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Expert help when you need it- Q1:Submit your solutions on Gradescope. 1. [Total: 16 pts] The figure below shows a schematic control block diagram of the control of respiration, with the respiratory controller representing the respiratory chemoreflexes, brain respiratory neural centers and the respiratory muscles, and the lungs representing the CO₂ exchange in the lungs. In amyotrophic lateral sclerosis (ALS, also known as Lou Gehrig's disease), motor neuron degeneration results in weakness and eventual paralysis of the respiratory muscles. Note that the regulation of ventilation model here is slightly different (more simplified) from the one we discussed in class. V/₁ Respiratory controller Lungs Pacoz a) [2 pts] Suppose that, in a particular ALS patient, the (steady-state) respiratory controller equation (which characterizes the chemoreflex response) is given by the following equation: V₁ = Paco2 - 37 Where V represents the alveolar ventilation (in L/min), and Pacoz is the partial pressure for CO₂ in the arterial blood (in units of mmHg). Draw (as accurately as possible on the provided graph) the line representing the steady-state controller response to Paco2- Note that we are neglecting the effects of O₂ here. Label this line as "(a)". b) [2 pts] Assume that gas exchange in this patient is normal and can be characterized by the following plant equation: Paco2 = 200/V Draw (as accurately as possible on the provided graph) the relationship between Pacoz and V. Label the curve as "(b)"./nVdotA (L/min) 6.0 5.5 5.0 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0 40 41 (mm Hg) c) [2 pts] Estimate the steady-state operating values of Pacoz and V₁ in this patient. d) [4 pts] In a normal healthy person, the controller response is given by V₁ = 2(Paco2-37). Draw this controller response on the graph below. Estimate the steady-state operating values of Paco2 and V in the normal subjects. Label the curve as "(d)". 35 36 37 38 39 P aCO2 42 43 44 45 e) [4 pts] A pressure support ventilator can be used to provide assistance to the ALS patient - such a ventilator would produce an increase of x L/min on top of the subject's own natural ventilatory output, independent of the Pacoz level. However, the ventilator has to be triggered by a minimal inspiratory effort by the patient himself. If the patient does not generate any effort, the ventilator does not provide any ventilatory assistance. Draw on the graph below the total controller response (patient+ ventilator) required to restore the steady-state V and Pacoz values to the levels seen in the normal subject. Label the total controller response as "(e)". f) [2 pts] What is the value of x (L/min)?See Answer
- Q2:2. [15 pts] Assume the metabolic hyperbola for CO₂ given by the following equation: 863 - Vcoz V₁ PACO2 Pico2+ where the normal steady-state CO₂ production is 235 mL/min and the inspired CO₂ concentration (or volumetric fraction) is 0. Also, assume a dead-space ventilation rate of 1 L/min. Also, suppose the steady-state ventilatory response to CO₂ is given by the following equation: 32 Vc = Drive external +(1.46 + (Paco2-37) and Vc 20 Pa02-38.6) Note that the above equation is slightly modified from what we derived in class in that a constant term, Drive external is added to the equation. This drive represents an additional source of control that affects ventilatory response e.g., sleep-wake state, alertness, etc. At normal state (resting and awake), let Drive external = 0. a) [5 pts] Use MATLAB to plot the metabolic hyperbola for CO₂ and the ventilatory response to CO₂ under normal condition. Show both graphs on the same figure (see hold function). Label both axes with appropriate units. Also indicate which graph represents the me the metabolic hyperbola for CO₂ and which graph represents the ventilatory response to CO₂ (see legend function). The plot should show the range of ventilation from 0-20 L/min and the range of PACO₂ from 30-60 mmHg (see xlim and ylim functions). Determine the normal steady-state values of ventilation and Pacoz from the plot (e.g., click on the plot where you want to obtain the x-y coordinates). Note: For the metabolic hyperbola for CO₂, please plot V against PACO₂ i.e., you would take the dead-space ventilation into consideration. b) [4 pts] The onset of sleep causes