Performance and Methodological Aspects in Positron Emission Tomography

Performance standards for Positron emission tomography (PET) were developed to be able to compare systems from different generations and manufacturers. This resulted in the NEMA methodology in North America and the IEC in Europe. In practices, the NEMA NU 2- 2001 is the method of choice today. These standardized methods allow assessment of the physical performance of new commercial dedicated PET/CT tomographs. The point spread in image formation is one of the factors that blur the image. The phenomenon is often called the partial volume effect. Several methods for correcting for partial volume are under research but no real agreement exists on how to solve it. The influence of the effect varies in different clinical settings and it is likely that new methods are needed to solve this problem. Most of the clinical PET work is done in the field of oncology. The whole body PET combined with a CT is the standard investigation today in oncology. Despite the progress in PET imaging technique visualization, especially quantification of small lesions is a challenge. In addition to partial volume, the movement of the object is a significant source of error. The main causes of movement are respiratory and cardiac motions. Most of the new commercial scanners are in addition to cardiac gating, also capable of respiratory gating and this technique has been used in patients with cancer of the thoracic region and patients being studied for the planning of radiation therapy. For routine cardiac applications such as assessment of viability and perfusion only cardiac gating has been used. However, the new targets such as plaque or molecular imaging of new therapies require better control of the cardiac motion also caused by respiratory motion. To overcome these problems in cardiac work, a dual gating approach has been proposed. In this study we investigated the physical performance of a new whole body PET/CT scanner with NEMA standard, compared methods for partial volume correction in PET studies of the brain and developed and tested a new robust method for dual cardiac-respiratory gated PET with phantom, animal and human data. Results from performance measurements showed the feasibility of the new scanner design in 2D and 3D whole body studies. Partial volume was corrected, but there is no best method among those tested as the correction also depends on the radiotracer and its distribution. New methods need to be developed for proper correction. The dual gating algorithm generated is shown to handle dual-gated data, preserving quantification and clearly eliminating the majority of contraction and respiration movement

Sairaalan kolmen yksikön kapasiteetin käytön kehittäminen

Tässä tutkimuksessa selvitettiin Etelä-Karjalan keskussairaalan sädehoitoyksikön, päiväkirurgisen yksikön sekä synnytysten ja naistentautien yksikön käyttämän kapasiteetin kustannuksia eri käyttöasteilla. Yksiköiden toiminta ja niiden keskeiset resurssit kuvattiin. Tiedot kerättiin käyttäen haastatteluja, käyttöomaisuuskirjanpitoa ja laskentatoimen talousraportointijärjestelmää. Yksiköiden tuloslaskelmien perusteella arvioitiin niiden muuttuvia ja kiinteitä kustannuksia. Kapasiteettimalleja arvioitiin voitavan hyödyntää esimerkiksi toiminnan seurannassa, suunnittelussa ja tavoiteasetannassa. Kapasiteetin määrittely ja kapasiteetin kustannusten laskenta erilaisille kapasiteetin käyttöasteille onnistui kaikissa yksiköissä. Parhaiten kapasiteetin kustannustieto kuvasi sädehoitoa ja heikoiten synnytyksiä. Käyttämätöntä kapasiteettia tunnistettiin sädehoitoyksikössä ja päiväkirurgisessa yksikössä. Toiminta-asteen noston vaikutukset yksikkökustannuksiin laskettiin kaikissa yksiköissä ja niissä yksiköissä, joissa oli käyttämätöntä kapasiteettia, tehtiin lisäksi tarkempia laskelmia ja ehdotuksia toiminnan kehittämiseksi.

Salivary gland cancer in Finland: Incidence, histological distribution, outcome and prognostic factors

Salivary gland cancer (SGC) is a rare cancer. The histological classification of SGC is complex and its biological behavior highly variable: it may vary from a low-grade tumor to a high-grade and often fatal malignancy. These circumstances make this cancer a diagnostic and therapeutic challenge. Older age and exposure to ionizing radiation are known risk factors. The mainstay of treatment is surgery combined with adjuvant radiation therapy, when appropriate. In addition to the histological type, the only well known prognostic factor is the TNM classification, which describes the tumor size and the amount of metastases. This study was performed using a full population-based nationwide cohort of SGC patients and tumors diagnosed in Finland in 1991-1996. The annual incidence of SGC in the entire population was, on average, 47.7 per year. By histological re-evaluation of 237 specimens the most frequent histological types were the adenoid cystic carcinoma (n=65; 27%), the mucoepidermoid carcinoma (n=45; 19%) and the acinic cell carcinoma (n=41; 17%). The highest 10-year disease-specific survival rate occurred among patients with acinic cell carcinoma (90%), followed by mucoepidermoid carcinoma (81%) and adenoid cystic carcinoma (60%). A high volume-corrected index (VCI) of Ki-67 correlated with worse survival of patients with SGC. Computer-assisted morphometric analyses of CD34-positive vessels indicated an unfavorable prognosis for patients with mucoepidermoid carcinoma and an association with poor survival among patients with acinic cell carcinoma. A high level of expression of matrix metalloproteinase-9 (MMP-9) showed a trend for a poorer prognosis in salivary duct carcinoma, and a high level of MMP-13 and a low level of MMP-1 had a trend for a poorer prognosis of patients with SGC. A low level of MMP-7 was associated with a poor prognosis of patients with acinic cell and mucoepidermoid carcinoma.