Anatomy in Magnetic Resonance Imaging - Assignment Example

1- Femoroacetabular Impingement (FAI) can be an indication for MRI of the hip. Define and discuss this condition. FAI is a condition of abnormally shaped hip bones that do not fit perfectly together as shown in figure 1. As a result, they rub against each other damaging the joint. Hip refers to the ball-and-socket joint formed by acetabular; upper end femur. The Articular cartilage is a slippery tissue that covers ball and socket surface. This creates smooth and low friction surface that enhances easy gliding of the bones (Abe, Harada, Oinuma, Kamikawa, Morita and Moriya 2000, p.576-581). The strong fibrocartilage known as Labrum rings the acetabular forms a gasket in the socket. This creates a tight seal that improves stability of the joint. Figure 1: FAI of the Hip Source: Maeurer, J., & Flaig, W. (2004). Imaging strategies for the shoulder Often, an MRI of the hip acts as confirmation for damage or labral tears to the joint surface. The acquisition of scans in orthogonally planned coronal, sagittal and planned axial planes. Results of the scan indicate true parallel slices of unique anatomical perspective. The orthogonally planned slices normally compromise the acetabular circumference resulting into partial anatomy volume. Radial imaging is remarkably accurate when used in diagnosis of the acetabular labral lesions (Motoyuki and Toshikazu, 2000). MRI is useful in eliminating some causes of the non-FAI hip pain like tumors and vascular necrosis. Normal MRI does not prevent the cartilage injury, FAI or labral tears. Mostly, the Supine AP Pelvis view and the Hip Cross Lateral View enhance the diagnosis. An MRI must be ordered as a right or left hip study taking into consideration the intra-Articular gadolinium inside the contrast dye and the pain test (Rakhra, Sheik, Allen, and Beaule 2009, p.660-665). Typically, pain test entails placing a local anesthetic into the hip joint containing the contrast dye, and the pain test enhances the assessment of whether the pain is from the hip joint. MRI consists of a labral tear, which comprises of a thick labrum that does not have any recesses. There also tends to be increased signal intensities when it comes to T1 imaging, as well as a labrum whose shape is irregular. It becomes challenging to clearly distinguish discrete labral tears that may be found on MRI. Surface coil plays a crucial role in the imaging of the hips. Bony abnormalities within the within the hip joint can be detected through MRI arthography; it also helps in the diagnosis of tears that may be found in the acetabular labrum (Keogh & Batt 2008, p.873). The femur’s round head comes into contact with acetabulum. There are two types of impingement that pinch the soft tissue. These are cam type and pincer type impingements. The cam-type impingement results when the roundness of the femur’s head is not as expected, and it becomes more of the pistol grip in shape. This results to shearing force on Labrum and Articular cartilage. This can occur by itself or as a result of problems with the hip. On the other hand, the cam-type impingement is most common among women, and can be caused by hip dysplasia, complication after the osteotomy, or it can be as a result of retroversion. After the detection of chondral abnormalities, the alterations ought to be performed in the subchondral bone; this may entail the subchondral edema development, as well as sclerosis and cysts development (Cahir 2007, p. 1163-1171). 2- Discuss coil selection and describe how you would position a patient for MRI of hips. Easy achievement of positioning of the patient happens by either putting the feet-first or head-first on the table. The choice is dependent on the patient’s comfort for an MRI scan. Several options are available for using the coil. Actual choice depends on availability at the site. The feet of the patient should be turned inward to pronate the trochanters, and the position should be supported using the Velcro straps wrapped on the feet. The placement of sponge happens between the ankles in order to maintain an inward position for the feet and toes. The intravascular interventions guided by MR require the rate of update of approximately ten images a second (Rakhra, Sheik, Allen, and Beaule 2009, p.660-665). This can be achieved through parallel imaging that requires several coil elements. This increases the reconstruction time and compromises the reconstruction in real time. Dynamic coil selection algorithm selects a subset of the received coils in order to reduce the reconstruction times for the image. Centre-of-sensitivity coordinates the intensities for the relative signals should be determined for each coil during the prescan (Karantanas 2005, p. 22-31). In coil selection, planning