[Development of a Striatal and Skull Phantom for Quantitative 123I-FP-CIT SPECT]

Abstract

Background: ¹²³Iodine-labelled N-(3-fluoropropyl) -2β-carbomethoxy-3β-(4-iodophenyl) nortropane (¹²³I-FP-CIT) single photon emission computerized tomography (SPECT) images are used for differential diagnosis such as Parkinson's disease (PD). Specific binding ratio (SBR) is affected by scattering and attenuation in SPECT imaging, because gender and age lead to changes in skull density. It is necessary to clarify and correct the influence of the phantom simulating the the skull.

Purpose: The purpose of this study was to develop phantoms that can evaluate scattering and attenuation correction.

Methods: Skull phantoms were prepared based on the measuring the results of the average computed tomography (CT) value, average skull thickness of 12 males and 16 females. ¹²³I-FP-CIT SPECT imaging of striatal phantom was performed with these skull phantoms, which reproduced normal and PD. SPECT images, were reconstructed with scattering and attenuation correction. SBR with partial volume effect corrected (SBR_act) and conventional SBR (SBR_Bolt) were measured and compared.

Results: The striatum and the skull phantoms along with ¹²³I-FP-CIT were able to reproduce the normal accumulation and disease state of PD and further those reproduced the influence of skull density on SPECT imaging. The error rate with the true SBR, SBR_act was much smaller than SBR_Bolt.

Conclusion: The effect on SBR could be corrected by scattering and attenuation correction even if the skull density changes with ¹²³I-FP-CIT on SPECT imaging. The combination of triple energy window method and CT-attenuation correction method would be the best correction method for SBR_act.

Keywords: 123Iodine-labelled N-(3-fluoropropyl)-2β-carbomethoxy-3β-(4-iodophenyl) nortropane (123I-FP-CIT); computed tomography attenuation correction (CT-AC); dopamine transporter single photon emission computed tomography (DAT SPECT); specific binding ratio (SBR); triple energy window (TEW).