Medical Imaging and Radiation Absorption Quiz

Medical Imaging Techniques and Radiation Absorption

• Arrays in non-visual medical imaging systems represent physical positions and signal strength with user-defined color and brightness values.
• Ionizing radiation with a frequency > ~1 x 1015 Hz can break atomic bonds and free electrons, occurring at wavelengths < ~300 nm (UV).
• X-rays are absorbed differently by materials, with heavy elements like calcium being strong absorbers, while soft tissues have similar absorption characteristics.
• Dual Energy X-ray Absorptiometry (DEXA) determines bone density and fracture risk using two low-dose X-rays with different absorption coefficients.
• DEXA provides bone mineral density (BMD) measurements, compared to norms of healthy young adults and age-matched adults to determine T-score and Z-score.
• World Health Organization defines bone density levels as Normal, Low bone mass, Osteoporosis, and Severe (established) osteoporosis based on T-scores.
• Bone fracture risk doubles with every standard deviation below normal bone density, guiding treatment to prevent future fractures.
• Computerised Tomography (CT) uses multiple x-ray projections to obtain detailed absorption information and construct 3D images of the body.
• CT scans involve passing thin x-ray beams through the body and using mathematical manipulation to calculate absorption as a function of position.
• Modern CT machines use circular gantries with x-ray sources and detectors, creating spiral motion to capture multiple x-ray projections.
• Absorption of radiation in biological tissue is governed by the Lambert-Beer Law, and the attenuation of x-ray beams is influenced by absorption and scattering processes.
• Medical imaging techniques involve identifying the object to be imaged, applying appropriate technology, measuring the received signal as a function of location, and using user-defined color scales for visualization.

Lower Limb Anatomy and Ultrasound Summary

• Lower limb is divided into gluteal, thigh, leg, and foot regions, with important transition areas at the femoral, popliteal, and ankle levels
• Pelvic bones consist of the irregularly shaped ilium, pubis, and ischium, with various bony landmarks including the iliac crest, pubic tubercle, and ischial spine
• The femur features key anatomical structures such as the head, neck, trochanters, and condyles, with the deep fascia of the thigh providing strong support and forming the iliotibial tract
• Superficial veins of the leg include the small saphenous vein on the lateral side and the great saphenous vein on the medial side, with varicose veins being a common issue in the lower limbs
• Varicose veins are dilated, elongated, and tortuous superficial veins with incompetent or absent valves, often leading to pain, leg swelling, and skin changes
• Muscles of the lower limb are categorized into anterior, posterior, and medial compartments, with distinct actions and innervations
• The anterior compartment includes the quadriceps group and sartorius, while the posterior compartment comprises the hamstring group and adductors of the thigh
• The femoral triangle is a wedge-shaped depression in the upper thigh, formed by muscles, and serves as an important anatomical landmark
• The lower limb muscles follow specific rules, with all muscles passing at least one joint and working on that joint, and different muscle groups such as prime movers, antagonists, and synergists
• Testing the quadriceps group involves applying resistance to leg extension and observing for compensatory movements or muscle recruitment
• Varicose vein treatment options include vein obliteration, support stockings, leg elevation, and exercise
• The lower limb anatomy and ultrasound information is derived from the "Gray’s Surface Anatomy and Ultrasound" and "Weir & Abrahams' Imaging Atlas of Human Anatomy" books by Elsevier Health Sciences

Eukaryotic Cell Structure and Function Overview

• The eukaryotic cell is not a simple "bag of molecules" but has a complex internal structure with many specialized organelles and different internal microenvironments.
• The cell membrane is made up of a lipid bilayer with inserted proteins and attached carbohydrates, serving as a barrier, regulating molecule movement, and maintaining intracellular pH.
• The cytoplasm is a viscous, aqueous solution that suspends organelles, solubilizes cellular molecules, and hosts various cellular processes.
• The cytoskeleton consists of filaments and tubules, preserving cell shape, enabling shape change, and providing a framework for cell movement and material transport.
• The nucleus is surrounded by a double layer of membrane, contains chromatin, nucleoli for ribosome assembly, and nucleoplasm, and regulates DNA fate based on cell signals.
• The endoplasmic reticulum (ER) is a network of membranous tubules involved in protein synthesis (rough ER) and lipid metabolism (smooth ER).
• The Golgi apparatus modifies and sorts proteins and lipids, preparing them for secretion and distribution to other organelles within the cell.
• The mitochondrion, with a double membrane and inner folds, contains enzymes for energy production through oxidative phosphorylation and is abundant in high-energy-demanding cells.
• Lysosomes, with a single-layer membrane and acidic pH, contain degradative enzymes for digesting biological molecules and destroying aged cell organelles.
• The proteasome is a multi-subunit enzyme complex arranged in four rings around a central hollow core, involved in degrading proteins within the cell.
• The eukaryotic cell's complex internal structure and the functions of its organelles are integral to its overall functioning and cellular processes.
• Understanding the basic structure and functions of the eukaryotic cell is crucial for comprehending cellular processes, molecular biology, and the overall functioning of living organisms.

