Radiation and Cancer Physics

SS 18 - Physics 4 - Imaging for Response Assessment I

138 - Quantitative Neuroimaging and Neurocognitive Assessments to Determine Radiation Dosing Parameters to Memory Network Structures and Associated Memory Decline

Tuesday, October 23
7:45 AM - 7:55 AM
Location: Lila Cockrell Theatre

Quantitative Neuroimaging and Neurocognitive Assessments to Determine Radiation Dosing Parameters to Memory Network Structures and Associated Memory Decline
J. Burkeen1, R. Karunamuni1, K. R. Tringale1, T. M. Seibert1, T. Nguyen1, D. C. Marshall1, K. Leyden1, M. K. Gorman2, C. McDonald1, and J. A. Hattangadi-Gluth1; 1University of California, San Diego, La Jolla, CA, 2UC San Diego, La Jolla, CA

Purpose/Objective(s): While much research has focused on radiation dose effects on the hippocampus and subsequent memory decline, identifying other structures in the memory network and associated radiation sensitivities is important. We investigated whether RT to the memory network, including hippocampus (HC), entorhinal cortex (EC), fornix, and cingulum affected verbal and non-verbal memory, with an objective of better determining dosimetric parameters to aid future RT planning.

Materials/Methods: Volumetric neuroimaging was obtained on 27 patients with brain tumors prior to RT, as well as 3- and 6-months post-RT, in a prospective, observational trial. Radiation dosing parameters included minimum dose, maximum dose, mean dose, median dose, D2, D98, and V5-V60 in 5Gy increments. Memory tests included the Hopkins Verbal Learning Test (HVLT) for verbal memory and the Brief Visuospatial Memory Test (BVMT) for non-verbal memory. Reliable change indexes (RCIs) were calculated to determine significant baseline to 6-month memory changes. General linear modeling and univariate analyses were performed using SPSS. Alpha was set to 0.05 to determine significance for all analyses.

Results: From baseline to 6-months post-RT, mean HVLTtotal declined by 0.2907 (range of -0.305 to 1.52) and mean HVLTdelayed declined by 0.387 (range of -3.03 to 1.82). Significant dosimetric parameters included dose minimum (mean = 12.4 Gy, p = 0.022) and D2 (mean = 13.2 Gy, p = 0.016) to the left hippocampus. Dose minimum (mean = 13.3 Gy, p = 0.005), D2 (mean = 13.9 Gy), p = 0.007), and V35 (mean = 26%, p = 0.002), V40 (mean = 23.3%, p = 0.001), V45 (mean = 20.6%, p = 0.001), V55 (mean = 13.1%, p = 0.014), and V60 (mean 9.1%, p = 0.009) were significant for the left cingulum closest to the parahippocampal gyrus (CPG). Also, dose mean (mean = 17.4 Gy, p = 0.033) and dose maximum (mean = 31 Gy, p = 0.015) were significant for the left cingulum closest to the cingulate gyrus (CCG). See table 1 for results summary, including significant dosimetric parameters for structures involved in non-verbal memory.

Conclusion: This longitudinal study and dosimetry analysis confirms the regional vulnerability of various structures in the memory network in contributing to both verbal and non-verbal memory decline following RT. Further investigation and analysis may help guide RT planning to better preserve memory function.
Memory test Structure RT Dosimetry Parameters Parameter Means p values
HVLT L hippocampus Dose minimum, D2 12.4 Gy, 13.2 Gy 0.022, 0.016
HVLT L cingulum closest to parahippocampal gyrus Dose minimum, D2, V35, V40, V45, V55, V60 13.3 Gy, 13.9 Gy, 26%, 23.3%, 20.6%, 13.1% 9.1% 0.005, 0.007, 0.002, 0.001, 0.001, 0.014, 0.009
HVLT L cingulum closest to cingulate gyrus Dose mean, dose maximum 17.4 Gy, 31 Gy 0.033, 0.015
BVMT R entorhinal cortex Dose minimum, dose maximum, D2, D98, V35, V40, V45 16.7 Gy, 37.4 Gy, 19.5 Gy, 35.4 Gy, 32.8%, 27.9%, 25.6% 0.041, 0.032, 0.018, 0.009, 0.002, 0.003, 0.022
BVMT R fornix V20, V25, V30 42.3%, 39.2%, 27.2% 0.006, 0.018, 0.024

Author Disclosure: J. Burkeen: None. R. Karunamuni: None. T.M. Seibert: None. T. Nguyen: None. C. McDonald: None. J.A. Hattangadi-Gluth: Research Grant; Varian Medical Systems.

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138 - Quantitative Neuroimaging and Neurocognitive Assessments to Determine Radiation Dosing Parameters to Memory Network Structures and Associated Memory Decline



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