Magnetic Resonance Imaging In Soft Tissue Studies
Introduction
Magnetic resonance imaging (MRI) is a technique in radiology where internal structures are visualized in detail. MRI does not utilize ionization radiation like the traditional X-rays but instead it makes use of powerful magnetic field which aligns the atoms in the body then utilizing the radio frequency fields to alter the arrangement of the magnetic filed. The nuclei then produce a rotating magnetic field which is detected by the scanner to provide an image of the scanned area. Soft tissues are made up of connective, supportive and cushion tissues in the body such as the adipose tissue, tendons, skin and synovial membranes. The MRI has been the most preferred modality for soft tissue studies due to a number of advantages such as the good contrast which is provided between various soft tissues in the body.
Discussion
Method
The human body is made up of mostly water molecules which comprise of two hydrogen protons and an oxygen atom. These protons are essential during MRI procedures as the magnetic moments of the protons change to align according to the direction of the magnetic fields. The radio frequency transmitter of the MRI machine is then turned on briefly to produce an electromagnetic field. This field has photons with the right amount of energy called resonance frequency that flips the spin of the already aligned protons in the body (Choo, 2008). Similarly more spins are affected as the intensity and time span of the field increases until the field is turned off and the protons decay to their original spins such that the difference between these two states yields a photon. The photons are responsible for the production of electromagnetic signals which the scanner detects. The electromagnetic signals are dependent on the strength of the magnetic field and the amount of energy which was absorbed when the magnetic field was active (Bassen, et, al. 2005).
The images that are constructed after the photons have sent the electromagnetic signals are different in different tissues as the equilibrium states of the protons are often varied. Similarly, the protons return to their original state at various rates hence a major difference which is easily detected. The images of the different body tissues can be constructed by use of various variables which are altered to create the required contrast. The parameters are spin density, the relaxation times T1 and T2, flow and spectral shifts of the tissue. There are also other elements of enhancing the appearance of tumors and blood vessels such as intravenous injection of contrast agents. After incorporation of these measures MRI produces clear images for every part of the body especially the parts which have high hydrogen nuclei and little density contrast as is common in the soft tissues (Costelloe, et, al. 2007).
According to a recent research the MRI is a useful tool in identifying the recurrent soft tissue tumors from normal soft tissue mainly because of the excellent contrast resolution of the soft tissue. The recurrent tumors have been known to portray a signal intensity which is higher in the T2 images and the appearance is enhanced after use of the intravenous contrast agents. By using the MRI, the radiologist is able to construct images which differentiate between the tumor and post-therapeutic alterations in the soft tissues. Subsequent, imaging of the scars often shows reduced size or similarly the same size is retained. The understanding of the soft tissue imaging variations is dependent on prior knowledge of the primary tumor to evaluate the difference while knowledge of the typical imaging characteristics makes it easier to identify the nature of tumor in the soft tissue (Bassen, 2005).
When carrying out imaging of recurrent tumors by the MRI machine, there are advantages which are derived over existing imaging authorities such as identification of the extent of the diseases. This is made possible by the exquisite contrasting resolution of the soft tissue which enables the radiologist to point out the proximity of other vital structures. The other advantage is that the MRI modality can be used to detect minute recurrent nodules more explicitly than other techniques (Fernebro, et. al, 2006).
MRI modality an be used to determine the difference between soft tissues which are infected and those which have formed a healthy mass of soft tissue. The fluid signal of the abscess is demonstrated by the MRI is low on T1 weighted images while the T2 signal is higher especially with use of gadolinium which is introduced intravenously. This is essential in identifying infections on the bones where the synovial membrane or connective tissue has been infected. Such an image using MRI demonstrates the presence of osteomyelitis which is an extensive inflammation of the soft tissues around the bones (Choo, 2008).
ients undergo extensive imaging of the tumors such as the establishing the growth pattern of the tumor. The MRI machines exhibits various growth patterns of the tumor for instance infiltrative where the tumor has an irregular surface. The other radiography modalities were unable to point out such fine details of tumors as was shown by the MRI (Teh and Whitely, 2007).
Research has shown that in the imaging of soft tissue anterolateral impingement of the ankle, use of contrast agents and fat-depressed elements which increase appearance of the image. Therefore, for patients who undergo routine radiography, the physician can take note of their progress by examining the MRI images of the soft tissue in their ankles (Costelloe, 2007).
