Key Point of Acquisition, Processing and Display for Standardized Images with Clinical Usefulness (Myocardial SPECT) (Masuda, et al)
Myocardial SPECT checklistAcquisition• Choice of nuclide• Dose• Time between
administration andstart of acquisition• Stress method(exercise/pharmacological)

Checklist

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A Tl or Tc agent is used for myocardial perfusion imaging, a Tc-99m agent isadvantageous for gated SPECT, BMIPP is used for fatty acid metabolism assessment, 2and MIBG for sympathetic nervous function detection. When an I-123 agent isused, the collimator must also be chosen with care.
At least 111 MBq is recommended for Tl, while for Tc agents 592-740 MBq isrecommended for the study at rest, with this dose increased by at least 2.5 times forthe second study if performed during the same day according to stress-rest or rest- 2
stress protocols, with an upper limit of a total of 1110 MBq. For BMIPP and MIBG,
111 MBq is recommended, and all these doses must be adjusted appropriately forchildren.
Tl at rest : 20 min after administration. Tl stress redistribution : 5-10 min and 3-4 hafter administration. Tc agents : Generally 30-60 min after administration(however, the accumulation of Tc agent in the hepatobiliary system varies during
exercise stress, pharmacological stress, and at rest, and individual variation also 2occurs, meaning that it should be taken into account before the start of acquisition).
BMIPP : 15-20 min after administration and in some cases 3-4 h afteradministration. MIBG : 15-20 min and 3-4 h after administration.
Pharmacological stress is effective if sufficient exercise stress is difficult.
the timings of drug and RI administration.

Comply with 2

If Tl is used, patients must fast from 4 h before the test until the scan is complete. If aTc agent is used, some institutions do not ask patients to fast, and others ask them to 2
fast before administration but permit food consumption afterwards. Fasting isrequired for BMIPP, and for MIBG attention must be paid to the use of other drugs.
The degree of scatter and attenuation varies depending on patient body type and sex• Patient body type/sex (the pectoral muscles in males, breasts in females, etc.)
Tl : Generally 71 KeV±10%-15%, sometimes with an additional 167 KeV±10%. 2• Energy window
Tc : Generally 140 KeV±10%. I : Generally 159 KeV±10%.
Multidetector devices are most suitable, and single-detector devices are limited to an 1
• Number of detectors
acquisition range of 180°.
Triple-detector devices have the detectors arranged in a triangle, while with dual• Positioning of detectors detector devices it is possible to choose between opposing positions, a 90°L-shape, or 1
a 76°acute angle.
360°acquisition is stable, with little distortion of the inferior and posterior walls, and• Acquisition range
little change in count from the apex to the base of the heart. 180°acquisition 1(180°/360°/207°)
provides particularly high contrast and good resolution of the anterior wall.
In general, LEHR and LEGP collimators can be used with both Tc and TI, but inparticular, when Tl is used with a short acquisition time or gated acquisition, anLEGP collimator may be used if the count is insufficient. I agents have a 529 keV• Collimatorpeak in addition to the main peak at 159 keV, and the effect of down scatter must 1
therefore also be taken into account. Collimators are chosen with reference to their
5% penetration energy and taking the balance between sensitivity and resolution intoaccount.
• Pixel size (matrix size
Pixel size = standard visual field/matrix/acquisition magnification. From sampling 2and magnification)
theorem, a pixel size of 5-7 mm and sample angle of 5-6°are appropriate.
• Number of sampling
In general, sampling is carried out from 72 directions with a sample angle of 5°and 2
directions
from 60 directions with a sample angle of 6°.
Generally, the acquisition time for a single direction is set within the range 20-40 s,
but this is dependent on the dose and body type. The effect of a decline in count due
to washout must be taken into account for Tl late images. Limitations imposed by 2
• Acquisition timethroughput affect the total acquisition time, as do the number and positioning ofdetectors and the acquisition range. The longest time for which patients can endurekeeping their arms raised and remain motionless is around 20 min.
Continuous rotation acquisition has a number of merits, including a shorter total• Acquisition mode
acquisition time and fewer artifacts, caused by factors such as body movements. 2
Only step acquisition can be used for gated SPECT.
For patients with a standard body type, the diameter of rotation is 200-250 mm, close 3• Diameter of rotation
to the body.
A close-proximity trajectory increases the contrast but may also cause artifacts, and an• Circular trajectory/
extremely elliptical trajectory should therefore be avoided. When using 180°
close-proximity
reconstruction, an extremely close-proximity trajectory may result in so-called eleventrajectoryo’clock false defects.
• Number of R-R
For Tl , in principle 8 divisions are used. With Tc agents, some institutions believe it 2divisions
is possible to use up to 16 divisions.
• Pretreatment

