By Vvon Engineering Team | Published | Updated
Compare gamma-camera collimator requirements, camera compatibility, handling and quotation scope with the department's clinical and medical-physics team.
Nuclear medicine RFQ checklist (TXT)
A camera purchase should include the radionuclides and clinical applications planned for the service. A conventional low-energy collimator may be unsuitable for I-131 imaging, and adding compatible hardware later can affect both cost and availability. Confirm supported emissions and configuration before award.
Collimation strongly affects sensitivity and spatial resolution. Reconstruction can model some system response but cannot restore arbitrary lost information or replace appropriate hardware selection. Evaluate the complete detector, collimator and reconstruction combination.
Do not assume interchangeability. Provide the camera manufacturer, exact model, detector configuration and existing collimator identification. Ask for written confirmation of mounting, handling and imaging-system compatibility for the offered replacement. Start with the camera catalogue and include photographs of the identification plate in your technical enquiry where appropriate.
The department's qualified clinical and medical-physics team should define the studies, radionuclides, imaging geometry and required performance. The comparison below explains the selection factors; it does not replace the camera manufacturer's approved configurations or your department's protocol.
Specify the compatible camera and collimator, quantity, storage and handling equipment, delivery, installation responsibilities and agreed inspection or acceptance checks. Confirm whether this is a new system accessory or a replacement. Send the camera and study requirements.
A gamma camera detector records where a photon landed but not the direction it came from. Without a collimator, every point in the patient illuminates the whole detector and the image is a uniform blur. A parallel hole collimator is a lead honeycomb placed in front of the detector: photons travelling roughly parallel to the holes pass through, and photons arriving at an angle are absorbed by the septa between them. The image is formed by rejection. Only a very small fraction of emitted photons make it to the crystal, which is why nuclear medicine acquisitions are measured in minutes rather than milliseconds.
In parallel-hole designs, hole size, length, septal thickness and packing affect geometric resolution, sensitivity and penetration. A narrower acceptance angle often trades sensitivity for resolution, but there is no single sensitivity-versus-resolution rule covering every change or collimator geometry.
For conventional parallel-hole systems, increasing source distance generally degrades geometric resolution. Maintain safe manufacturer-approved proximity. Longer acquisition can improve counting statistics, and validated reconstruction may alter effective resolution, but neither removes all consequences of an unsuitable collimator.
Almost all routine work uses Tc-99m at 140 keV, so most departments live inside the low energy family. The three common members are the same idea at different settings.
| Collimator | Bias | Typical use |
|---|---|---|
| Low energy high resolution (LEHR) | Resolution over counts | Bone scans, renal cortical imaging, most planar and SPECT work with Tc-99m where the patient can lie still long enough |
| Low energy general purpose (LEGP or LEAP) | Balanced | Mixed lists, dynamic studies where frames are short, larger or restless patients, departments that own only one pair |
| Low energy high sensitivity (LEHS) | Counts over resolution | Selected count-limited studies where the complete protocol demonstrates adequate spatial information; paediatric use is not automatic |
Compare candidate collimators using required studies, photon spectrum, supported reconstruction, representative patient size and validated image quality. LEHR, general-purpose and high-sensitivity choices are not ranked by one universal first-purchase rule. Dedicated systems may use a fixed or integrated design instead of interchangeable pairs.
Septal thickness has to scale with photon energy, because higher energy photons penetrate lead more readily. Push an isotope beyond what a collimator was designed for and photons travel through the septa rather than the holes. The result is a characteristic star or haze pattern, a loss of contrast, and counts appearing in places where there is no activity.
Tc-99m is commonly imaged with suitable low-energy collimation. Tl-201 and I-123 also require consideration of their higher-energy emissions and scatter or septal penetration, not just the principal image window. Ga-67, In-111, I-131 and Lu-177 require configuration-specific assessment of their full spectra. Conventional cameras may use medium- or high-energy collimators; dedicated CZT systems can use different validated designs. Confirm the manufacturer's radionuclide and correction support rather than requiring a high-energy pair on every camera.
Parallel hole collimators map the patient one to one onto the detector. Where the organ is much smaller than the detector, that wastes most of the field of view, and a different geometry does better.
Pinhole imaging can provide useful magnification for selected small structures. Field of view, source distance, aperture, magnification and geometry affect sensitivity and interpretation. It is not automatically the best approach for every thyroid, parathyroid or paediatric examination; use the supported configuration and clinical protocol.
Fan-beam, converging, diverging and slant-hole designs provide different field-of-view and sampling trade-offs. Confirm organ coverage, truncation risk, reconstruction support and manufacturer compatibility for the intended study. A design that suits brain imaging is not automatically limited to that organ or superior on every camera.
| Study | Radionuclide or tracer | Example on conventional cameras; verify the exact system |
|---|---|---|
| Whole body bone scan and bone SPECT | Tc-99m MDP or HDP | LEHR |
| Renography and other dynamic renal work | Tc-99m DTPA, MAG3 or EC | LEHR or LEGP, depending on frame length |
| Thyroid uptake and nodule imaging | Tc-99m pertechnetate or I-123 | Pinhole or approved parallel-hole design; consider I-123 high-energy emissions where applicable |
| Post-therapy and whole body iodine imaging | I-131 | Manufacturer-approved I-131 configuration; often high-energy on conventional cameras |
| Infection and inflammation imaging | Ga-67 or labelled leucocytes with In-111 | Medium energy |
| Myocardial perfusion SPECT | Tc-99m sestamibi or tetrofosmin | LEHR |
| Gated blood pool and first pass | Tc-99m labelled red cells for blood-pool imaging; an appropriate tracer for the particular first-pass study | LEGP for gated work, LEHS for first pass |
| Brain perfusion SPECT | Tc-99m HMPAO or ECD | Fan beam where available, otherwise LEHR |
Collimator damage can alter image quality and may need specialist repair or replacement. Construction differs between lead, tungsten and dedicated designs; not every mark proves bent septa, and a flood is not the only relevant assessment. Isolate and evaluate suspected damage through the approved service and physics procedure.
Use only the manufacturer's exchange, lifting and storage procedure with suitable trained staff, carts, cradles and interlocks. Protect exposed surfaces, prevent unintended loading and identify each collimator in QA records. Set post-exchange inspections and tests from the system and physics programme; an extrinsic flood after every exchange is not universal and should not be framed as a way to blame the last operator.
Collimator specifications are where a low bid quietly becomes an expensive machine. A line reading collimators as required is an invitation to supply the minimum.
Send Vvon the camera model, radionuclides and planned studies to discuss compatible collimation and QA. Confirm availability, handling equipment and demonstrated performance for the offered configuration. Contact +8801805987890 or info@vvon.com.bd.
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