İntrakranial tümörlerin Halcyon cihazı ile yoğunluk ayarlı volumetrik ark ışınlamalarında plan kalitesinin araştırılması
Evaluation of plan quality for intracranial tumors treated in intensity-modulated volumetric arc radiotherapy with Halcyon
Yazar: SELEN ENER
Danışman: PROF. DR. HATİCE BİLGE BECERİR
İstanbul Üniversitesi / Sağlık Bilimleri Enstitüsü / Temel Onkoloji Ana Bilim Dalı / Sağlık Fiziği Bilim Dalı
Derece: Yüksek Lisans, 2023
Konu: Fizik ve Fizik Mühendisliği = Physics and Physics Engineering ; Radyasyon Onkolojisi = Radiation Oncology

Özet:
Araştırmamız yeni nesil Halcyon cihazı ile C-kollu Lineer hızlandırıcı Trilogy cihazı arasındaki tedavi plan parametrelerinin farklılıkların ortaya konulması ve bu iki teknolojinin birbirlerine göre üstünlüklerinin  belirlenmesini  hedeflemiştir.
Intrakranial lezyonu olan  büyük hacimli tümöre sahip 10 GBM  ve küçük hacimli tümöre sahip 10 metastatik kanserli hastanın Trilogy (6 MV FF) cihazı için Eclipse TPS 17.0.1 sisteminde VMAT tekniği kullanılarak hazırlanmış retrospektif ve Halcyon cihazı için (6 MV FFF) yeniden planlanmış tedavi planları üzerinden karşılaştırma yapılmış; doz dağılımı ve plan kalitesini belirleyen faktörler incelenmiştir. 
Çalışmamızda Glioblastoma hastaları için toplam 60 Gy (2Gy/fr) ; Beyin metastazı hastalarının toplam hipofraksiyone tedavi dozu 24 Gy (8Gy/fr)'dir. Tüm planlarda PTV'nin %95'i reçete edilen dozun %100'üne normalize edilmiştir. Ancak Stereotaktik radyoterapi planlanlarında hedef hacmin tamamının verilmek istenen tümör dozunun %100'nü almasına özen gösterilmiştir. Tedaviler 2 full arc , 30֯, 330֯ kolimatör açısı ve coplanar planlar şeklinde dizayn edilmiştir. Foton volum doz hesaplama modeli AAA version 17.0.1 ve optimizasyon için PO 17.0.1 algoritması kullanılmıştır. SRT planlarında grid boyutu 1 mm olarak ayarlanmıştır. Doz hesaplaması neticesinde DVH'ında  hedef hacim, kritik organ dozları, konformite (CI) , homojenite (HI), gradient indeks (GI) ve monitor unit (MU) değerleri bakımından değerlendirilmiştir. 
Çalışmanın sonunda, küçük hacimli metastatik beyin tümörlerinin  VMAT tekniği ile ışınlamalarında plan kalitesini belirleyen  CI ve HI değerlerinin benzer olduğu, büyük hacimli GBM tümörlerinin planlarında ise CI benzer iken HI Trilogy cihazında daha düşük olduğu bulunmuştur. Kritik organ koruması bakımından iki cihazla elde edilen planlarda  benzer dozlar aldığı ve kabul edilir doz limitlerinin altında kaldığı tespit edilmiştir. MU değerleri Halcyon cihazında Trilogy cihazıyla karşılaştırıldıklarında  daha yüksek bulunmuştur. Halcyon cihazının doz hızının ve gantry dönüş hızının yüksekliği düşünüldüğünde hastaya verilen doz çok daha kısa sürede verildiği için bir dezavantaj oluşturmamaktadır.

Abstract:
Our research aimed to put forward the differences and advantages of the treatment plan parameters for each other of the new generation accelerator Halcyon and the C-arms Linear accelerator Trilogy. 
The retrospective treatment plans of 10 GBM patients with large-volume intracranial tumors and 10 metastatic cancer patients with small-volume tumors, planned using the VMAT technique in the Eclipse TPS 17.0.1 system for the Trilogy (6MV FFF) and Halcyon (6 MV FF) device was examined in terms of dose distribution and factors determined plan quality.
In this study, the total treatment dose for Glioblastoma patients is 60 Gy (2Gy/fr); the total hypofractionated treatment dose for brain metastasis patients is 24 Gy (8Gy/fr). On all plans, 95% of the PTV was normalized to 100% of the prescribed dose. However, the entire target volume was cared to receive 100% of the desired tumor dose in stereotactic radiotherapy plans. Treatments were designed as 2 full arcs, 30֠, 330֠ collimator angles and coplanar plans. Photon volume dose calculation model AAA version 17.0.1 and PO 17.0.1 algorithm were used for optimization. In SRT plans, the grid size was set to 1 mm. As a result of dose calculation, DVH was evaluated on the basis of target volume, critical organ doses, conformity (CI), homogeneity (HI), gradient index (GI), and monitor unit (MU) values.
At the end of this study, it was determined that the CI and HI values, which indicate the plan quality in the irradiation of small-volume metastatic brain tumors by using the VMAT technique, were similar. In the plans of the GBM tumors, the CI value was similar, whereas the HI value was seen to be lower for the Trilogy device. In terms of critical organ protection, the plans evaluated for the two devices received similar doses and remained below the acceptable dose limits. MU values were found higher in the Halcyon device compared to the Trilogy device. Considering the high dose rate and gantry rotation speed of the Halcyon device, it does not pose a disadvantage as the dose given to the patient is given in a much shorter time.

Our research aimed to put forward the differences and advantages of the treatment plan parameters for each other of the new generation accelerator Halcyon and the C-arms Linear accelerator Trilogy. 
The retrospective treatment plans of 10 GBM patients with large-volume intracranial tumors and 10 metastatic cancer patients with small-volume tumors, planned using the VMAT technique in the Eclipse TPS 17.0.1 system for the Trilogy (6MV FFF) and Halcyon (6 MV FF) device was examined in terms of dose distribution and factors determined plan quality.
In this study, the total treatment dose for Glioblastoma patients is 60 Gy (2Gy/fr); the total hypofractionated treatment dose for brain metastasis patients is 24 Gy (8Gy/fr). On all plans, 95% of the PTV was normalized to 100% of the prescribed dose. However, the entire target volume was cared to receive 100% of the desired tumor dose in stereotactic radiotherapy plans. Treatments were designed as 2 full arcs, 30֠, 330֠ collimator angles and coplanar plans. Photon volume dose calculation model AAA version 17.0.1 and PO 17.0.1 algorithm were used for optimization. In SRT plans, the grid size was set to 1 mm. As a result of dose calculation, DVH was evaluated on the basis of target volume, critical organ doses, conformity (CI), homogeneity (HI), gradient index (GI), and monitor unit (MU) values.
At the end of this study, it was determined that the CI and HI values, which indicate the plan quality in the irradiation of small-volume metastatic brain tumors by using the VMAT technique, were similar. In the plans of the GBM tumors, the CI value was similar, whereas the HI value was seen to be lower for the Trilogy device. In terms of critical organ protection, the plans evaluated for the two devices received similar doses and remained below the acceptable dose limits. MU values were found higher in the Halcyon device compared to the Trilogy device. Considering the high dose rate and gantry rotation speed of the Halcyon device, it does not pose a disadvantage as the dose given to the patient is given in a much shorter time.