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核医学技術• Tolerance• Acquisition countstandards

A few dozen heartbeats must be monitored prior to gated SPECT acquisition, and thewindow set so that the base of the histogram is not lost.
A region of interest (ROI) is set in the myocardial region of the LAO45°of theprojection data, and the myocardial projection count is measured. The acquisition 3time should ideally be set to obtain over 100 counts per pixel in the myocardium.

Reconstruction• Body movement
correction• Scatter correction• Preprocessing filters• FBP/OSEM(Iterations, subsets)• Attenuation correction• Image reformatting

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Checklist
SPECT scan is susceptible to upward creep and body movements. If bodymovements occur, SPECT images are often shown up as defective. Try using
correction software if this is available. Correction cannot be performed, however, if
the patient has turned over, or has given a large cough or taken a deep breath duringacquisition from one direction. At best, correction can only be performed for the Xand Y axes for each direction of projection.
The TEW method is often used, but although it is capable of improving the contrast
between the cardiac cavity and the myocardium, the values for the inferior wall arelowered as a result of correction. The count may decrease by 30%-40%. Scattercorrection is rarely used alone for the myocardium.
The higher the cutoff frequency of a Butterworth filter, the better is the resolution butthe greater the amount of noise, and the lower the cutoff frequency, the lower is theresolution and the smoother the image obtained. The visual inspection of clinicaldata is important.
OSEM can also be employed to reduce streak artifacts caused by the high uptake ofTc agents outside the myocardium. X-ray CT attenuation correction may also beperformed by using OSEM. As a guideline, each subset should include data for 10
projections, with 5 iterations. For example, 6 subsets and 5 iterations are used for 60
projections. A low number of data updates (subsets × iterations) may result inincomplete convergence in the defect area.
Attenuation correction methods (such as Chang’s method) that assume homogeneousabsorbers cannot provide accurate correction because the chest is composed ofheterogeneous absorbers such as the lungs, spine, heart, and mammary glands.
OSEM can be incorporated into the processing if X-ray CT can be used to create an
attenuation map, but simultaneous scatter correction is essential.
Select a central slice of the myocardium, and join the centers of the anterior andposterior walls, passing through the apex and the centers of the lateral wall andseptum.

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Check that the maximum count in the myocardium is shown as 100%. If any
extramyocardial hotspots are present, carry out count truncation. If this is not• Count normalization
feasible, decrease the upper level so that the maximum count in the myocardium
become to the highest color.
Generally, the upper level is set at 100%-110% and the lower level at 10%-20%. If• Cut level
scattering correction has been carried out, however, the lower level is set at 0%.
Take care to ensure that the maximum counts in the myocardium are consistent.
A exponential or quadric function is recommended for black-and-white images, and alinear gradient for colored images. This enables the accurate assessment of ischemia• Gradientand viability, and assessment of the right ventricle and background, which also
provide important data on cardiac function.
as positive images. A exponential or quadric function is recommended.
• Black and white images Display
An excessive lower cut should be avoided.
Be aware that the choice of color coding may have a major effect on evaluation.
Avoid an excessive lower cut when using a linear gradient. Coding with the• Color images
maximum myocardial count displayed in white or pink is appropriate for diagnostic
purposes.
In image display, the vertical long axis runs from the septum to the side of the lateral
the short axis from the base of the heart to the apex, and the horizontal long axis
• Display slice thickness wall,from the inferior wall to the anterior wall, with slice thickness of 5-7 mm, displayed ina total of 9-16 divisions.
Arrange the same slices for every axis to compare stress images to rest images. Use• Layout
techniques such as arranging images on two levels to make them easier to view.

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