High Z elements in human sarcomata: assessment by multienergy CT and neutron activation analysis

"Tumor equivalent" phantoms containing inorganic salts (KH2PO4, CH3COOK, NaCl and Kl) were scanned on an EMI 5005 body scanner at 140 kVp, 28 mA; 120 kVp, 33 mA; and 81 kVp, 42 mA. Significant signal gain for the detection of higher atomic number elements by multiple energy scanning was noted. Certain sarcomas are known to accumulate high Z elements. Accordingly, excised specimens of various histologies of human sarcomata (chondrosarcoma, liposarcoma, and malignant fibrous histiocytoma) were scanned at 140 kVp and 81 kVp. Using selected areas of interest in the computed tomographic (CT) image to direct the in vitro biopsy of various regions of excised tumors, interesting correlations between the CT number variation and the respective, high Z elemental composition variation, as determined by thermal neutron activation analysis were observed. Further investigation with phantoms and excised sarcomata at 62 kVp and 42 mA suggested that dual energy CT scanning (at 140 kVp and 62 kVp) may be a method of monitoring "effective Z" and heavy element compositional changes. The authors are also attempting to develop these same low kilovoltage techniques as a method for the noninvasive clinical monitoring of an antisarcoma chemotherapeutic agent, cis-diammineaichloroplatinum (11).