Coordinates, Movement of Radiotherapy Machines: Varian IEC 601-2-1

July 24, 2010 · Posted in Equipment, Treatment Planning · 5 Comments 

You can move the table, collimator, XY jaws, and gantry in the right direction without entering the treatment room if you familiarize yourself with the IEC scale convention of your machine. I have mostly used Varian machines during my career in medical physics and recently commissioned a Varian Trilogy linear accelerator at our cancer center. During commissioning, it became necessary (for productivity’s sake) to move the jaws, table, gantry and collimator from outside treatment room. Normally, Varian machines conform to either the Varian standard, Varian IEC (601-2-1) or IEC1217. Our Trilogy coordinates, movements and scales follow the Varian IEC (601-2-1) scale. Therefore, here are a few tips on this Varian IEC 601-2-1 scale that I generated during the commissioning of my machine. For a better understanding, these “tips” are explained in question and answer format. However, since some of us may not know what IEC stands for, here is a short paragraph taken from the IEC website before proceeding to the main topic:

IEC (International Electronic Commissioning) is the world’s leading organization that prepares and publishes International Standards for all electrical, electronic and related technologies.  Wherever you find electricity and electronics, you find the IEC supporting safety and performance, the environment, electrical energy efficiency and renewable energies.  The IEC also manages conformity assessment systems that certify that equipment, systems or components conform to its International Standards.

Out of the four components (the couch, jaws, collimator and gantry), we cover the couch and the gantry in this post and will discuss the jaws and the collimator in next post.

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The answer is 4.5 cm.
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The answer is 998.5 cm.
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The answer is 8.5 cm.
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The answer is 994.5 cm.
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The answer is 79 cm.
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The answer is 55 cm.
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The answer is 25 degrees.
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The answer is 105 degrees.

Couch: Vertical Movement
The couch vertical is at 8.5 cm. You need to move the table 4 cm upward toward the ceiling. At what do you set the new vertical position of the table from outside the treatment room: 12.5 cm or 4.5 cm?
Click on this link for the answer. Depending on your screen resolution, you may have to scroll up to see the answer window.
The couch vertical is at 2.5 cm. You need to move the table 4 cm upward toward the ceiling. At what do you set the vertical position of the table from outside the treatment room: 6.5, -1.5 or 998.5 cm?
Click on this link for the answer.
Tip: Table vertical position is at 0 degrees at iso-center. Moving the couch toward the floor down from iso-center, the number increases on this coordinate axes. If you move the couch toward the ceiling up from iso-center, the number decreases from 1000.

Couch: Lateral Movement
The couch lateral position is at 4.5 cm. You need to move the table 4 cm toward the right of the gantry if you face the gantry. What do you set the new lateral position of the table from outside the treatment room: 8.5 cm or -8.5 cm?
Click on this link for the answer.
The couch lateral position is at 2.5 cm. You need to move the table 8 cm toward left of the gantry if you face the gantry. What do you set the new lateral position of the table from outside the treatment room: -5.5 cm or 994.5 cm?
Click on this link for the answer.
Tip: Table lateral position is at 0 degrees at iso-center. When moving the couch toward the right (facing the gantry) from iso-center, the number increases on this coordinate axes. If you move the couch toward left (facing the gantry) from iso-center, the number decreases from 1000.

Couch: Longitudinal Movement
The couch longitudinal is at 55 cm. You need to move the couch 24 cm toward the gantry. What do you set the new longitudinal position of the table from outside the treatment room: 79 cm or 31 cm?
Click on this link for the answer.
The couch longitudinal is at 105 cm. You need to move the couch 50 cm away from the gantry. What do you set the new longitudinal position of the table from outside the treatment room: -55 cm or 55 cm?
Click on this link for the answer.
Tip: Table longitudinal Position increases if the couch moves towards the gantry and decreases if the couch moves away from the gantry.

Gantry
The gantry is at 115 degrees. You need to move gantry 90 CCW. What do you set the position of the gantry from outside the treatment room: -25, 25, 205, or 335 degrees.
Click on this link for the answer.
The gantry is at 15 degrees. You need to move gantry 90 CW. What do you set the position of the gantry from outside the treatment room: -75, 105, or 255 degrees.
Click on this link for the answer.
Tip: The gantry on the Varian IEC 601-2-1 scale is at 0 degrees when the gantry is up at vertical position. The degree increases as gantry rotates CW. It goes to 90 degrees when the gantry is to the right (facing the gantry), to 180 degree when gantry is down at vertical position, to 270 degree when gantry is to the left (facing the gantry) and increases as it rotates CW to 359.9 and then 0 degree up at vertical position. Reversely, the angle decreases as gantry rotates CCW.

References:

  1. Varian resources
  2. S C Lillicrap et. al. “Radiotherapy equipment standards from the International Electrotechnical Commission” BJR 71 (1998), 1225-1228.
  3. Correspondense – BJR 72 (1999), 623
  4. Radiotherapy equipment-Coordinates, movements and scales. AS?NZS 4495:1997, IEC 1217:1996
  5. http://www.iec.ch/

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