Analysis of the layering pattern of the apparent diffusion coefficient (ADC) for differentiation of radiation necrosis from tumour progression.
OBJECTIVE
To evaluate the added value of diffusion-weighted imaging (DWI) to perfusion-weighted imaging (PWI) for differentiating tumour progression from radiation necrosis.


METHODS
Sixteen consecutive patients who underwent removal of a metastatic brain tumour that increased in size after stereotactic radiosurgery were retrospectively reviewed. The layering of the ADC was categorised into three patterns. ADC values were measured on each layer, and the maximum rCBV was measured. rCBV and the layering pattern of the ADC of radiation necrosis and tumour progression were compared.


RESULTS
Nine cases of radiation necrosis and seven cases of tumour progression were pathologically confirmed. Radiation necrosis (88.9 % vs. 14.3 %) showed a three-layer pattern of ADC with a middle layer of minimum ADC more frequently. If rCBV larger than 2.6 was used to differentiate radiation necrosis and tumour progression, the sensitivity was 100 % but specificity was 56 %. If the lesions with the three-layer pattern of ADC with moderately increased rCBV (2.6-4.1) were excluded from tumour progression, the sensitivity and specificity increased to 100 %.


CONCLUSIONS
The three-layer pattern of ADC shows high specificity in diagnosing radiation necrosis; therefore, combined analysis of the ADC pattern with rCBV may have added value in the correct differentiation of tumour progression from radiation necrosis.
Department of Radiology and Center for Imaging Science, Samsung Medical Center, Sungkyunkwan University School of Medicine, 50, Irwon-dong, Gangnam-gu, Seoul 135-710, Republic of Korea.
Jihoon
J
Cha
Sung Tae
ST
Kim
Hyung-Jin
HJ
Kim
Hye Jeong
HJ
Kim
Byung-Joon
BJ
Kim
Pyoung
P
Jeon
Keon Ha
KH
Kim
Hong Sik
HS
Byun
D000328:Adult; D000368:Aged; D000465:Algorithms; D001932:Brain Neoplasms / Q000175:diagnosis* / Q000209:etiology / Q000601:surgery*; D003937:Diagnosis, Differential; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods; D008297:Male; D008875:Middle Aged; D009361:Neoplasm Invasiveness / Q000473:pathology; D009381:Neoplasms, Radiation-Induced / Q000175:diagnosis* / Q000209:etiology*; D010363:Pattern Recognition, Automated / Q000379:methods; D016634:Radiosurgery / Q000009:adverse effects*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D016896:Treatment Outcome