Which statement about ultrasound of the thoracic aorta is least accurate?

Ultrasound of the thoracic aorta is primarily performed using external probes placed on the skin, which allows for the examination of the aorta without invasive procedures. This external approach is suitable for assessing structures like the thoracic aorta through non-invasive means.

In contrast, the use of internal probes, such as those required for transesophageal echocardiography, involves more patient preparation and sedation because they are inserted into the esophagus. Therefore, stating that ultrasound of the thoracic aorta requires external probes is accurate and reflects a standard practice within this imaging modality.

The other statements concerning transthoracic ultrasound are also modern practices. It does not necessitate sedation, making the procedure more accessible and efficient. Patient preparation is minimal, usually requiring only that the patient be in a comfortable position. The constraint in evaluating the distal arch and descending thoracic aorta highlights the limitations of the method, often requiring additional imaging for comprehensive assessment.

Thus, the notion that ultrasound of the thoracic aorta must utilize external probes correctly describes standard practice but does not encompass the complete context of thoracic aortic imaging options.