the external drive to breathe to drop by -5 L/min. State which parameter changes and to what value. Show the graphs representing this situation and report the steady-state values of ventilation and Pacoz. c) [4 pts] Follows from b), how would inhalation of a gas mixture containing 3% CO₂ in air (i.e., volumetric fraction of 0.03) during sleep affect the steady-state values of ventilation and Pacoz? State which parameter changes and to what value. Show the graphs representing this situation and report the steady-state values of ventilation and Pacoz. You may assume that the subject is at sea level. d) [2pt] Copy and paste the MATLAB code you used in this question (all parts). You may take a picture of your MATLAB script, but please make sure that the code is clearly readable from the image.See Answer
- Q3:3. [7 pts] At the onset of moderate exercise, the tensing of the muscles involved plus an increase in venomotor tone produces a decrease in venous compliance, thereby raising Pms- Sympathetic stimulation leads subsequently to an increase in heart rate by 40% and doubling Qc,max from its normal value. Vaso- and venomotor tone also increased by 40%. Then, local vasodilation of the muscular vascular beds produces a marked decrease in peripheral resistance by 40% in both arterial and venous vasculatures. The following are the parameter values under normal resting conditions: f CD Cs Qcmax РА Ppl RA Ry CA Cy V = 72 beats min¹² = 0.035 L mmHg ¹ = 0.0007 L mmHg¹ 13 L/min = 100 mmHg = -4 mmHg = 19.2 mmHg min L¹¹ = 0.4 mmHg min L²¹ = 0.028 L mmHg ¹ = 0.5 L mmHg¹¹ = 3.7 L (total blood volume that exerts stress, aka stress volum) a) [5 pts] Use MATLAB to plot the cardiac output and venous return curves during moderate exercise on the same plot as the normal curves (see hold function). Add legend to the plot (see legend function to indicate which graph is Qc or QR and under which condition - normal or exercise. b) [1 pt] From the plot, determine the steady-state operating value of cardiac output if an increase in heart rate and Qc,max are the only responses to moderate exercise. c) [1 pt] From the plot, determine the steady-state operating value of cardiac output when heart responses change with the systemic circulation. d) [1 pt] Copy and paste the MATLAB code you used in this question. You may take a picture of your MATLAB script, but please make sure that the code is clearly readable from the image.See Answer
- Q4:2. [5 pts] Contrast agents are substances used to enhance the radiodensity of a targeted tissue by altering the way that electromagnetic radiation or ultrasound waves pass through the body. A patient is administered contrast agent intravenously. The contrast agent first gets distributed in the plasma. The contrast agent can diffuse from the plasma into the targeted tissue as well as diffuse from the targeted tissue back into plasma. The contrast agent is eliminated by glomerular filtration in the kidneys and leaves the body with urine. Draw a flow diagram to show how the contrast agent travels through the body (from when it enters the body to when it leaves the body). Use arrows to represent the flow. Make sure that you capture all the main components of the described process. [Continues on next page]See Answer
- Q5:3. [Total: 19 pts] Blood glucose and insulin regulation The equations that characterize the steady state regulation of glucose and insulin can be derived by taking into account the main factors that affect the appearance and disappearance of each of these substances in the body. The mass balance for blood glucose (x) is given by: Q₁ = λx +vxy (Eqn. 1) where Q₁ represents the flow-rate (assume to be constant) at which glucose enters the blood through absorption from the gastrointestinal tract or through production from the liver, xx represents the rate at which the body tissues utilize glucose without help from insulin, and vxy is the rate at which glucose is metabolized with facilitation from insulin. The blood concentration of insulin is represented by y, and λ and v are constant parameters. Thus, Eqn. 1 represents the "glucose response to insulin". By applying similar mass-balance considerations to the production of insulin from the pancreas and the subsequent destruction of insulin, we can derive the following expression for the "insulin response to glucose": (Egn. 2a) (Eqn. 