A comparison of diagnostic and radiotherapeutic planning protocols in lung cancer: a comparison with positron emission tomography and computer tomography

Uvod: Incidenčna stopnja raka v Sloveniji in svetu nenehno narašča. Med petimi najpogostejšimi raki v Sloveniji ima najslabšo prognozo pljučni rak, kjer je pet letno preživetje pri obeh spolih le 14,6% in se izboljšuje. Pri nekaterih tipih pljučnega raka je obsevanje najugodnejša metoda zdravljenja. Priprava na obsevanje pljučnega raka poteka na aparatu za pozitronsko emisijsko tomografijo z računalniško tomografijo po klasičnem protokolu, ki se izvaja na oddelku za nuklearno medicino in radioterapevtskem protokolu za planiranje obsevanja. Protokola se razlikujeta po tehničnih parametrih kar rezultira v prejeti dozi za bolnika. Namen: Primerjati klasični protokol slikanja z radioterapevtskim protokolom slikanja za potrebe planiranja v radioterapiji, ugotoviti razlike med njima in predlagati morebitne izboljšave pri optimizaciji doze prejete ob slikanju z računalniško tomografijo pri radioterapevtskem protokolu. Metode dela: V retrospektivni raziskavi smo s statistično analizo primerjali podatke o dozni obremenitvi bolnikov z računalniško tomografijo pri klasičnem in radioterapevtskem protokolu. Primerjali smo tudi podatke o dozni obremenitvi bolnikov z računalniško tomografijo pri klasičnem protokolu pred in po uvedbi izboljšane iterativne rekonstrukcijske metode SAFIRE. Podatke za statistično analizo smo pridobili na Onkološkem inštitutu Ljubljana v obdobju od 1.1.2017 do 1.12.2018. Rezultati: S statistično analizo smo ugotovili, da pri slikanju z računalniško tomografijo pri klasičnem in radioterapevtskem protokolu obstajajo statistično značilne razlike v dozi na bolnika (p < ?10?^(-3)). Statistično značilne razlike smo ugotovili tudi pri slikanju z računalniško tomografijo pri klasičnem protokolu pred in po izboljšavi iterativne rekonstrukcijske metode (p=0,001). Razprava in zaključek: Z raziskavo smo želeli ugotoviti, kakšne so razlike pri klasičnem in radioterapevtskem protokolu ter kako uvedba in izboljšava iterativne rekonstrukcijske metode pri računalniško-tomografskem slikanju posredno vpliva na dozo za bolnika. Dozna obremenitev pljuč z računalniško-tomografskim slikanjem pri klasičnem protokolu z iterativno rekonstrukcijsko metodo IRIS je bila v primerjavi z radioterapevtskim protokolom nižja za 67,5 %. Uvedba izboljšane iterativne rekonstrukcijske metode SAFIRE je, v primerjavi s predhodno iterativno rekonstrukcijsko metodo IRIS, dozo na bolnika še dodatno znižala in sicer za 34,2 %. V prihodnje je za rekonstrukcijo računalniško-tomografskih slik, možnost uvedbe izboljšane iterativne rekonstrukcijske metode v radioterapevtski protokol z upoštevanjem vpliva nižje doze na natančnost vrisovanja tarčnih volumnov.Introduction: The incidence rate of lung cancer has been steadily increasing during the recent years domestically and worldwide. Amongst the five most prevalent cancers in Slovenia, lung cancer has the worst prognosis. Lung cancer patients, both male and female, have an average five years survival rate of 14.6 %, with the number increasing annually. Radiotheraphy is the preferred method of treatment for certain types of lung cancer. Treatment planning has been done on positron emission tomography with compudet tomography machine via the established classic protocol and radiotheraphy planning protocol. These two methods mainly differ in technical parameters, which results in different radiation dose for the patients. Purpose: We intended to establish the difference between the classic positron emission tomography and compudet tomography protocol for lung cancer screening and treatment planning positron emission tomography with compudet tomography protocol, compare computed tomography radiation doses on patients and try to find an optimized approach to both. Methods: A descriptive method to explain the basic concepts of positron emission tomography with compudet tomography planning and parameters involved was used. Statistical analysis has been implemented to compare radiation dose data between the two methods, as well as the dose before and after an improved iterative reconstruction SAFIRE has been used. The results were presented in a qualitative and quantitative manner with a commentary on efficiency and viability of methods used. Results: It was established that there are statistically significant differences between radiation doses that patients receive in the classic positron emission tomography with compudet tomography protocol for lung cancer screening and treatment planning positron emission tomography with compudet tomography protocol (p < 〖10〗^(-3)). Statistically significant differences were also found in radiation dose on patients before and after the improvement of iterative reconstruction method (p=0.001). Discussion and conclusion: We observed a 67.7 % lower radiation dose on patients when the iterative reconstruction was used on a classic positron emission tomography with compudet tomography protocol, while the dose was further lowered by additional 34.2 % when the improved iterative reconstruction method SAFIR was implemented. Our results and the studied sources suggest that iterative reconstruction may becoming increasingly viable in radiotheraphy treatment planning procedures. It would be prudent to further research the effect of lower patient dose on selecting and defining target volumes for radiation treatment