Tiêu đề 2024 radology.pdf ✅

Rodgers et al Radiology: Volume 312: Number 2—August 2024 ■ radiology.rsna.org 3 Early Development The terms related to early development considered by the panel were based on the American Institute of Ultrasound in Medicine practice parameters, including the number of gestational sacs (GS), yolk sacs, and embryos and presence of cardiac activity (1) (Fig 2). In the setting of a multigestation pregnancy, descriptors for chorionicity and amnionicity are required but are beyond the scope of this lexicon; the reader is referred to the published literature for these terms (18). It is important to note that visu- alization of an embryo is required to determine whether there is a singleton or twin pregnancy. For instance, an early monochori- onic twin pregnancy will appear as a single GS. Therefore, before visualization of an embryo, this appearance should be reported as a single GS rather than as a ‘single pregnancy.’ To be clear, all measurements and timing of visualization of structures in early pregnancy are applicable to transvaginal US imaging. Gestational sac, yolk sac, and intracavitary fluid.—A GS, intra- uterine or ectopic in location, is the earliest sonographic finding of pregnancy and is typically visualized at 5 weeks GA (19,20) as a round or oval fluid collection surrounded by a hyperechoic rim of trophoblastic tissue (21). The yolk sac, a thin-rimmed circular structure eccentrically located within a GS, is visualized at ap- proximately 5 1⁄2 weeks GA (22) and typically measures less than 6 mm (23,24). The presence of a yolk sac within an intrauterine fluid collection is incontrovertible evidence of a pregnancy, and the sonogram should be interpreted as demonstrating a definite GS or definite pregnancy. Without visualization of a yolk sac or embryo, the fluid collection is still highly likely to represent a pregnancy (25,26). To reflect this slightly less definitive situa- tion, an empty sac should be reported as a probable GS or prob- able pregnancy (27,28). The intradecidual sign (29–31) (Fig 3) and double decidual sac sign (32) (Fig 4) can be used to increase confidence in in- terpreting an empty GS as an intrauterine pregnancy (IUP). These signs are highly specific but not sensitive, with reported poor interobserver agreement (33). Thus, the presence of these signs is not required to diagnose an IUP but may be helpful when present. The mean sac diameter can be used to calculate the GA before visualization of an embryo. Fluid in the endometrial cavity in a pregnant patient may have an appearance that mimics a GS and historically has been called a ‘pseudosac’ or ‘pseudogestational sac’ (34,35). These terms were introduced when obstetric US originated but should be avoided, as they may lead to clinical errors. For example, a pseudosac interpreted as evidence of an ectopic pregnancy (EP) without any other findings of an EP may lead to treatment potentially harming an early IUP. Conversely, a pseudosac may be mistaken for an intrauterine GS, dismissing the possibility of an EP. Fluid in the endometrial cavity with pointed or noncurved margins and variable internal echoes should therefore be described as intracavitary fluid or fluid in the endometrial cavity. Embryo and fetus.—An embryo with cardiac activity is typi- cally visualized at 6 weeks GA (19,20). Many societies use Figure 1: General terms. Lexicon terms (bolded and/or italicized) applicable to pregnancy but not specific to imaging are listed in this table.