DOES LESION T1 SIGNAL INTENSITY RELATIVE TO LIVER PARENCHYMA PREDICT VISIBILITY ON ULTRASOUND? A clinical tool to determine feasibility of ultrasound-guided percutaneous interventions Timothy L. Miao 1, Ania Z. Kielar 2,3, Rebecca M. Hibbert 2, Nicola Schieda 2,3 1. Faculty Of Medicine, University Of Ottawa, Ottawa, ON. 2. Department Of Medical Imaging, The Ottawa Hospital, Ottawa, ON. 3. Ottawa Hospital Research Institute, University Of Ottawa, Ottawa, ON. www.ottawahospital.on.ca
DISCLOSURES None of the authors have any disclosures related to this presentation 2
BACKGROUND Image-guided percutaneous interventions for focal liver lesions (FLL): Biopsy, radiofrequency ablation (RFA) Ultrasound (US) has advantages over CT and MRI for image guidance: Cost, ease of access Real time tracking of needle and FLL Limitation: FLL detected on cross-sectional imaging may not be visible on US Delays in scheduling Altered treatment plans 3
BACKGROUND Lack of US visibility of FLL A common cause precluding RFA Kim JE et al. (2011): over 70% of US-guided RFA ultimately deemed not feasible were due to FLL non-visibility Previously described features (Lee MW et al. 2010 and Kim PN et al. 2012): Small size Subphrenic location 4
PURPOSE From our experience, we noted that FLL that are isointense on fat suppressed T1-weighted gradient recalled echo (FS-T1W-GRE) MRI are harder to see on US Purpose of this study: To determine whether T1W SI predicts visibility of FLL on US 5
METHODS Patients and Enrollment Criteria Using PACS, identified all patients who underwent US consultation for possible RFA of the liver Between 2010-2015 Single institution Included: patients with both pre-rfa MRI (including FS-T1W-GRE) and planning US Excluded: patients referred for recurrence or progression of disease in an area of previous RFA or surgery 6
METHODS MRI Evaluation Blinded to US results Size and segmental location of FLL Presence of hepatic steatosis Signal intensity (SI) of FLL on FS-T1W-GRE sequences: Hyperintense (clearly of increased SI compared to adjacent liver) Hypointense (clearly of lower SI compared to adjacent liver) Isointense (approximately same SI as the adjacent liver). 7
METHODS US Evaluation Performed by both an US technologist and 1 of 5 abdominal radiologists who perform RFA Each US was a consultation prior to RFA Feasibility (including visibility of FLL) was recorded Original radiologist s report was retrospectively reviewed: Visibility or non-visibility of FLL on US was recorded Another radiologist re-reviewed the US images for lesion visibility To ensure that in cases with >1 FLL, the correct lesions corresponded to the appropriate MRI findings 8
Lesion visible on FS-T1W-GRE Lesion visible on planning US 9
Lesion not visible on FS-T1W-GRE Lesion not visible on planning US 10
RESULTS Table 1. Patient demographics (N=109) Age (years) [mean ± SD] 66.9 ± 10.9 Range (years) 34 89 Gender male / female 71.6% / 28.4% Number of FLL 177 Hepatocellular carcinoma 132 (74.5%) Metastases 44 (24.9%) Cholangiocarcinoma 1 (0.6%) Patients with a solitary FLL 64 (58.7%) Patients with multiple FLL Range (number of FLL in a single patient) 45 (41.3%) 2 6 Number of FLL visible on US 123 (69.5%) Number of FLL not visible on US 54 (30.5%) 11
RESULTS Size of FLL significantly associated with visibility on US 18.0 ± 8.0 mm (visible) versus 12.3 ± 5.4 mm (not visible), p<0.0001 Location of FLL by liver segmental anatomy No association with FLL visibility on US, p=0.294 Hepatic steatosis 20.2% (22/109) No association with FLL visibility on US, p=0.670 12
RESULTS Signal intensity Visible on US Non-visible on on FS-T1W-GRE (N=123) US (N=54) Hyperintense 25 5 Hypointense 57 22 Isointense 41 27 FLL isointense to liver on FS-T1W-GRE MRI significantly associated with non-visibility on US (p=0.036) Sub-group analysis excluding patients with hepatic steatosis Strengthened the association between non-visibility of FLL on US and isointensity on T1W imaging (p=0.014) 13
DISCUSSION We demonstrated that small size is significantly associated with non-visibility This corresponds with previous studies (Lee MW et al. 2010 and Kim PN et al. 2012) We also demonstrated that isointensity on FS-T1W-GRE MRI is associated with US nonvisibility To our knowledge, no study has investigated individual MRI imaging characteristics on specific MRI sequences as predictors of visibility of FLL on US Lesion location and hepatic steatosis were not predictive of non-visualization on US 14
LIMITATIONS Retrospective assessment of lesion visibility on US images However, a dedicated fellowship-trained radiologist performed each US prospectively MRI and planning US were not performed on the same day Possible that size or SI could have changed in the interval between MRI and US Histopathologic diagnoses were not obtained, some lesions may not have represented true tumor All cases discussed at multidisciplinary case conferences 15
CONCLUSION Small size and FS-T1W-GRE isointensity of FLL affect sonographic visibility FS-T1W-GRE isointensity stronger association in non-steatotic livers These characteristics can help plan US-guided interventions for FLL 16
THANK YOU! 17
RESULTS Table 2. Comparison of appearance between hepatocellular carcinoma (HCC) and metastases on ultrasound (US) and fat-suppressed T1-weighted gradient recalled echo (FS-T1W-GRE) MRI HCC (N=132) Metastases (N=44) p Appearance on FS-T1W-GRE <0.0001 Hypointense 47 (35.6%) 31 (70.5%) Hyperintense 30 (22.7%) 0 (0%) Isointense 55 (41.7%) 13 (29.5%) Visibility on US 0.850 Seen on US 92 (69.7%) 30 (68.2%) Not seen on US 40 (30.3%) 14 (31.8%) 18