Daily Archives: June 17, 2019

PLAX view: Orientation

The parasternal long axis view or the PLAX is obtained by placing the transducer to the left of the sternum in 3rd or 4th intercostal space with the orientation marker toward patient’s right shoulder or 10 o’ clock position, which is essentially the ‘long axis’ of the heart. For better understanding of the procedure, watch my video 3 (~19:33) and video 8 (~5:22).

The following figures demonstrate the plane in which we are slicing the heart to obtain PLAX view.

PLAX plane
Orientation to the PLAX view in lying down position

Normal sonographic anatomy of the PLAX view:

In a technically ‘good’ PLAX view, both the mitral valve and the aortic valve will be clearly seen and will be roughly in the center of the image, stacked on top of each other. The base of the left ventricle (LV), but not the apex, will be visible. The right ventricular outflow tract (RVOT) will be seen on the top of the image. Note that the right ventricle has noticeably thinner and smaller walls compared to the LV. The right atrium (RA) is not visible in this view. On the right, the left atrium (LA), aorta and RVOT each should roughly take up one-third of the image. Pericardium appears as a bright border and the descending thoracic aorta is visible at the bottom of the image, as a circle outside the LA.

Hepatic Hemangioma

This image demonstrates hepatic hemangioma incidentally found while imaging the kidney. On ultrasound, hepatic hemangiomas appear as well-defined, hyperechoic, homogeneous lesions. Some of them may have posterior acoustic enhancement. The hyperechogenicity probably results from multiple fibrous interfaces between vascular spaces. If the lesion is in a fibrotic liver, that is background echogenicity, it may appear hypoechoic. Lesions >5 cm can have mixed echogenicity because of intratumoral thrombosis and fibrosis.

Ultrasound has a good accuracy in differentiating hepatic hemangioma from malignant hyperechoic masses (sensitivity of 94.1% and specificity of 80.0% for lesions less than 3 cm diameter). The absence of blood flow on Doppler exam is also a reliable sign to differentiate hemangioma from hepatocellular carcinoma, which frequently has intra- or peri-tumoral vascularity. Though the lesion is vascular, the blood flow is too slow to be picked up by Doppler usually. In hypoechoic lesions, a peripheral echogenic rim favors hemangioma, while a perilesional hypoechoic rim, known as the ‘target sign’, strongly suggests malignancy.

Asymptomatic patients with lesions <1.5 cm, but also including those with lesions ≤5 cm, can be reassured and observed without follow-up imaging. On the other hand, close radiologic follow-up of should be considered in patients with lesions >5 cm (e.g. CT scan yearly), particularly those in a subcapsular location. In the absence of symptoms, prophylactic resection is usually not recommended [UpToDate].

This image demonstrates a lesion of mixed echogenicity in a non homogeneous liver (cirrhosis) and ascites. It was diagnosed as HCC.