2b) where and are constant parameters. Insulin is not produced when glucose is lower than the threshold parameter (Eqn.2a). Note that the insulin production and destruction rates are combined into one parameter, (zeta). By using empirically derived values for the model parameters (Q₁, A, v, 3, 4) in Egns. 1 and 2a/b, these equations allow us to predict the blood concentrations of glucose (x) and insulin (y) under various conditions. The figure below displays the plots corresponding to these responses in normal and diabetic subjects. Point N is the operating point of a normal subject. B с D Insulin concentration (mu.mL-¹) 0.2 0.15 y = 0, x≤0 y = {(x-4), x> 0.1 0.05 0 0.2 0.4 0.6 0.8 N 1 1.2 1.4 1.6 1.8 2/na) [2 pts] Estimate from the figure the operating values of glucose and insulin in the blood of a normal subject. b) [3 pts] Suppose this person eats junk food everyday and does not exercise, and after many years, develops "insulin resistance" (i.e., the body requires more and more insulin to metabolize the same amount of glucose). Assuming his pancreas still functions normally. Which parameter(s) need to change to simulate this condition? Determine his new operating values of glucose and insulin. Label the new operating point "b". Briefly explain how you arrived at your answers. c) [3 pts] After many years of untreated insulin resistance, this subject's pancreas can now operate at half of its full capacity. Which parameter(s) need to change to simulate this condition? Determine his new operating values of glucose and insulin. Label the new operating point "c". Briefly explain how you arrived at your answers./nd) [5 pts] The subject does nothing to change his lifestyle and the pancreas eventually fails. Suppose that his pancreas is removed and replaced by a machine that continuously infuses insulin into his body independent of the glucose level. The machine is adjusted such that it infuses the appropriate amount of insulin, restoring the plasma glucose concentration to the normal level. Sketch as accurately as possible in the provided figure to reflect the described condition. Label the curve(s) "d". Briefly explain how you arrived at your answer. e) [3 pts] From the provided figure, is it possible for you to estimate the parameter of a normal healthy person? If so, provide your best estimate of pp. Briefly explain how you arrived at your answer. f) [3 pts] From the provided figure, is it possible for you to estimate the parameter < (Eqn. 2b) of a normal healthy person? If so, provide your best estimate of and from which graph. Briefly explain how you arrived at your answer.See Answer
- Q6:4. [Total: 23 pts] Cardiac output and venous return The figure below displays the cardiac output (Qc) and venous return (Q₂) curves that represent the steady state characteristics of the heart and the rest of the circulation of a subject who is bleeding badly from a knife wound in the abdomen. Point N shows the steady state operating point of the system under normal circumstances prior to the stabbing and subsequent bleeding. Venous return and cardiac output (mL/min) 2800 2400 2000 1600 1200 800F 400 E 0 G -8 B D -4 0 4 8 Right atrial pressure (mmHg) a) [3 pts] Bleeding reduces blood volume and increases circulatory resistance. Which curve (A, B, C, D, E, F or G) best represents these changes from the normal case? Briefly explain the reason for your selection. 12/nb) [5 pts] From the information displayed in the figure, provide a rough estimate of the total volume of blood lost, assuming that the sum of arterial and venous compliances is 0.53 L-mmHg¹. Briefly explain how you arrived at your answer. c) [4 pts] In the compensated stage of shock from the bleeding, the heart becomes hypereffective (i.e., it generates a higher cardiac output for the same Pra). Label on the figure "c", the new steady state equilibrium values of Pr. and cardiac output in the compensated stage of shock following blood loss. Briefly explain your answer. d) [3 pts] If this subject remains in this state without medical care, the irreversible stage of shock sets in. The heart is no longer able to sustain its hypereffective performance and deteriorates progressively. Which curve (A, B, C, D, E, F or G) best represents this situation? Briefly explain your selection. Label on the figure "d", the new steady state equilibrium values of Pra and cardiac output in the irreversible stage of shock./ne) [4 pts) Assuming arterial pressure (PA) to be 40 mmHg and pleural pressure (Pi) to be -4 mmHg, provide your best estimate of what the ratio of systolic to diastolic compliance (Cs/Co) of the heart would be in the irreversible stage of shock from the bleeding, based the information displayed in the figure. f) [4 pts] if the subject were to receive blood transfusion at the irreversible stage of shock, can the blood transfusion restore the cardiac output to the normal level? Assume that the body has not yet adjusted to the replenished blood volume. Explain your answer.See Answer
