Comparison of electronic portal image and port film in pelvic irradiation

Abstract

OBJECTIVES In this study electronic portal images (EPIs) and port films were compared to detect set up errors and adequacy of image quality. METHODS In total 40 EPIs and 40 portal films from 20 patients receiving pelvic radiotherapy were evaluated. Image quality was graded by visibility of the selected anatomic landmarks and set-up deviations were examined in the x, y and z axes of the coordinate system. EPIs and port films were compared in terms of Image quality and shifts. RESULTS Visibility was significantly better for port films than EPIs. In both imaging techniques acetabulum, pelvic rims and symphisis pubis were more visible landmarks. Mean set-up displacements at the x, y and z axes were 1.47, 2.51 and 3.99 mm for port films; 2.16, 3.09 and 3.81 mm for EPIs respectively. Set-up errors were in acceptable levels in all directions, maximum errors were seen in z axis for both images. CONCLUSION Electronic portal imaging is used widely and takes places of port films. The use of EPI could provide more quick and practical evaluation of set-up errors than port films and also pretreatment correction of set-up errors and digital storage of the images are possible. However the major disadvantage of EPIs than port films is insufficient evaluation of the anatomical structures due to worse image quality.

Keywords

• Pelvis,Radiotherapy,Diagnostic Imaging

Pelvik bölge radyoterapi uygulamalarında port film ve elektronik portal görüntülemenin karşılaştırılması

Öz

AMAÇ Bu çalışmada elektronik portal görüntü (EPI) ve port filmlerinin, ayar 'set-up' hatalarını değerlendirmedeki etkinliği ve görüntü kaliteleri karşılaştırıldı. GEREÇ VE YÖNTEM Pelvik radyoterapi alan 20 hastaya ait toplam 40 EPI ve 40 port film değerlendirildi. Görüntü kalitesi, seçilen anatomik yapıların görülebilirliğine göre derecelendirildi; 'set-up' hataları ise koordinat sisteminin x, y ve z eksenlerinde hesaplandı. EPI ve port filmler görüntü kalitesi ve hesaplanan alan kaymaları yönünden karşılaştırıldı. BULGULAR Görüntü kalitesi port filmlerde EPI'ye göre anlamlı olarak daha iyi bulundu. Her iki görüntüleme tekniğinde de en iyi görülebilen anatomik yapılar; asetabulum, pelvik rimler ve Symphysis pubis idi. Ortalama 'set-up' kaymaları x, y ve z eksenlerinde sırasıyla port filmlerde 1.47, 2.51 ve 3.99 mm; EPI'de ise 2.16, 3.09 ve 3.81 mm idi. 'Set-up' hataları tüm yönlerde kabul edilebilir düzeyde olduğu halde en fazla alan kayması her iki görüntüleme yönteminde de z eksenindeydi. SONUÇ Elektronik portal görüntüleme çok yaygın olarak kullanılmakta ve port filmlerin yerini almaktadır. Elektronik portal görüntü kullanımı port filmine göre 'set-up' hatalarını daha hızlı ve pratik değerlendirme olanağı vermektedir. Ayrıca 'set-up' hatalarının tedavi öncesi düzeltilmesi ve görüntülerin dijital ortamda arşivlenmesi mümkündür. Ancak EPI'nin port filmlerine göre en önemli dezavantajı görüntü kalitesinin kötü olması nedeniyle anatomik yapıların net değerlendirilememesidir.

Anahtar Kelimeler

• Elektronik portal görüntüleme, pelvik radyoterapi, port film.

Kaynakça

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