Nano-Sized CT Contrast Agents *
Valerio Voliani in Nanomaterials and Neoplasms, 2021
Barium sulfate suspensions and water-soluble aromatic iodinated compounds are currently used as CT contrast agents [5]. Owing to the inherent toxicity of Ba2+ ions, the use of barium sulfate is restricted only to gastrointestinal (GI) tract imaging. Currently available injectable CT contrast agents are composed of iodinated compounds. However, the short circulation time of iodinated contrast agents prevents wider application. In addition, although iodinated agents are generally safe [6], a severe adverse reaction sometimes occurs owing to their high osmolality and viscosity [7]. Despite the demand for new safer CT contrast agents and more sensitive imaging, to date, little progress has been made due to the low sensitivity of CT. For example, while MRI can detect micromolar concentrations of contrast agents, millimolar concentrations are required for successful CT imaging [8]. The strong magnetic field generated by magnetic nanoparticles allows MR imaging of objects smaller than voxel size [9], and even single cells (c.a. 10 µm) are readily revealed [10]. However, such an amplification effect is almost impossible for CT because CT contrast is related to the interaction between heavy atoms and X-rays. In addition, materials that are effective for X-ray attenuation have high atomic weights, and most of them are very toxic.
Practice Paper 8: Answers
Anthony B. Starr, Hiruni Jayasena, David Capewell, Saran Shantikumar in Get ahead! Medicine, 2016
Oesophageal rupture is a relatively rare but life-threatening condition. Rupture is usually iatrogenic and occurs during instrumentation of the oesophagus (endoscopy). Rarely, it can occur following severe and prolonged bouts of vomiting (Boerhaave’s syndrome). The initial investigation of choice in suspected oesophageal rupture is a chest X-ray, which may show pneumomediastinum, pleural effusion and subcutaneous emphysema. The next investigation is an oesophageal contrast study to show the size and anatomical location of any perforation. The most commonly used contrast agent in investigating the gastrointestinal tract is barium sulphate. However, barium is contraindicated as a contrast agent in patients with potential perforation, since its leakage outside the tract can result in a severe fibrotic reaction. Gastrografin (diatrizoate meglumine/diatrizoate sodium solution) is an iodine-based water-soluble contrast medium that is used as an alternative when barium is contraindicated. Patients with proven oesophageal rupture often require surgery, as medical management is associated with a poor prognosis.
Chemistry
Stephen P. Coburn in The Chemistry and Metabolism of 4′-Deoxypyridoxine, 2018
The solution was heated at 90° C for six hours and finally brought to a boil for a few minutes. Barium sulfate was removed by filtration and a few drops of dilute sulfuric acid were added to the filtrate in order to precipitate any remaining barium ions. An excess of sulfuric acid should be avoided. The clear filtrate was treated with charcoal and evaporated to near dryness. The 4′-deoxypyridoxine hydrochloride was recrystallized from ethanol (yield: 45%; M.P. 264°C). It seems likely that the charcoal treatment may have contributed to the low yield reported for this step.
An update on nanoparticle-based contrast agents in medical imaging
Published in Artificial Cells, Nanomedicine, and Biotechnology, 2018
Neda Naseri, Elham Ajorlou, Fatemeh Asghari, Younes Pilehvar-Soltanahmadi
CT images naturally appear in grayscale, which is based on the coefficient attenuation of the different tissues in body. More strongly X-ray attenuating matter such as bone display a light gray or white image, because attenuation in bone is very efficient while soft tissues appear dark gray or black in the image [28,29]. There is a large intrinsic contrast under normal conditions between bone and its surrounding tissues that differentiate them. However, it is not efficient to distinguish normal organ/tumors or soft tissues such as fat/muscle owing to their similar mass attenuation coefficients [1]. Many CT scans that are used currently involve intravenously injected iodine-based or oral barium sulfate suspensions as contrast agents in clinical use, in order to enhance the sensitivity of the scan. However, clinical procedures indicate that these agents are not optimal because they have many shortcomings such as short blood half life, nonspecific biodistribution, fast clearance, slight renal toxicity and poor contrast in fat patients [1,30,31].
Visualizing the macroscale spatial distributions of biofilms in complex flow channels using industrial computed tomography
Published in Biofouling, 2020
Yang Xiao, Barbara Sawicka, Yaoze Liu, Bo Zhou, Peng Hou, Yunkai Li
Due to the similarity in X-ray absorption coefficients of the emitter materials (polyethylene), biofilms, and aqueous phases, a contrast agent was required to image biofilms using ICT. The contrast agent was obtained by mixing water with barium sulfate (BaSO4) turbid liquid (0.33 g ml−1) and potassium iodide (KI) solution (0.10 g ml−1). After the dyeing process, excessive contrast agent and water remained in the channels of the emitters. Thus, the residual contrast agent needed to be removed. The dyeing device used in this test is shown in Figure S1 (Supplemental material) with the dyeing process detailed in the Supplemental material.
Using online content uniformity measurements for rapid automated process development exemplified via an X-ray system
Published in Pharmaceutical Development and Technology, 2019
Bernhard Wagner, Thomas Brinz, Johannes Khinast
To that end, the following experiment was performed. A small auger filler (diameter 5 mm) was used to dose powder into 49 capsules with various amounts of powder. First, barium sulfate was filled. Next, lactose was added. Random fill durations were applied to achieve random amounts of powder in the capsules. Since the capsules were weighed before and after barium sulfate was filled, the exact amount of barium sulfate was known (it ranged from 16.2 mg to 69.9 mg). After adding lactose, the total weight of the capsule was measured (it ranged from 337.7 mg to 463.6 mg). Additionally, capsules containing only the excipient were added. For details, refer to Appendix A1.
Related Knowledge Centers
- Barium
- Gastrointestinal Tract
- Inorganic Compound
- Sulfate
- Enema
- Barium Sulfate Suspension
- Radiocontrast Agent
- X-Ray
- Medical Imaging
- Upper Gastrointestinal Series