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Barometers-Thermometers-Accessories : Tel-Align ™

Tel-Align ™

TEL-ALIGN Teletherapy Alignment Gauge

Alignment Accuracy


Accuracy begins with bean alignment. It is impossible to deliver the carefully calculated plan if the beam position is not verified. The TEL-ALIGN™ verifies the coincidence of the light radiation fields and checks the iscenter varation and the optical back pointer when the gantry is rotated ±90º.


The TEL-ALIGN™ consists of a rectangular plastic base with a removable vertical scale. The top surface of the base contains lead markers that form a square (10 x 10cm) for visualization on film. A cross hair in the center of the square lines up with two additional sets of cross hairs, one on each outer edge of the base.

After the machine field size (10 x 10cm) has been set, the table height is adjusted until the base surface is at the isocenter distance. The collimator rotation angle is set at 0º. When positioned properly, the edges of the light field should coincide with the inscribed square. The field center should intersect the center cross hair, and the side lights should agree with the corresponding cross hairs at the edges of the base.

The vertical scale is placed on the base to check the optical distance indicator, or a film can be placed under the base to check the light field versus the radiation field. By rotating the gantry angle at ±90º, the isocenter variation and optical back pointer are also checked. If adjustment of the machine geometry is needed, it can be done readily with the TEL-ALIGN ™ Teletherapy Alignment Gauge (Model 37-001) in place.

Permits checks of:
  • Optical distance indicator (over a 15cm range)
  • Collimator and central cross hair
  • Head rotation and pitch
  • Isocenter variation
  • Side lights and optical back pointer
  • Light field vs. radiation field
  • Base 5.51(w)x 7.09 (d) x 0.79 in (h) (14x18x2 cm)
  • Vertical scale 7.09 in (h) (18cm)
  • Weight 2 lb (0.91kg)
  Available model(s)
  • Model 37-001: TEL-ALIGN™ Teletherapy Alignment Gauge


TEL-ALIGN Teletherapy Alignment Gauge - Printable Information Sheet (.PDF format)


* Designed and developed by Medical Physics Dept., Memorial Hospital, New York, NY