FAQs
3D Guidance Trackers
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Q. What trackers make up the new 3D Guidance product line?
Q. How do they differ from Ascension's earlier magnetic trackers?
Q. Aren't all magnetic trackers the same?
Q. How do the new 3D Guidance trackers differ from one another?
Q. What are the differences between earlier 3D Guidance / microBIRD trackers and
medSAFE?
Q. Are 3D Guidance trackers compatible with legacy (older model) Ascension
trackers?
Q. What is the difference between a short-range transmitter with an air core
versus a short-range transmitter with a ferrite core?
Q. Is the new short-range transmitter light enough to mount on a person?
Q. How close can we put two sensors?
Q. What does hot swapping of sensors mean?
Q. What do you mean by time stamping of records?
Q. Do any of the trackers support a button mode?
Q. How is button status reported in the data file?
Q. Is there any way to synchronize the trakSTAR with other data acquisition
equipment in our lab?
Q. Can we plug in any device and use your button?
Q. Power-line noise once was a problem with DC magnetic trackers. How do 3D
Guidance trackers handle this problem?
Q. What is the difference between measurement rate and update rate?
Q. How do 3D Guidance trackers interface to host computers?
Q. What software is provided?
Q. If I need a firmware upgrade, must I return my tracker or insert new proms in
my tracker's electronics unit?
Q. What regulatory standards do 3D Guidance trackers meet?
PRODUCTS OVERVIEW:
Q. What trackers make up the new 3D Guidance product line?
A. The 3D Guidance line includes three trackers:
·
medSAFE
·
driveBAY
·
trakSTAR
Q. How do they differ from Ascension's earlier magnetic trackers?
A. They represent a new generation of Ascension trackers, designed with the latest
advancements in digital signal processing, passive sensing of DC magnetic fields,
Kalman filtering, dynamic noise suppression, and micro miniaturization of sensor
components. They enable you to track the instant position and orientation of miniaturized
sensors at unprecedented high speed and high accuracy with minimal noise. Each
product contains self-diagnostics and run-time monitoring for improved tracker reliability
and safety.
medSAFE is the first Ascension tracker to meet the highest medical compliant
standards. It is a Class 1, Type CF, Defib Proof tracker, which means its sensors can be
used in cardiac applications once users meet FDA/CE and/or IRB requirements.
driveBAY and trakSTAR are the first Ascension trackers to fully meet RoHS and WEEE
standards as well as all pertinent medical, electrical and safety standards.
Q. Aren't all magnetic trackers the same?
A. No, there are several generations of trackers on the market. These range from 1st
generation AC electromagnetic technology, first patented by Polhemus Inc. in the 1970s,
and later enhanced by medical device companies, including Biosense, GE, Medtronic,
MediGuide, NDI, and SuperDimension; 2nd generation trackers patented by Ascension
in the 1990s that employ pulsed DC magnetic technology; and now 3rd generation DC
magnetic technology, also patented by Ascension. 3D Guidance technology offers the
latest improvements and innovations in magnetic tracking technology.
First generation trackers are notoriously susceptible to distorted measurements in the
presence of common metals, such as carbon steel, aluminum, and even stainless steel.
Second generation DC trackers exhibit only 1/5 the sensitivity to non-magnetic
conductive metal as their earlier counterparts. As a result their sensors can be attached
to ultrasound scanheads, titanium instruments, and non-magnetic stainless steel objects
without discernable loss of accuracy. However, their sensors contained fluxgates that
limited sensor miniaturization to 5 mm in diameter, were subject to ferrous metal
distortion, and were too complex to achieve truly low cost.
Third generation magnetic tracking represents the state-of-the-art in real-time tracking. It
includes six degrees-of-freedom sensors as small as 0.94mm in diameter, low cost,
disposable sensor pricing, special transmitters that block distortions emanating below
the tracking volume, and advanced processing and calibration techniques for robust
performance in all kinds of environments.
Q. How do the new 3D Guidance trackers differ from one another?
A. Here is a chart of key differences:
Features
medSAFE
trakSTAR
driveBAY
Number of Sensors
8
4
4
(When Using Mid and
Short-Range Transmitters)
·
·
·
Transmitter Options
Mid Range
Mid Range
Mid Range
·
·
·
Short Range
Short Range
Short Range
·
Flat
External Box with
Electronics
External Box with
Module Fitting into
Built-in Power
Packaging
Built-in Power
PC Drive Bay; Uses
Supply (No "brick")
Supply (No "brick")
PC's Power Supply
Yes
Yes
Yes
Immunity to
Distortion from
Common Hospital
Metals &
Composites
(Stainless-Steel--300
Series, Titanium, Brass,
and Aluminum)
Yes (Area Beneath Flat
Ferrous Metal
No
No
Transmitter Tablet)
Immunity
Class 1, Type B
Class 1, Type B
Medical Compliance Class 1, Type CF,
Applied Part
Applied Part
Defib Proof
Level
List Price
$7,895
$3,790
$3,640
(Single 8mm Sensor with
Mid-Range Transmitter)
Q. What are the differences between earlier 3D Guidance/microBIRD trackers and
medSAFE?
