The use of multiparametric 18F-fluoro-L-3,4-dihydroxy-phenylalanine PET/MRI in post-therapy assessment of patients with gliomas.

PURPOSE: To determine the utility of F-fluoro-L-3,4-dihydroxy-phenylalanine (F-DOPA) PET/MRI versus cross-sectional MRI alone in glioma response assessment and identify whether the two techniques demonstrate different tumour features. METHODS: F-DOPA PET/MRI studies from 40 patients were analysed. Quantitative PET parameters and conventional MRI features were recorded. Tumour volume was assessed on both PET and MRI. Using dynamic susceptibility contrast perfusion-weighted imaging, maps of cerebral blood flow (CBF) and cerebral blood volume (CBV) were obtained. Within volume of tumours of tumour features and normal-appearing white matter (NAWM) drawn on MRI, standardised uptake value (SUV)max, CBF and CBV were recorded. Presence of residual active tumour was assessed by qualitative visual assessment. Receiver operating characteristic analysis was performed univariately and on parameter combination to analyse ability to determine presence/absence of disease. Reference standard for presence of viable tissue was biopsy or clinical follow-up. RESULTS: Median SUVmax was 3.4 for low-grade glioma (LGG) and 3.3 for high-grade glioma (HGG). There was a significant correlation between PWI parameters and WHO grade (P < 0.001), but no correlation with SUVmax. Median F-DOPA volume was 8216.88 mm for HGG and 6284.94 mm for LGG; MRI volume was 6316.57 mm and 5931.55 mm, respectively. SUVmax analysis distinguished enhancing and nonenhancing components from necrosis and NAWM and demonstrated active disease in nonenhancing regions. Visually, the modalities were concordant in 37 patients. Combining the multiparametric PET/MRI approach with all available data-enhanced detection of the presence of tumour (area under the curve 0.99, P < 0.01). CONCLUSION: MRI and F-DOPA are complementary modalities for assessment of tumour burden. Matching F-DOPA and MRI in assessing residual tumour volume may better delineate the radiotherapy target volume.

68Ga-Prostate-Specific Membrane Antigen PET/CT: Incidental Finding of a Liposarcoma.

This case highlights that liposarcoma shows Ga-prostate-specific membrane antigen avidity and should be included in the differential diagnosis of patients with avid muscle lesions to avoid an incorrect diagnosis of metastasis.

First case of 18F-choline uptake in acoustic schwannoma after stereotactic radiotherapy.

A 69-year-old male patient, with bilateral hypoacusia and tinnitus, had a diagnosis of left vestibular schwannoma with synchronous meningioma on the left frontal lobe. After partial surgical resection of the acoustic schwannoma, this was followed by stereotactic radiosurgery on the residual lesion. The patient had a metachronous prostate cancer treated with conformal radiotherapy associated to 6 months of hormone therapy with luteinizing hormone/releasing hormone analog. During follow-up, prostate-specific antigen value increased to 0.27 ng/mL and the patient underwent 18F-methylcholine positron emission tomography/computed tomography (18F-choline PET/CT). The whole-body scan demonstrated a focus of increased uptake at level of the left cerebellopontine angle and at the left frontal lobe, corresponding to the known vestibular schwannoma and meningioma. A subsequent brain contrast-enhanced magnetic resonance imaging (MRI) showed an increased dimension of the left cerebellopontine neuroma and dimensional stability of the left frontal meningioma compared with previous MRI of 6 months earlier. To the best of our knowledge, we describe the first case of a 18F-choline PET/CT demonstrating a relapse of a vestibular schwannoma after stereotactic radiotherapy.

Incidental detection of Os acromiale mimicking a fracture on 18F-Fluoride PET-CT.

Os acromiale represents an unfused accessory centre of ossification of the acromion of scapula. It may cause shoulder impingement, rotator cuff tear or degenerative acromio-clavicular joint disease. A 38-year-old male with history of degenerative disc disease presented with persistent backache. MRI of the lumbar spine had earlier showed left paracentral disc protrusion of L5/S1 vertebrae impinging the left S1 nerve root for which the patient underwent fluoroscopic guided nerve root block. Due to persistent bilateral sciatica and worsening leg pain a decompression surgery was planned. A bone scan was requested to exclude other causes of pain prior to surgery for which the patient underwent 18F- Fluoride PET-CT examination. We report a case of incidental detection of Os acromiale mimicking fracture. As the management strategy for both is quite different this case highlights the importance of correct recognition of this identity for appropriate management.

First case on fluorodeoxyglucose positron emission tomography/computerized tomography of a distant skip metastases to parotid node from esophageal adenocarcinoma.

We are presenting the first case of a gastro-oesophageal junction adenocarcinoma with metastasis only to the intraparotid lymph node simulating Warthin's tumor. A 66-year-old man underwent an esophagogastroduodenoscopy that found circumferential ulcerated esophageal tumor beginning 40 cm from incisors resulting in stricture and two discrete erosions in the proximal third of esophagus. Biopsies from the stricture have demonstrated a poorly differentiated gastric adenocarcinoma. Computerized tomography (CT) confirmed the site of primary without evidence of distant metastasis. Positron emission tomography/CT showed high uptake in the known carcinoma in distal esophagus involving the gastro-oesophageal junction extending into the cardia of the stomach, the maximum standardized uptake value (SUVmax) 7.4. Furthermore, there was a focus of high-grade tracer activity, SUVmax 6.2, in the left intraparotid nodule which was initially thought to represent Warthin's tumor rather than metastasis; there was no evidence to suggest metastases elsewhere. Fine needle aspiration and biopsy from the enlarged intraparotid lymph node revealed that the histology was consistent with a poorly differentiated adenocarcinoma, metastasis from upper gastrointestinal tract.

PET imaging in glioma: techniques and current evidence.

PET holds potential to provide additional information about tumour metabolic processes, which could aid brain tumour differential diagnosis, grading, molecular subtyping and/or the distinction of therapy effects from disease recurrence. This review discusses PET techniques currently in use for untreated and treated glioma characterization and aims to critically assess the evidence for different tracers ([F]Fluorodeoxyglucose, choline and amino acid tracers) in this context.