Page 43 - Bio Engineering Approaches to Cancer Diagnosis and Treatment

40 CHAPTER 2 Diagnostic imaging in cancer

than air or lung. The change in positron position and the site of annihilation causes
positron range blurring, decreasing the spatial resolution of PET systems. Another
reason of limiting special resolution is related to the angle between annihilation pho-
tons. Positron and electron annihilate during motion which cause the created angle
between emitted photons are not precisely 180°C (as shown with “b” in Fig. 2.5).
This random variation in the predicted angle of 180°C lead to the additional decrease
in spatial resolution called angle blurring [44]. These errors can be magnified based
on the position of the detectors and the scanners’ diameter.
It should be noted that the scattering of photons before detecting by the detector
may cause additional decrease of image resolution.

2.6.2 Advantages and disadvantages
The advantages of PET/CT imaging technic are:
• Apply for several tumors
• Preforming whole-body imaging which will be helpful to detect metastasis
tumor
• High resolution with perfect attenuation, resolution, and scattering correction
• Based on metabolic activity it can have high sensitivity
• Calcium scarring
• Having high accuracy due to the combined with CT
The disadvantages of using PET/CT imaging technic are explained as follow:

• Nonspecific for tumor type
• Costly
• Not applicable for infected or inflammation region
• Image artifacts may occur
• Inadequate information for surgical planning
• Shielding for CT
After introducing the effect of nonbiological systems in cancer diagnosis, in the
following chapter, the effect of biological components will be reviewed.

References

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