A. Ascension's original 3D Guidance tracker -- with full medical compliance for
navigation of miniaturized sensors -- was released in 2007. It succeeded microBIRD that
had been released in 2005 as a laboratory tool for medical researchers. microBIRD
enabled one to track miniaturized sensors, but it did not carry a medical certification for
use in internal medical procedures.
medSAFE is a 2008 update of last year's 3D Guidance tracker. It tracks up to 8 six-
degrees-of-freedom sensors simultaneously, and offers improved dynamic performance,
hot swapping, time stamped records, on-board flash reprogramming, customizable
settings, biocompatible sensors, and extensive self-test and run-time diagnostics for
improved reliability and safety.
medSAFE also supports tracking of the world's smallest six degrees-of-freedom sensor:
0.94mm in diameter X 7.6mm in length. It is small enough to fit into the distil tip of a 19-
gauge hollow needle.
Q. Are 3D Guidance trackers compatible with legacy (older model) Ascension
trackers?
A. Yes, 3D Guidance trackers are drop-in replacements for many Ascension magnetic
trackers that you once used.
trakSTAR is fully compatible with Ascension magnetic trackers that use RS-232 and
USB interfaces. trakSTAR supports Flock of Birds, miniBIRD and all other Ascension
magnetic tracker using the RS-232 Interface, running winBIRD, CBIRD, SBIRD and
SOCKET programs, and employing Windows drivers.
3D Guidance (older model), microBIRD, and pciBIRD users can substitute new USB and
DLL (drivers) and continue to use old applications. Note, however, 3D Guidance trackers
do not presently support the extended range transmitter that is available with legacy
products. If you need extended range tracking, you can still obtain it by buying a Flock or
MotionStar tracker.
HARDWARE:
Q. What is the difference between a short-range transmitter with an air core
versus a short-range transmitter with a ferrite core?
A. The biggest difference is range. Both transmitters enable six degrees-of-freedom
sensor tracking, but the ferrite version produces a stronger signal than the air core
version. At 17 inches of separation, the position and angular noise for a ferrite
transmitter will be about one half that of the air core. For this reason, we recommend
that the air core transmitter be used in very short-range applications, such as tracking a
sensor referenced to a transmitter that is no greater than 8 -12 inches away.
Q. Is the new short-range transmitter light enough to mount on a person?
A. As long as the transmitter is mounted on a bracket (and therefore not in direct contact
with a person), it can be used for body tracking. The "air core " version weighs just 230
grams. As stated above, it is specifically designed for close range applications. For some
medical applications, it can be mounted on a swing arm or insulated band attached to
the patient for tracking miniaturized sensors within the body. In at least one new
application, this new transmitter is attached to a headband for tracking sensors and
instruments on and near the face. Sensor measurements can be referenced relatively to
one another or absolutely from their geometric center to the center of the transmitter.
Q. How close can we put two sensors?
A. 8mm sensors should maintain a center-to-center separation distance of
approximately 1.3 inches (33mm) for best performance.
Q. What does hot swapping of sensors mean?
A. Each sensor is individually calibrated and can be used with any electronics unit.
Sensors can also be unplugged and re-plugged into the electronics unit and data
reporting will resume as soon as a new connection is made.
Q. What do you mean by time stamping of records?
A. A temporal stamp is applied at the time of data acquisition with 100-microsecond
resolution. The time stamp is provided in UTC format and is synchronized with your host
computer's clock when initialized by our DLL.
Q. Do any of the trackers support a button mode?
A. Yes, trakSTAR allows you to append an external switch or button, to each data
record. See below for additional information.
Q. How is button status reported in the data file?
A. Three data formats are provided in our API that include the button status as a
member of the data format structure. (See: DOUBLE_POSITION_ANGLES_
TIME_Q_BUTTON_RECORD on pages 164 and 165 of the trakSTAR Operations
Guide.)
With these formats, the state of the button is returned as a button value with each data
record (regardless of state of button). When a switch/button is connected, a 1 in the
button value indicates the contact or switch is CLOSED, and a 0 indicates the contact is
OPEN. The button input is sampled by the electronics once per transmitter axis
measurement (i.e. 3 times per system measurement cycle for a mid or short range
transmitter).
Q. Is there any way to synchronize the trakSTAR with other data acquisition
equipment in our lab? In other words, can the trakSTAR accept a TTL signal to
either start the acquisition (with no delay) or to record this signal as a high-low
signal synchronized with the recorded data?
A. Although we do not support use of an external sync to drive the acquisition, there are
two ways to correlate time events with the sensor data records:
a. Timestamps As noted above, several of our data formats include time
stamped records. As the timestamp is synchronized to the host PC's time clock
during initialization, any other device connected to the PC using the PCs
timestamp can be matched up to a given sensor's data record.
b. Button Mode We include a data format in the API that gives you the status of
an external button/switch (simple contact closure - no TTL required) with each
record. You can use this button input to represent an external event (i.e. from
another device) and be reflected in the sensor's data stream.
