OtherBasic Science Investigations

Impact of Nodal Regression on Radiation Dose for Lymphoma Patients After Radioimmunotherapy

Christine L. Hartmann Siantar, Gerald L. DeNardo and Sally J. DeNardo
Journal of Nuclear Medicine August 2003, 44 (8) 1322-1329;

Article Figures & Data

Figures

  • FIGURE 1.
    FIGURE 1.

    Empiric, analytic fit to Monte Carlo-simulated absorbed fraction data for water spheres ranging in size from 0.01 to 1,000 g. R2 is square of R for fitted curve.

  • FIGURE 2.
    FIGURE 2.

    Relationship between administered activity, initial nodal mass, initial nodal activity concentration, and nodal regression half-time, 131I biologic half-life. Initial nodal activity concentrations appear to be more related to nodal mass (A) than to administered activity (B). 131I biologic half-life did not appear to depend strongly on initial nodal mass (C). Nodal regression half-time is >10 d in all nodes for those patients treated with 700–1,000 MBq/m2 injected activities and is <10 d for all except 2 nodes in patients treated with >2,800 MBq/m2 (D). In contrast, nodal regression half-time does not appear to depend strongly on node’s initial activity concentration (E). Wide variation in nodal regression half-times, ranging from <1 d to no change in mass (arbitrarily assigned to 300 d for plotting on graph), were associated with relatively small variation in 131I biologic half-life (F). X marks in B and E identify pairs of dissimilar masses that were imaged in same ROI and assigned same activity per nodal mass. Pt = patient.

  • FIGURE 3.
    FIGURE 3.

    Greater corrected absorbed radiation doses were generally associated with shorter nodal regression half-times. Line shows least-squares fit, which has P = 0.004. Pt = patient.

  • FIGURE 4.
    FIGURE 4.

    Corrected and uncorrected absorbed radiation dose. Dose correction generally increases with increasing absorbed radiation dose. Plot does not include nodes whose regression half-time was shorter than activity effective half-life. Plot does include line of identity for corrected and uncorrected absorbed radiation dose. Pt = patient.

  • FIGURE 5.
    FIGURE 5.

    Correction factor for absorbed radiation dose resulting from nodal regression. Plot does not include nodes whose regression half-time was shorter than 131I effective half-life. Pt = patient.

  • FIGURE 6.
    FIGURE 6.

    Nodal regression compared with uncorrected (black symbols) and corrected (red symbols) absorbed radiation dose (A) and dose correction factor (B). In A, uncorrected dose is shown with black symbols and corrected dose with red symbols, and red line shows least-squares fit (P = 0.005) to nodal regression vs. corrected absorbed radiation dose. Absorbed radiation dose was calculated by integrating only to final measurement time. Pt = patient.

  • FIGURE 7.
    FIGURE 7.

    Nodes with highest doses were small in size (A), which was consistent with higher initial 131I activity concentration, and were located in patients who received high administered activities (B). Pt = patient.

Tables

  • TABLE 1

    Summary of Administered Dose, Number of Accessible Nodes, Number of Nodes With Activity Measurements, and Number of Nodes Carried Through Study

    Patient no.Administered dose (GBq/m2)Accessible nodes*Accessible nodes with activity measurementsNodes carried through study†
    13.151287
    22.85722
    32.92333
    43.45201414
    52.68332
    60.781776
    71.03633

    • ↵* Measured with calipers.

    • ↵† Had both activity and caliper measurements and met assessment criteria.

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