Segmentation of pelvic structures under clinical conditions from axial MR images acquired after the insertion of a transurethral ultrasound device for prostate cancer treatment. (1) Transurethral device; (2) Prostate; (3) Rectum; (4) Bones.
Clinical MR images from previous studies on two different patients. (a) Zoomed axial view and critical angle for rectal safety without transurethral device insertion; (b) Change in the conformation of the prostate due to the insertion of the ultrasound device in the urethra of a patient. The urethra was shifted toward the anterior region of the prostate, affecting the prostate radius distribution and the critical rectal angle.
Dual-frequency principle. A crossover radius (RCO) is defined to switch between fundamental frequency (flow) and third harmonic (fhigh) for optimization of targeting accuracy and treatment speed. Three slices of the same prostate are shown.
Full prostate gland treatment with nine-slice simultaneous MR control. Experimental results in gel phantom on the biggest prostate (Patient 6). The three first columns show the temperature distribution at different time points. The right column shows the maximum cumulative temperature after the treatment has completed.
Influence of frequency in achieving full prostate heating for three prostate models. Experimental results in gel phantom at Pmax = 20 W cm−2. View of the middle prostate slice. Decreasing frequency from 8.1 MHz to 4.6 MHz enabled sufficient heat deposition for a wider range of prostate radii (7–30 mm).
Illustration of the benefits provided by dual-frequency transurethral ultrasound exposures for full human prostate boundaries heating. Experimental results in gel phantom at Pmax = 20 W cm−2. Patient 2: Enhancement of the treatment homogeneity at the apex (slice 8) and reduction of the heating outside the prostate in the posterior-anterior direction. Patient 4: Improved targeting accuracy in all prostate slices.
Effect of acoustic power, fundamental ultrasound frequency, and dual-frequency ultrasound exposures on targeting accuracy after full prostate transurethral ultrasound treatment. Experimental results in gel phantom. 3D surface visualization of the radial targeting accuracy measured in axial planes in six human prostate geometries. The gray regions show excellent targeting accuracy corresponding to ±2 pixels in the thermal map. Hot colors and cool colors correspond, respectively, to over- and undertreatments. The benefit of some parameter combinations depends on the individual prostate shape.
Modeling of rectal wall safety during transurethral ultrasound treatment of whole human prostate gland (Patient 2). Efficacy of the rectal cooling in preventing superficial irreversible damages in the rectum (<0.3% of the rectal wall at risk). Treatment at 20/10 W cm−2, and dual-frequency exposure at 4.6/14.4 MHz. 2D temperature distribution in the axial middle slice of the prostate (top), 3D view of the prostate/rectum and rectal wall damage (bottom).
Modeling of pelvic bones during full prostate transurethral ultrasound treatment and consequences on treatment safety in surrounding soft tissues. Maximum temperature distribution at prostate apex after: (a) a single frequency treatment; (b) a dual-frequency treatment.
Control algorithm: calculating rotation rate, acoustic power and frequency.
Dimensions of prostate profiles studied during in vitro ultrasound treatment.
Description of the groups involved in the in vitro gel phantom comparison study.
Prostate tissue and bone parameters used during numerical modeling of transurethral ultrasound prostate treatment.
Effect of prostate tissue perfusion on transurethral ultrasound full prostate heating.
Results of the in vitro gel phantom comparison study in five groups. Report of parameters related to full gland treatment feasibility, treatment speed, treatment accuracy, and treatment safety.
Treatment safety in rectal wall on Group E.
Treatment safety in pelvic bones and damages in surrounding soft tissues due to bone heating.
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