Q. Can we plug in any device and use your button?
A. Any contact closure switch or button that meets the electrical requirements stated in
the trakSTAR Operations Guide can be used. Note: your device must be wired to mate
with the external BNC connector on the rear panel of the trakSTAR.
Q. Power-line noise once was a problem with DC magnetic trackers. How do 3D
Guidance trackers handle this problem?
A. 3D Guidance trackers support a new and improved wide notch filter that dramatically
reduces 60Hz noise without exacting a noticeable penalty in dynamic performance.
Q. What is the difference between measurement rate and update rate?
A. With previous generation trackers, there was no difference. Measurement rate was
the update rate. With 3D Guidance trackers, however, a new tracking solution (full 6DOF
output) is iteratively computed after each transmitter axis excitation. With a mid-range or
short-range transmitter, this means that by the time each transmitter axis has been
energized, three solutions have been derived and output to your host computer. If the
measurement rate is set at 80HZ and you are using one of our dipole (cubic)
transmitters, you will receive 80Hz X 3 or 240 solutions in each measurement cycle.
Update rate is independent of the number of sensors tracked so the update will remain
constant regardless of the number of sensors tracked.
Q. Can you explain how measurement and update rates are calculated?
A. The calculations differ in the speed in which new tracking solutions are available for your use:
·
Measurement Rate is the rate at which the tracker acquires a complete measurement
set from all available axes in the transmitter.
·
Update Rate is the rate at which a new (unique) position and orientation solution for the
sensor is computed by the tracker.
Legacy (Older) Ascension Trackers:
In previous generation ATC trackers, a position and orientation solution would only be available
after all transmitter axes had been energized. Thus the update rate was equal to the system
measurement rate.
1
UpdateRate =
Hz
a *tA
Where:
a = Number of transmitter axes
1
t A = Axis cycle time =
(sec)
Measurement Rate * a
For example, for an older tracker configured to run at a measurement rate of 80Hz with a
standard mid-range transmitter (3-axis transmitter), the update rate would be computed as:
1
UpdateRate =
= 80Hz
3 * 4.167mS
3D Guidance Trackers
Ascension's new generation of 3D Guidance trackers compute a new position and orientation
solution at the end of each transmitter axis cycle (see Figure 1 below). Both dipole and flat
transmitter-based systems use proprietary new algorithms to advance the solution in time so
there is minimal skew of the data. This yields an update rate that is:
1
UpdateRate =
tA
= a ∗ Measurement Rate
Where again:
a = Number of transmitter axes
Using the same example of a system running at a measurement Rate of 80Hz with a
standard mid-range transmitter (3-axis), the update rate is:
Update Rate = 3 ∗ 80Hz = 240Hz
System Cycle = 12.5mS
(Measurement Rate Setting = 80Hz)
Axis 1
Axis 2
Axis 3
Transmitter excitation
waveform
Axis Cycle = 4.2mS
4.2mS
4.2mS
Update Rate = 240Hz
P&O
P&O
P&O
Figure 1: Transmitter excitation waveform for a 3-axis transmitter running at a measurement rate of 80Hz.
For 3DGuidance trackers, this yields an update rate of 3*80 = 240Hz.
Q. How do 3D Guidance trackers interface to host computers?
A. medSAFE and trakSTAR communicate via high speed USB or serial RS-232 ports.
driveBAY outputs are available over your computer's USB port.
SOFTWARE / FIRMWARE:
Q. What software is provided?
A. You will receive a Windows API, which is compatible with APIs available for legacy
trackers (pciBIRD, microBIRD and 3D Guidance) configuration utility, sample programs,
and a number of demo utilities. The Cubes utility is a graphically based demo program
that lets you checkout the tracker's performance prior to incorporating it into your
application. A virtual dice cube on your monitor mimics the motion of your sensor in free
space. Cubes also presents a numerical representation of the absolute position and
orientation of each sensor as it moves. These programs are contained on a CD-ROM
provided with your tracker for loading onto your computer.
Q. If I need a firmware upgrade, must I return my tracker or insert new proms in
my tracker's electronics unit?
A. No, we can provide on-board flash reprogramming of your unit for most upgrades. In
some cases, a hardware upgrade will be required to add new features to a medSAFE
tracker.
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REGULATORY:
Q. What regulatory standards do 3D Guidance trackers meet?
A. medSAFE is a Class 1 medical device per IEC 60601-1. Its sensors are designed
and tested to the Type CF, Defib Proof Applied Part designation. The system complies
with electrical, safety, and electromagnetic compatibility requirements set forth in IEC
60601-1 and 2.
driveBAY and trakSTAR are Class 1 medical devices per IEC 60601-1. Their sensors
meet Type B Applied Part standards. They also carry the CE mark and meet IEC 60601-
1-2, Class B Limits for EMC.
INSTANT HELP:
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