case_images: PMC11440987_01
case_images: [18F]FDG PET and CT acquisition performed after the first doubtful MRI, showing large hypometabolic right frontal area (A) and no significant abnormal uptake in the left cerebellar region (B).
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case_images: PMC11440987_01_fnume-04-1287240-g001.jpg
case_images: F1
case_images: A subsequent [18F] fluorodeoxyglucose (FDG) positron emission tomography (PET), performed on a Vision 600 (Siemens Healthineers) with a 125 MBq injection, revealed only a large non-specific hypometabolic area in the right frontal region, superimposable to the edema on MRI (Figures 1, 2).
case_images: MRI (left) and [18F]FET PET (right), for frontal (up) and cerebellar (down) lesions, before (A) and after surgery (B).
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case_images: PMC11440987_01_fnume-04-1287240-g002.jpg
case_images: F2
case_images: A subsequent [18F] fluorodeoxyglucose (FDG) positron emission tomography (PET), performed on a Vision 600 (Siemens Healthineers) with a 125 MBq injection, revealed only a large non-specific hypometabolic area in the right frontal region, superimposable to the edema on MRI (Figures 1, 2). Therefore, a [18F] fluoroEthyl-L-tyrosine (FET) PET scan was performed on the same camera with a 147 MBq injection, showing a significant annular uptake of the right frontal region with a photopenic center and a mean tumor to brain ratio (TBR) of 2.03 (SUVmax = 2.7) and a significant uptake rounded left cerebellar lesion (SUVmax = 4.1) with a mean TBR of 2.48 (Figure 2A). To ensure that the cerebellum lesion was also radionecrotic despite the higher TBR and another follow-up MRI examination that was still doubtful, we performed a second [18F]FET PET scan 1 month postoperatively (Figure 2B), with a 144 MBq injection.
case_images: TACs of frontal and cerebellar lesion before and after surgery, showing the evolution of SUVmax during the first 40 min after [18F]FET injection.
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case_images: PMC11440987_01_fnume-04-1287240-g003.jpg
case_images: F3
case_images: Both values exceeded the reported mean TBR cutoff of 1.9, indicating potential tumor progression for frontal and cerebellum lesions, and time-activity curves (TACs) showing slow and progressive accumulating uptake (pattern I), with a time to peak (TTP) at 30 min or more, evocating this time radionecrosis (cerebellum and frontal before surgery TACs) (Figure 3). In the surgical right frontal region (SUVmax = 3.4), a slightly higher mean TBR of 2.1 was found with an doubtful TAC (TTP at 20 min followed by a plateau, more suggestive of a pattern II than I) (Figure 3), in the context suggesting a non-specific accumulation probably inducted by postoperative large blood-brain barrier (BBB) rupture (postoperative frontal TAC) (Figure 3). TBR of 2.46 with a strictly identical curve, suggesting the absence of scalability (postoperative cerebellum TAC) (Figure 3). The most recent MRI scan showed a sagging of the right frontal excision cavity and discreet reduction of the flair hypersignal of the left cerebellar lesion rather in favor of radionecrosis, all still in agreement with the final conclusions from the [18F]FET PET scan (Figure 4).
case_images: Timeline.
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case_images: PMC11440987_01_fnume-04-1287240-g004.jpg
case_images: F4
case_images: TBR of 2.46 with a strictly identical curve, suggesting the absence of scalability (postoperative cerebellum TAC) (Figure 3). The most recent MRI scan showed a sagging of the right frontal excision cavity and discreet reduction of the flair hypersignal of the left cerebellar lesion rather in favor of radionecrosis, all still in agreement with the final conclusions from the [18F]FET PET scan (Figure 4).