Seeing with Sound: Diagnostic Ultrasound Imaging
Suzanne Amador Kane, Boris A. Gelman in Introduction to Physics in Modern Medicine, 2020
What, exactly, is the ultrasound instrument doing to produce the images? The transducer's operation is quite simple: it emits a chirp of sound with a pitch so high that it falls outside our range of hearing (hence the term ultrasound). This pulse of sound travels in a specific direction through the body, encountering blood vessels, organ walls, etc. Many of these structures will reflect an echo back in the original direction. The transducer then “listens” for these echoes, and keeps track of the time from when the original ultrasound chirp was emitted to when the echoes are detected. These echo return times are then used to determine the location of the structure that generated them. The ultrasound transducer repeats this process for many different directions within the body, and compiles the resulting information to create an image of a cross section of the body tissue that generates echoes. The sonar methods used by ships and dolphins to detect underwater obstacles utilize the same idea, and bats have evolved a version of this system (echolocation) to navigate in the dark.
Normal Fetal Anatomy
Asim Kurjak in CRC Handbook of Ultrasound in Obstetrics and Gynecology, 2019
The most important applications of ultrasound in obstetrics are assessment of gestational age and fetal growth, and prenatal detection of fetal malformations. In both fields a basic prerequisite to obtain successful results is a good and accurate knowledge of normal fetal anatomy and its variants. Different anatomical structures like the cavum septi pellucidi or the intrahepatic portion of the umbilical vein serve as useful landmarks to define reference planes for biparietal diameter (BPD) or abdominal circumference (AC) measurements, thus enabling reproducible studies of fetal biometry. The importance of understanding normal fetal anatomy is also emphasized by the nonspecificity of sonographic findings in the majority of detectable fetal abnormalities. Diagnosis of a fetal abnormality is primarily based on absence or distortion of normally present anatomical structures, rather than on meticulous analysis of an apparently abnormal structure.
Imaging techniques in the evaluation of neurogenic bladder dysfunction
Jacques Corcos, David Ginsberg, Gilles Karsenty in Textbook of the Neurogenic Bladder, 2015
Ultrasound is a very safe modality because it does not expose the patient or practitioner to ionizing radiation. But ultrasound can, in theory, cause cavitation of microbubbles within an acoustic field. If enough cavitation occurs, tissue loss can occur through thermal and mechanical changes. Consequently, ultrasound outputs are measured through thermal and mechanical indexes as safety requirement. Thermal index estimates temperature rises when ultrasound travels through soft tissues. Mechanical index estimates the risk of tissue cavitation during evaluation.21 Although, cavitation rarely occurs during diagnostic ultrasound settings, practitioners should be aware of how ultrasound outputs are measured and take precautions to use ultrasound equipment within the recommended parameters.
The effect of ultrasound or phonophoresis as an adjuvant treatment for non-specific neck pain: systematic review of randomised controlled trials
Published in Disability and Rehabilitation, 2022
Kinley Dorji, Nadine Graham, Luciana Macedo, Janelle Gravesande, Charles H. Goldsmith, Geoffrey Gelley, Maureen Rice, Patricia Solomon
Therapeutic ultrasound is a common therapeutic modality often used in conjunction with exercise or manual therapy to treat various musculoskeletal conditions, including neck pain. Ultrasound is defined as a “sound wave or pressure wave with a frequency above the limit of the human hearing (16 to 20 kHz)” [9, p 410]. Therapeutic ultrasound used in rehabilitation treatments utilises frequencies within 1–3 MHz with intensities of 0.1–2.0 W/cm2 [9]. Ultrasound at 1 MHz can penetrate deep into the tissues from 2 to 4 cm, while ultrasound at 3 MHz has been demonstrated to penetrate 1–2 cm [10]. The two theories explaining the biophysiological effect of ultrasound include thermal and non-thermal effect theory [11]. However, it is difficult to separate the therapeutic effects caused by ultrasound into thermal and non-thermal as these coexist as the application of ultrasound on tissues continually produces mechanical and thermal effects. Thermal effects are generally used to manage pain, muscle spasm, and improve connective tissue disorders in sub-acute and chronic conditions [9,12]. Non-thermal effects are typically used in acute conditions to manage pain, reduce oedema and to stimulate tissue repair [12]. Overall, the thermal and non-thermal effects promote healing of the tissues and control pain which would theoretically result in reduced pain and improved function and disability during both acute and chronic stages
Handheld transabdominal ultrasound, after limited training, may confirm first trimester viable intrauterine pregnancy: a prospective cohort study
Published in Scandinavian Journal of Primary Health Care, 2021
Judith Krossøy Pedersen, Cecilie Sira, Jone Trovik
Although ultrasound is increasingly used in primary health care, not many studies have described the use as a diagnostic tool in early pregnancy. Everett [2] performed a prospective 2-year study from four semirural practices at a health centre in UK. Of 550 confirmed pregnancies, 117 women (21%) experienced bleeding during early pregnancy and 85 of these were investigated by (transabdominal) ultrasound by their GP. For 44 women vital pregnancy was confirmed by the GP ultrasound, while 4 investigations were initially inconclusive and needed a referral for confirmation. This rate of 92% confirmation of vital pregnancies by GPs performing abdominal ultrasound examinations is comparable to our rate of 87% of pregnancies confirmed as vital by handheld POCUS ultrasound examination performed mostly by fourth-year medical students. The study by Everett illustrates that early pregnancy ultrasound may be useful in a GP practise. The volume of possible patients (fertile women) per GP practice will likely be an important factor in considering if early ultrasound examinations should be introduced.
The difficult process of autonomous choice: using I-poems to understand experiences of abortion-seekers in The Netherlands
Published in Sexual and Reproductive Health Matters, 2023
Lianne Holten, Rosalie van der Wolf, Marit S. G. van der Pijl
This fits in Beynon-Jones’ distinction of various “repertoires” used when speaking about pre-abortion ultrasound viewing from the perspective of the abortion-seeker. In the normative repertoire, ultrasound is a tool of maternal-fetal bonding. The personification of the fetus inherent in this discourse makes the ultrasound morally and emotionally laden and can be upsetting for the abortion-seeker. In the current study, abortion seekers spoke of not being a “hypocrite” and “taking responsibility” and feeling the obligation to see what they later would have removed. In this way, according to Beynon-Jones, the ultrasound can also represent “a means of articulating the loss, or ending, of a relationship – rather than signifying its beginning (p.711)”.28 The other repertoire is one of medical objectification in which ultrasound can be seen as a tool of fetal de-personification. Herein the ultrasound is used as a medical assessment that helps to facilitate the ending of pregnancy and as evidence that the embryo is developmentally and morally insignificant. The participants in this study spoke of the relief of seeing only “a little circle” or a “little bean”. Being aware of which repertoire abortion seekers use could help reduce anxiety by meeting individual needs concerning pre-abortion ultrasound.
Related Knowledge Centers
- Bone Conduction
- Cochlea
- Middle Ear
- Skull
- Sound
- Hearing Range
- Sonochemistry
- Ultrasonic Hearing
- Nocturnality
- Ultrasound Avoidance