for radial scans requires a significant number of scans carried out to correct complex anatomical angulations for the acetabulum, as well as providing the geometric angulations and offsets for sequences. The performance of angulations and offsets happens in radial sequence in such a way that radial axis is perpendicular to acetabulum. Planning produces a series of images that demonstrate the acetabular Labrum, acetabular at the incremental angulations and the femoral head. Several methods enhance planning for a radial scan. The preferred method uses two initial surveys as well as a radial survey (Cho 2000, p. 214-30). The two initial surveys required should be of high quality for clear demonstration of the anatomical detail. The surveys are on out in coronal slices and in orthogonal true axis that may be combined in a multi-stack sequence. The selection of coronal and axial slices shows the acetabulum midpoint to plan the radial set-up survey with the double angulations. Red arrows usually indicate the acetabular points used in aligning radial set-up survey that provides double-edged angulated view for the femoral head. This contains all the angulations required for the radial scan (Cahir, M. (2007, p.1163-1171). The intervention coils come from the reconstruction with the use of coil ranking, which tends to be based on current slice distance. Hip MRI appearance tends to vary with regard to the sequence acquisition, as well as the skeletal maturity for the patient (Abe, Harada, Oinuma, Kamikawa, Morita and Moriya 2000, p.576-581). Sequence cortical bone tends to produce a black and thin line at the cavity of medullary in the acetabulum and femoral cavity. In the case of adults, the epiphysis contains the fatty marrow resulting in high signal for the pulse sequences (Cahir 2007, p. 1163-1171). 3- "Tennis Elbow" is a common indication for elbow MRI. Define and discuss this condition. Tennis elbow, also known as lateral epicondylitis, is an injury that causes pain at the outside bump of elbow. As a result of tennis elbow, the muscles at the forearm bend the wrist that in turn connects muscles to the bone (shown in figure 2). As such, the muscles act by pulling on one end of tendon, they can build up after gripping something like hitting a tennis ball in backhand swing and other similar actions (Kroslak and George 2007, p. 75-79). Based on studies, tennis elbow is caused by extremely small racket grip that increases the working of the muscles, extremely tight strings that increase energy and shock transmitted to the forearm, playing with wet heavy balls and repetitive activities like painting and typing. Diagnosis of tennis elbow cannot be achieved through blood tests. As such, the diagnosis of tennis elbow entails prescription of pain around the elbow after which the doctor gives the prescription for the appropriate medication. The prescription of the appropriate medication is crucial as it helps in treating the condition (Kroslak and George 2007, p.75-79). Figure 2: Tennis Elbow Source: Maeurer, J., & Flaig, W. (2004). Imaging strategies for the shoulder It is crucial to state that the overuse of tendons and muscles of elbow and forearm may lead to the development of tennis elbow. The repetitive activities may strain the elbow tendons. Such activities do not comprise the high level sports. Acute injury involves the body undergoing an inflammatory response. The inflammatory cells migrate to the injured tissue to enhance healing. Nevertheless, tennis elbow does not involve inflammation. The problem involves problems with the tendon cells (tendonitis) that involve wear and tear, leading to degeneration of the tissue. Studies show that degenerated tissue comprises of abnormal arrangement for the collagen fibers (Kroslak and George 2007, p.75-79). It is worth noting that the human body produces fibroblasts cells that make the collagen lose the strength; it becomes fragile and may easily break under injury. After the breaking of the collagen fibers, the body responds through the formation of scar tissue within the tendon. Eventually, there is thickening of tendon from the extra scar tissue. Tennis elbow causes tenderness and pain from the lateral epicondyle of elbow and spreads down to the forearm and may go back to the middle and the ring fingers. The muscles at the forearm may feel sore and tight. The pain worsens after bending the wrist backward, holding something or turning the palm upwards. The diagnosis involves physical diagnosis of the tennis elbow and X-ray. For unclear diagnosis, MRI scan plays a key part by using exceptional imaging test, which uses the magnetic waves for creating pictures for the elbow in slices. MRI scan indicates both the tendons ad bones (Morrey & Sanchez-Sotelo, 2009). 