Important Medical Imaging Concepts

Diathermy is a medical treatment that uses high-frequency electric currents to generate heat in body tissues. It can be used for both surgical and therapeutic purposes.

Diathermy machines can cut tissue, cauterize bleeding vessels (coagulation), and destroy abnormal tissue (fulguration) through the application of electric currents.

Diathermy can be used to treat various conditions by applying heat to specific areas of the body. It can help reduce pain, inflammation, and muscle spasms.

The principle of diathermy is based on the conversion of electrical energy into heat energy. This heat is generated within the body tissues as the electric currents pass through them.

Diathermy uses high-frequency alternating electric currents. This type of current minimizes tissue damage compared to direct current.

In induction field diathermy, heat is generated by inducing an electrical current within body parts using a magnetic field, which causes molecules to vibrate and produce heat.

Substances with a low dielectric constant and conductivity, such as bone, fat, and dry skin, tend to resist the flow of electricity.

Substances with a high dielectric constant and conductivity, such as muscle, blood vessels, and moist skin, readily allow the flow of electricity.

An electric field will converge onto substances with a high dielectric constant, meaning the electric field lines will crowd together near these substances.

The process of destroying cancer cells using radiation is called radiotherapy. It utilizes high-energy radiation to damage and kill cancerous cells.

Compton and photoelectric scattering are crucial for diagnostic imaging. Compton scattering provides information about tissue density, while photoelectric absorption helps visualize bone structures.

Electrophoresis separates charged particles using an electric field. Molecules with different charges and sizes move at different speeds, allowing for separation.

The Swedish scientist Arne Tiselius developed electrophoresis in the 1930s. He used it to separate proteins and other biomolecules based on their charge and size.

A transverse slice in helical CT represents a plane that cuts through the body perpendicular to the scan axis. Think of it like slicing a loaf of bread horizontally.

Pitch in helical CT is the ratio of table movement during one 360-degree gantry rotation to the beam width, measured in millimeters.

High pitch techniques are useful for fast scans, as they allow for more rapid table movement, which reduces scan times. This makes them suitable for situations where minimizing scan duration is important.

Low pitch techniques are most helpful for detecting subtle structures, as they provide higher image resolution. More detailed imaging is achieved due to higher data acquisition per scan.

The Dose Length Product (DLP) is a measure of the total radiation dose delivered to the patient during a CT scan. It takes into account both the dose per slice and the number of slices.

Effective dose is estimated at the scanner and reflects the stochastic risk of cancer development for a given scan. It considers the radiation sensitivity of different tissues and organs.

CT Dose Index (CTDI) is a measure of the radiation dose received from a single slice of a CT scan. It represents the average dose delivered across the beam width.

Radiation dose in CT is generally higher at the skin surface than in the center of the body. This is primarily due to the beam attenuation and scattering effects as the x-ray beam passes through the body.

Decreasing kilovoltage (kV) in CT improves tissue contrast by enhancing the differences in attenuation between different tissues. This means that structures with different densities, like bone and soft tissue, will appear more distinct on the image.

Automated exposure compensation (AEC) uses the scout image, which is like a low-resolution X-ray taken before the main scan, to determine the appropriate tube current (mA) to use for each slice. This helps ensure that the images have consistent brightness and contrast, even for patients of varying sizes.

The main challenge in cardiac CT is temporal resolution, which refers to how accurately the scanner can capture moments in time during the beating heart. Achieving good temporal resolution requires fast scan speeds and precise synchronization with the cardiac cycle.

Gantry rotation speed is the primary factor determining temporal resolution in CT. Faster rotation times allow the scanner to acquire data more quickly, resulting in more accurate imaging of moving organs.

One small square on an EKG represents 0.04 seconds (1 mm) in duration. This is the basic unit of measurement for EKG analysis.

One large square on an EKG represents 0.20 seconds (5 mm) in duration, which is five times the duration of a small square.

The inferior leads (II, III, aVF) represent the electrical activity of the inferior wall of the heart.

The left lateral leads (I, aVL, V5, V6) provide information about the electrical activity of the left side of the heart.

A biphasic P wave on an EKG is characterized by a positive and a negative deflection, suggesting an abnormal rhythm or conduction.

A deep S wave indicates a deep down-going deflection after the R wave, often seen in leads V1 and V2.

A tall R wave signifies a tall upward deflection, typically observed in leads V5 and V6, indicating a strong signal from the left ventricular depolarization.

The transition zone refers to the area where the electrical signal changes direction, often shown as a biphasic complex with a positive and negative deflection.

R wave progression refers to the increasing amplitude of the R wave as you move from leads V1 to V6, indicating the progression of electrical activity.

The ST segment represents the initial depolarization of the ventricles, often indicated by the flat line between the QRS complex and the T wave.

The ST segment is important because an elevation or depression in this segment might indicate a serious heart condition.

The T wave on an EKG represents the repolarization of the ventricles, an electrical event that allows the ventricle to relax after contracting.

An ideal operational amplifier (op-amp) has an infinitely high input impedance, meaning it draws negligible current from the input source.

Wideband amplifiers, often used in audio applications, have relatively low gain compared to narrowband amplifiers. Their gain ranges from less than 100 to 300.

Wideband amplifiers are mostly constructed with a single-ended output configuration, where the output is referenced to a common ground.

The IC741 is a commonly used integrated circuit (IC) that can be configured as an op-amp. It is a versatile and widely available component used in various amplifier applications.

All op-amp configurations, like differential, inverting, and non-inverting amplifiers, are possible with appropriate circuit designs.

Ultra-high frequency (UHF) therapy uses electromagnetic waves, specifically radio waves, to generate heat in tissues. These waves are located in the electromagnetic spectrum.

Millimetric wave therapy, which uses extremely short wavelengths, penetrates a very shallow depth into tissues, typically around 0.2-0.6 mm.

In X-ray spectrometers, the sample is placed after a collimator. The collimator shapes and focuses the X-ray beam onto the specimen.