RadioProcessor-G
Important Considerations:
•
By default, the shape of the carrier signal is a sin wave, so unless a non sinusoidal signal is desired for output,
only the frequency, phase, and amplitude of the carrier signal must be defined.
•
If no envelope shaping is required, then the 7
th
envelope register can be used. When this is done, the carrier
signal is sent to the output without being multiplied by the envelope signal.
•
When making a shaped RF pulse, it is important to set the envelope frequency register to 7 before the pulse, as
this will make certain the phase starts at zero.
Relevant MRI SpinAPI functions:
Carrier signal related:
spmri_set_frequency_registers()
spmri_set_phase_registers()
spmri_set_amplitude_registers()
spmri_set_carrier_shape()
Envelope related:
spmri_set_envelope_frequency_registers()
spmri_set_envelope_shape()
Step 3: Data Acquisition Parameters
The acquisition system of the RadioProcessor-G is very similar to that of the original RadioProcessor. More
information on the general operation of the acquisition system can be found in the RadioProcessor manual.
Once the RadioProcessor-G has been instructed to acquire data, there are two parameters that will influence the length
for which data will be recorded; these are the Spectral Width and the Number of Points.
Spectral Width
is the bandwidth of the captured data, which can also be thought of as the frequency at which data is
recorded.
Number of Points
is the amount of complex baseband points that will be captured. The maximum amount of points
that may be recorded is 16384.
Acquisition Time
for a scan can be calculated using the Spectral Width and the Number of points. The relationship
is:
In order for data to be acquired as accurately as possible, it is important to set the DC offset for the ADC to be set to a
proper value. To determine this value, you must run the program entitled adc_offset.exe, which is included with MRI
SpinAPI package, after your RadioProcessor-G has been successfully installed. You will then be given a number, which
can then be used to properly set the ADC DC offset for data acquisition.
Relevant MRI SpinAPI functions:
spmri_set_num_samples()
spmri_set_num_segments()
spmri_setup_filters()
spmri_set_adc_offset()
2017-09-04
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Number of Points
Spectral Width
Acquisition Time =
