Magnetic Resonance Imaging of Bone Marrow: A Systematic Diagnostic Approach - Essay Example

? MRI TECH ESSAY SUBMITTED BY: ---------------------- An effective combination of certain pulse sequences is utilized to determine the normal bone marrow appearance in MRI. It also helps to determine the sensitivity and specialty for diagnosing the disorders. Single or combined sequences of MR pulses such as (a) Spin echo T1 weighted, (b) T2 weighted fat saturated fast spin echo and (c) Short Time Inverse Recovery sequence (STIR) to determine the bone marrow compositions and the abnormalities. ( Feller, 2002) The yellow or fatty marrow has a composition of 80 % fat, 15 % water and 5 % protein. Therefore, with T1 weighted MRIs, the images will appear to be bright (high intensity). This is because the major composition of yellow marrow is fat and fat possess very short T1 relaxation phase. The red or hematopoietic marrow is framed up with 40% of water and fat and 20% protein. Water holds a longer T1 relaxation phase and therefore, the images of red marrow is low intense or dark in nature due to very low signal intensity. The diagnoses of bone marrow lesion on yellow marrow background are effective using T1 weighted MRIs but it can be difficult with the case of lesion on a red marrow. With T2 weighted images, the red marrow and yellow marrow cannot be easily distinguished. STIR is more effective than T2 weighted spin images. (Dimopoulos, Moulopoulos, 1997). The figure shows dark signals highlighted with small arrows that indicate the red marrow in the spinal region and bright signals highlighted with long arrows indicates yellow marrow around femoral epiphyses as well as apophyses. This is an image of a normal bone marrow of a child. (Dimopoulos, Moulopoulos,1997). An abnormal situation characterized by severe pain and irritation in the knee as a result of high level of pressure offered from patella or kneecap is referred as Chondromalacia (cluett, 2010). The patella is normally covered with a smooth layer composed of cartilage. The cartilage moves effortlessly and flexibly across our knee and thus, facilitates easy bending of the knee joint. The case is different with patients affected with chondromalacia wherein the patella inclines to rub against one or another side of the joint. This results in irritation and pain in the knee. Chondromalacia patella symptoms include distributed knee pain mainly in the front and back side of knee cap. It is accompanied with worsening of pain while arising from an elongated sitting posture, climbing upstairs, wearing heels, kneeling or jumping. (Cluett, 2010) MRI appearance of chondromalacia comprises of signal heterogeneity surrounded by hyaline cartilage, predominantly with T2 weighted MR images, hyaline cartilage covered focal hyperintensity, mainly showing linear or focal abnormalities in the hyaline cartilage and asymmetrical configuration to the hyaline cartilage surface. It is required to use the modifier “severe” when variations that are greater than one cm in diameter are observed. If high density central defects are present then also the severe modifier need to be used. These defects can be distinguished from usual chondral defects by comparing the centralization of the final lesion that are widely spread and lacks surroundings (Loren, 2008) Full thickness chondral defect is appeared with high signal joint surface lesion represented in black arrow is covered by normal low intense hyaline cartilage on this spin echo T2 weighted image. (Loren, 2008) Osteochondritis dessecans is a medical condition that arises when certain amount of cartilage in a joint connected with a thin boney layer separates from the rest of the bone. The affected person usually experience server pain, irritation and discomfort near a bone ending position. (Kennedy, no date) OCD is usually seen with larger joints such as the hips, knees and the ankles. The condition is also accompanied by severe rib pain. In association with rib pain, the uneasiness normally occurs in breastbone or in the spine where the ribs get connected. The major cause of OCD is certain type of repetitive injury or stress that makes a joint damage. An injury caused due to an automobile accident may also lead to rib discomfort or pain with OCD. This abnormal condition occurs with repeated stress or blows around a period of time, which ultimately ends up with pain. Heredity and blocked blood circulation are other factors that lead to OCD. Osteochondritis normally affects the teenagers and youngsters who actively participate in sports and games and have experienced repeated injury and stress that resulted in traumas. (Kennedy, no date) MRI is the best choice to detect OCD of various stages. With MRI T2 weighted scan, a major sign of OCD with unstable lesion is represented by an increased signal intensity layer between the cartilage and the underlying bony layer. Appearance of joint fluid with hyper intensity of signal passing across the subchondral bone place also shows abnormality evident to an articular fracture. A fluid filled cyst appearing with T2 weighted images can also reperesent an unstable osteochondritis dessicans. The MRI system is appropriate to differentiate intact cartilage lesions from that of linear lesions