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Comparison of HIFU Devices
Key Differences Between Ablatherm® HIFU & Sonablate® 500
TURP required?
|
At Maple Leaf HIFU, fewer than 2% of patients
have required a TUR-P prior to Ablatherm HIFU. |
Willing to treat larger prostates but frequently
require TURP post treatment or prolonged catheterization. |
| Image Quality |
Dual US Transducers in treatment probe provides
superior 7.5 MHZ imaging while allowing optimum High Intensity
Shock Wave Production with separate generator. |
Single 4.0 MHZ transducer compromises image
quality
and treatment results. |
| Nerve Detection |
Superior imaging allows precise visualization and localization
of neurovascular bundles allowing improved nerve sparing. |
No data available on preservation of erectile function
with suboptimal visualization of 4.0 MHZ probe. |
| Energy Control |
Computer controlled. Auto detection of possible danger
to rectum allows uniform application of energy level to effectively
treat prostate. |
Requires physician input to reduce power and, in some cases,
this could result in a failure to completely treat prostate
tissue. |
| The Probe |
After initially positioned
by physician, probe is fine tuned by robotic control and
image recognition software to ensure accurate treatment.
Allows very accurate delivery of energy to tolerance of 0.1
mm. Fully automated. |
Probe must be manually placed
and manipulated. Very operator dependent. |
| Power Adjustment |
Three scientifically tested
and optimal energy levels for de novo, radiation failure
or HIFU retreatment conditions. |
Must vary energy based on
visual clues to avoid periprostatic tissue injury. Significant
risk of rectal injury. |
| Precision |
Variable lesion height in
single probe allows energy to be delivered in pattern conformed
to prostate anatomy |
Probe geometry poorly configures
to prostate anatomy. |
| Safety
Features |
Four safety features including
external motion detector, rectal wall temperature monitoring,
rectal wall thickness and “probe to rectal wall” distance
protect against rectal or preprostatic tissue injury. Automatic
disengagement of firing device if parameters are violated.
Image guided robotic fine tuning of probe position to ensure
effective treatment. |
Safety devices require constant
operator attention to monitor limited safety parameters and
adjust device energy output to prevent rectal injury (fistula)
or injury to surrounding tissue. |
| Treatment
Time |
Integrated imaging with single
probe and automated control keep treatment time under 2 hours
in the majority of cases. |
Poor image quality and small
treatment field extend treatment time up to 8 hours with
an average treatment time of 2.8 hours. |
Real-Time Imaging: What Is It, Who Has It & Why Is It Important?
"Real-time imaging" is a continuously up-to-date image.
Confused? Think of live football on television. If you are watching
a football game live you are actively participating in real-time
imaging. At every moment, the image on the screen is up-to-date
and reflects what is going on at that split second in time.
When it comes to HIFU, real-time imaging means that during the
treatment the physician is always looking at an up-to-date ultrasound
image of the prostate. Although this is possible with both the
Ablatherm® and Sonablate 500 devices there is a big difference
between the two in terms of image quality. It is a simple law
of physics that the higher the frequency of an ultrasound probe,
the better the image quality.
The Ablatherm® uses an ultrasound crystal that operates
at almost twice the frequency as the one used by the Sonablate.
The significant difference between the image quality (4 MHz for
the Sonablate and 7.5 MHz for the Ablatherm) is like watching
regular television versus High-Definition Television. Consequently,
the image generated by the Ablatherm® is much more crisp
and clear and allows the physician to be much more accurate during
the procedure. As a patient, this is what you want.
Simply put, you need high resolution for accurate cancer treatment.
Sonablate touts its 3-D imaging and color Doppler as superior
technology when the fact of the matter is that higher resolution
imaging is the most important factor here. Ablatherm does not
incorporate a color Doppler into its device because with a 7.5
MHz probe the region of the neurovascular bundle can be accurately
located. Color Doppler is a necessity on the Sonablate device
because of the low quality image provided by the 4 MHz transducer.
The bottom line is image quality counts and improved image quality
improves treatment quality.
