Van Staden, J. A.Du Raan, H.Ramonaheng, Keamogetswe2015-08-112015-08-112014-08http://hdl.handle.net/11660/816English: Accurate activity quantification is important for its application in radiation dosimetry. Planar image quantification plays an important role in the quantification of whole body images which provide a full assessment of bio-distribution from radionuclide administrations. In the Department of Nuclear Medicine at Universitas Hospital, 123I meta-iodobenzylguanidine [123I]-MIBG quantification of neuroendocrine tumours is performed prior to therapeutic radionuclide treatment. The bio-distribution of activity in these studies is mostly in the abdominal region. Factors influencing quantification include scatter, attenuation, background activity and close proximity of organs with radioactivity uptake. The aim of this study was to evaluate the effect of tumour geometry on the quantification accuracy of 99mTc and 123I in planar phantom images, by applying scatter and attenuation corrections, with the focus on neuroendocrine tumours. The tumour geometry investigated included: various tumour sizes, various tumour-liver distances and two tumour-background ratios (0.5 % and 1.0 %). The quantification technique was first developed with the readily available 99mTc and subsequently applied to the more costly 123I used for imaging neuroendocrine tumours. Adjustments were necessary due to the difference in physical properties between the two isotopes. An in-house manufactured abdominal phantom was developed to mimic the clinical geometries under investigation. The phantom was equipped with cylindrical inserts used to simulate tumours (diameters of the tumours were 63 mm, 45 mm, 34 mm and 23 mm) and a slider to vary the tumour-liver distance. The processing technique incorporated the use of the geometric mean method with corrections for scatter and attenuation performed on image counts. Scatter correction was performed using a modified triple energy window scatter correction technique for 99mTc and 123I, according to gamma camera manufacturer specifications. Attenuation correction was performed using transmission images obtained with an uncollimated 99mTc printed source. Scatter contribution from the abdominal phantom and transmission source combination was limited by setting the detector transmission source distance to 73 cm. A system calibration factor, processed in the same manner as the tumour quantified data was used to convert the image counts to units of radioactivity. Partial volume effect (PVE), was compensated for by the manner in which regions for tumour activity distribution were defined. The activity measured in the dose calibrators served as a reference for determining the accuracy of the quantification. The largest percentage deviation was obtained for the smallest tumours. The average activity underestimations were 29.2 ± 1.3 % and 34.6 ±1.2 % for 99mTc and 123I respectively. These large underestimations observed for the smallest tumours were attributed to PVE, which diminished with increasing tumour sizes. Better quantification accuracy was observed for the largest tumour with overestimations of 3.3 ± 2.6 % and 3.1 ± 3.0 % for 99mTc and 123I respectively. PVE compensation resulted in improved quantification accuracy for all tumour sizes yielding accuracies of better than 9.1 % and 12.4 % for 99mTc and 123I respectively. Scatter contribution to the tumours from the liver had minimal effect on the quantification accuracy at tumour-liver distances larger than 3 cm. An increased tumour-background ratio resulted in an increase in the quantification results of up to 16.6 % for calculations without PVE compensation. This contribution was increased to 26.3 % when PVE were compensated for, using larger regions. The literature often report accurate planar quantification results, however, this study shows that it is important to consider the specific tumour geometry for the study. It remains the responsibility of the user to evaluate the clinical available software and implement it in a responsible manner. When applying all relevant corrections for scatter, attenuation and PVE without significant background, quantification accuracy within 12 % was obtained. This study has demonstrated successful implementation of a practical technique to obtain planar quantitative information.Afrikaans: Akkurate kwantifisering van aktiwiteit is belangrik vir gebruik in stralingsdosimetrie. Planare beeld kwantifisering speel ʼn belangrike rol in die kwantifisering van heelliggaam beelde, wat ʼn volledige beoordeling van die bio-verspreiding van die