STAT 5303 Assignment 7

Predicting Skeletal Spongiosa Volume From Simple Body Measurements

A primary goal in molecular radiotherapy is to optimize various treatment parameters - radionuclide, carrier molecule (peptide, antibody, pharmaceutical), administered activity, use of pre-therapy drugs (cold antibody, amino acids, etc.) - in order to maximize tumor cell kill while minimizing toxicity in non-targeted tissues. Active bone marrow is one of the more radiosensitive tissues in the human body and hence it is important to predict and possibly avoid myelotoxicity in radionuclide therapies (e.g. chemotherapy). Current procedures used to calculate marrow dose generally require knowledge of the patient total skeletal active marrow mass, a value which at present cannot be directly measured. Theoretically, the active marrow mass can be calculated given knowledge of the Total Skeletal Spongiosa Volume (TSSV). Your goal in this study is to build a multiple regression model to predict TSSV based on simple skeletal measurements obtainable from a CT scan or radiograph. In a recent study, 17 different body measurements were recorded from whole-body CT images of 40 cadavers (20 male and 20 female), whose ages ranged from roughly 40-80 years, as representative of cancer patients potentially treated with radionuclide therapy. For each cadaver, TSSV was calculated by manual segmentation, a laborious process involving cadaver dissection. A description of the variables appearing in the dataset along with abbreviated names is as follows.

  1. Sex: Sex (male=1, female=0).
  2. Age: Age (years).
  3. HT: Total body height measured on the CT scout images (cm).
  4. OC.W: Maximum width of the os coxae in the coronal plane (cm).
  5. OC.H: Average of the maximum heights of the left and right side of the os coxae in the coronal plane (cm).
  6. Bi.B: Distance between the outermost portions of the greater trochanters in the coronal plane (cm).
  7. ASH: Distance from the anterior sacral promontory to the apex of the sacrum in the sagittal plane (cm).
  8. S.W: Maximum width of the sacrum in the transverse plane (cm).
  9. L5.T: Thickness of the fifth lumbar (L5) vertebrae in the sagittal plane (cm).
  10. S1.B: Longest diameter of the S1 sacral plate in the transverse plane (cm).
  11. P: Average of the maximum perimeter of the left and right femoral heads in the coronal plane (cm).
  12. FD: Average of the Feret's diameter for the right and left femoral heads measured in the coronal plane (cm).
  13. Max.H: Maximum height of the femoral head in the coronal plane, calculated as the average of the left and right femoral heads (cm).
  14. Max.W: Maximum width of the femoral head in the coronal plane, calculated as the average of the left and right femoral heads (cm).
  15. HH: Distance between the outermost portions of the right and left proximal humeral heads in the CT scout image (cm).
  16. FH: Maximum height of the femoral bones in the CT scout image, calculated as the average of the left and right femoral bones (cm).
  17. TSSV: Total skeletal spongiosa volume (cubic cm).

Note that the TSSV measurement for the cadaver labeled CAD-26 was not recorded (the period denotes a missing observation). Using these data, build a multiple regression model to predict TSSV from the remaining variables, and summarize your findings. In your quest for a suitable model, you should:


Instructions: