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Screening for Cerebral Metastases with FDG PET in Patients Undergoing Whole-Body Staging of Non–Central Nervous System Malignancy¹

¹ From the Department of Radiology, Duke University Medical Center, Durham, NC. From the 2000 RSNA scientific assembly. Received May 14, 2001; revision requested June 27; final revision received May 6, 2002; accepted May 14. Address correspondence to E.M.R., Department of Nuclear Medicine, Charlton 1N, Mayo Clinic, 200 First St SW, Rochester, MN 55905 (e-mail: Rohren.Eric@mayo.edu).

View larger version (98K): [in a new window]   Figure 1a. Hypermetabolic metastases in a 72-year-old man with non-Hodgkin lymphoma, with accurate delineation of disease extent. (a) Transverse FDG PET scan of the brain shows conspicuous hypermetabolic lesions (arrows), with radiotracer uptake in the metastases exceeding that of normal gray matter. In the right frontal lobe, the effect of vasogenic edema can be seen as loss of FDG activity (arrowheads) in the adjacent cortex. (b) Transverse T1-weighted contrast-enhanced MR image (500/11) shows three enhancing metastases in the right cerebral hemisphere. The number and location of cerebral metastases were accurately depicted at FDG PET in this patient.

View larger version (149K): [in a new window]   Figure 1b. Hypermetabolic metastases in a 72-year-old man with non-Hodgkin lymphoma, with accurate delineation of disease extent. (a) Transverse FDG PET scan of the brain shows conspicuous hypermetabolic lesions (arrows), with radiotracer uptake in the metastases exceeding that of normal gray matter. In the right frontal lobe, the effect of vasogenic edema can be seen as loss of FDG activity (arrowheads) in the adjacent cortex. (b) Transverse T1-weighted contrast-enhanced MR image (500/11) shows three enhancing metastases in the right cerebral hemisphere. The number and location of cerebral metastases were accurately depicted at FDG PET in this patient.

View larger version (94K): [in a new window]   Figure 2a. Hypermetabolic leptomeningeal carcinomatosis in a 45-year-old woman with rectal carcinoma. (a) Transverse FDG PET scan of the posterior fossa shows increased radiotracer accumulation (arrows) that conforms to the subarachnoid space that surrounds the cerebellar hemispheres. (b) Transverse T1-weighted contrast-enhanced MR image (500/8) obtained through the posterior fossa demonstrates diffuse leptomeningeal enhancement (arrows) due to carcinomatosis.

View larger version (136K): [in a new window]   Figure 2b. Hypermetabolic leptomeningeal carcinomatosis in a 45-year-old woman with rectal carcinoma. (a) Transverse FDG PET scan of the posterior fossa shows increased radiotracer accumulation (arrows) that conforms to the subarachnoid space that surrounds the cerebellar hemispheres. (b) Transverse T1-weighted contrast-enhanced MR image (500/8) obtained through the posterior fossa demonstrates diffuse leptomeningeal enhancement (arrows) due to carcinomatosis.

View larger version (103K): [in a new window]   Figure 3a. Hypometabolic metastases in a 68-year-old man with melanoma, with underestimation of lesion number. (a) Transverse FDG PET scan shows three hypometabolic lesions in the right cerebral hemisphere. The FDG activity in these lesions is substantially less than that of gray matter. The two larger lesions (arrows) in this image were identified at PET, and other lesions elsewhere in the brain were also identified. However, the smallest lesion (arrowhead) in this image was not prospectively identified at PET, and this resulted in underestimation of lesion number. (b) Transverse T1-weighted contrast-enhanced MR image (600/14) shows three hyperintense masses in the right cerebral hemisphere.

View larger version (149K): [in a new window]   Figure 3b. Hypometabolic metastases in a 68-year-old man with melanoma, with underestimation of lesion number. (a) Transverse FDG PET scan shows three hypometabolic lesions in the right cerebral hemisphere. The FDG activity in these lesions is substantially less than that of gray matter. The two larger lesions (arrows) in this image were identified at PET, and other lesions elsewhere in the brain were also identified. However, the smallest lesion (arrowhead) in this image was not prospectively identified at PET, and this resulted in underestimation of lesion number. (b) Transverse T1-weighted contrast-enhanced MR image (600/14) shows three hyperintense masses in the right cerebral hemisphere.

