Carl Jansen

Myocardial Perfusion Color Scintigraphy with MAA

Macroaggregates of albumin labeled with 99mTc and 131I were injected into the coronary arteries in 400 patients undergoing coronary arteriography. The three major coronary artery systems were divided into six groups, based upon coronary arteriography and myocardial perfusion color scintigraphy. Myocardial perfusion could not be predicted uniformly by angiography alone. Myocardial perfusion patterns of each group are presented, together with cases illustrating collateral perfusion, myocardial aneurysms, cardiomyopathy, and venous by-pass grafts. If the size and number of particles injected are carefully controlled, the procedure involves insignificant morbidity and no mortality. Myocardial perfusion scintigraphy with radioactive particles reflects the status of the myocardium beyond diseased coronary arteries.

The Abnormal Bone Scan in Intracranial Lesions

In 43 patients with abnormal brain scans restudied within 2-7 days with 99mTc-labeled ethane-1, hydroxy-1, diphosphonate (EHDP), cerebral infarctions, primary and metastatic neoplasms, chronic subdural hematoma, arteriovenous malformations and inflammatory lesions were visualized. The localization of EHDP in primary and metastatic neoplasms is usually less apparent than pertechnetate. Conversely, the localization of EHDP in cerebral infarctions is usually more apparent than pertechnetate. 99mTc-EHDP, in conjunction with pertechnetate, may become useful in differentiating cerebral infarctions from neoplasms. Further, skull scans must be interpreted with the appreciation that bone-seeking radiopharmaceuticals may localize in a variety of intracranial lesions.

Deadtime of scintillation camera systems—definitions, measurement and applications

Fast quantitative dynamic studies with scintillation camera systems require deadtime correction. Although such systems are semiparalyzable, they are most conveniently treated either as paralyzable or nonparalyzable. Paralyzing deadtime (τ) is that deadtime during which a system is unable to provide a second output pulse unless there is a time interval of at least τ between two successive events. Paralyzable systems are characterized by Poisson statistics, so that the “true” counting rate N = R e N τ , where R is the observed counting rate. Nonparalyzing deadtime (T) is that deadtime during which a system is insensitive after each observed event. The period of insensitivity is not affected by any additional “true” events before full recovery occurs. For nonparalyzable systems the corrected counting rate N = R / (1 − RT) . A two‐source method protocol is presented for deadtime measurement. The paralyzing deadtime is calculated by a 5‐dimension Newton–Raphson iteration. The nonparalyzing deadtime is calculated by a quadratic equation. Approximation equations are also presented not requiring a computer. Deadtimes are fitted to polynomial equations as dependent variables of measured counting rate. Algorithms incorporating the polynomials are presented for the deadtime correction of histogram curves. Using either the paralyzing or the nonparalyzing approach, precise deadtime corrections are demonstrated.

The Quantitative Display Of Radioisotope Image Data As Computer Generated Color Coded Isocount Contours --Comparison With Digital Printout

Medical radioisotope scintigrams are most commonly produced as photographic images in which count densities are displayed in various shades of grey. Such photographic grey scales are used both for recording the live images from a rectilinear scanner or scintillation camera and also for digitized images displayed with computer controlled data processing systems (Fig 1). Altho gh trade-offs are usually made between the conflicting demands for high photographic contrast and wide dynamic range or latitude), conventional photographic methods are often inadequate for the display of the entire range of count densities. Moreoever, these grey scale images lack quantitative information.