with cartilaginous defects, namely tears, clefts or fissures. The intravenous administration of a contrast agent typically gadolinium is enhanced additionally with MR technique to assess OCD perfectly. The gadolinium administration helps to augment the signal strength between the Major bone and the fragment that evidently depicts loose section and the primary underlying granulation cells. (Kijowski, De Smet, 2004) The figure shows an area of low signal strength on T1 weighted sagittal MRI image and represents osteochondritis dissecans and inflammation. (Kijowski, De Smet, 2004) Majority of scanning centers perform the MRI technique for metatarsal scan by making the patient lying on supine position and by placing the foot in a position that is neutral and with toes that points to upward directions. Another possible method to investigate the metatarsals is to make patient lay in prone position along with a plantar twisted foot. The second position compared with the first proves to be more advantageous because it prevents motion artifacts directly from the toes. (Beggs, no date) Another main advantage of the prone position is that the metatarsal defects especially the Morton neuromas appears clearly when the foot remains plantar flexed while the patient lies in prone position. The flexed joint makes the traction forces to drag the neurovascular bundle that carries the Morton neuroma much deeper to the metatarsal interior space. This in turn gives a way for more extension space amid the metatarsal heads. This is the reason for wider and clear appearance of metatarsal disorders in a prone plantar flexed position. (Weishaupt, Zanetti, 2005) Achilles tendon forms the largest as well as the strongest tendon in our body that connects the calf muscles to the calcaneum. The gastrocnemius and soleus muscle in the body bond together to form the Achilles tendon. These muscles along with Achilles tendon are located in the posterior exterior section of the calf region. The Achilles tendon plays a major role in facilitating us to stand upon our toes and to support us while walking, exercising, playing, jumping and running. It holds a typical length that varies from 3 to 11 centimeters. (Karasick, Schweitzer, 2000) To examine the archilles tendon, make the patient lie down in prone position and keep the foot outside the examination table in a hanging position. With this particular position can compare the two sides to notice significant changes. The position also helps to examine the tendon form the myotendinous junction leading to the calcanear intrusion with respect to the longitudinal and transverse planes. To put forward the Achilles tendon for scanning, remember to place it on short axis planes in order to evaluate peritendinous envelope on either side by tilting the probe. The foot while scanning needs to be extended to about 15 to 30 degrees for exact results. (Karasick, Schweitzer, 2000) Normal MR appearance of Achilles tendon represents 4-7 mm thickness, a semi-circular shape and 12 to 25 mm width. It is usually dark on all types of imaging. The MR appearance of acute Achilles tendonitis signifies the Achilles as distally thickened with unclear and nonspecific longitudinal hyper intensity. The figure below shows a case with insertional tendonitis seen on an adult male runner. The axial T2 weighted images that are fat suppressed shows vaguely coagulated distal tendon with lateral insertional signal. This is represented with short arrow. The solid arrow represents extreme retrocalcaneal bursitis and long arrows shows peritondonitis. (Karasick, Schweitzer, 2000) A case of acute tendonitis. (Karasick, Schweitzer, 2000) The patient presented for an MRI of mid femur is asked to lie down in supine position. The body array coil as well as the wraparound coil is utilized when the tumors are large in size. It is advisable to utilize proper surface or volume coil while positioning the patient. Ensure that the femur is centered on to the film. The legs need to be cushioned to offer comfort to the patient. There are various MR protocols suggested by the professionals to evaluate soft tissue mass and sarcomas in mid femur region. Due to the high intrinsic soft-tissue contrast of MR images, the soft-tissue masses are invariably seen on MR images without the utilization of intravenous gadolinium contrast agents. For the assessment of soft-tissue masses on MR images, an intravenous contrast agent is introduced to distinguish the cystic from the solid structures, to show the relative vascularity of the soft masses, and to help point out the tissue planes to enhance in assessing the correct degree of invasion of the mass into the vessels and other structures. (Wu, Hochman, 2009) 1. The first protocol includes the STIR or TIRM: This forms the first sequence that is coronal crosswise both the extremities. Make arrangements for an oblique style predestination for better comparison. STIR can be included for single investigations. For instance, For 1.5 and 1.0 T, indicate TR is 6500, TE is 14, T1 be 140 then arrange flip angle as 180 degree. For 1.0 and 0.5 T, let TR be 1600 to 2000, TE be 60, TI be 100 to 140, then arrange flip angle to 90 degree. Another option with sequence, we can select T2 weighted imaging, which is fat-saturated. In this sequence, input the TSE, FS values; TR between 2000 to 3500, TE between 90 to 100, slice thickness of 4-6 mm, twenty percentage of the slice thickness as slice gap, FOV: 450 to 500 mm. Set the saturation slab with a position that is axial higher to the saturation slices of the vessels. 