by: Prof.Dr. Hosna Moustafa Cairo University, Egypt Brain Imaging by: Prof.Dr. Hosna Moustafa Cairo University, Egypt

Brain Imaging Radionuclide brain imaging is differnet from anatomic imaging as C.T., M.R.I. in being functional imaging. Radionuclides may be used to study: Brain tumour: Tl-201 Tc99m-MIBI Tc99m-DMSA(V) Fl18- FDG

Radiopharmaceuticals in Brain Tumors KeV Scan start time Dose 80 KeV 20 min, 3 hours 3 mCi Tl-201 140 KeV 30 min, 20 mCi Tc99m-MIBI 1 hour, Tc99m- DMSA (V) 511 KeV 1 hour 5 - 10 mCi Fl18- FDG

Main clinical indications Detection of residual functioning tumour following surgery, for planning radiotherapy. Assessment of treatment response. Detection of residual or recurrent brain tumors following radiotherapy or chemotherapy.

Scan Findings If residual or recurrent tumor is present, a focal area of increased uptake is seen. Post-radiation or chemotherapy gliosis shows no uptake.

A B C Residual viable astrocytoma grade III in right occipital region using Tl-201. CT with equivocal residual brain lesion. 6 weeks after radiotherapy, no viable tumour in the same area.

Limitation of Tl-201 Imaging Poor physical characteristics (low photon energy 80 kev). Longer half life (73 h) which limit the injected dose to 3 mCi. Normal uptake in salivary gland, thyroid, heart, kidneys, and muscles. Not available for daily used (Abdel Dayem et al., 1998).

99mTc-MIBI and 99mTc-Tetrafosmine Imaging Higher doses 5-10 times more than Tl-201 lead to higher image quality and better resolution. Early imaging at 20-30 minutes in both isotopes and late imaging (MIBI) at 2-3 hours Available as daily kits. Main limitation is uptake in choroid plexus which may interfere with interpretation of small deep para-ventricular brain lesions.

CT: Recurrent glioblastoma in both frontal regions with solid and cystic changes. TC-Myoview: Recurrent viable glioblastoma in both frontal regions with radiotracer uptake in solid area in CT.

Tc V-DMSA scan MRI: Recurrent temporal astrocytoma grade II following radiotherapy. SPECT: Viable tumour in the left temporal region.

99mTc-(v)DMSA: Viable tumour in the left temporal region with no uptake in midline. 99mTc-MIBI: Viable tumour in the left temporal region with overlap of choroid plexus uptake in midline.

FDG-PET in recurrent brain tumor Fluorine-FDG is metabolic agent, which reflect the metabolism of glucose High uptake is seen in high grade tumors as well as GMF. Carbon-11 methionine can be used in evaluation of low grade tumors.

Recurrent glioblastoma in frontal lobe evidenced in MRI with viable tumor in FDG PET.

Advantages of Radionuclide Brain Tumour Imaging Good indicator of tumour viability. Can assess tumour response to therapy. Can detect residual or recurrent tumours. Can differentiate post therapy fibrosis from recurrent tumour, if CT or MRI are equivocal.

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