HepaFat for Clinicians
Why Use HepaFat to Measure Liver Fat
MRI is the safest and most accurate method for non-invasively measuring liver fat. Histopathological assessment from a liver biopsy is commonly considered the gold standard for clinical assessment of liver fat. However, it is subjective, has a poor reproducibility and significant sampling error and suffers from the risks associated with an invasive procedure. Ultrasound, while widely available, has poor sensitivity to discriminate between mild and high levels of steatosis, and is additionally hampered by factors such as obesity, fibrosis, edema and extrahepatic adipose tissue. CT is also a widely available, but its reliance on ionising radiation means it is unsuitable for children and for longitudinal monitoring of adults. CT has low sensitivity for mild-moderate steatosis and attenuation can be affected by sources unrelated to fat (iron, copper, glycogen, fibrosis, edema).
MR techniques like HepaFat are widely accepted as superior compared to ultrasound and CT and are now considered the leaders in the quantitative assessment of fat. HepaFat is one of the few MR techniques to be independently validated against biopsy and has very high sensitivity and specificity at all clinical thresholds. HepaFat-AI and HepaFat-Scan is vendor agnostic and is used in conjunction with a specific MRI data acquisition protocol that is a variation of the three point Dixon Method. Image data acquisition for a HepaFat takes a single breath hold and no contrast agents are required.
Key Benefits of HepaFat-AI
- Comprehensive, all-in-one, rapid results reporting from MRI images
- Notifies in cases of suspected high liver iron content
- Highly repeatable and reproducible
- Fully standardised work flow processing from image acquisition to analysis and report generation
- Ideally suited for single and multi-center NASH clinical trials
- Fits easily into existing workflows
- Quantitative results available in real-time
- Uses non-invasive, contrast free MRI scan images acquired during single-breath-hold
- No new MRI scanner hardware or software required
- Suitable for use with 1.5 Tesla and 3 Tesla MRI scanners
- Standardised metrics across multiple MRI vendors
- Clear report layout for easy interpretation, including fat map for quick overview of fat distribution
- HepaFat-AI has regulatory clearances from the US FDA, Australian TGA, and European CE marking
Key Benefits of HepaFat-Scan
- Unique acquisition provides superior sensitivity, particularly for small changes in fat levels;
- Outputs volumetric liver fat fraction in tissue (%) which means Hepafat-Scan results are directly equivalent to quantitative liver biopsy observations;
- Validated against 3 independent quantitative biopsy measurements of liver fat from very low to very high liver fat levels in non-alcoholic fatty liver disease (NAFLD), non-alcoholic steatohepatitis (NASH), and autoimmune hepatitis;
- Clinically insignificant bias compared with biopsy (1.4%);
- Standardised approach to MRI centre set up, data acquisition, and analysis;
- Standard imaging analysis utilises two large regions of interest (ROI) ~300 times larger than biopsy, reducing sampling error (multiple ROI are available upon request);
- Easy to implement on multiple MRI platforms (Siemens, GE, Philips);
- Single breath-hold data acquisition;
- No additional hardware required or expensive licensing of specialist applications;
- HepaFat-Scan has FDA, TGA and CE Mark regulatory clearance for the quantitative assessment of hepatic steatosis;
- Centralised image analysis in accordance with rigorous standard operating procedures to ensure accuracy and reproducibility of the results. Quality controlled to ISO13485 ensuring reliable results.
Why Choose our Fat services over other PDFF techniques (of which there are several)
- Complex-based MRI-PDFF sequences are generally available only on the latest-generation scanners. Even if available, the sequences may require the purchase of a license to enable their use. Our fat solutions require no additional software or hardware, and require no license or additional payments for use;
- HepaFat has better precision than PDFF measured by MRI because of the higher signal to noise ratio in the raw image data. This higher precision results in higher sensitivity and specificity. An estimate of the precision, called the repeatability coefficient, is 2.1 for HepaFat-Scan. In comparison, the repeatability coefficient for PDFF measurements is 4.7;
- HepaFat reports the volumetric liver fat fraction (VLFF). Note that VLFF is numerically equivalent to the area of fatty vesicles seen in liver biopsy sections. Hence HepaFat measurements are directly relatable to biopsy observations;
- PDFF measurements are not directly relatable to VLFF seen in biopsies (i.e. are not numerically equal). PDFF does correlate to VLFF in biopsies but in a curvilinear fashion. Note that there are several different ways of measuring PDFF and the closeness of the correlation will likely depend on the method being used;
- To date, only two MR liver fat measurement techniques have been “calibrated” against histopathological assessment of steatosis grade and subsequently tested in an independent cohort of patients (see Table). The subsequent testing is sometimes known as “validation”. Validation uses the “cut-points” established in the “calibration” study and applies them to the “validation” study to see how good the sensitivity and specificity of the technique really are when reproduced on a different scanner with different patients. HepaFat is one of the two methods that has been validated in this way and the only method to have been validated in different cohorts (adults, paediatrics). The results showed that HepaFat had superior sensitivity and specificity in the validation study (see Table). The results also show that the “cut-points” used to define steatosis using PDFF methods (MRI or MRS) vary considerably and are dependent on the specific acquisition parameters used (see Table);
- HepaFat has been calibrated against PDFF methods (both MRI and MRS) allowing PDFF equivalent results to be provided.