a 35-year - old woman was admitted complaining of a headache over the last two months .
she had undergone a right temporal lobectomy for generalized tonic - clonic seizures 10 years earlier .
laboratory tests were normal except for an increased erythrocyte sedimentation rate of 45 mm / hr . a pre - contrast ct showed a linear calcification surrounded by a lobular - shaped mass of increasing attenuation in the right frontal lobe ( fig .
the mass was accompanied by extensive edema surrounding it , with a midline shifting to the left side . on mr
imaging , the mass showed a heterogeneous dark signal intensity on t2-weighted images ( fig .
moreover the mass had an irregular margin and was classified as an intra - axial mass with cortical involvement .
three regions of interest ( roi ) were determined based on the gradient - echo echo planar imaging source images and the matching t2 and gadolinium - enhanced t1-weighted images .
the roi with the highest regional cerebral blood volume ( rcbv ) was selected and was found to be almost the same as that of the contralateral side ( rcbv ratio = 1.04 ) ( fig .
localized proton mr spectroscopy was performed using a multivoxel point - resolved spectroscopy sequence with an echo time of 144 msec .
the spectroscopic data showed a slightly elevated choline ( cho ) and slightly decreased creatine ( cr ) and n - acetyl aspartate ( naa ) peaks with a small increase in the choline / creatine ( cho / cr ) ratio in the enhancing lesion ( fig .
this diagnosis was based on the strong enhancement of the mass accompanied with severe peritumoral edema and a mass effect .
however , the perfusion data and mr spectroscopy findings suggested that the mass was benign .
the mass was surgically removed and the pathology revealed a foreign body - associated granulomatous inflammation with marked lymphocytic and histiocytic infiltration , microcalcification , and fibrous scar tissue formation ( fig . 1j , k ) . following surgery ,
the chemical agents used in neurosurgery to achieve intra - operative hemostasis can cause foreign body reactions .
historically , several terms such as textiloma , gossypiboma , gauzoma , and muslinoma have been employed , reflecting the hemostatic materials involved . in our case
the signal intensities of the foreign body granulomas are variable on the t1- and t2-weighted images .
. variable signal intensity on t2-weighted images may reflect a complex pathology including acute or chronic inflammation , granuloma formation , fibrosis , collagen deposition , and degeneration of foreign materials . in our patient ,
the low signal intensity proportion of the t2-weighted images may be explained by the fibrosis seen in the histologic specimen . in the case of ring - enhancing mass lesions ,
these represent degenerated foreign material and may be helpful in distinguishing a muslinoma from brain abscess ( 7 ) .
this was true of our patient based on the mr imaging findings showing intense mass enhancement with severe surrounding edema . however ,
on perfusion mri , the rcbv did not increase and , on multi - voxel mr spectroscopy , the mass cho / cr ratio increased only slightly , which was not consistent with a high - grade tumor .
previous reports on perfusion and mr spectroscopic findings in patients with non - neoplastic tumor - mimicking masses showed mildly decreased - to - increased perfusion , and small rises in cho / cr ratios , with decreased naa .
perfusion mri and mr spectroscopic findings from our patient were very similar to those of patients from previous reports with non - neoplastic mass lesions ( 8 , 9 ) . retrospectively
, we think we could have excluded the possibility of malignancy in our patient based on the perfusion mri and mr spectroscopy , although benign tumorous conditions may not be totally excluded by such exploratory modalities .
although the perfusion mri and mr spectroscopic findings are not specific for foreign body granulomas , these techniques may be helpful in excluding a high - grade tumor diagnosis , which may be the most important differential diagnosis . by combining clinical history of any previous operation , conventional mr imaging findings , and perfusion mri and mr spectroscopy , it may be possible to correctly diagnose a foreign body granuloma . in summary ,
conventional mri findings in foreign body granuloma patients may sometimes mimic those of brain tumors . to differentiate the diagnoses , the performing a perfusion mri and mr
 we report a case of intracranial foreign body granuloma that showed features of a high grade tumor on magnetic resonance ( mr ) imaging . 
 however , the relative cerebral blood volume was not increased in the enhancing mass on perfusion mri and the choline / creatine ratio only slightly increased on mr spectroscopy . 
 the results suggest that the lesion is benign in nature . 
 perfusion mri and mr spectroscopy may be helpful to differentiate a foreign body granuloma from a neoplastic condition . 