Present Perfect, Relative Clauses, and Medical Imaging Terms
Present Perfect Tense: Usage and Examples
The present perfect tense is used for:
- Something that started in the past and continues in the present
- When we are talking about our experience up to the present
- Something that happened in the past but is important at the time of speaking
- When the speaker wants to emphasize the result
- Talking about something that happened recently
Key Words with Present Perfect
- Since: Used with dates, times, and past events (e.g., “since 1995,” “since 2 o’clock,” “since I was a child”).
- For: Used with periods of time of any length (e.g., “for two hours,” “for a week,” “for a long time”).
- Yet: Meaning “already,” “not yet,” or “still.” It is always placed at the end of a sentence in questions or negative statements.
- Ever: Meaning “at any time.” It is used in questions (e.g., “Have you ever been to London?”).
- Never: Meaning “at no time.” It is used with “has/have” in negative sentences (e.g., “I have never seen that movie.”).
Defining and Non-Defining Relative Clauses
- Defining clauses: Identify the specific person or thing we are talking about in a larger group. They are not separated by commas, and the meaning of the sentence changes significantly if the clause is removed.
- Non-defining clauses: Provide additional information about the person or thing we are talking about. They are set off by commas or parentheses, and the sentence’s core meaning remains if the clause is removed.
Relative Pronouns
- Who: Refers to people.
- Which: Refers to things or animals.
- Which: Can also mean “the fact that,” referring to a whole clause.
- Whose: Indicates possession.
- Whom: Used as the object of a verb or preposition, especially in formal writing, and often appears between commas.
- When: Refers to times or dates.
- Where: Refers to places.
- Why: Refers to reasons.
Medical Imaging and Radiology Terminology
Common Terms in Medical Imaging
- Computed tomography (CT): A technique that produces cross-sectional images of the body.
- Contrast studies: Procedures involving the injection of a radiopaque material to enhance image clarity.
- Gamma camera: A device used to detect gamma rays emitted by radiopharmaceuticals.
- Gamma ray: High-energy rays emitted by radioactive substances, often used in tracer studies.
- Interventional radiology: Therapeutic or diagnostic procedures performed by a radiologist, such as needle biopsies.
- In vitro: A process, test, or procedure performed, measured, or observed outside a living organism, typically in a test tube or petri dish.
- In vivo: A process, test, or procedure performed, measured, or observed within a living organism.
- Half-life: The time required for a radioactive substance to lose half of its radioactivity.
- Ionization: The transformation of electrically neutral substances into charged particles.
- Magnetic resonance imaging (MRI): A technique that uses magnetic fields and radio waves to create sagittal, coronal, and axial images.
- Roentgenology: The study of X-rays.
- Scan: An image of an area, organ, or tissue obtained from various imaging techniques, such as ultrasound.
- Scintigraphy: A diagnostic nuclear medicine test using radiopharmaceuticals and a gamma camera.
- Tracer studies: Studies where radionuclides are used as tags or labels attached to chemicals to track their movement or activity within the body.
Nuclear Medicine and Related Terms
- Nuclear medicine: The medical specialty that uses radioactive substances (radionuclides) for diagnosis and treatment.
- Fluorescence: The emission of glowing light from a substance exposed to radiation.
- Cineradiography: The use of motion picture techniques to record X-ray images.
- Fluoroscopy: A technique where X-ray beams are focused on the body to produce real-time moving images.
- Positron emission tomography (PET): A technique where intravenously administered radioactive substances create cross-sectional images.
- Radioimmunoassay: A method that combines radioactive chemicals and antibodies to detect specific substances in the blood.
- Radioisotope: A radioactive form of an element.
- Radiolabeled compound: A radiopharmaceutical used in nuclear medicine studies.
- Radiology: The medical specialty concerned with the study of X-rays and other imaging techniques.
- Radiolucent: Permitting the passage of X-rays, appearing black on an X-ray image.
- Radiopaque: Obstructing the passage of X-rays, appearing white on an X-ray image.
- Radiopharmaceutical: A radioactive drug administered safely for diagnostic or therapeutic purposes.
- Ultrasonography: A diagnostic technique that projects and retrieves high-frequency sound waves to create images.
- Ultrasound transducer: A handheld device used to transmit and receive ultrasound waves.
- Uptake: The rate of absorption of a radionuclide into an organ or tissue.
- Radiographer: A professional who aids physicians in administering radiologic procedures.