- Q7:5. [Total: 8 pts] Muscle stretch reflex The figure below shows a simplified model of muscle stretch reflex in an experimental anesthetized animal. The model describes how the muscle stretch reflex regulates the muscle length. All variables shown have been linearized and represent fluctuations around its mean value under normal resting condition. Z represents external neural frequency stimulating the spinal cord. fa represents the total change in afferent neural frequency. The spinal cord, represented by the gain Gc, converts the incoming neural input to the neural output fe- The changes in the efferent neural frequency, fe, are relayed through motor neurons to the muscle. The muscle converts the efferent neural frequency to changes in muscle length L. The gain of this conversion is-G. Note that the gain is negative because increases in efferent neural frequency lead to decreases in muscle length. The change in the muscle length is sensed by the muscle spindle. The muscle spindle relays the neural output, fs, to the spinal cord through sensory neurons. This process is represented by the gain Gg. fa fe Gc Z -GM Gs fs L a) [4 pts] Suppose that animal A is injected with a drug that disrupts neurotransmission, blocking the sensory neurons. Under such condition, is the system operating as a negative feedback system? Explain your answer. Please also state which gain(s) is affected by the sensory nerve blockade. b) [4 pts] Under which condition between normal and sensory nerve blockade would result in stronger muscle contraction for the same level of the external stimulation Z? Explain your answer.See Answer
- Q8:6. [Total: 9pts] Chemical regulation of ventilation An investigator wants to investigate the effect of exercise on ventilation and Pacoz in a healthy volunteer. Assume that the baseline ventilatory response to CO₂ and the subject's metabolic hyperbola prior to participating in the study yields an operating point labeled "BL" in the figure below. In order to measure ventilation during the exercise study, when the volunteer has to be on a treadmill, she has to wear a face mask connected to a long breathing tube which is then connected to a device used to measure ventilation. This device does not provide any ventilation support, but it can provide different levels of inhaled oxygen. The graph below shows metabolic hyperbolas and ventilatory response to CO₂ under different conditions. в с VdotE or VdotC (l/min) BL A Measures ventilation PACO₂ or P or Pacoz (mmHg) O E F a) [3 pts] First, the subject's ventilation and Pacoz are measured while she is standing at rest on the treadmill and she breathes in air (21% O₂). Considering the long tube in this experimental setup, which curve (A, B, C, D, E or F) best represents this situation? Briefly explain your selection. Label on the figure "a", the new steady state equilibrium values of Pacoz and ventilation for the volunteer at rest.See Answer
- Q9:1. [5 pts] Construct the glucose-insulin regulation model in Simulink as outlined in Fig. 3. The parameter values shown in Fig. 3 are the values of a normal adult. Set the Simulink model to run simulations for a total duration of 24 hours. Although Simulink generally assumes time to be measured in seconds, the units of the model parameters give time in hours-so, you can treat the durations you enter into Simulink as hours (instead of seconds). The initial conditions of normal blood glucose and insulin concentrations are 0.81 mg/mL and 0.055 mU/mL, respectively. These initial values of blood glucose and insulin concentrations should be set in the respective Integrator blocks (shown as in Simulink). To set the initial values in the integrator block, double click the block to open the Block Parameters window. Enter the initial value (e.g., 0.81 for glucose) in the Initial Condition field, and click OK. Run a simulation for a normal adult (Subject N) over 24 hours without any external glucose input (i.e., U(t) = 0). Show the graph of glucose and insulin concentrations as a function of time as 2-by-1 subplots i.e., the glucose concentration is the top subplot and the insulin concentration is the bottom subplot. Label all axes. You may plot using the Scope in Simulink or plot in MATLAB using the simulation results that are sent to MATLAB Workspace. Save this Simulink model as "glucose_N.slx".See Answer