radionuklied verspreiding moontlik maak. In die Departement Kerngeneeskunde by Universitas Hospitaal, word 123I meta-iodobenzylguanidine [123I]-MIBG kwantifisering van neuro-endokriene tumors uitgevoer alvorens radioaktiewe terapeutiese dosisse toegedien word. Die bioverspreiding van aktiwiteit in hierdie studies kom meestal in die abdominale gebied voor. Faktore wat die kwantifisering beïnvloed sluit onder andere verstrooiing, attenuasie, agtergrondaktiwiteit en naby geleë organe met radioaktiwiteit opname in. Die doel van die studie was om die effek van geometrie op die akkuraatheid van kwantifisering van 99mTc en 123I planare fantoom beelde te evalueer, deur die toepassing van verstrooiing en attenuasie korreksies, met die geometrie soos aangetref by neuro-endokriene tumore. Die tumor geometrie wat ondersoek is, sluit verskeie tumor groottes, verskeie tumor-lewer afstande en twee verskillende tumor-agtergrond verhoudings (0.5 % en 1.0 %) in. Die kwantifiseringstegniek was aanvanklik ontwikkel vir 99mTc wat geredelik beskikbaar is en is later aangepas vir die duurder 123I wat gebruik word vir neuroendokriene tumor beelding. Aanpassings was nodig as gevolg van die verskillende fisiese eienskappe van die twee nukliedes. ʼn Abdominale fantoom was in-huis ontwikkel en vervaardig om die kliniese tumor geometrie wat ondersoek is, na te boots. Die fantoom het silindriese insetsels gehad om tumors te simuleer (deursnee van die tumore was 63 mm, 45 mm, 34 mm en 23 mm) asook ʼn skuifstaaf om die tumor-lewer afstand te varieer. Die verwerkingstegniek maak gebruik van die geometriese gemiddelde metode met verstrooiings- en attenuasiekorreksies wat op die tellings in die beelde uitgevoer word. Die verstrooiingskorreksie was uitgevoer deur gebruik te maak van ‘n aangepaste drievensterverstrooiingskorreksie- tegniek vir 99mTc en 123I, volgens die gamma kamera vervaardiger se spesifikasies. Attenuasie korreksie was uitgevoer deur gebruik te maak van transmissie beelde wat verkry is met ʼn ongekollimeerde gedrukte 99mTc bron. Die verstrooiingsbydrae van die fantoom transmissiebron kombinasie was beperk deur ʼn detektor transmissiebron afstand van 73cm te gebruik. ʼn Stelsel kalibrasiefaktor, waarvan die data soortgelyk aan die tumor kwantifiseringsdata verwerk is, is gebruik om die beeldtellings om te skakel na aktiwiteit. Die parsiele volume effek (PVE) is in ag geneem deur die manier waarop die gebiede van die tumor aktiwiteitverpreiding is. Tumor-aktiwiteit kwantifiseringsakkuraatheid (%) is bepaal met verwysing na aktiwiteitmetings in die bronkalinreerder. Die grootste persentasie afwyking in aktiwiteitopname het voorgekom in die kleinste tumore. Die gemiddelde aktiwiteitsonderskattings was 29.2 ± 1.3 % en 34.6 ± 1.2 % vir 99mTc en 123I respektiewelik. Hierdie groot onderskattings wat waargeneem is by die kleinste tumore word toegeskryf aan die PVE wat onbeduidend raak met toename in tumorgrootte. Die grootste tumor het ʼn beter kwantifiseringsakkuraatheid getoon, met oorskattings van 3.3 ± 2.6 % en 3.1 ± 3.0 % vir 99mTc en 123I onderskeidelik. Kompensasie vir PVE het gelei tot verbeterde kwantifiseringsakkuraatheid vir alle grootte tumore, met akkuraathede beter as 9.1% en 12.4 % vir 99mTc en 123I respektiewelik. Die verstrooiingsbydrae wat die lewer-aktiwiteit op die kwantifisering van die tumor gehad het, was minimaal vir tumor-lewer afstande van 3cm en meer. ʼn Toename in die tumor-agtergrond verhouding het gelei tot ʼn toename in die kwantifiseringsresultate tot 16.6 % vir berekenings sonder PVE kompensasie. Hierdie bydrae het vergroot tot 26.3 % wanneer PVE kompensasie deur middel van groter gebiede van belang toegepas is. In die literatuur word akkurate planare kwantifiseringsresultate dikwels vermeld, maar hierdie studie toon dat die spesifieke tumor geometrie altyd in ag geneem moet word. Dit bly verder die verantwoordelikheid van die gebruiker om die kliniese beskikbare sagteware te evalueer en op ‘n verantwoordelike wyse te implementeer. Indien alle relevante korreksies vir verstrooiing, attenuasie en PVE aangebring word, sonder betekenisvolle agtergrondsbydrae, was ‘n akkuraatheid van beter as 12 % verkry. Hierdie studie toon die suksesvolle implementering van ʼn praktiese tegniek om planare kwantifiserings inligting te verky.enRadioactivity quantificationPlanarAccuracyGeometryAttenuationScatterTriple energy windowTumour sizeTumour distanceMedical physicsRadiation dosimetryNuclear medicineTumorsNeuroendocrine tumors -- TreatmentDissertation (M.Med.Sc. (Medical Physics))--University of the Free State, 2014DissertationUniversity of the Free State