Biomedical Engineering Reference
In-Depth Information
(a)
(b)
(c)
Lesions
Transducer
Probe tip
(d)
(e)
(f)
FIGURE 11.2 Transrectal HIFU devices commercially available for prostate thermal ablation: (a) Sonoblate 500 system, with (b) transducer
motion and sequential thermal lesion formation through target regions (Koch et al. 2007 [30]) and (c) real-time US monitoring during procedure
(Courtesy of Dr. Naren Sangvhi); (d) Ablatherm system with integrated imaging and therapy transducer, (e) transducer rotation and sequential
lesion formation within axial slice, and (f) typical MR contrast image after treatment demonstrating complete and contiguous ablation of target
zones through summation of smaller focal lesions. (Courtesy of EDAP TMS France, and reprinted with permission from Crouzet, S. et al., Int J
Hyperthermia , 26, 8, 2010.)
cancer [31]. The Sonoblate has been used for treating BPH [32-
35], where the target zone is defined as the anterior-lateral peri-
urethral tissue between the bladder neck and verumontanum,
and on some later studies has included the proximal 5 mm of the
bladder neck. Both systems have shown strong clinical efficacy
for treating localized prostate cancer, either primary, recurrent,
or salvage therapy [29,36-40], and can target whole gland or
regions of localized disease. Overall treatment durations range
to ~2 hours for large prostate glands or target regions, while
precisely avoiding damage to rectum, external sphincter, and
NVB. Typical follow-up image post-treatment of T1-contrast
enhanced MRI demonstrating complete and contiguous abla-
tion zone defined by summation of the individual focal ablations
is depicted in Figure 11.2f adapted from Crouzet [27].
dynamic electrical scanning (no applicator movement) and
increased flexibility in focal shape, beam patterns, and position-
ing. These include MRI compatible intracavitary applicators that
facilitate simultaneous MRI temperature imaging for treatment
monitoring and control [45, 46].
Currently, the ExAblate Prostate System (InSightec LTD, Tirat
Carmel, Israel) is the only commercially sponsored MRg phased
array applicator available for endorectal treatment of prostate
cancer. The transducer consists of 23 mm wide × 40 mm long
piezocomposite array with 990 individual elements operating at
2.3 MHz (Figure 11.3). The transducer assembly can be translated
and rotated within an endorectal housing, which is encased in
an expandable balloon with water cooling to 10-15°C. The sys-
tem can be integrated to the patient table and control system of
a GE 1.5T or 3.0T MR imaging scanner. Standard MR imaging
provides anatomic detail and geometric orientation for accu-
rate treatment planning and guidance in the treatment position.
MR temperature imaging [14,16,47] provides an accurate means
11.2.2.2 Mr-Guided Endorectal phased array
Phased array applicators have been investigated for transrec-
tal delivery of HIFU [41-44] as a means to provide for faster
 
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