- Q10:2. [5 pts] Customize the model in Q.1 for a type-1 diabetic subject (Subject D1) by altering B, the model parameter that controls the production rate of insulin by the pancreas. Reduce B to 20% of the normal subject's value. Establish the equilibrium conditions for type-1 diabetic subject by running the simulation over 24 hours without any external glucose input (i.e., U (t) = 0). Show the graph of glucose and insulin concentrations as a function of time (similar to Q.1). Report the final values of blood glucose and insulin concentrations that appear at the end of your simulations. Assuming that both glucose and insulin concentrations have settled into a steady state, these final values can now be used as the initial values in the respective integrators for subsequent simulations of a type-1 diabetic subject. Save this Simulink model as "glucose_D1.slx".See Answer
- Q11:3. [5 pts] Simulate the oral glucose tolerance test (OGTT) in N and D1 subjects. During the OGTT, a large amount of glucose is infused rapidly and the corresponding blood glucose and insulin trajectories are tracked over a period of up to 5 hours. Assume the total amount of glucose infused is 25,000 mg and the infusion is carried out in the form of a bolus lasting 15 minutes (0.25 h), starting from t = 1 h. Plot the trajectories of blood glucose and insulin predicted by both models. To aid comparison across the 2 cases (N and D1), plot the glucose responses of both N and D1 cases using the same time- and glucose concentration axes i.e., there are two graphs in the top subplot for glucose concentration. Similarly, plot the insulin responses of both cases on the same axes. Label all axes and add a legend indicating which graph belongs to which case. You may plot these simulation results in MATLAB using the simulation results that are sent to the MATLAB Workspace. Report the values of blood glucose and insulin from your simulations: just before you impose the glucose challenge, and at times 1, 2 and 3 hours following the start of the challenge. Glucose concentration (mg/mL) Insulin concentration (mU/mL) D1 N D1 N Time Before OGTT Time = 1 hr Time = 2 hr Time = 3 hrSee Answer
- Q12:4. [5 pts] Modify glucose_N.slx and glucose_D1.slx to simulate glucose-insulin dynamics under more realistic conditions where each of these subjects eats 3 meals over 24 hours: - Breakfast starts at hour = 1, duration=30 minutes, glucose infusion rate = 15,000 mg/hr - Lunch starts at hour = 5, duration=45 minutes, glucose infusion rate = 10,000 mg/hr - Dinner starts at hour = 12, duration=1 hour, glucose infusion rate = 12,000 mg/hr You may assume that the glucose rate per meal is constant within the given duration (i.e., the external glucose infusion rate takes the form of rectangular pulses with different durations). Note that in this question, we are not incorporating any oral glucose tolerance test (as in Q.3). In this question, you would create 3 subplots: i) Plot the trajectories of the external glucose infusions (i.e., the meals). ii) Plot the trajectories of blood glucose predicted by both models (normal and type-1 diabetic) over 24 hours on the same axes. iii) Plot the trajectories of blood insulin predicted by both models (normal and type-1 diabetic) over 24 hours on the same axes. Label all axes. For the glucose and insulin subplots, add a legend indicating which graph belongs to which case (normal or type-1 diabetic). From the simulation results, calculate and report the average and standard deviation of blood glucose and insulin concentrations over 24-hour period. Glucose concentration (mg/ml) N D1 Average SD Insulin concentration (mU/mL) N D1See Answer
