[Development and application of dynamic MR imaging in the evaluation of perfusion changes in rectal carcinoma during radiotherapy in clinical routine. Preliminary results].
OBJECTIVE
This study was aimed at measuring microcirculatory parameters and contrast medium accumulation within the rectal carcinoma during fractionated radiotherapy in the clinical setting.


METHODS
Perfusion data were observed in patients with rectal carcinoma (n = 8) who underwent a pre-operative combined chemo/radiotherapy. To acquire perfusion data, an ultrafast T1 mapping sequence was carried out on a 1.5-Tesla whole body imager to obtain T1 maps at intervals of 14 or 120 seconds. The overall measurement time was 40 minutes. The transaxial slice thickness (5 mm) was chosen in such a way that both arterial vessels and the tumor could be clearly identified. The gadolinium-DTPA (Gd-DTPA) concentration time curve was evaluated for arterial blood and tumor after intravenous constant rate infusion. The method allows a spatial resolution of 2 x 2 x 5 mm and a temporal resolution of 14 seconds. Patients underwent MR imaging before and at constant intervals during fractionated radiotherapy.


RESULTS
Spatial and temporal resolution of dynamic T1 mapping was sufficient to reveal varying CM accumulation levels within the tumor and to identify the great arteries in the pelvis. In 6 patients Gd-DTPA concentration-time-curves were evaluated within the tumor during radiation. Pi index of Gd-DTPA versus radiation dose showed a significant increase in the first or second week of treatment, then either returned slowly to pretreatment level or a renewed increase was observed. The average Pi-value at the beginning was 0.16 (+/- 0.049), reaching highest level of 0.23 (+/- 0.058). In all groups the rise from the Pi-value to the Pi-maximum was statistically significant. The relative increase in perfusion ranged between 20 to 83%.


CONCLUSIONS
The results show, that the ultrafast MR-technique described above provide a suitable tool for monitoring tumor microcirculation during therapeutic interventions and offers the potential for an individualized optimization of therapeutic procedures.
de Vries
A
A
Universitätsklinik für Strahlentherapie-Radioonkologie, Osterreich. Alexander.deVries@uibk.ac.at
Griebel
J
J
Judmaier
W
W
Kremser
C
C
Gneiting
T
T
Hoflehner
J
J
Peer
S
S
Ofner
D
D
Brandl
M
M
Schocke
M
M
Rettl
G
G
Debbage
P
P
Aichner
F
F
Lukas
P
P
D000368:Aged; D003287:Contrast Media; D019583:Dose Fractionation, Radiation; D019786:Gadolinium DTPA; D006801:Humans; D016014:Linear Models; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008833:Microcirculation; D008875:Middle Aged; D011879:Radiotherapy Dosage; D012004:Rectal Neoplasms / Q000098:blood supply* / Q000532:radiotherapy* / Q000601:surgery; D013997:Time Factors
D003287:Contrast Media; D019786:Gadolinium DTPA
Entwicklung und Anwendung dynamischer MRT-Messungen zur Evaluierung von Perfusionsveränderungen bei Rektumkarzinomen unter Bestrahlung in der klinischen Routine. Erste Ergebnisse.