RTI Piranha Reference Manual

5. Measurements with the Piranha System
CT
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Piranha & QABrowser Reference Manual
With the calibration C1 the total filtration can be measured and the Piranha
automatically corrects the kV value accordingly. It is optional to set a known total
filtration instead, see the table below. To achieve optimal measurements of the total
filtration, first perform a measurement at a low kV, preferable 80-100 kV. The measured
total filtration is displayed on the screen. Press "Keep" to store the value and carry on
with measurements. Now you can be certain to have a correct total filtration and kV-
value throughout the measurements. Further information about the total filtration can be
found in section HVL & Total Filtration or in the Application Note 1-AN-52020-14
from RTI Electronics AB, see your product CD or www.rti.se.
Essential for correct measurements are correct settings of the CT. The book "Radiation
Exposure in Computed Tomography" by H.D. Nagel, contains useful information about
how correct settings are done on different types of CT scanners. A computer application
CT-Expo based on the book may also be of great help. CT-Expo is an MS Excel
application written in Visual Basic used to calculate patient dose values resulting from
CT examinations. The program is applicable for all existing scanner models and can be
of assistance to make correct settings.
References
1. Nagel, H. D. Radiation Exposure in Computed Tomography. Fundamentals, Influencing
parameters, Dose Assessment, Optimisation, Scanner Data, Terminology. 4th Edition,
Hamburg, Germany, December 2002, CTB Publications, D-21073 Hamburg, ctb-
publications@gmx.de
2. Stamm, G., Nagel, H. D. Software CT-Expo, Medizinische Hockschule Hannover, D-30625
Hannover, stamm.georg@mh-hannover.de
5.7.3 Quick-HVL and Total Filtration
Use the same procedure as for the normal radiography measurement, however see
section CT kVp about using the topogram program.
Tube Current Probes5.8
The mAs probes are used to measure mAs (current time product) and mA (tube
current). Tube current is normally measured only for fluoroscopy or when long exposure
times are possible to allow read-out during the exposure. When tube current is
presented for exposures it has been calculated from the measured mAs and from
measured exposure time.
For pulsed fluoroscopy it is possible to measure pulse mA in addtion to the mA value.
The difference between the pulse mA and the traditional mA is explained in the picture
below.
(Note that for DC waveform, pulse mA and mA gives the same value.)
You can measure mAs as a single parameter or multi-parameter together with the
Piranha. When using only the mAs-probe the measurement always starts when the
mAs-probe detects a signal. When using multi-parameter you can choose to trig
individually or to trig with the Piranha:
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RTI Piranha Specifications

General

Brand	RTI
Model	Piranha
Category	Multimeter
Language	English