we use ultrasound to interrogate tissue and provide information about tissue stiffness Virtual Touch: Siemens Applications and Technologies   Four Strain Imaging Technology Methods in Elasticity Visualization/ Quantification   Virtual Touch Quantification*  ARFI Technology Among the ten major causes of death in the United States Chronic hepatitis and cirrhosis progress over several decades Fibrosis histological staging is the key factor in determining liver health  in these patients Liver fibrosis arises after liver damage from liver diseases such as Hepatitis (mainly C), NASH (non-Alcoholic SteatoHepatitis), and NAFLD (Non-Alcoholic Fatty Liver Disease) which arise mainly from obesity Staging is currently accomplished by a single core needle biopsy Not well tolerated Small sample size from a focal area Misdiagnosis of stage occurs in 20-40% of cases Incidence of Liver Disease, USA NASH represents the most severe histologic form of nonalcoholic fatty liver disease (NAFLD), which is defined by fat accumulation in the liver exceeding 5% of its weight. Uniform criteria for diagnosing and staging NASH are still debated Insulin resistance is related to obesity The disease can remain asymptomatic for years, or can progress to cirrhosis and hepatocellular carcinoma (HCC)   Final result of a wide variety The extent of fibrosis and not the alteration of liver enzymes has the key role in prognosis Progressive fibrosis predicts progression to cirrhosis in HCV+ patients (Poynard T, 2006 Relationship between fibrosis and outcome:  fibrosis may predict clinical decompensation and complications (ascites, variceal bleeding). (Blasco A, Hepatology 2006; Mayo M, Hepatology 2006)   Hepatitis C - Most Common Hepatitis Virus in USA Fibrosis Assessment Clinical Pathway Intervention (Treatment) Points Current Methods to Stage Liver Fibrosis   Current Tools - Blood Tests  AUROC unsatisfactory (generally <0.90 even for cirrhosis Lab values fluctuate => suboptimal reproducibility Inter-lab variability Results not immediately available Tests cost money Not accurate in discriminating intermediate stages of fibrosis     Strong Need for a Non-invasive Readily Available Testing (Liver) Clinical Pathways in Fibrosis Assessment: How Would a Clinician Use Virtual Touch™ Quantification*? Fibrosis Stage (Metavir) vs. Shear Wave Speed Clinical Application Virtual Touch Quantification - Scanning Technique Factors that can affect measurement repeatability and reproducibility: Excessive tissue motion (cardiac/breathing) Tissue attenuation Poor scan window Depth of ROI Tissue stiffness Local vessels/interfaces For Best Results: Minimal scan pressure Exclude data that varies significantly Minimize breathing and avoid cardiac motion Optimal window is intercostal R Lobe Invalid Measurement  Example of invalid measurement resulting in Vs=XXX m/s Virtual Touch Quantification Scanning Technique: Liver Patient Positioning: Supine or Left Lateral Decubitus Right arm maximum abduction Acquisition Technique: IntercostalRT Lobe Approach Liver Segment 5/8 (Lowest SD) 1-3 cm from Liver Surface Avoid Vessels & BiliaryStructures Minimal scan pressure Patient breathes normally Acquire measurement as patient is asked to stop breathing momentarily Liver Evaluation  Use VTq   Scan liver in native state, without deep inspiration or pre-compression – best approach is through right intercostalspaces Need to focus on optimizing depth of ROI to B-mode ratio Acquire at least 10 samples in same place for an adequate number of measurement samples (fewer may be appropriate  if resulting shear velocity value is consistent) Try to avoid deep inspiration. Normal breathing will give more reproducibility Sampling in multiple locations will improve confidence level Need to focus on optimizing view of lesion to bring within the 10 cm depth range More manipulation required Try to avoid deep inspiration. Normal breathing will give more reproducibility Optimize depth for ROI to B-mode ratio Repeat acquisition 3 to 5 times. When using VTq in a lesion Acquire shear velocity value in lesion and in surrounding tissue       To delete any measurements from this worksheet click on the eraser button VTQ Technical Overview Shear Wave Velocity increases with Liver Fibrosis Stage Virtual Touch Quantification  (VTq) is available on the following transducers and presets: Transducers: 4C1 4V1 6C1 HD 9L4 Exam types: Abdomen Breast Thyroid ROI Size (Not adjustable): 10 x 5 mm (curved and Vector), 5 x 5 mm (9L4) Maximum ROI Depth 8.0 cm (Curved), 5.5 cm (9L4) Maximum Shear Velocity Displayed: 5.5 m/s (curved), 8.4  (9L4)     Position patient in the left lateral decubitus position with right arm in maximum abduction. Best approach is through the right intercostal spaces. The transducer should be parallel to the ribs to reduce rib shadowing. The liver should be in its native state without deep inspiration     Choose Liver Assessment to designate the site that you are measuring and have the data stored in the patient report      Once the appropriate window is obtained, activate VTq from the Virtual Touch menu     Under the assessment menu choose either the site number or the liver segment.   VTQ ROI is perpendicular to and approximately 2cm below the liver capsule. •  VTq measurements will continue to be labeled by the original selected site until changed.   •  As additional VTq measurements are taken, there will be a Total / Valid count indicator for the selected Liver Assessment label.    •  10 measurements per site are recommended to ensure technical accuracy.   •  When moving on to a different site or Liver Segment, open the Liver Assessment and select the desired label.   B mode image is sub-optimal causing shear wave velocity measurement failure. •  Shear wave measurements may frequently display "x.xx m/s" in the measured results.   •  The result indicates measurement failure and typically caused by a low shear wave signal-to-noise ratio (SNR)   ROI should be positioned 2 cm below and perpendicular to the liver capsule.     Once ROI is properly positioned instruct the patient to stop breathing and select update. System will automatically freeze the image and acquire a shear wave value. The value is displayed in m/sec. NOTE: Advise the patient to breathe normally and to momentarily stop breathing and then take measurements. Avoid taking measurements during deep inspiration and breath hold as the literature cites that this action increases central venous pressure. Elevated central venous pressure can artificially elevate shear wave velocity measurements       The system will display an onscreen progress bar that counts down time until transducer is cooled and ready to acquire again. NOTE: Be sure to store data after each acquisition to ensure that the measurement is entered into the report