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1. Introduction
The pterygopalatine fossa (PPF) is an inverted pyramidal space located inferior to the orbital apex, which contains the pterygopalatine ganglion (PPG) and various arteries, veins, lymphatics, and nerves. Preganglionic parasympathetic facial nerve fibres synapse in the PPG, while postganglionic sympathetic fibres from the superior cervical ganglion and sensory fibres from the maxillary nerve pass through the ganglion without synapsing. The PPF communicates with the orbit, nasal cavity, and oral cavity, and through the orbit with the maxillary sinus and upper teeth, which makes it an important cranial neurovascular crossroad as well as a common site for invasion and perineural spread of malignant disease [1]. The neural content of the PPF plays an important role in the pathophysiology of pain syndromes with cranial autonomic features such as cluster headache and Sluder’s neuralgia [2, 3]. These syndromes are invalidating and may require invasive treatment, such as PPG blockage, for refractory cases [4]. Thus, studying the PPF in head and neck imaging is of importance, for both diagnostic and preoperative purposes.
Previous studies have shown that on magnetic resonance imaging (MRI) at 1.5 Tesla, small PPF structures remain obscured, whereas the PPG and the sphenopalatine segment of the maxillary artery and some of its branches can easily be identified [5]. The recent development of MRI at 7 Tesla (7 T MRI) holds the promise of an increased signal-to-noise ratio (SNR). In various human anatomical regions, the increased SNR of 7 T MRI has been used to produce high-definition images with ultrahigh resolution and identification of previously unidentified detail [6, 7].
The aim of the present study is to correlate MR findings to cryosections in order to determine which part of the PPF and its contents can be identified on 7 T MRI.
2. Materials and Methods
2.1. Tissue Preparation
One undissected human head was obtained from a male postmortem, 73 years of age. The head was perfused with 0.9% NaCl under physiologic pressure and frozen at −25°C.
2.2. Whole-Mount Preparation
The head was transected on the median plane using a band saw and trimmed to a block containing the PPF and parts of the orbit, nasal and paranasal cavities, and oral cavity.
2.3. Imaging
The specimen was examined on a whole-body clinical 7 T MRI system (Philips Healthcare, Cleveland, OH,...