Planar scan vs. SPECT/low-dose CT for estimating split renal function by ^99mTc-DMSA scintigraphy in children

Area of Science:

• Nuclear Medicine
• Pediatric Imaging
• Renal Function Assessment

Background:

• ^99mTc-dimercaptosuccinic acid (DMSA) scintigraphy is crucial for evaluating split renal function (SRF) in pediatric patients.
• Planar DMSA scintigraphy commonly uses geometric mean (GM) for SRF estimation.
• Single photon emission tomography combined with low-dose CT (SPECT/ldCT) provides volumetric data and attenuation correction for improved accuracy.

Purpose of the Study:

• To compare SRF estimates between planar DMSA scintigraphy (GM method) and SPECT/ldCT (VOI-based analysis) in pediatric patients.
• To identify discrepancies in SRF assessment between the two imaging modalities across various diagnostic subgroups.
• To determine the clinical impact of using SPECT/ldCT over planar DMSA for SRF evaluation in children.

Main Methods:

• Retrospective analysis of 68 pediatric ^99mTc-DMSA scintigraphies (planar and SPECT/ldCT) performed between 2011 and 2016.
• SRF estimation using the geometric mean (GM) method for planar scans.
• SRF estimation using volume of interest (VOI)-based analysis (VBA) on SPECT/ldCT data.
• Blinded review by two experienced physicians using Bland-Altman analysis to compare methods.

Main Results:

• A total of 68 scintigraphies were analyzed, comparing GM-based SRF with VOI-based SRF.
• Bland-Altman analysis revealed a bias of 2.1% and limits of agreement from -7.5% to +11.7%.
• Significant discrepancies were observed outside the normal SRF range (45-55%), with approximately 25% of abnormal planar SRF findings being normal on SPECT/ldCT.

Conclusions:

• Planar DMSA scintigraphy may overestimate abnormal SRF in pediatric patients, potentially due to underestimation of poorly functioning kidneys without attenuation correction.
• SPECT/ldCT offers a more accurate assessment of SRF, with a notable proportion of abnormal findings on planar imaging being reclassified as normal.
• Supplementing planar DMSA scintigraphy with SPECT/ldCT is recommended for pediatric patients with abnormal SRF findings to ensure accurate diagnosis and management.