Endoluminal MR-guided ultrasonic applicator embedding cylindrical phased-array transducers and opposed-solenoid detection coil.
OBJECTIVE
MR-guided high-intensity contact ultrasound (HICU) was suggested as an alternative therapy for esophageal and rectal cancer. To offer high-quality MR guidance, two prototypes of receive-only opposed-solenoid coil were integrated with 64-element cylindrical phased-array ultrasound transducers (rectal/esophageal).


METHODS
The design of integrated coils took into account the transducer geometry (360° acoustic window within endoluminal space). The rectal coil was sealed on a plastic support and placed reversibly on the transducer head. The esophageal coil was fully embedded within the transducer head, resulting in one indivisible device. Comparison of integrated versus external coils was performed on a clinical 1.5T scanner.


RESULTS
The integrated coils showed higher sensitivity compared with the standard extracorporeal coil with factors of up to 7.5 (rectal applicator) and 3.3 (esophageal applicator). High-resolution MR images for both anatomy (voxel 0.4 × 0.4 × 5 mm(3)) and thermometry (voxel 0.75 × 0.75 × 8 mm(3), 2 s/image) were acquired in vivo with the rectal endoscopic device. The temperature feedback loop accurately controlled multiple control points over the region of interest.


CONCLUSIONS
This study showed significant improvement of MR data quality using endoluminal integrated coils versus standard external coil. Inframillimeter spatial resolution and accurate feedback control of MR-guided HICU thermotherapy were achieved.
INSERM, Therapeutic Applications of Ultrasound, U556 (currently LabTAU - U1032), Université de Lyon, Lyon, F-69003, France.|Université de Lyon, Université Claude Bernard Lyon 1, Lyon, F-69003, France.
Mihaela
M
Rata
INSERM, Therapeutic Applications of Ultrasound, U556 (currently LabTAU - U1032), Université de Lyon, Lyon, F-69003, France.|Babes-Bolyai University, Faculty of Physics, Cluj-Napoca, Romania.
Vlad
V
Birlea
INSERM, Therapeutic Applications of Ultrasound, U556 (currently LabTAU - U1032), Université de Lyon, Lyon, F-69003, France.
Adriana
A
Murillo
Université de Lyon, VetAgro Sup, EA 4174, Marcy l'Etoile, F-69280, France.
Christian
C
Paquet
Université de Lyon, Université Claude Bernard Lyon 1, Lyon, F-69003, France.|MR Unit, Radiology Department, Lyon Sud University Hospital, Hospices Civils de Lyon, Pierre-Bénite, F-69495, France.
François
F
Cotton
INSERM, Therapeutic Applications of Ultrasound, U556 (currently LabTAU - U1032), Université de Lyon, Lyon, F-69003, France.|Radiology Department, Faculty of Medicine, University of Geneva, Geneva, CH-1211, Switzerland.
Rares
R
Salomir
D000818:Animals; D004867:Equipment Design; D019544:Equipment Failure Analysis; D057086:High-Intensity Focused Ultrasound Ablation / Q000295:instrumentation*; D007089:Image Enhancement / Q000295:instrumentation*; D053783:Magnetic Resonance Imaging, Interventional / Q000295:instrumentation*; D059346:Magnets; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013552:Swine; D013817:Thermography / Q000295:instrumentation*; D014159:Transducers
MRI-guided contact ultrasound; RF receiver coil; active temperature control; cancer therapy; opposite solenoid; phased-array transducer