- Q13:5. [5 pts] Modify the Simulink model for D1 subject to incorporate the use of an insulin pump in your simulations. Assume the same schedule and sizes of meals as in Q.4. Show clearly how you are changing the model and what Simulink block you are using to simulate the insulin pump. Suppose this first insulin pump is capable of delivering a constant infusion of insulin over 24 hours. Determine the insulin infusion rate (in mU h-1) required to reduce blood glucose concentration in D1 to approximately the same level as that in N by the end of 24 hours (refer to your simulations results in Q.4. The Subject N does not use any insulin pump!). Plot the trajectories of the meals and blood glucose and insulin of D1 (i.e., 3 subplots as in Q.4 but only has D1 simulated results). Calculate the standard deviation of blood glucose of D1 over the 24-hour duration. How large is the standard deviation of blood glucose in this situation compared to the corresponding standard deviation of blood glucose in D1 that you obtained in Q.4 (report as %)?See Answer
- Q14:6. [10 pts] Here, we assume that D1 uses a programmable insulin infusion pump, instead of the first one that was only able to generate a constant infusion rate. This new pump is capable of infusing insulin in rectangular pulses of different durations and insulin amounts at various times during the 24-hour period. Imagine you are subject D1, program your insulin pump to achieve the following goals: a) Bring your mean blood glucose level over 24 hours as close as possible to the corresponding level in Subject N; b) Reduce the fluctuation in blood glucose level (as measured by the standard deviation) to as low as possible over the 24 hours; and c) Minimize the total amount of insulin (in mU) infused over 24 hours, since insulin is an expensive drug. Explore a variety of insulin infusion patterns. After some trial and error, try to learn from the results what you think are the best strategies. Select the 3 infusion patterns that best satisfy the above criteria. For each pattern that you design, plot the trajectories of: i) glucose infusion, ii) insulin infusion, iii) blood glucose concentration and iv) blood insulin concentration over 24 hours of simulation. For each of these three selected cases, quantify the metrics that correspond to the 3 criteria (a, b and c) described above. Be sure you specify the formulas employed to arrive at each of the 3 criteria. Case N (from Q.4) I 24-h mean glucose conc. (mg/mL) 24-hr glucose conc. fluctuations (mg/mL) Total insulin infused over 24 hours (mU) Briefly justify why you chose these 3 patterns to be your "best 3", and what considerations you used to arrive at each pattern. Save the Simulink model, the best of the 3 cases, as glucose_D1_pump.slx.See Answer
- Q15:Submit your answer in a Word document via Blackboard. Question #1 (10 points): A research group conducted a study on factors influencing 5-year survival in breast cancer patients. They were particularly interested in patient's age and the number of positive lymph nodes removed during surgery. The following figure shows the data from 8 patients who survived after 5 years (the survivor group, green dots) and data from 9 patients who died within 5 years (the deceased group, red blocks). Please draw the decision boundary using the nearest neighbor method (k-1) based on Euclidean distance. Instructions: Identify pairs of closest data points from the survivor group and the deceased group. Draw a perpendicular bisector for each pair. Connect these bisectors into a continuous decision boundary. No of Positive Lymph Nodes 42 10 14 12 8 O + 2 IN 0 35 40 45 50 55 60 65 70 AgeSee Answer
- Q16:1. You are imaging two types of tissue. Image parameters are matrix size 256 x 256, FOV 5 cm, slice thickness 0.5 mm, one slice. Tissue A has T1=1310 ms, T2=70 ms, T2*=62ms. Tissue B has T1-850 ms, T2=115 ms, T2*-57 ms. Proton density is similar for the two tissues. Calculate the contrast between the two tissues for: a. A SE sequence with TR sufficiently long to allow full relaxation between successive lines of k space and a TE of 85 ms b. A GE sequence with a flip angle of 65 degrees, a TR of 450 ms, and a TE of 8 msSee Answer
- Q17:2. Assume that the RF pulse length is 10 ms, the dephasing gradients last 1 ms, PE blips last 0.2 ms, the rise time for the readout gradient is 0.3 ms, and the time between readout samples is 0.1 ms. a. Calculate the minimum echo time for a single-shot gradient echo EPI sequence with a matrix size of 128x128. b. What is the minimum echo time for a 4-shot sequence?See Answer