View larger version (110K): [in a new window]   Figure 4a. Small cortical and subcortical metastases in a 64-year-old man with melanoma that resulted in a false-negative PET scan. (a) Transverse FDG PET scan obtained in a patient with cerebral metastases was interpreted as normal. Even at retrospective review, no abnormal FDG activity was discernable against the background activity of the brain. (b) Transverse T1-weighted contrast-enhanced MR image (550/14) shows an 8-mm metastatic lesion (arrow) in the right subinsular region. (c) Second transverse FDG PET scan in this patient also showed no focal abnormality of tracer uptake. (d) Corresponding transverse MR image (550/14) shows an additional 5-mm metastasis (arrow) in the cortex of the right parietal lobe. In this case, these undetected lesions resulted in a false-negative PET scan.

View larger version (141K): [in a new window]   Figure 4b. Small cortical and subcortical metastases in a 64-year-old man with melanoma that resulted in a false-negative PET scan. (a) Transverse FDG PET scan obtained in a patient with cerebral metastases was interpreted as normal. Even at retrospective review, no abnormal FDG activity was discernable against the background activity of the brain. (b) Transverse T1-weighted contrast-enhanced MR image (550/14) shows an 8-mm metastatic lesion (arrow) in the right subinsular region. (c) Second transverse FDG PET scan in this patient also showed no focal abnormality of tracer uptake. (d) Corresponding transverse MR image (550/14) shows an additional 5-mm metastasis (arrow) in the cortex of the right parietal lobe. In this case, these undetected lesions resulted in a false-negative PET scan.

View larger version (115K): [in a new window]   Figure 4c. Small cortical and subcortical metastases in a 64-year-old man with melanoma that resulted in a false-negative PET scan. (a) Transverse FDG PET scan obtained in a patient with cerebral metastases was interpreted as normal. Even at retrospective review, no abnormal FDG activity was discernable against the background activity of the brain. (b) Transverse T1-weighted contrast-enhanced MR image (550/14) shows an 8-mm metastatic lesion (arrow) in the right subinsular region. (c) Second transverse FDG PET scan in this patient also showed no focal abnormality of tracer uptake. (d) Corresponding transverse MR image (550/14) shows an additional 5-mm metastasis (arrow) in the cortex of the right parietal lobe. In this case, these undetected lesions resulted in a false-negative PET scan.

View larger version (140K): [in a new window]   Figure 4d. Small cortical and subcortical metastases in a 64-year-old man with melanoma that resulted in a false-negative PET scan. (a) Transverse FDG PET scan obtained in a patient with cerebral metastases was interpreted as normal. Even at retrospective review, no abnormal FDG activity was discernable against the background activity of the brain. (b) Transverse T1-weighted contrast-enhanced MR image (550/14) shows an 8-mm metastatic lesion (arrow) in the right subinsular region. (c) Second transverse FDG PET scan in this patient also showed no focal abnormality of tracer uptake. (d) Corresponding transverse MR image (550/14) shows an additional 5-mm metastasis (arrow) in the cortex of the right parietal lobe. In this case, these undetected lesions resulted in a false-negative PET scan.

View larger version (23K): [in a new window]   Figure 5. Graph shows number of individual metastatic lesions distributed by tumor type. The number of lesions detected (black bars) and not detected (white bars) at PET are indicated. Although the majority of undetected lesions occurred in patients with melanoma, the relationship between tumor type and lesion detection was not considered to indicate a statistically significant difference (P = .237).

View larger version (13K): [in a new window]   Figure 6. Plot shows the relationship between the size of individual metastatic lesions and detection at FDG PET. The average size of lesions detected at PET (PET+) was 2.3 cm, and the average size of lesions not detected at PET (PET-) was 0.7 cm. The relationship between size and detection at PET indicated a statistically significant difference (P < .001).

View larger version (23K): [in a new window]   Figure 7. Graph shows probability of lesion detection at FDG PET according to lesion size at MR imaging, as judged by use of the logistic regression model with a generalized estimating equation adjustment for the clustering of lesions within subjects. Mean values (solid line) and 95% CIs (dashed lines) are shown.