4- Discuss coil selection and describe how you would position a patient for MRI of an elbow ? Positioning of the patients and choice of proper coils for the MRI study is essential in minimizing motion artifact. This helps achieve motion artifacts, as well as obtain an optimum value for signal-to-noise ratios. GE normally offers a variety of coils to be selected. Imagination and expertise enhance the identification of the coil for each application. Coil selection entails matching the coil to the underlying anatomy in order to optimize SNR for desired scan time. FOV should be matched to coil size to avoid aliasing of outside FOV signals to FOV when the receiver coil is larger than FOV (Berquist 2013, p. 706-710). The coil type used, gantry limitations, as well as the clinical status, can cause suboptimal examinations in the upper extremity. Confining nature of the highest field strength reduces the options in positioning. Imaging may be accomplished with the open lower field strength or the extremity units. The 1.5 and 3.0 units are the most common for elbow examinations (Müller, Reiner, Peter, Sven Sebastian, Wolfhard, and Michael 2006, p.1156-62). Normally, coils help achieve superior image quality. The selection depends on investigated patient’s position and body part. For instance, research on the shoulder lesion happens to use large multichannel phased array coil that includes the upper extremity area. Circumferential volume extremity coil gives a signal with greater uniformity, which must be positioned in the centre of gantry containing most imagers. It is crucial to understand, manipulate and recognize the coil to avoid and reduce the coil-induced artifacts that can appear in the images. Improper patient position, improper coil usage, poor selection of FOV and wrong configuration of the coil act as principal causes for image artifacts and proper selection of the coil eliminate such disadvantages (Müller, Reiner, Peter, Sven Sebastian, Wolfhard, and Michael 2006, p.1156-62). For examination of elbow, there are recommendations for additional surface coils. The can be circular or flat with 6-8cm diameter Patient positioning for elbow MRI is dependent on the equipment available. A patient is comfortable supine more than prone. The numerous motion artifacts derail the prone positioning. The arm should be elevated above the head, essentially achieved through unrestricted motion for elbow and shoulder. The arm should be placed along the body with lower arm in Pronation. The palm of the hand must be rested on the thigh, especially for long examinations. The cushions for head and shoulder are critical to improve compliance on the patient and control the motion artifacts at the lower section. The overhead position enhances positioning of the elbow near the epicenter for the magnetic field. The positioning of the elbow can be achieved with arm overhead at oblique positioning of the patient (Kroslak, M., and George 2007, p.75-79). 5- Calcifying tendonitis of the rotator cuff is a common disorder. Discuss: (a) Clinical presentation; (b) Development and course of this entity; (c) Appearance on Xray and MRI. Calcific tendonitis refers to calcium disposition (hydroxyapatite crystal) in the tendon, especially the Rotator cuff. This can be secondary to local decrease in the tension of oxygen due to fibrocartilaginous metaplasia that eventually results to calcification. The clinical presentation varies where the condition acts as self-limiting. The symptoms may last for some days and can be chronic. The prediction of the causes of diseases is not clearly defined. Time required for the disappearance of the symptoms is considerably longer for QoL patients. The clinical manifestation is sub-acute with low-grade pain on the shoulder, which increases during the night (DFlemming 2001, p. 965-972). The chronic phase involves the presence of calcific deposits asymptomatic while the acute painful phase involves the disability, severe pain and nocturnal discomfort. The mechanical phase results to impingement of the tendon and decreased pain as compared to the acute phase. The progression of calcific tendonitis is predictable, and it eventually resolves without surgery. The typical course involves three key phases (Splete 2007, p. 1-23) Precalcification Stage This stage there is no symptoms on the patient. The development site for the calcifications undergoes cellular changes, which predispose tissues and allow for development of calcium deposits. Calcific Stage: Involves the formative, resting and resorptive phases This phase is characterized by coalescence of calcium excreted from the cells to form calcium deposits. This is referred as formative phase Calcium has a chalky appearance, and after calcification, the resting phase begins. This is not painful and may last for a