title: Puncturing Plaques.
abstract: To test and validate magnetic resonance imaging (MRI) sequences for peripheral artery lesion characterization and relate the MRI characteristics to the amount of force required for a guidewire to puncture peripheral chronic total occlusions (CTOs) as a surrogate for immediate failure of endovascular therapy.
  
  
  
  Diseased superficial femoral, popliteal, and tibial artery segments containing 55 atherosclerotic lesions were excised from the amputated limbs of 7 patients with critical limb ischemia. The lesions were imaged at high resolution (75 μm3voxels) with T2-weighted (T2W) and ultrashort echo time (UTE) sequences on a 7-T MR scanner. The MR images (n=15) were validated with micro-computed tomography and histology. CTOs (n=40) were classified by their MR signal characteristics as "soft" (signals indicating fat, thrombus, microchannels, or loose fibrous tissue), "hard" (collagen and/or speckled calcium signals), or "calcified" (calcified nodule signals). A 2-kg load cell advanced the back end of a 0.035-inch stiff guidewire at a fixed displacement rate (0.05 mm/s) through the CTOs, and the forces required to cross each lesion were measured.
  
  
  
  T2W images showed fat as hyperintense and hardened tissue as hypointense. Calcium and thrombus appeared as a signal void in conventional MRI sequences but were easily identified in UTE images (thrombus was hyperintense and calcium hypointense). MRI accurately differentiated "hard," "soft," and "calcified" CTOs based on associated guidewire puncture force. The guidewire could not enter "calcified" CTOs (n=6) at all. "Hard" CTOs (n=9) required a significantly higher (p<0.001) puncture force of 1.71±0.51 N vs 0.43±0.36 N for "soft" CTOs (n=25).
  
  
  
  MRI characteristics of PAD lesions correlate with guidewire puncture forces, an important aspect of crossability. Future work will determine if clinical MR scanners can be used to predict success in peripheral vascular interventions.
authors.affiliation: 1 Schulich Heart Program and the Sunnybrook Research Institute, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada.|2 Division of Vascular Surgery, Department of Surgery, University of Toronto, Ontario, Canada.
authors.forename: Trisha
authors.initials: T
authors.lastname: Roy
authors.affiliation: 1 Schulich Heart Program and the Sunnybrook Research Institute, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada.|3 Department of Medical Biophysics, University of Toronto, Ontario, Canada.
authors.forename: Garry
authors.initials: G
authors.lastname: Liu
authors.affiliation: 4 Division of Engineering Science, University of Toronto, Ontario, Canada.
authors.forename: Noor
authors.initials: N
authors.lastname: Shaikh
authors.affiliation: 1 Schulich Heart Program and the Sunnybrook Research Institute, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada.|2 Division of Vascular Surgery, Department of Surgery, University of Toronto, Ontario, Canada.
authors.forename: Andrew D
authors.initials: AD
authors.lastname: Dueck
authors.affiliation: 1 Schulich Heart Program and the Sunnybrook Research Institute, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada.|3 Department of Medical Biophysics, University of Toronto, Ontario, Canada.
authors.forename: Graham A
authors.initials: GA
authors.lastname: Wright
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000066491:Clinical Decision-Making; D057510:Endovascular Procedures; D005260:Female; D005263:Femoral Artery / Q000000981:diagnostic imaging* / Q000473:pathology; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D018579:Patient Selection; D058729:Peripheral Arterial Disease / Q000000981:diagnostic imaging* / Q000473:pathology / Q000628:therapy*; D058226:Plaque, Atherosclerotic; D011150:Popliteal Artery / Q000000981:diagnostic imaging* / Q000473:pathology; D011237:Predictive Value of Tests; D011677:Punctures; D015203:Reproducibility of Results; D016909:Tibial Arteries / Q000000981:diagnostic imaging* / Q000473:pathology; D061205:Vascular Calcification / Q000000981:diagnostic imaging* / Q000473:pathology / Q000628:therapy*
keywords: angioplasty; atherosclerosis; calcification; chronic total occlusion; displacement force; endovascular treatment/therapy; ex vivo study; guidewire; histology; imaging; magnetic resonance imaging; microCT; peripheral artery disease; plaque morphology; popliteal artery; superficial femoral artery; tibial artery; ultrashort echo time sequence