The effect of calibration factors and recovery coefficients on 177Lu SPECT activity quantification accuracy : a Monte Carlo study

BACKGROUND: Different gamma camera calibration factor (CF) geometries have been proposed to convert SPECT data into units of activity concentration. However, no consensus has been reached on a standardised geometry. The CF is dependent on the selected geometry and is further affected by partial volume effects. This study investigated the effect of two CF geometries and their corresponding recovery coefficients (RCs) on the quantification accuracy of 177Lu SPECT images using Monte Carlo simulations.

METHODS: The CF geometries investigated were (i) a radioactive-sphere surrounded by non-radioactive water (sphere-CF) and (ii) a cylindrical phantom uniformly filled with radioactive water (cylinder-CF). Recovery coefficients were obtained using the sphere-CF and cylinder-CF, yielding the sphere-RC and cylinder-RC values, respectively, for partial volume correction (PVC). The quantification accuracy was evaluated using four different-sized spheres (15.6-65.4 ml) and a kidney model with known activity concentrations inside a cylindrical, torso and patient phantom. Images were reconstructed with the 3D OS-EM algorithm incorporating attenuation, scatter and detector-response corrections. Segmentation was performed using the physical size and a small cylindrical volume inside the cylinder for the sphere-CF and cylinder-CF, respectively.

RESULTS: The sphere quantification error (without PVC) was better for the sphere-CF (≤ - 5.54%) compared to the cylinder-CF (≤ - 20.90%), attributed to the similar geometry of the quantified and CF spheres. Partial volume correction yielded comparable results for the sphere-CF-RC (≤ 3.47%) and cylinder-CF-RC (≤ 3.53%). The accuracy of the kidney quantification was poorer (≤ 22.34%) for the sphere-CF without PVC compared to the cylinder-CF (≤ 2.44%). With PVC, the kidney quantification results improved and compared well for the sphere-CF-RC (≤ 3.50%) and the cylinder-CF-RC (≤ 3.45%).

CONCLUSION: The study demonstrated that upon careful selection of CF-RC combinations, comparable quantification errors (≤ 3.53%) were obtained between the sphere-CF-RC and cylinder-CF-RC, when all corrections were applied.

Medienart:

E-Artikel

Erscheinungsjahr:

2021

Erschienen:

2021

Enthalten in:

Zur Gesamtaufnahme - volume:8

Enthalten in:

EJNMMI physics - 8(2021), 1 vom: 18. März, Seite 27

Sprache:

Englisch

Beteiligte Personen:

Ramonaheng, Keamogetswe [VerfasserIn]
van Staden, Johannes A [VerfasserIn]
du Raan, Hanlie [VerfasserIn]

Links:

Volltext

Themen:

177Lu
Calibration factor
Journal Article
Monte Carlo
Quantification
Recovery coefficients
SIMIND

Anmerkungen:

Date Revised 31.03.2024

published: Electronic

Citation Status PubMed-not-MEDLINE

doi:

10.1186/s40658-021-00365-8

funding:

Förderinstitution / Projekttitel:

PPN (Katalog-ID):

NLM322950996