Rectal movement during neoadjuvant irradiation: introduction to the adaptive radiotherapy

Uvod: Tumorje rektuma glede na višino vznika razdelimo v tri podskupine: spodnja, srednja in zgornja tretjina rektuma. Pri bolnikih z rakom rektuma in pri bolnikih z drugimi malignomi v mali medenici vsakodnevne spremembe rektuma in polnjenosti sečnega mehurja pogosto povzročajo velike deformacije tarčnih volumnov, ki jih ni mogoče popraviti s prilagoditvijo obsevalne mize. Namen: Namen magistrskega dela je bil pridobiti celovit vpogled v gibanje rektuma v zgornji, srednji in spodnji tretjini med neoadjuvantnim obsevanjem pri bolnikih s karcinomom rektuma. Metode dela: V raziskavo smo vključili 50 predoperativno obsevanih bolnikov. Izvedbo raziskave smo razdelili na štiri poglavitne dele: pregled baze podatkov, vrisovanje anatomskih struktur na posnetke CBCT, zbiranje podatkov odstopanj in izpis podatkov, kjer smo ločeno izvajali poravnavo na kostne strukture – sakrum in poravnava na zadnjo rektalno steno. Na koncu je sledila še statistična analiza in obdelava podatkov. Rezultati: Analiza je pokazala, da so pri poravnavi na kostne strukture – sakrum statistično značilne razlike v posteriorni, levi in desni smeri, medtem ko sta pri poravnavi na zadnjo rektalno steno statistično značilne razlike v levi in desni smeri. Pri ugotavljanju razlik med poravnavo na kostne strukture – sakrum/zadnjo rektalno steno smo opazili, da so statistično značilno odstopale razlike v levi smeri in pri kostnih strukturah. Odstopanja so v zgornji, srednji in spodnji tretjini rektuma medsebojno različna. Največje odstopanje je bilo izraženo v zgornji, sledila je srednja in nato spodnja tretjina rektuma. Analiza premera rektuma po osi X in Y je pokazala, da je dnevna vrednost rektuma lahko večja ali manjša od referenčne vrednosti, kar nakazuje na dnevno nihanje v polnjenosti rektuma. Rezultati analize razlik med dnevnim in referenčnim volumnom rektuma in sečnega mehurja so pokazali, da je dnevni volumen rektuma v povprečju manjši od referenčnega volumna za 2 cm3, medtem ko je volumen sečnega mehurja v poprečju manjši za 10 cm3 od referenčnega volumna sečnega mehurja. Razprava in zaključek: Položaj rektuma v zgornji, srednji in spodnji tretjini se vsakodnevno spreminja pri poravnavi na kostne strukture – sakrum, kot tudi pri poravnavi na zadnjo rektalno steno.Introduction: Rectal tumors are divided into three subgroups according to the location or height of their origin: the lower, middle and upper third of the rectum. In patients with rectal cancer and in patients with other pelvic malignancies, daily variations in rectal and bladder volume often result in large deformations of target volumes that cannot be corrected by adjusting the radiation couch. Purpose: The aim of the Master\u27s thesis was to obtain a comprehensive insight into the movement of the rectum in the upper, middle and lower third during neoadjuvant irradiation in patients with rectal carcinoma. Methods: Fifty preoperatively irradiated patients were included in the study. The implementation of the research was divided into four main parts: database review, drawing of anatomical structures on CBCT images, data collection of deviations and data output, where alignment to bone structures – the sacrum and alignment to the posterior rectal wall were performed separately. The final stage included statistical analysis and data processing. Results: The analysis revealed that there are statistically significant differences in the posterior, left and right directions when aligning to the bone structures – sacrum, while when aligning to the posterior rectal wall there are statistically significant differences in the left and right directions. When determining the difference between the alignments to the bone structures – sacrum/posterior rectal wall, we noticed that there were statistically significant differences in the left direction and in the bone structures. Deviations were mutually different in the upper, middle and lower third of the rectum. The greatest deviation was expressed in the upper, followed by the middle and then the lower third of the rectum. The analysis of the diameter of the rectum along the X and Y axes showed that the daily value of the rectum can be greater or less than the reference value, which indicates a daily variation in the rectal filling. The results of the analysis of the variations between the daily and reference volumes of the rectum and urinary bladder showed that the daily rectal volume is, on average, smaller than the reference volume by 2 cm3, while the bladder volume, on average, is smaller than the reference bladder volume by 10 cm3. Discussion and conclusion: The position of the rectum in the upper, middle and lower thirds changes daily in alignment with the bone structures – sacrum, as well as in alignment with the posterior rectal wall