2. Sequence two forms T1 weighted imaging: This is represented with TR between 450 to 600, TE between 10 to 25, 4 to 6 cm slice thickness, and slice gap around 20 % of the thickness. Saturation slabs same as that of the previous case that is the axial superior. 3. Sequence three forms T2 weighted axial imaging, where TR is 2000 to 4000, TE 100 to 130, slice thickness is 6 to 8 mm, slice gap forms 20 to 50 percentage of the thickness. FOV is 450 to 500 mm. The saturation slab is placed axial or parallel and superior to the saturation slices of the vessels. 4. Sequence four forms T1 weighted sagittal, where TR is represented with 450 to 600, TE 10 to 25, 6-8 cm slice thickness and slice gap is 20 percentage of the slice thickness. A phase encoding AP or HF gradient with oversampling effect is induced. FOV of 350 to 380 mm without any saturation slab. 5. Sequence five is same as sequence four but a contrast agent is administered before the scanning. The agent is GD-DTPA in the amount 0.2 mm ol per kg body weight. 6. Sequence six forms T1 weighted axial imaging with fat saturation along with contrast. 7. Coronal t1 and sagittal t1 post contrast. (Wu, Hochman, 2009) Specific criteria are administered to stage soft tissue sarcomas or tumors and they include the size of the tumor, status of the node, grades and the metastasis. These factors help to evaluate the sarcoma staging to help induce the adequate treatment plans. The lesion is marked with respect to grades G0 to G2. This is done in association with the histological as well as radiological appearance. The size of the lesion is calculated based on T0- to T2. If the lesion is restricted to its capsule, it is marked as T0. If it is extracapsular and restricted to its compartment of origin then it is marked as T1. An extended leision is marked as T2. Similarly, metastasis is represented from M0 to M1. The MRI staging needs to be performed before the biopsy. This is because an inflammation or bleeding inside the tumor or in the nearby tissues could lead to overestimation of the staging and results in confusion in identifying the tumor history. (Wu, Hochman, 2009) References 1. John. F. Feller. (2002), “MRI of Bone Marrow” Advanced MRI from Head to Toe. http://mri.cpson.com/pdf/MRI_of_the_Bone_Marrow.pdf, accessed on May 10, 2011 2. Moulopoulos. Lia, Dimopoulos. Meletios. (1997). ”Magnetic Resonance Imaging of the Bone Marrow in Hematologic Malignancies” JOURNAL OF THE AMERICAN SOCIETY OF HEMATOLOGY. http://bloodjournal.hematologylibrary.org/content/90/6/2127.fullaccessed on May 10, 2011 3. Taccone A, Oddone M, Dell’ Acqua A, Occhi M, Ciccone MA. MRI “roadmap” of normal age-related bone marrow. PediatrRadiol 1995; 25:596–606 4. Cluett, Jonathan. “ Chondromalacia,” November 05, 2010, post on blog Orthopedics, http://orthopedics.about.com/cs/patelladisorders/a/chondromalacia.htm, access on May 11, 2011. 5. Loren, Karl. “Standard Magnetic Resonance Imaging of the Knee,” May 20, 2008, post on blog Orchacliation, http://www.oralchelation.com/calcium/DegenerativeKneeJoint/p1.htm, accessed on May 10, 2011. 6. Kennedy, Neal. “Osteochondritis Dessicans-What Is It, Why Does It Cause Ribcage Pain?”. Post on blog Articlesnatch. http://www.articlesnatch.com/Article/Osteochondritis-Dissecans---What-Is-It--Why-Does-It-Cause-Ribcage-Pain-/1675277, accessed on May 10, 2011. 7. Kijowski. Richard, De Smet. Arthur, “MRI Findings Of Osteochondritis Dissecans of the Capitgellum with Surgical Correlation.” December 6, 2004, post on American Journal of Roentgenology. http://www.ajronline.org/cgi/content/full/185/6/1453?maxtoshow=&HITS=10&hits=10&RESULTFORMAT=&fulltext=Osteochondritis+Dissecans+&searchid=1&FIRSTINDEX=0&sortspec=relevance&resourcetype=HWCIT. Accessed on May 11, 2011. 8. Beggs. Ian. “Musculoskeletal Ultrasound Technical Guidelines,” European Society of Musculoskeletal Radiology. (no date) http://www.essr.org/html/img/pool/ankle.pdf, accessed on May 10, 2011. 9. Karasick. David,, Schweitzer. Mark .E, “MR Imaging of Disorders of the Achilles Tendon,” Department of Radiology. February 24, 2000, post on American Journal of Roentgenology. http://www.ajronline.org/cgi/content/full/175/3/613#SEC9, accessed on May 11, 2011. 10. Witschey WR. T1? MRI quantification of arthroscopically-confirmed cartilage degeneration, MRM (in press) 11. Weishaupt. Dominik, Marco. Zanetti., “MR Imaging of the Forefoot: Morton Neuroma and Differential Diagnoses,” November 3, 2005. http://www.hopkinsradiology.org/bin/a/r/mortonneuroma.pdf, access on May 11, 2011. (Weishaupt, Zanetti, 2005) 12. Wu. S Jim, Hochman. G. Mary, “Soft Tissue Tumors and Tumorlike Lesions: A Systematic Imaging Approach.” November 2009, posted on Radiology Journal. http://radiology.rsna.org/content/253/2/297.full, accessed on May 11, 2011. 13. Tirman. Philip. F.J, “ MRI of Soft Tissue Tumors and Tumor Mimickers,” http://mri.cpson.com/pdf/MRI_of_Soft_Tissue_Tumors_and_Tumor_Mimickers.pdf, accessed on May 11, 2011. Read More