AAPM Task Group Report 238: 3D C-arms with volumetric imaging capability.

This report reviews the image acquisition and reconstruction characteristics of C-arm Cone Beam Computed Tomography (C-arm CBCT) systems and provides guidance on quality control of C-arm systems with this volumetric imaging capability. The concepts of 3D image reconstruction, geometric calibration, image quality, and dosimetry covered in this report are also pertinent to CBCT for Image-Guided Radiation Therapy (IGRT). However, IGRT systems introduce a number of additional considerations, such as geometric alignment of the imaging at treatment isocenter, which are beyond the scope of the charge to the task group and the report. Section 1 provides an introduction to C-arm CBCT systems and reviews a variety of clinical applications. Section 2 briefly presents nomenclature specific or unique to these systems. A short review of C-arm fluoroscopy quality control (QC) in relation to 3D C-arm imaging is given in Section 3. Section 4 discusses system calibration, including geometric calibration and uniformity calibration. A review of the unique approaches and challenges to 3D reconstruction of data sets acquired by C-arm CBCT systems is give in Section 5. Sections 6 and 7 go in greater depth to address the performance assessment of C-arm CBCT units. First, Section 6 describes testing approaches and phantoms that may be used to evaluate image quality (spatial resolution and image noise and artifacts) and identifies several factors that affect image quality. Section 7 describes both free-in-air and in-phantom approaches to evaluating radiation dose indices. The methodologies described for assessing image quality and radiation dose may be used for annual constancy assessment and comparisons among different systems to help medical physicists determine when a system is not operating as expected. Baseline measurements taken either at installation or after a full preventative maintenance service call can also provide valuable data to help determine whether the performance of the system is acceptable. Collecting image quality and radiation dose data on existing phantoms used for CT image quality and radiation dose assessment, or on newly developed phantoms, will inform the development of performance criteria and standards. Phantom images are also useful for identifying and evaluating artifacts. In particular, comparing baseline data with those from current phantom images can reveal the need for system calibration before image artifacts are detected in clinical practice. Examples of artifacts are provided in Sections 4, 5, and 6.

Hearing voices: does it give your patient a headache? A case of auditory hallucinations as acoustic aura in migraine.

OBJECTIVE: Auditory hallucinations are generally considered to be a psychotic symptom. However, they do occur without other psychotic symptoms in a substantive number of cases in the general population and can cause a lot of individual distress because of the supposed association with schizophrenia. We describe a case of nonpsychotic auditory hallucinations occurring in the context of migraine. METHOD: Case report and literature review. RESULTS: A 40-year-old man presented with imperative auditory hallucinations that caused depressive and anxiety symptoms. He reported migraine with visual aura as well which started at the same time as the auditory hallucinations. The auditory hallucinations occurred in the context of nocturnal migraine attacks, preceding them as aura. No psychotic disorder was present. After treatment of the migraine with propranolol 40 mg twice daily, explanation of the etiology of the hallucinations, and mirtazapine 45 mg daily, the migraine subsided and no further hallucinations occurred. The patient recovered. DISCUSSION: Visual auras have been described in migraine and occur quite often. Auditory hallucinations as aura in migraine have been described in children without psychosis, but this is the first case describing auditory hallucinations without psychosis as aura in migraine in an adult. For description of this kind of hallucination, DSM-IV lacks an appropriate category. CONCLUSION: Psychiatrists should consider migraine with acoustic aura as a possible etiological factor in patients without further psychotic symptoms presenting with auditory hallucinations, and they should ask for headache symptoms when they take the history. Prognosis may be favorable if the migraine is properly treated. Research is needed to explore the pathophysiological mechanism of auditory hallucinations as aura in migraine.