JPNM Physics

Design Changes for 511 keV Collimators

ADAC	Elscint	General Electric	Hitachi	Park Medical
Picker	Siemens	SMV	Toshiba	Trionix

1. ADAC: Vertex

   Comments of Sharon Thorpe and Kim Rutty:

   Mechanical:

   No changes in motor Horse power, only in gantry rotate gear ratio on Genesys; Vertex model was over-designed and no changes were necessary to accommodate the weight.

   Electrical:

   No change in signal handling - software upgrade to provide for energy spectrum display

   Dual Isotope:

   Capable of acquiring dual isotope. Only capable of applying one correction map to both windows as of June, 1996. Usually a Tc-99m (140 keV) intrinsic map is applied to both the Tc data and the 511 keV data.

   COR:

   No problems with COR reported. Upon installation of new software, COR correction factors had to be stored at Beth Israel Hospital, Boston

   Collimator Exchange:

   No changes in collimator exchange. The "semi-automatic" exchanger requires rolling one collimator at a time, and this is more difficult yet possible with the 511 keV collimators.

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2. ELSCINT: Helix and Varicam

   Comments of Ed Weinfeld:

   Mechanical:

   The a special dedicated collimator exchange cart with large wheels was designed for the collimators.

   Electrical:

   A software command is issued which changes the HV on the PMTs and the energy scale displayed in the pulse height analysis. No problems have been reported with COR.

   Dual Isotope:

   "Special" sensitivity maps are stored for each energy peak.

3. GENERAL ELECTRIIC: Maxxus

   Comments of Brian Prejna:

   Mechanical:

   No modifications necessary.

   Electrical:

   No hardware boards or jumpers. All that was needed was a software calibration to extend signal range.

   Dual Isotope:

   will get back to me

   COR:

   No issues

4. HITACHI: T20

5. PARK MEDICAL: Isocam II

   Comments of Raffi Kayayan:

   Mechanical:

   No modifications necessary. Gantry was designed to support the heavy weight of the UHE collimators and detector shielding.

   Electrical:

   No modifications necessary. The digital detector electronics were designed to image from 50 to 561 keV energies without changing the high voltage of the PMTs.

   Dual Isotope:

   Capable of applying two uniformity correction maps with dual isotope studies. Spectral uniformity corrections (up to 16 maps) can also be used with spectral acquisitions. Energy range for simultaneous dual isotope and spectral acquisitions is from 50 to 560 keV.

   COR:

   No problems

   FOV:

   16.5" x 22.3" (41.9 cm x 56.6 cm)

6. PICKER: Prism 3000 and 2000 (in progress)

   Comments of Hugh Morgan:

   Mechanical:

   Prism 2000 (dual-head) design is being modified to accommodate the collimators. Changes will be implemented in both the gantry design and the collimator exchange mechanism. Prism 3000 collimator storage mechanism had to be modified, both in size and strength, to hold the collimators.

   Electrical:

   The HV is changes via software to bring signal level down. Dynamic range still allows 140 and 511 keV to be acquired simultaneously. Image Registration Correction (IRC) did not have to be modified to accommodate the collimators. No electrical or mechanical COR problems have been reported.

   Dual Isotope:

   Dual window acquisition: same flood is used to correct both windows. Extrinsically acquired Tc flood. For a single window 511 keV acquisition, an F-18 extrinsic correction is recommended.

7. SIEMENS: MS/2

   Comments of Vilim Simcic:

   Mechanical:

   No changes necessary since it was originally "overengineered". Increased the travel length to raise the patient opening due to the long bore of the collimators. Collimator exchange modification needed - other collimators are horizontally oriented and two per cart. EHE collimators are one per cart.

   Electrical:

   A jumper needed to be changed on an amplifier board.

   Dual Isotope:

   Uniformity is dominated by the collimator - not the intrinsic performance due to light pipe. Extrinsic is stored with fillable Tc-99m. One customer uses extrinsic flood with 511 keV source.

   COR:

   No problems reported

   FOV:

   didn't ask

8. SMV: FX-80, DST, and DST-XL

   Comments of Phil Vernon and John Engdahl:

   Mechanical:

   No gantry changes. Minor changes in attachment mechanism - latches, brackets - can be upgraded in the field. Collimator exchange is one at a time and no changes have been necessary to accommodate the heavier collimators.

   Electrical:

   Change the HV to reduce the signal.

   Dual Isotope:

   separate flood corrections for the two energy windows. Intrinsic ⁶⁸Ge point source is used. One customer uses fillable flood source and ¹⁸F and claims superior results.

   COR

   No problems reported

   FOV:

   same as low energy collimators

9. TOSHIBA:

10. TRIONIX: Biad

    Comments of Rick Keene:

    Mechanical:

    Minor changes in mounting hardware. Minor changes in the collimator storage cabinet to accommodate larger hole depth. No changes to basic camera or gantry motors.

    Electrical:

    Always have had the ability to change PMT HV in software.

    Dual Isotope:

    Store correction maps for combination of isotope and collimator - can apply any map to any energy window.

    COR:

    no problems reported

    FOV:

    same as that of low energy collimators.

Version 2 modified January 10, 1997

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