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Background: Aim of the study was to assess the value of scintimammography using Tc-99m sestamibi in the evaluation of tumor response to neoadjuvant chemotherapy. Material and Methods: Results were calculated for 9 patients undergoing neoadjuvant chemotherapy. Scintimammography using 740 MBq Tc-99m sestamibi was performed before, during and after chemotherapy, and sestamibi uptake was scored visually and semiquantitatively to evaluate tumor response. Results: In the case of complete response (n = 3) sestamibi uptake decreased 8 days after beginning neoadjuvant chemotherapy and normalized in the following course. Focal uptake decreased more slowly in patients with partial response (n = 3), who showed clear, persisting tracer accumulation after therapy. The patients without response (n = 3) showed a persisting high tumor activity even after chemotherapy was completed. Conclusions: The preliminary data suggest that in contrast to other imaging modalities scintimammography appears to yield early information regarding tumor response to neoadjuvant chemotherapy.

A suitable physical parameter of radiation quality must represent not only the mean but also the fluctuation of the energy deposition per particle passage through that microscopic site of tissue in which proximity between radiation-induced lesions is decisive for the action mechanism. For sites of nanometre dimensions restricted LET is considered to have this property because (a) the distribution moments j and j2/j of the number j of ionisations per delta ray within the site are almost independent of the type and energy of the primary particle, and (b) the Poisson fluctuation of the number of primary ionisations within the site is determined by its mean value, which is proportional to restricted LET. Corresponding to this theoretical qualification as a suitable parameter, restricted LET has been experimentally identified as determining the yield factor a of various cellular radiation effects.

ZusammenfassungBei 31 Patientinnen mit mammographisch suspektem Befund wurden präoperativ beide Mammae emissionstomographisch (SPECT) untersucht. 30 und 120 Min. nach der Injektion von 370 MBq (10 mCi) 99mTcDTPA wurde jeweils eine Emissionstomographie durchgeführt. Die fokale Aktivitätsanreicherung in beiden Mammae wurde in den transversalen Rekonstruktionsschichten mittels ROI-Technik quantitativ analysiert. Sowohl benigne Veränderungen (n = 12) als auch Karzinome (n = 19) speicherten vermehrt 99mTc-DTPA im Vergleich zur mammographisch und klinisch gesunden Brust. Betrachtet man als Kriterium für Malignität eine 20% übersteigende Mehrspeicherung im Vergleich zur Gegenseite sowohl in der 30-Min.-als auch in der 120-Min.-Aufnahme, so betrug bei der Erkennung von malignen Tumoren die Sensitivität 74%, die Spezifität 64% und die Treffsicherheit 70%. Im Gegensatz zu Untersuchungen mit planarer Szintigraphie zeigten die Ergebnisse der quantitativen SPECT, daß auch benigne Veränderungen vermehrt 99m-Tc-DTPA akkumulieren können.

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