Lower Limb Anatomy and Ultrasound Imaging

• Lower limb divided into gluteal, thigh, leg, and foot regions
• Pelvic bone irregular in shape, made up of ilium, pubis, and ischium
• Key bony landmarks include iliac crest, ischial spine, and sacral canal
• Thigh anatomy includes femur, deep fascia (fascia lata), and superficial veins
• Superficial veins of the leg include small and great saphenous veins
• Varicose veins are dilated, tortuous superficial veins with incompetent valves
• Musculoskeletal rules include prime movers, antagonists, and synergists
• Anterior compartment of the thigh contains quadriceps group and sartorius
• Posterior compartment includes hamstring group and adductors of the thigh
• Anterior thigh muscles include rectus femoris, vastus intermedius, vastus lateralis, and vastus medialis
• Medial compartment muscles include psoas, sartorius, and adductor group
• Testing the quadriceps group involves applying resistance to leg extension and observing compensatory movements

Pelvic Girdle and Gluteal Region Anatomy Overview

• Pelvic girdle bears upper body weight while sitting and standing
• It transfers weight from axial to lower appendicular skeleton for walking
• The pelvic girdle provides attachment for powerful locomotion muscles
• It contains and protects pelvic viscera
• The femoral artery's lateral floor is formed by the pectineus muscle
• The pelvic bone consists of the ilium, pubis, and ischium
• Ligaments like sacrospinous and sacrotuberous stabilize the sacrum
• The pelvic wall has various apertures and getaways for vessels and nerves
• Herniation beneath the inguinal ligament passes through the femoral ring
• The gluteal region is mainly responsible for hip abduction, extension, and rotation
• The gluteal muscles consist of superficial and deep groups with distinct functions
• The sacral plexus gives rise to nerves like the sciatic, superior and inferior gluteal, and pudendal nerves

Autonomic Nervous System: Receptor Types and Pharmacological Interventions

• The autonomic nervous system (ANS) includes ionotropic and metabotropic receptors, with nicotinic and muscarinic receptor types
• Nicotinic receptors are found on all postganglionic ANS cell bodies and are activated by ACh or nicotine, while muscarinic receptors are found on effector cell membranes and are activated by ACh or muscarine
• Nicotinic ACh receptors are ionotropic, leading to rapid responses and depolarization of postsynaptic cells
• Muscarinic receptor types M2 and M3 have inhibitory and excitatory responses, respectively, and are located in cardiac tissue and the digestive system
• Adrenergic receptors, including a1, a2, b1, b2, and b3, are found at effector organ synapses and couple to G proteins with intracellular coupling differing
• Effector organs/tissues express receptors for both postganglionic parasympathetic and sympathetic nerves, with varying effects on contraction
• Acetylcholine is destroyed by acetylcholinesterase at synapses, while noradrenaline is re-uptaken and metabolized/recycled
• Steps of neurochemical transmission, including neurotransmitter release and degradation, are potential targets for pharmacological intervention
• ANS drugs can selectively mimic or inhibit ANS responses at receptors, with examples such as atropine (muscarinic antagonist), salbutamol (b2 adrenergic agonist), and atenolol (b1 adrenergic antagonist)
• Autonomic dysfunction, such as dysautonomia, can manifest in various forms including orthostatic hypertension, neurocardiogenic syncope, and chronic stress disorders
• Deficiency of sympathetic activity can result in conditions like Horner's syndrome, characterized by drooping eyelid, pupil constriction, and decreased sweating
• The text suggests resources for further study, including the books "Neuroscience: Exploring the Brain," "Medical Physiology" by Boron and Boulpaep, and "Medical Physiology: Principles for Clinical Medicine" by Rhoades