###### Abstract  
One of the most widely used modalities of clinical imaging is computed tomography (CT). Recent reports of new contrast agents toward CT imaging have been numerous. The production of gold nanoparticles (AuNPs) as contrast agents for CT is primarily a topic of intense interest. AuNPs have beneficial features for this application, including excellent X-ray attenuation, flexible sizes and shapes, tailorable surface chemistry, excellent biocompatibility and high levels of contrast generating matter. AuNPs with a size of about 18.5 nm and semi-spherical shape were synthesized using a sonochemical method. The attenuation rate of X-rays as measured in Hounsfield units per unit concentration (HU/mg) was measured. Ultrasound treatment for a duration of five min has been shown to produce highly stable AuNPs in different media (AuNPs in water and phosphate-buffered saline (PBS) was \(-42.1\) mV and \(-39.5\) mV, respectively). The CT value (HU = 395) of the AuNPs increased linearly with an increase in the AuNP dosage. The results confirm the use of ultrasonic treatment for the production of metal nanostructures, particularly highly stable non-toxic AuNPs, with good morphology and high-quality crystal structure using an easy and fast method. Synthesized AuNPs have the potential to be used as a CT contrast agent in medical imaging applications. s onochemical method; AuNPs; zeta potential; highly stable +
Footnote †: journal: Applied  
clinical imaging techniques, such as magnetic resonance imaging (MRI) and nuclear imaging, the lack of CT sensitivity to contrast agents is a major drawback [5]. Consequently, biomedical researchers are spending considerable efforts in developing a novel CT contrast agent. Gold nanoparticles (AuNPs) have attracted increased attention due to their distinctive and exceptional physicochemical features, such as electrical conductivity, low toxicity, high absorption spectrum, photothermal effects, adjustable size and shape-dependent optical properties, biocompatibility, chemical stability and easy functionality, relevant to a wide range of applications in biomedicine, catalysis, material science and quantum dots technology [6; 7; 8; 9; 10; 11; 12]. The usefulness of the nanoparticles colloids for biomedical application depends on their stability and biocompatibility of the nanoparticles in solution [13]. Since nanoparticles are transported through cavities, canals, waterways and aquifers [14], their stability in aqueous systems is vital to the formulation of predictive and transport models [15]. In addition, the toxicity of nanoparticles (NPs) has been shown to be dependent on their stability [16], which has also led to a need to understand the behavior of NP suspensions to be settled. Generally, the stability of NPs is influenced by their physical and chemical characteristics such as size [17], morphology, material composition [18], and surface coating [19]. Although several studies have been carried out on the sonochemical synthesis of AuNPs, none of them investigated the significant effect of their stability and their potential for CT [20; 21; 22; 23; 24; 25; 26; 27; 28; 29]. Sonochemical synthesis is one of the most widely used methods for nanomaterial synthesis due to the critical features that can be generated from acoustic cavitation [30; 31; 32]. It involves the nucleation, expansion and collapse of microbubbles by propagating a pressure wave through a liquid. This involves the implosive collapse as well as subsequent release of massive energy at high pressure (1000 atm) and high temperatures (5000 K), which, in turn, produces shear forces, turbulence, microjets and shock waves [33]. It is a valuable instrument for escalating the mass transfer process at the surface and disrupting the adsorbent interface [34]. Nanomaterials can be produced and modified by utilizing ultrasonic irradiation to aid the synthesis process in aqueous solutions.