Frühe dynamische 18F-FDG PET/CT-Untersuchung bei Patienten mit chronischer Osteomyelitis nach Fraktur der unteren Extremität

Untersucht wurde, ob mit frühen dynamischen Positronenemissionstomographie/ Computertomographie-Aufnahmen (edPET/CT) unter Verwendung von 18F–Fluorodesoxyglukose (FDG) bei Patienten mit chronischer Osteomyelitis (COM) der unteren Extremität zwischen betroffener und nicht betroffener Seite unterschieden werden kann. Bei 9 konsekutiven Patienten (1 Frau, 8 Männer; Alter 54 ± 13 Jahre) wurden vor einer Standard-PET/CT-Untersuchung 10 edPET/CT-Studien über 5 Minuten mittels List-Mode- Akquisition durchgeführt. Es erfolgte die Rekonstruktion von acht konsekutiven Zeitintervallen, vier 15-s und anschließend vier 60-s Intervalle. Zur Quantifizierung der frühen Anflutung und Anreicherung wurden in jedem Zeitintervall der maximale und mittlere ed-standardized uptake value (edSUVmax, edSUVmean) mit Hilfe von volumes-of-interest (VOI) ermittelt. Es erfolgte der Vergleich der betroffenen mit der nicht betroffenen kontralateralen Extremität. Das betroffene Knochenareal zeigte bereits ab dem Zeitintervall 31-45s signifikant höhere edSUVmax und edSUVmean als die gesunde kontralaterale Seite. In der Standard-PET/CT konnte ebenfalls ein signifikanter Unterschied zwischen betroffener und gesunder Seite festgestellt werden. Die Ergebnisse lassen vermuten, dass edPET mit FDG eine sinnvolle Zusatzuntersuchung zur Standard-FDG-PET/CT darstellt. Das Potential sollte in einer prospektiven Studie mit größeren Fallzahlen validiert werden

How Much Is the Dose Varying between Follow-Up CT-Examinations Performed on the Same Scanner with the Same Imaging Protocol?

PURPOSE:To investigate the dose variation between follow-up CT examinations, when a patient is examined several times on the same scanner with the identical scan protocol which comprised automated exposure control. MATERIAL AND METHODS:This retrospective study was approved by the local ethics committee. The volume computed tomography dose index (CTDIvol) and the dose-length-product (DLP) were recorded for 60 cancer patients (29 male, 31 female, mean age 60.1 years), who received 3 follow-up CT examinations each composed of a non-enhanced scan of the liver (LI-CT) and a contrast-enhanced scan of chest (CH-CT) and abdomen (AB-CT). Each examination was performed on the same scanner (Siemens Definition FLASH) equipped with automated exposure control (CARE Dose 4D and CARE KV) using the identical scan protocol. RESULTS:The median percentage difference in DLP between follow-up examinations was 9.6% for CH-CT, 10.3% for LI-CT, and 10.1% for AB-CT; the median percentage difference in CTDIvol 8.3% for CH-CT, 7.4% for LI-CT and 7.7% for AB-CT (p<0.0001 for all values). The maximum difference in DLP between follow-up examinations was 67.5% for CH-CT, 50.8% for LI-CT and 74.3% for AB-CT; the maximum difference in CTDIvol 62.9% for CH-CT, 47.2% for LI-CT, and 49% for AB-CT. CONCLUSION:A significant variance in the radiation dose occurs between follow-up CT examinations when the same CT scanner and the identical imaging protocol are used in combination with automated exposure control

Correlation analysis between the differences in the radiation exposure and the differences in the parameters that varied between the follow up examinations.

<p>Correlation analysis between the differences in the radiation exposure and the differences in the parameters that varied between the follow up examinations.</p

a-f: Scout views of three follow-up CT examinations of a 54 year old male patient with superimposed modulation of the tube current.

<p>While the differences in the radiation dose between the chest CT examinations can be explained by differences in the table height (TH) and the scan length (SL), the difference in dose between the abdominal CT scans d and f, cannot be explained by these factors due to the fact that in d and f the table height as well as the scan length had been virtually the same. However, the positioning of the thighs was different between these examinations, which resulted in a different tube current modulation and consecutively in different radiation dose.</p

Schematic summary of the direct and indirect determinates of the radiation exposure in CT.

<p>Schematic summary of the direct and indirect determinates of the radiation exposure in CT.</p

Multiple linear regression analysis to predict differences in the radiation exposure between follow-up examinations.

<p>Multiple linear regression analysis to predict differences in the radiation exposure between follow-up examinations.</p

Influence of the phantom’s positioning on the CT table on the radiation dose.

<p>Except of the phantom’s positioning all other imaging parameters were kept constant between the measurements.</p