RSD PHANTOMS FOR STEREOTACTIC RADIOSURGERY

 

Spherical Phantom to Check Mechanical and Dosimetric Parameters of Treatment Units

 

Spherical Phantom in Stereotactic Frame

 

  • Homogenous dry water phantom with precise spherical shape - 16 cm diameter
  • Dose variation at center of sphere will relate to accuracy and stability of the treatment unit
  • Checks the dose-calculation algorithm based on a homogeneous sphere

DOSIMETRY IN THE SPHERICAL PHANTOM 

When the center of the sphere is used as the target for testing the treatment unit, it must indicate the relationship between the point of maximum dose and the target. These should closely coincide for an accurate system. 

A three-dimensional dosimetry unit was chosen for the center of the sphere to evaluate both the deviation of the maximum dose from the target and the gradient of the dose along the three orthogonal axes of the sphere. 

The Dosimetric Cylinder

 This dosimetry unit is a cylinder, built up of alternating disks of dry water (4.0 cm diameter, 2.74 mm thick) and radiochromic film (0.26 mm thick), with a dry-water disk terminating the cylinder at each end. All disks have two accurately positioned 3-mm diameter holes for orientation and assembly of all disks. 

The stack of disks is assembled tightly into a cylinder by threaded nylon rods, passing through holes with blind cylindrical nuts at each end of each rod. The nuts mate with recesses in the sphere for precise and repeatable location. 

There are 11 film disks and 12 dry water disks. Each film disk is marked with numerals from 1 to 11, with the numerals located superiorly and posteriorly on each disk. 

5-mm diameter holes are drilled through the centers of two dry-water disks, immediately superior and inferior to the film disk at the central plane of the cylinder. These holes are filled with pins that are denser than dry water to present a target. 

Because of the cost of radiochromic film, it will be desirable in many cases to use standard film disks at the non-central planes of the cylinder (when restricted data are adequate). In such cases the cylinder assembly can be completed with exposed standard film. 

Spherical Phantom with Cone and Adapter for Insertion of Dosimetric Cylinder

 STANDARD CONE 

This is a cone mating precisely with a recess in the sphere. It houses the dosimetric cylinder. For TLD dosimetry, all film is removed from the cylinder, and an adaptor disk is placed at the center of the cylinder with the thickness needed to compensate for film removal. The disk has a recess to house 5 TLD chips, side by side, (3.17 x 3.17 x 0.89 mm thick) at the center of the sphere. 

Adapter for TLD Chips

 OPTIONAL CONE 

This is molded to locate the measuring volume of an ion chamber at the center of the sphere. This cone is custom molded to suit the particular ion chamber specified by the customer.

 
 

Head Phantom to Check Accuracy of the Treatment 

 

 

  • Total System Quality Assurance
  • Measures the dose delivered to intracranial lesions

DOSIMETRY IN THE HEAD PHANTOM 

Provisions are made for installation of the dosimetric cylinder at two locations in the cranium. One is on the CC axis of the head close to the apex. The other is near one side of the head at about ear level. Both cylinders are perpendicular to the transverse planes of the head. 

Since the dose at only one target location is to be measured at a time, the other location is filled with a dry-water cylinder with no dosimetric provisions. The target location can be defined uniquely by an initial CT scan. 

Exploded View of Head to Show Access to Cylinders

 

 
 

EXPOSED RADIOCHROMIC FILMS

Maximum dose displaced from center film (target)

 

ORDERING INFORMATION

MODEL

DESCRIPTION 

ST-1100

Complete Spherical Phantom System  

Includes: 

 

  • ST-1101 Sphere with Standard Recess for Truncated Cones
  • ST-1102 Truncated Cone for TLD and Film Dosimetry
  • ST-1103 Dosimetric Cylinder
  • ST-1104 Adapter for Dosimetric Cylinder

 

OPTIONS

ST-1105

Adapter for TLD Chips

ST-1106

Truncated Cone for Ion Chamber (includes molding to suit ion chamber as specified by customer) 

Note: If both the sphere and head are purchased, only one dosimetric cylinder is needed.

 

ST-1150

Head Phantom 

Includes: 

 

  • One Dosimetric Cylinder and one One-Piece, Dry-Water Cylinder to fill other cavity.
  • 4 Spare nylon assembly rods and 8 Spare blind nylon nuts

 

 

SPARE PARTS (for both Sphere and Head)

ST-1107

Dosimetric Cylinder

ST-1108

Radiochromic Film Disks (Set from No.1 to No.11)

ST-1109

Single Radiochromic Film Disk (any number)

ST-1110

Disks of Exposed Standard Film

ST-1111

Cylinder Assembly Rod

ST-1112

Cylinder Assembly Nut

ST-1113

Cylinder Target Rod-Film

ST-1114

Cylinder Target Rod-TLD

 


Elimpex-Medizintechnik, Spechtgasse 32, A-2340 Moedling, Austria

phone +43-2236-410450

fax +43-2236-410459