A woman with fever and confusion

A 37-year-old HIV-positive woman presented to the emergency department with fever, headache, confusion, and seizures for 3 days. Computed tomography of the head with contrast demonstrated multiple ring-enhancing masses. An eccentric mural nodule in ring-enhanced mass characterizes eccentric target sign, which is pathognomonic for cerebral toxoplasmosis. The patient received anti-toxoplasmic therapy and had marked clinical improvement.

Quantitative, Multi-institutional Evaluation of MR Thermometry Accuracy for Deep-Pelvic MR-Hyperthermia Systems Operating in Multi-vendor MR-systems Using a New Anthropomorphic Phantom

Clinical outcome of hyperthermia depends on the achieved target temperature, therefore target conformal heating is essential. Currently, invasive temperature probe measurements are the gold standard for temperature monitoring, however, they only provide limited sparse data. In contrast, magnetic resonance thermometry (MRT) provides unique capabilities to non-invasively measure the 3D-temperature. This study investigates MRT accuracy for MR-hyperthermia hybrid systems located at five European institutions while heating a centric or eccentric target in anthropomorphic phantoms with pelvic and spine structures. Scatter plots, root mean square error (RMSE) and Bland–Altman analysis were used to quantify accuracy of MRT compared to high resistance thermistor probe measurements. For all institutions, a linear relation between MRT and thermistor probes measurements was found with R2 (mean ± standard deviation) of 0.97 ± 0.03 and 0.97 ± 0.02, respectively for centric and eccentric heating targets. The RMSE was found to be 0.52 ± 0.31 °C and 0.30 ± 0.20 °C, respectively. The Bland-Altman evaluation showed a mean difference of 0.46 ± 0.20 °C and 0.13 ± 0.08 °C, respectively. This first multi-institutional evaluation of MR-hyperthermia hybrid systems indicates comparable device performance and good agreement between MRT and thermistor probes measurements. This forms the basis to standardize treatments in multi-institution studies of MR-guided hyperthermia and to elucidate thermal dose-effect relations.

Concentric and Eccentric Target MRI Signs in a Case of HIV-Associated Cerebral Toxoplasmosis

Cerebral toxoplasmosis is one of the most common causes of focal brain lesions in immunocompromised patients, such as those with human immunodeficiency virus (HIV). Differentiating toxoplasmosis from other central nervous system (CNS) lesions provides a significant clinical challenge. Magnetic resonance (MR) imaging of the brain is key to prompt diagnosis and treatment of cerebral toxoplasmosis. Several specific signs on MRI of brain have been described in recent literature including the “concentric target sign” and “eccentric target sign.” We report a case of successfully treated HIV-associated cerebral toxoplasmosis in which both MRI signs were present simultaneously.