Optimization of computerized tomography protocols for preoperative planning and postoperative evalution of total knee artroplasty

[M. S. Stojadinović]

56 str.

medicina - radiologija i nuklearna medicina / medicine - radiology and nuclear medicine

osteoartritisa. Kurtz i saradnici prognoziraju porast broja TKA za 673% u Sjedinjenim Državama u periodu između 2005. i 2030. godine. Ključni faktori za uspešnost TKA procedure su precizno pozicioniranje komponenti proteze i pravilno podešavanje mekih tkiva. Perth CT protokol je metod koji je veoma efikasan za preoperativno planiranje i postoperativnu procenu poravnanja, posebno rotacionog poravnanja. Svaki oblik snimanja koji uključuje upotrebu jonizujućeg zračenja predstavlja potencijalni rizik od genetskog oštećenja i razvoja maligniteta. Cilj: Cilj istraživanja je da pokaže mogućnosti optimizacije Perth CT protokola uz zadržavanje zadovoljavajućeg kvaliteta slike. Materijal i metode: U studiji preseka učestvovalo je 16 bolesnika za preoperativno planiranje i postoperativnu evaluaciju TKA. Svi bolesnici su pregledani na 160 detektosrkom CT aparatu (Toshiba, Aqulion Prime Otawara, Japan) prema standardnom i optimizovanom Perth CT protokolu uz korišćenje naprednih tehnika (automatske kontrole ekspozicije (Sure expose), iterativne rekonstrukcije slike (Adaptive Iterative Dose Reduction 3D-AIDR 3D) kao i SEMAR (single-energy projection-based MAR (metal artifact reduction) tehnike za redukciju artefakata od proteze)). Postproceduralno, efektivna doza zračenja je određivana na osnovu doznog izveštaja tj. korišćene su vrednosti CTDIvol(mGy) i DLP (mGy×cm) prema formuli: E=k×DLP (mSv). Kvalitet slike je određivan prema subjektivnim (vizuelni skor) i objektivnim (vrednostima odnosa signala i šuma (SdNR) i figure of merit (FOM)) kriterijumima. Rezultati: Efektivna doza zračenja kod optimizovanog protokola je značajno niža u odnosu na standardni protokol (0.180±0.013 prema 0.900±0.034, (p<0.001). Interesantno je da se efektivna doza zračenja kod pacijenata sa protezom kolena sa optimizovanim protokolom povećava značajno manje u odnosu na standardni protokol. Nema statistički značajne razlike u subjektivnim kriterijumima za kvalitet slike između protokola (p>0.05). Prema analizi objektivnih kriterijuma za kvalitet slike, SdNR i FOM, evidentno je da su vrednosti SdNR kod optimizovanog protokola niže, a FOM-a više. Nema statistički značajne razlike u kvalitetu slike koristeći SdNR i FOM u specifičnim protokolima prema delu ekstermiteta. Takođe, nema statistički značajne razlike u kvalitetu slike koristeći SdNR i FOM u specifičnim protokolima u odnosu na postojanje proteze. Interesantno je da su vrednosti SdNR kod bolesnika sa protezom kolena kod optimizovanog protokola više u odnosu na one bez proteze, što se objašnjava upotrebom SEMAR tehnike. Zaključak: Poštujući ALARA (As Low As Reasonably Achievable) principe, moguće je optimizovati Perth CT protokol. Prvo, redukcijom vrednosti kV i mAs kao i promenom kolimacije i povećanjem pič faktora. Takođe, napredne tehnike iterativne rekonstukcije (IR) su korišćenje u oba protokola, a automatske kontrole ekspozicije (AEC) samo u optimizovanom. Efektivna doza zračenja se može smanjiti pet puta, a da kvalitet slike bude zadovoljavajući.

Introduction: Total knee arthroplasty (TKA) has become the treatment of choice for advanced osteoarthritis. Kurtz et al. have projected a 673% increase in total knee arthroplasty (TKA) in the United States between 2005 and 2030. Accurate positioning of the component and proper adjustment of soft tissue are recognized as crucial factors in achieving a successful knee arthroplasty. Perth CT Protocol is method which is highly effective for preoperative planning and postoperative assessment of alignment, particularly rotational alignment. Any form of imaging that involves the use of ionizing radiation poses a potential risk of genetic damage and malignancy. Aim: The aim of this paper was to show the possibilities of optimization Perth CT protocol which maintaining satisfactory image quality. Material and methods: The cross-sectional study comprised 16 patients for preoperative planning or postoperative evaluation TKA. All patients were examined on a 160 detector CT scanner (Toshiba, Aqulion Prime Otawara, Japan) according to the standard and optimized Perth CT protocol with using advance technique (automatic exposure control (Sure expose), iterative image reconstruction (Adaptive Iterative Dose Reduction 3D-AIDR 3D) as well as SEMAR (single-energy projection–based MAR (metal artifact reduction) algorithm) for eliminating prosthesis artifacts). Postprocedurally, the effective radiation dose was determined based on the dose report (values of CTDIvol(mGy) and DLP (mGy×cm)) according to the formula: E=k×DLP (mSv). Imaging quality is determined according to subjective (the visual scores) and objective (values of signal to noise ratio (SdNR) and figure of merit (FOM)) criteria. Results: The effective radiation dose with optimized protocol is significantly lower compared to the standard protocol (0.180±0.013 vs 0.900±0.034, (p<0.001). It is interesting that the effective dose of radiation in a patient with the knee prosthesis with the optimized protocol increased significantly less compared to the standard protocol. No significant difference is observed in the subjective evaluation of image quality between protocols (p>0.05). Upon analyzing the objective criteria for image quality, namely SdNR and FOM, it is evident that optimized protocols result in lower SdNR values and higher FOM values. No significant difference of image quality is determined using the SdNR and FOM as per the specified protocols and parts of extremities. Also, no significant difference of image quality is determined using the SdNR and FOM as per the specified protocols and the presence of prosthesis. Interesting, SdNR in patients with knee prosthesis in optimized protocol was larger compared to those without prosthesis, which can be explained by using SEMAR technique. Conclusion: Retrospecting the ALARA (As Low As Reasonably Achievable) principles, it is possible to optimized the Perth CT protocol. First by reducing the kV and mAs values, as well as by changing the collimation and increasing the pitch factor Also, advanced iterative reconstruction (IR) techniques were used in both protocols and automatic exposure control (ACE) in optimized protocol. The effective dose of radiation can be reduced five time and the image quality will be satisfactory.

totalna artroplastika kolena, Pert CT protokol, optimizacija

total knee arthroplasty, Pert CT protocol, optimization

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