Interval Change in Diffusion and Perfusion MRI Parameters for the Assessment of Pseudoprogression in Cerebral Metastases Treated With Stereotactic Radiation.

OBJECTIVE: Apparent increases in the size of cerebral metastases after stereotactic radiosurgery (SRS) can be caused by pseudoprogression or true disease progression, which poses a diagnostic challenge at conventional MRI. The purpose of this study was to assess whether interval change in DWI and perfusion MRI parameters can differentiate pseudoprogression from progressive disease after treatment with SRS. MATERIALS AND METHODS: Patients with apparent growth of cerebral metastases after SRS treatment who underwent pre- and post-SRS DWI, dynamic susceptibility contrast (DSC)-MRI, and perfusion dynamic contrast-enhanced (DCE)-MRI were retrospectively evaluated. Final assignment of pseudoprogression or progressive disease was determined at 6-month follow-up imaging using the Response Assessment in Neuro-Oncology Brain Metastases criteria. Mean values of apparent diffusion coefficient (ADC), DCE-MRI-derived volume transfer constant (Ktrans), and DSC-MRI-derived relative cerebral blood volume (CBV) from pre- and post-SRS MRI scans were compared between groups using univariate and regression analysis. Fisher exact test was used to compare interval change of imaging biomarkers. RESULTS: Of 102 cerebral metastases evaluated, 32 lesions in 29 patients met our inclusion criteria. The mean duration of follow-up was 7.2 months (range, 6-14 months). Twenty-two lesions were determined as pseudoprogression, and 10 lesions were determined as progressive disease using the Response Assessment in Neuro-Oncology Brain Metastases criteria at 6-month follow-up MRI. The interval change pattern of our imaging parameters matched the expected patterns of treatment response for ADC (23/32 lesions; 72%; p = 0.055; odds ratio, 5.1), Ktrans (24/32 lesions; 75%; p = 0.006; odds ratio, 19.2), and relative CBV (27/32 lesions; 84%; p = 0.001; odds ratio, 25.3). CONCLUSION: Pseudoprogression can be distinguished from disease progression in cerebral metastases treated with SRS via an interval decrease in relative CBV and Ktrans values.

Brachytherapy for Central Serous Chorioretinopathy.

Brachytherapy is widely used for the treatment of choroidal melanoma and has recently been explored for the treatment of wet age-related macular degeneration. We propose the use of low dose radiation via episcleral brachytherapy in refractory cases of central serous chorioretinopathy (CSCR). The pathogenesis of CSCR involves dilatation and hyperpermeability of large choroidal vessels. Low dose radiation can induce intimal proliferation in large choroidal vessels and decrease their hyperpermeability. Concerns about the use of brachytherapy in CSCR include damage to the choriocapillaris or the retinal vessels. This can be addressed with the use of a specialized device through which a very precise and appropriate dose can be delivered. The dose of the radiation delivered decreases exponentially at a depth of approximately 0.5-1.5 mm from the devise-sclera interface. Considering an increased choroidal thickness in cases of CSCR, delivery of a safe dose can be assured.

Medulloblastoma with extensive nodularity undergoing post-therapeutic maturation to a gangliocytoma: a case report and literature review.

We present a report of a 12-year-old boy diagnosed with medulloblastoma at 22 months of age. A gross total resection was performed followed by adjuvant systemic chemotherapy due to his young age; however, the tumor recurred locally in the posterior fossa 7 months later. The recurrent tumor was excised and he received craniospinal radiation with a boost given to the posterior fossa followed by high-dose chemotherapy. He remained disease free for approximately 10 years without major neurologic deficit and only mild cognitive impairment. A routine follow-up MRI of the brain revealed an enhancing mass. The patient underwent surgical debulking and pathological examination revealed no residual immature medulloblastoma cells but instead mature ganglion cells, consistent with a gangliocytoma. The apparent maturation of primitive medulloblastoma cells is a rare phenomenon, which may have ensued from the long-term effects of adjuvant therapies inducing advanced cellular maturation.