Adjustable Power Levels and Hands-on Physician Control
Effectively treating the prostate with HIFU is a science not
an art. Precise power levels have been determined and validated
and modifying them during the procedure may result in under-treatment
of the cancer. The three power levels of the Ablatherm are scientifically
based – the foundation of which is the thermal properties
of the prostate which is different for the three situations (primary,
repeat HIFU, and salvage (post radiation treatment)). There is
no long term data to back up a variable power level, and long
term data is critical in analyzing the effectiveness of prostate
cancer treatments.
The "adjustable power levels" which are promoted
as a Sonablate 500 advantage because they allow for customization
are actually a disadvantage. The risk of reducing the power in
order to protect the rectum from injury is that it may result
in tissue sparing. The same risks apply when decreasing power
when encroaching on the neurovascular bundles as this involves
treating the lateral posterior parts of the prostate, a region
known to often contain cancer.
When a computer guided system is used to deliver the treatment,
the optimal treatment power can be used throughout the entire
prostate without endangering sensitive nearby structures. HIFU
is a technology based procedure and ‘Hands on Physician
Control’ has been replaced with automated computer guided
control in the Ablatherm to provide the most precise treatment
possible. The precise power levels employed with the Ablatherm® can
be used without fear of damage to the rectum since the Ablatherm
has an automatic safety system which stops the machine from treating
if treatment comes too close to the rectum. Because of this safety
system the appropriate level of energy needed to effectively
treat can be uniformly given to all areas of the prostate by
computer guidance.
Show Me the Data!
In comparison to other cancers, prostate cancer progresses relatively
slowly. This certainly doesn’t mean it can be ignored,
but it does mean that it takes many years for a treatment to
become established. Generally, patients need to be followed for
at least five years before it is possible to pass judgment on
whether or not a treatment really works well.
There are several long term studies published in medical journals
with mean follow-ups in excess of five years available for patients
treated with the Ablatherm. The data in these studies is used
by physicians to justify their use of the procedure. There are
no long term follow-ups of patients treated with the Sonoblate
500, and the longest studies available are still only from one
source and have not been substantiated.
One study involves a multi-center experience with the Sonoblate
500 with 18 month results which was presented at the USHIFU 2005
User's Group Meeting which was part of the 15th International
Prostate Cancer Conference, Vail, Colorado in February 2005.
The named presenters and/or authors of the study were Drs. George
Suarez, Raphael Estrella, and Carlos Garcia. Eighty-seven patients
with T-1 or T-2 prostate cancer were included in the study, and
each of them had a Gleason score of 7 or less and a PSA of 10
or less. Of the 87 patients treated 70 maintained a PSA of nadir
but 17 patients (20%) had PSAs which persisted between 1 and
2ng/ml. This presumpted failure rate of 20% is of great concern
because none of these patients had high risk prostate cancer.
Another study using the Sonablate 500 was published in December
2007. An analysis of those results can be found here.
Infrared Motion Detection & Automatic Shut Off
If a patient moves during a HIFU procedure the treatment must
be stopped immediately. Why? Simply put: because the target,
which is the prostate, has moved. It could be the case that a
structure (like the rectal wall) is now in the line of fire.
The Ablatherm® uses an advanced infrared detection system
to detect any patient movement. If the patient does move the
treatment is stopped automatically and the physician checks to
see if there are any problems. If movement goes undetected injury
could result. Sonablate does not have this warning system and
does not automatically cut off.
Treatment Time
Time is of the essence. The less time a patient is "under" during
a procedure the better. HIFU, with the Ablatherm® takes,
on average, between 1½ and 2 hours. That is considerably
less than the time it takes to treat with the Sonablate 500.
It is hard to come by solid data regarding the Sonablate due
to the absolute lack of published data. However, one of the few
studies published in the medical literature clearly addressed
the treatment time with the Sonablate: Uchida’s multicenter
trial treated 72 patients who, on average, had a prostate volume
of 22.1cc (this is a small average volume). The treatment time,
as clearly stated in the paper was, on average, 169 minutes (2.8
hours) and ranged from 65 minutes (1.1 hours) to 485 minutes
(8.1 hours).
A Note About TURPs
At Maple Leaf HIFU, fewer than 2% of patients required a TURP
prior to Ablatherm HIFU treatment. A TURP will be required for
excessively large prostates in order to treat using either of
the devices. Failure to do so will result in leaving tissue (and
potentially cancer) behind.
A more detailed analysis of the two devices can be
found by clicking
here (PDF) .
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