considerable amount of time. Resorptive phase begins immediately after the resting phase, and it is the most painful stage of the calcific tendonitis. This phase is characterized by calcium deposits appearing like toothpaste. Patients seek treatment at this painful resorptive phase while some have the deposits identified during the evaluation of impingement syndrome (Mitsui et. al. 2012, p. 1-4). Postcalcific Stage This phase is painless. The calcium deposits disappear and are replaced by the normal cuff tendon. Development and course of calcifying tendonitis entity Other shoulder pathologies should be ruled out since Calcific tendonitis can only be diagnosed through imaging since it is an injury to the soft tissue. The initial stages entail anteroposteriorly view in the internal, neutral and external rotation. Normally, imaging enhances the rule out of other pathologies by providing definitive proof for the build-up of calcific on the bone spurs. Ultrasound done rules out the differential diagnosis on the soft tissue like the Rotator cuff tear. Some of the cases are bilateral while others are symptomatic. Identification enhances treatment and decreases the possible expenses of the patients on future visits. The physical examinations help in rule-out of conditions rather than rule-in. Most systematic diseases result to increased risk for calcification like hypercalcemia, rheumatic and gout (Bittmann 2004, p.180-181). Some of the complaints include night pain, constant dull ache, increase in pain with increased AROM stiffness complaints and radiating pain in the sub-occipital region (Splete 2007, p. 1-23) Appearance of calcifying tendonitis on X-ray and MRI The x-ray appearance of calcium happens in the Rotator cuff tendon. Calcium resolves and accumulates simultaneously among most patients (shown in Figure 3 below). However, some patients end up having the Rotator cuff tear with the compromise of calcium to the tendon structure. Good stretching should be followed in order to keep with full ROM. The calcific deposits entail the cloudy areas or lumps. Cloudy areas appear when the when the calcium is in the re-absorption process during which the pain is extremely intense. The lumps appear when calcium is in the resting phase. Poor correlation happens between appearance of the calcific deposits on ordinary x-rays and the consistency on needling (Splete 2007, p. 1-23). Figure 3: X-ray Appearance of Calcifying Tendonitis (Source: Maeurer, J., & Flaig, W. (2004). Imaging strategies for the shoulder. Contrary, the appearance on magnetic resonance imaging, MRI indicates elongated T1 and T2 hypo intense signal in supraspinatus tendon in its proximal to insertion at high tuberosity. A calcific density of specified measurements is evident (shown in figure 4 below). Epiphysis is usually intact with the fracture of the bone. A T2 hyperintense signal records for the supraspinatus muscle and the sub deltoid-sub acromial soft tissue that indicates an oedema. T1 entails the hypo-intense homogenous signal, enhancement surrounding the deposit and thickening of adjacent tendon while T2 involves the hypo-intense calcium deposits, hyper-intense sub acromial-sub deltoid bursal fluid and the hyper-intense signal in peripherally due to the oedema. On the other hand, T2* show blooming calcifications (Maeurer and Flaig 2004, p.130-135). Figure 4: MRI Appearance of Calcifying Tendonitis Source: Maeurer, J., & Flaig, W. (2004). Imaging strategies for the shoulder References List Abe, I.. Harada, Y., Oinuma, K., Kamikawa, H., Morita, F. & Moriya, H. (2000). Acetabular Labrum: Abnormal Findings at MR Imaging in Asymptomatic Hips. Radiology 216: pp. 576-581. Bittmann, O. (2004). Calcific tendonitis of the supraspinatus tendon in children. Euro J Orthop Surg Traumatol 14. pp. 180-1. Berquist, T. H. (2013). MRI of the musculoskeletal system, Philadelphia, Wolters Kluwer/Lippincott Williams & Wilkins Health. Pp. 706-710. Cahir, M. (2007). CT and MRI of Hip Arthroplasty. Clinical Radiology 62 (12), pp. 1163-171. Cho, K. (2000). Ultrasound of the Adult Hip. Seminars in Ultrasound, CT, and MRI 21.3: pp. 214-30. DFlemming, M. (2001). Osseous Involvement in Calcific Tendinitis. A Retrospective Review of 50 Cases. Am. J. Roentgenol. 181(4): pp. 965 - 972. Karantanas, A. H. (2005). Imaging of Hip and Groin Athletic Injuries." 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Calcific Tendonitis of the Rotator Cuff: An Unusual Case, Case Reports in Orthopedics, Vol. 2012, pp. 1-4. Rakhra, K. S., Sheik, A. M., Allen, D., and Beaule, E. P. (2009). Comparison of MRI Alpha Angle Measurement Planes in Femoroacetabular Impingement, Clin Ortho Relat Res. 467 (3): 660-665. Splete, H. (2007). Needling Resolved Calcific Tendonitis. Family Practice News 37 (24), pp. 1-23. Read More