JESÚS SILVA-RODRÍGUEZ, PABLO AGUIAR, INÉS DOMÍNGUEZ-PRADO, MICHEL HERRANZ, ÁLVARO RUIBAL 18F-Choline: Is shine-through effect an issue for prostate SUV quantification?

Introduction: Imaging on prostate cancer Imaging techniques such as CT, MRI and TRUS are useful, but have demonstrated limited sensitivity PET and PET/CT could potentially increase accuracy for the diagnosis of prostate cancer FDG showed limited sensitivity for the detection of prostate carcinomas and local recurrence NEED: New radiotracers Farsad et al: “PET/CT and choline: diagnosis and staging.”. Q J Nucl Med Mol Imaging. 2012

Introduction: Choline

Biochemical recurrence. Clinically suspected prostate cancer, with multiple negative biopsies. Patient stratification with respect to surgery or radiotherapy. Lymph node and bone metastasis. Biochemical recurrence. Clinically suspected prostate cancer, with multiple negative biopsies. Patient stratification with respect to surgery or radiotherapy. Lymph node and bone metastasis. 11C-choline and 18F-choline are increasingly prescribed for: Introduction: Choline in prostate cancer Schwarzenböck et al: “Choline PET and PET/CT in Primary Diagnosis and Staging of Prostate Cancer”. Theranostics. 2012

Introduction: Choline in prostate cancer First clinical studies presented partially controversial results. Detection sensitivity (73%-100%) and specificity (67-98%). NEXT STEP: Diagnosis of primary prostate cancer.

Introduction: SUV in prostate cancer Attempts to use quantitative parameters such as SUV has also delivered mixed and contradictory results QUESTION: Is F18-choline suitable for the use of these quantification values? Tissue18F-Choline SUV Normal prostate tissue Prostate cancer Local Recurrence

Introduction: Shine-Through Liu et al: ”Invalidity of SUV Measurements of Lesions in Close Proximity to Hot Sources due to “Shine-Through” Effect on FDG PET-CT Interpretation” Radiology Research and Practice 2012

Introduction: 11C vs 18F choline The main difference is the early appearance of 18 F-Choline in the urinary tract due to an incomplete tubular re-absorption

Introduction: Shine-Through QUESTION: Is shine-through a problem for the use of SUV measurements in 18F-choline scans?

Methods: Experiment Workflow Our Workflow: 18F Choline Phantom Sinograms Reconstruction Estimated prostate SUVs MonteCarlo simulation (SIMSET) Tomographic reconstruction (STIR) Theo. Prostate SUV Theo. Bladder SUV Comparison Scatter & att correction Silva-Rodriguez et al: “Simulated FDG-PET studies for the assessment of SUV quantification methods”. Rev Esp Med Nucl Ima Mol 2014

Methods: Experiment Workflow

A single patient representing the average Spanish man (172 cm, 76 Kg) was generated using the XCAT phantom*. Methods: Phantom The bio-distribution of choline was derived from literature A hot spot was added in the prostatic left lobe to emulate a primary prostate tumor or local recurrence (24 cm3). (*) Seagars et al: “4D XCAT phantom for multimodality imaging research.” Med. Phys. 2010

Methods: Scanner The simulated scanner geometry was based on the GE Advance Nxi. Attenuation, scatter correction and reconstruction were also based on the protocols performed by this scanner. Silva-Rodriguez et al: “Correction for FDG PET dose extravasations: Monte Carlo validation and quantitative evaluation of real patient studies” Med Phys 2014

Methods: Simulation and Reconstruction Total injected dose was 370 MBq for all the studies. Studies were simulated for  Lesion SUVs of 3.03 and 6.06  Bladder SUVs of 1.1, 3.03, 7.58, 13.64, SIMSET package was used to perform the simulation. (5 repetitions/point) Sinograms were reconstructed using the STIR library OSEM. (stir.sourceforge.net) SUVmax was measured on the simulated lesion for all the lesions. Total injected dose was 370 MBq for all the studies. Studies were simulated for  Lesion SUVs of 3.03 and 6.06  Bladder SUVs of 1.1, 3.03, 7.58, 13.64, SIMSET package was used to perform the simulation. (5 repetitions/point) Sinograms were reconstructed using the STIR library OSEM. (stir.sourceforge.net) SUVmax was measured on the simulated lesion for all the lesions. Thielemans et al: “STIR: Software for Tomographic Image Reconstruction Release 2”, PMB 2012

Results Theoretical SUV = % +5.6% +19.8% +24.1% +27.4% +41.3%

Results -2.3% +0.1% +0.7% +7.9% +16.2% +23.4% Theoretical SUV = 6.06

Results

Discussion The effect becomes specially relevant when bladder SUV is higher than the lesion SUV, showing a strong dependency on tumor/bladder ratio. Avoiding bladder accumulation is essential for an accurate quantification of lesions on the prostatic region Urinary excretion and high accumulation in the bladder can compromise not only detectability, but also quantification results when using 18F-choline (up to 40%).

Conclusions 11C-choline might be more reliable for quantitative evaluation of the prostatic region If 18F-choline is used, a correction method will be mandatory for the quantitative evaluation of prostate cancer Bladder accumulation of 18F-choline significantly biased the measurements of prostatic lesions SUV

Molecular Imaging Reseach Group INVESTIGADOR PRINCIPAL: Álvaro Ruibal Morell Professor of Radiology and Medical Physics, University of Santiago de Compostela Head of the Nuclear Medicine Department, Santiago University Hospital MIEMBROS DEL EQUIPO Michel Herranz Pablo Aguiar Jesús Silva Julia Cortés Sonia Argibay Virginia Pubul Patricia Fierro Inés Domínguez Miguel Garrido María Pombo Jesús López Alejandro Bejarano

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