Improved sensitivity in diagnosing superior vena caval flow compromise through radionuclide ''phase'' imaging

Usual scintiangiography for venous obstruction ignores the quantitative advantages of nuclear medicine. This failing denies patients timely therapy in such cases as gradual evolution of superior vena cava obstruction. This study prospectively examined venous flow in 116 patients using bilateral injections of Tc-99m pertechnetate. A gamma camera collected 60 images for 3 seconds each. The data was digitized, processed and displayed. A first harmonic Fourier ''phase'' image was generated for each study with a single cycle extending from the appearance of tracer in the axillary veins to its emergence from the right ventricle. Three sets of criteria were used: strict, requiring interrupted or collateral venous flow; sensitive, recognizing distortion or narrowing of venous channels; and phase. The latter used the colors in the phase image to encode the relative time when activity reached any given level. Abrupt color changes were interpreted as flow abnormalities. Angiography, performed on 25 patients, showed the best sensitivity (SENS) with phase criteria (100%). Phase criteria maintained the highest SENS when the venous obstruction was diagnosed by radiography alone or by radiography and clinical follow-up. The accuracy (ACC) of the phase criteria (64-78%) was almost equal to that of the strict (SENS, 36-40%; specificity (SPEC), 93-100%; ACC 64-89%) and sensitive (SEN 85-93%, SPEC 30-67%, ACC 66-76%) criteria. Quantitative radioangiography is recommended to sensitively and non-invasively screen patients with right upper lobe tumors to identify those who might benefit from timely therapeutic intervention for comprised venous flow