Cerebral Perfusion SPECT:
This is used to evaluate cerebrovascular disesase, Dementia, Presurgical localization of epileptic foci, brain trauma, and herpes simplex encephalitis.

Patient Preparation:
1. Patients should be instructed, if possible, to avoid caffeine, alcohol on the day of the procedure.
2. Prior to injection ensure patient would cooperate and make the patient to sit in a quiet, dimly lit room with eyes & ears open.
3. Get an IV line access at least 10 min prior to injection.
4. Instruct the patient not to speak or read. Have no interaction with the patient prior to, during or up to 5 min post-injection.
5. Get all relevant reports like MRI, CT etc.
6. Explain the procedure to patient

Radiopharmaceutical:
In our setup always ECD is preferred than HMPAO
99mTc labeled ECD after labeling is stable only for a period of 4 hours
Quality Control if possible can be performed before injection.

Injection of ECD:
1. Dosage: Adults 15–30 mCi, Children 0.2–0.3 mCi/kg. Minimum dose is 3–5 mCi.
2. Patients should be injected in a quiet room always through an IV line.
3. 45min. to1-hour delay from time of injection would give the best quality images.
4. If sedation is required, it should be given after tracer injection.
5. If brain SPECT is performed for epilepsy focus detection, then the timing of injection becomes the most crucial. Normally patients are to be monitored under video EEG & when there is an EEG evidence of a seizure immediately (with in 30 sec) injection is given

Positioning & acquisition:
Cerebral SPECT can be done with single, dual and triple head gamma cameras. With meticulous attention to procedure, high-quality images can be produced even with single head gamma cameras with appropriately longer scan times
1. Patient should be comfortably positioned.
2. The patient’s head should be lightly restrained to facilitate patient cooperation in
Minimizing motion during acquisition.
3. Patient cooperation is necessary. Sedation may be used following the injection of radiopharmaceutical if patient is uncooperative.
4. Use the smallest radius of rotation possible with appropriate patient safeguards.
6. Use the highest resolution collimation available. High-resolution or ultra high-resolution collimation is recommended. All purpose collimation is not suitable. Fan-beam is generally preferable to parallel-hole as they provide improved resolution and higher count rates.
7. A 128 x 128 or greater acquisition matrix should be used.
8. Use 3° or 6° angular sampling, 48 or 64 stops, with step and shoot technique.
9. If you have detector digital pan and zoom capabilities then it should be activated. It ensures that the entire brain is included in the field of view while allowing the detector to clear the patient’s shoulders.

Image Processing:
1. First check the raw images for patient motion. Motion correct images if required.
2. For Reconstruction, Low-pass filter is generally be used. During reconstruction cerebellum, vertex all should be included. Reconstruct data at highest pixel resolution, i.e. one pixel thick.
3. If slices are to be summed it should be done only after reconstruction and oblique reorientation (if performed).
4. Reconstruct by filtered back projection with Ramp filter
5. Pixel size is 6mm (one pixel) thick transaxial, sagittal & coronal images to be reconstructed.
6. Attenuation correction can be performed in all cases if available. An attenuation coefficient of 0.15 is used.
7. Reformat transaxial data into at least three orthogonal planes. Generate transverse sections relative to a repeatable anatomic orientation (e.g., AC-PC line), and coronal and sagittal sections orthogonal to the transverse. Additional sections along a plane parallel to the long axis of the temporal lobes are frequently useful.
8. Images should be viewed on a computer screen rather than from film or paper copy to permit interactive adjustment of contrast, background subtraction and color table.
9. Caution must be used in selecting levels of contrast and background subtraction.
10. 3 D- renderings may be useful in appreciating overall patterns of disease.
11. If the study is for epilepsy evaluation then co registration of SPECT images with MRI images is done to accurately localize the focus.

99mTc MIBI / Tetrofosmin Brain SPECT:
A 99mTc MIBI or Tetrofosmin Brain SPECT is performed to differentiate neoplastic from a non-neoplastic etiology of brain Space occupying lesions (SOLs).
No special patient preparation needed for this procedure.
20 – 25 mCi of 99mTc MIBI or Tetrofosmin is injected IV.
10 min & 2 hours post injection SPECT brain images are obtained.
Acquisition parameters: 64 X 64 matrix, 32 views, step & shoot, 25 – 30 sec, circular / non-circular orbit.
Reconstruction parameters: Butterworth filter commonly used. As it is a low count study 4 order & 0.4 cutoff values can be used.
Quantitation: If the SOL concentrates tracer in initial & delayed images then target to non-target ratio in both initial & delayed images can be generated.

Display

• Image display should be done correctly for brain images. Choose correctly the initial and delayed SPECT images while selecting so that it appears in upper and bottom rows in transaxial, coronal and sagittal views.
• Arranging of image slices is equally important and should be congruent for all axis.
• Slices should be adjusted for threshold as for slice maximum/ study maximum as per images.
• Colours which highlight the defects should be selected for taking the print.