## 2 The Advantages of Ultrasound  
There are several advantages of ultrasound as an imaging modality: It has higher spatial resolution than CT and MRI, exquisite anatomical definition for superficial and many deeper structures, real time imaging capabilities, wide availability, and a broad range of clinical applications including surveillance, diagnosis, disease monitoring, and guidance of interventions [7, 8]. Additionally, US delivers no ionizing radiation and is significantly less expensive, with lower purchasing and maintenance costs than comparable imaging modalities such as MRI and CT [9].  
US can be applied in a traditional fashion, for examination of the abdomen by gastroenterologists and surgeons [10, 11, 12, 13, 14], the pelvis by gynaecologists [15, 16], the heart by cardiologists [17], the mediastum and lung by pneumologists, and other anatomical regions examined by their respective specialists. The role of radiology depends on historical issues and traditions [18, 19, 20, 21]. The performance of ultrasound by clinicians can be a rewarding and satisfying part of their practice, enabling the rapid delivery of a powerful diagnostic and therapeutic tool. There is no absolute need to delegate ultrasound scanning to nonphysicians, except in certain practice settings such as North America, where routine performance of US by physicians introduces logistical challenges and raises costs [20]. In such settings, it is usually necessary for routine exams to be performed by highly trained non-physician personnel (so called sonographers) under the supervision of radiologists or other physicians, while reserving physician scanning for complex exams or exams with unusual findings.  
In addition, US might be also applied as a problem solving tool (point-of-care US) in a defined clinical setting, for example, in the prehospital setting, emergency room and intensive care unit [8].  
The traditional way of performing US examinations can be termed comprehensive or conventional ultrasound. In contrast to conventional ultrasound, the use of mobile and portable US scanners allows examiners immediate access to clinical imaging for rapid and direct solutions. WFUMB (World Federation for Ultrasound in Medicine and Biology) has published a position paper which discusses the current status and future perspectives of point-of-care US [8]. According to this organization, point-of-care US is defined as \"ultrasound performed bedside and interpreted directly by the treating clinician or other specialist\" [8]. The authors of this editorial have added the qualifier \"or other specialists\" in recognition that in some settings (battlefield, ambulance, remote rural clinics, etc.) it may not be practical to mandate clinician-performed portable US. In some settings, other personnel (e.g., trained soldiers, paramedics, physician assistants) may need to perform the scanning.  
A recent article by [PERSON] [21] makes a strong argument for physician-performed US. \"The main message of the groundbreaking publication by [PERSON] in 1976 was that fast B-mode ultrasound represents an expansion of physical examination by technical means termed as \"clinical ultrasound\" [22, 23] and as a \"dialog-based examination method\" [24]. The probe acts as the palpating hand while the physician communicates verbally with the patient. This allows the clinician to record a more in-depth case history and also allows for a more precise determination of the problem. The critical synthesis of imaging and symptoms allows definitive diagnoses that would not be possible without US, clinical knowledge, and consultation with a physician\" [21]. While we agree in principle with the main concepts articulated by [PERSON], we recognize that highly trained nonphysician personnel can also perform many of the dialogue and communication tasks. There have been no prospective studies showing that physician-performed US provides higher accuracy, improves patient outcomes, or is preferred by patients compared to sonographer-performed US.