Medical Imaging Modalities involving X-rays and Medical Radiation

Whole Body PET-CT Scan

Medical imaging modalities, for example, include magnetic resonance imaging (MRI), ultrasound, medical radiation, angiography and computed tomography (CT) scanners.  In addition, several scanning techniques are used to visualise the human body for diagnostic and treatment purposes.  Also, these modalities are very useful for patient follow-up with regard to the progress of the disease state, which has already been diagnosed and/or is undergoing a treatment plan.  The vast majority of imaging is based on the application of X-rays and ultrasound (US).  These medical imaging modalities are involved in all levels of hospital care. In addition, they are instrumental in public health and preventive medicine settings as well as in curative and further extending to palliative care. The main objective is to establish the correct diagnoses.

Positron Emission Tomography (PET): Medical Radiation in Molecular Imaging

Medical imaging modalities in a clinical setting are a vital contribution to the patient’s overall diagnosis and help in the decision of an overall treatment plan. The utilisation of imaging techniques in medical radiation is increasing with new technological advances in medical sciences. Therefore, in the spectrum of a broad range of imaging modalities are the specialities of nuclear medicine, positron emission tomography (PET), magnetic resonance imaging (MRI) and ultrasound. Overall, imaging for medical radiation purposes involves a team of radiologists, radiographers and medical physicists.

Stages of PET scanning

Stages in PET imaging of the human body refers to a series of steps involved in performing a PET scan, a type of medical imaging that uses radioactive tracers to create images of the body's metabolic activity
Stages in PET imaging of the human body

Computed Tomography (CT): Expanding the Scope of X-ray Imaging in Diagnosis

Medical imaging modalities involve a multidisciplinary approach to obtain a correct diagnosis for the individual patient with the aim of providing a personalised approach to patient care. These imaging techniques can be applied as non-invasive methods to view the human body without any surgical intervention. They can be used to assist in the diagnosis or treat a variety of medical conditions. Medical imaging techniques utilise radiation that is part of the electromagnetic spectrum. These include imaging X-rays, the conventional X-ray, computed tomography (CT) and mammography. For example, a contrast agent can be used to improve X-ray image quality in angiography examinations.

X-rays are a type of medical imaging that uses electromagnetic radiation to create images of the inside of the body
X-rays of the head, chest, legs and hand.

Advances in Medical Imaging Modalities: Innovations in X-rays, MRI, and Ultrasound Technologies

Furthermore, imaging utilised in nuclear medicine and angiography can be attributed to several techniques to visualise biological processes. The radiopharmaceuticals used usually contain small amounts of radioactive markers, which are used in molecular imaging. Other non-radioactive types of imaging include magnetic resonance imaging (MRI) and ultrasound (US) imaging. MRI uses strong magnetic fields, which do not produce any known irreversible biological effects in humans. Diagnostic ultrasound (US) systems use high-frequency sound waves to produce internal body organs and soft tissue images.  Several medical imaging modalities use radiation using X-ray beams that are projected onto the body. When these X-ray beams pass through the human body, some are absorbed, and the resultant image is detected on the other side of the body.

MRI angiography is a type of medical imaging that uses magnetic resonance imaging (MRI) to create detailed images of blood vessels in the body
MRI angiography

Magnetic Resonance Angiography (MRA): Non-invasive Vascular Imaging with MRI

Some types of medical imaging function without ionising radiation; for example, magnetic resonance imaging (MRI), angiography, and ultrasound imaging have significant applications in diagnosing disease. Medical imaging modalities include single-photon emission computed tomography (SPECT), positron emission tomography (PET) and hybrid imaging systems such as PET/CT. Alternatively, other systems use the application of positron emission mammography (PEM) and radio-guided surgery (RGS). In addition, short- and long-lived radioisotopes are applied in research to develop new imaging agents and associated targeted therapies.  Other techniques include computed tomography (CT), magnetic resonance imaging (MRI), ultrasound imaging and planar X-ray (analogue, portable and digital) systems.

The main practical limitation of current medical imaging modalities is the special resolution required to elucidate detailed images of various structures within the human body. However, the rate of image acquisitions has increased over the last decade; this does not allow for the sensitivity required in order to express anatomical structure and function, which is limited by the radiation dose, amongst other factors.

Spatial Resolution in Medical Imaging: A Comparative Analysis of Different Modalities

Imaging modalitySpatial resolution (mm)

OPTICAL2-5 (Visible to IR)

Advancements in medical imaging modalities will not dictate their quality, but the objective will likely be to reduce cost and scanning time, including exposure to radiation. These technical innovations allow for the rational conclusion that medical radiation dose, scanning speed, image resolution, and sensitivity, including cost per patient, will all be elements of personalised medicine in the future.

Consequently, the medical physicist will play a pivotal role in furthering these challenges, especially in extending knowledge and understanding of the effect of which signals are used to construct 3-D time-dependent images.

In particular, it is important to account for the physical and biological factors that modulate the behaviour of different energy forms within the human body. Moreover, it is important to understand how to interpret images and derive more crucial information regarding the patient’s disease state in order to formulate a personal treatment plan.

As imaging continues to develop and improve, it is essential to understand the specific biological episode associated with each disease state. It would be crucial to design medical imaging modalities that can recognise a ‘fingerprint’ that can be attributed to a specific disease state.

Furthermore, new imaging modalities would be used to evaluate changes in tissue composition resulting from a disease like fibrosis. In this case, the physiological parameter would be the reduction of blood flow in arteries according to angiography. Other techniques could evaluate the change in conductivity or magnetic susceptibility of brain tissue. All of these improvements could help in the understanding of the contrast mechanisms in several medical imaging modalities.

In essence, it is important to make use of the data within digital images to develop more quantitative tissue characterisation from these anatomical scans. For example, functional magnetic resonance imaging (fMRI) has transformed the understanding of brain construction.

This imaging technique has provided the exact relationship between the MRI signals that map neural activity. However, fundamental neurochemical and electrophysiological processes are not well defined.

Diagnostic imaging tools provide powerful techniques to locate biological processes within the human body. This includes spatial heterogeneity and related changes to the different regions within the anatomical structure’s fine detail.

Advancements in medical imaging modalities will contribute to each patient’s overall personalised treatment plan. This can only be guaranteed by continuing translational research in the design of novel radiopharmaceuticals and biomarkers, which will increase efforts to devise robust personalised treatment plans for individual patients.

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