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. 2011 Mar;84(999):271-8.
doi: 10.1259/bjr/10315979. Epub 2010 Nov 2.

Clinical target volume delineation in glioblastomas: pre-operative versus post-operative/pre-radiotherapy MRI

P Farace  1 , M G Giri, G Meliadò, D Amelio, L Widesott, G K Ricciardi, S Dall'Oglio, A Rizzotti, A Sbarbati, A Beltramello, S Maluta, M Amichetti
Affiliations

Clinical target volume delineation in glioblastomas: pre-operative versus post-operative/pre-radiotherapy MRI

P Farace et al. Br J Radiol. 2011 Mar.

Abstract

Objectives: Delineation of clinical target volume (CTV) is still controversial in glioblastomas. In order to assess the differences in volume and shape of the radiotherapy target, the use of pre-operative vs post-operative/pre-radiotherapy T(1) and T(2) weighted MRI was compared.

Methods: 4 CTVs were delineated in 24 patients pre-operatively and post-operatively using T(1) contrast-enhanced (T1(PRE)CTV and T1(POST)CTV) and T(2) weighted images (T2(PRE)CTV and T2(POST)CTV). Pre-operative MRI examinations were performed the day before surgery, whereas post-operative examinations were acquired 1 month after surgery and before chemoradiation. A concordance index (CI) was defined as the ratio between the overlapping and composite volumes.

Results: The volumes of T1(PRE)CTV and T1(POST)CTV were not statistically different (248 ± 88 vs 254 ± 101), although volume differences >100 cm(3) were observed in 6 out of 24 patients. A marked increase due to tumour progression was shown in three patients. Three patients showed a decrease because of a reduced mass effect. A significant reduction occurred between pre-operative and post-operative T(2) volumes (139 ± 68 vs 78 ± 59). Lack of concordance was observed between T1(PRE)CTV and T1(POST)CTV (CI = 0.67 ± 0.09), T2(PRE)CTV and T2(POST)CTV (CI = 0.39 ± 0.20) and comparing the portion of the T1(PRE)CTV and T1(POST)CTV not covered by that defined on T2(PRE)CTV images (CI = 0.45 ± 0.16 and 0.44 ± 0.17, respectively).

Conclusion: Using T(2) MRI, huge variations can be observed in peritumoural oedema, which are probably due to steroid treatment. Using T(1) MRI, brain shifts after surgery and possible progressive enhancing lesions produce substantial differences in CTVs. Our data support the use of post-operative/pre-radiotherapy T(1) weighted MRI for planning purposes.

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Figures

Figure 1
Figure 1
To compare two differently delineated volumes (a), represented by continuous and dashed lines respectively, the overlapping volume (b) and the composite volume (c) were calculated.
Figure 2
Figure 2
Clinical target volumes (CTV) (in cm3) and the respective overlapping volumes in each patient examined by T1PRE, T1POST and T2PRE scans. For every pair of examinations, the volume of CTVI not covered by CTVII, i.e. the discordance clinical target volume DCTV, can be easily extrapolated.
Figure 3
Figure 3
Increased extent of blood–brain barrier leakage observed in patient 14. The contrast-enhancing tumour portion, which is visible on the pre-operative MRI (a), was reduced by surgical resection, as confirmed by early post-operative MRI (b) that was performed within 48 h after surgery. Tumour progression occurred during the time that elapsed before the beginning of radiotherapy, with an enlargement of the contrast-enhancing volume in the pre-radiotherapy images (c), which produced a T1POSTCTV larger than the T1PRECTV.
Figure 4
Figure 4
Pre-operative (white line) and pre-radiotherapy (black line) Clinical target volumes (CTV) contours of patient 8. Representative sections of T1 pre-operative (a), T1 pre-radiotherapy (b), T2 pre-operative (c) and T2 pre-radiotherapy (d) show a decrease in CTV because of the reduced mass effect and reduced oedema.
See this image and copyright information in PMC

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