- Q18:3. Draw a pulse sequence diagram for a gradient echo imaging sequence that obtains 4 lines of kspace after a single excitation pulse. Show how kspace is sampled when an interleaved sequential scheme is implemented. Then draw a pulse sequence diagram for the same type of sequence to obtain images at 3 echo times after a single excitation pulse, and show how kspace is sampled. Is image contrast the same or different for the two cases, and why? 4. You are imaging a liver and need to cover a volume of 19.2 cm x 19.2 cm x 10 cm at a resolutionSee Answer
- Q19:4. You are imaging a liver and need to cover a volume of 19.2 cm x 19.2 cm x 10 cm at a resolution of 1 mm in all directions. Compare the minimum total acquisition time and the SNR for a 2D GE sequence and a 3D GE sequence, assuming all other parameters are constant. Name at least one reasonable factor that might lead you to choose one sequence over another other than time and SNR.See Answer
- Q20: Cardiac MRI lab #2 Background The heart moves significantly during contraction - with a motion greater than the size of the MRI pixel. If imaging is done during this motion, significant blurring and artifacts will occur. The cardiac motion is repeated every heart beat so the ECG signal can be used as a gating trigger. Additionally, the heart moves with respiration, as it is located on top of the diaphragm. This respiratory motion motion is significantly less repeatable than the motion due to cardiac contraction, so often cardiac sequences are done during a breath-hold. The subjects' breath-hold duration puts a real world limit on the length of the scan. The most basic method of creating images of the heart over the cardiac cycle (cine imaging) is using prospective cardiac triggering (using the R-wave in the ECG as the trigger) and acquiring k-space in the segmented manner. See attached papers for background (especially figure 3.15 and 10.10). This method requires a balancing of the number of time frames acquired, the image resolution, the TR, and the overall scan time. Pre-lab exercises/questions 1. Read the posted papers on cardiac MRI, especially sections starting on 149-158. 2. Calculate the optimal flip angle for SSFP based on published values of T1 and T2 for blood myocardium and fat. Note that we will be scanning at 3.0 Tesla. Lab exercises 1. A subject will be placed into the scanner and ECG lead will be attached. Observe the ECG signal outside and inside the MRI scanner. Do you see any difference? What would be causing the difference if you see anything? (we can grab a screenshot of the ECG signal) 2. Localizer scan will be performed. A segmented, gradient echo sequence will be loaded and planned in short-axis orientation. A scan will be done with a ≈12 second breath-hold (giving instructions to subject). The scan will be repeated without breath-holding. Describe the difference in the image and explain the artifacts in terms of motion and k-space. 3. Suppose you want an image with twice the resolution. Adjust the resolution parameters (first image lines, then FOV). What does this do to the image and why? What will this do the scan time and SNR? 4. Suppose the subject can only do a breath-hold of 6 seconds. What can you do to keep the higher resolution, but reduce the overall scan time? Define a relationship between resolution TR, number frames, image resolution, and scan time. 5. Go back to the original scan loaded. Change the flip angle based on values you cannulated in the pre-lab. Calculate the ratio contrast to noise between blood and myocardium for the three flip angle values (assume the noise is the same in all). Which flip angle would you use? Why? 6. Switch to retrospective triggering. Set the time frame at the same number acquired previously. Then set this to the maximum number of frames possible. What did this do to the scan time? How does prospective triggering work? What is the limitation of it? 7. Acquire a set of short axis slices covering the left ventricle. Calculate the ejection fraction. 8. We will do a few other scans (Look-Locker, Phase Contrast Flow, Angiography as we have time)See Answer
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