Results
MRI imaging is widely used in soft tissues due to the high number of hydrogen protons in the tissues which makes it easier for the electromagnetic field to be produced hence yielding signals. In the other body tissues such as the skeletal tissue, the number of hydrogen nuclei is limited hence making it difficult for the MRI magnetic field to get spin the protons. This is probably one of the reasons as to why MRI is not explicitly used in other tissues as the ability of its magnetism to produce similar contrast is highly inhibited (Choo, 2008).
Based on past research on MRI and other imaging modalities, improvement on the nature of images formed after using the MRI technique. This is exhibited by the fact that not only are the tumors identified in the soft tissues but also the attributes of the tumor are singled out. Other characteristics of the soft tissues that were attained from the MRI tests include the margin, size, internal architecture and patterns which are presented by the tumors. All these attributes were made clearer by incorporation of contrast agents intravenously. Of all proposed contrast agents, gadolinium had the most impressive enhancement hence it was widely used by all the MRI research radiologists. The ability of gadolinium to blend easily with the existing cell sap and low solubility enhances chances of making the tumors more distinct when the MRI is being carried out (Teh, 2007).
Other than enhanced appearance of the tumor images after using MRI, the other most notable attribute of the modality is ability to distinguish between two abnormal masses of cells in the body. This is a rare occurrence as most imaging machines would not be in a position to distinguish between two or more closely related objects of concern. The fact that the MRI can differentiate between an abscess and a tumor with almost the same physical appearance depicts the high degree of contrast in the resolution of the image produced by MRI (Fernebro, 2006).
Discussion
The findings obtained in the results section shows that the MRI not only has a high resolution contrast in soft tissues imaging but that it also enables the radiologist to gain access to other attributes of the anomalies present. This is supports the thesis which has already pointed out that MRI is widely used in soft tissues whereas justifications on the thesis have been proven as valid (Costelloe, 2007).
Similarly, the results obtained were expected as recent and past researches on soft tissue imaging have demonstrated increased use of MRI. This and other studies on the use of MRI as the most reliable imaging modality laid the foundation of the most probable increased usage in soft tissue thus implying that more researchers are studying the relationship between MRI and soft tissue studies (Choo, 2008).
Further research is equally vital in this area to evaluate the impact of MRI on normal tissues as well as use of other contrast agents. This is because some radiologists may have no access to gadolinium or fat-suppressed 3D-FSPGR while other equally helpful agents may be available. Consequently, this study was only inclined on the stuffy of soft tissue tumors with no study on normal soft tissue. The other limitation in the study is on the limited role of the MRI in soft tissue studies as it only shows the anatomy of the tumor, as well as, its surrounding but not its histological traits. Hence MRI alone cannot be used in the soft tissue studies as other imaging modalities should be incorporated to complete the studies (Teh, 2007).
Conclusion
In conclusion, MRI is the most preferred modality in soft tissue studies as it portrays the highest degree of resolution contrast as compared to that of other imaging techniques. Various studies have been conducted using the MRI to identify tumors and surrounding tissues to treat various malignant, as well as, begnin growths. However, more research needs to be carried out in the area to identify other advantages of using MRI in soft tissue studies over use of other modalities.
References
Bassen, H; Schaefer, D J. ; Zaremba, L; Bushberg, J; Ziskin, M [S]; Foster, K R. (2005). “IEEE Committee on Man and Radiation (COMAR) technical information statement “Exposure of medical personnel to electromagnetic fields from open magnetic resonance imaging systems””. Health Physics 89 (6): 684–9.retrieved on November 27, 2010 from: doi:10.1097/01.HP.0000172545.71238.15
Choo, J.H., Suh, J., Huh, Y., Kim, S., Kim, M. and Lee, J. (2008), ankle MRI for anterolateral soft tissue impingement: increased accuracy with the use of contrast-enhanced fat-suppressed 3D-FSPGR MRI. Korean Journal of Radiology, vol. 9. pp.409-415. retrieved on November 27, 2010 from: synapse.koreamed.org/Synapse/Data/PDFData/…/kjr-9-409.pdf
Costelloe, C. M., Yasko, A. W., Murphy, W. A. R. Kumar, V. O. Lewis, P. P. Lin, R. J. Stafford & Madewell, J. E. (2007), (MRI Of Locally Recurrent Soft Tissue Tumors Of The Musculoskeletal System . The Internet Journal of Radiology. Volume 5 Number 2
Fernebro, J, Wiklund, M., Johnson, K., Bendahl, P., Rydholm, A., Nilbert, M. and Engellau, J. (2006), focus on the tumor periphery in MRI evaluation of soft tissue sarcoma: infiltrative growth signifies poor prognosis. Retrieved on November 27, 2010 from: doi: 10.1155/SRCM/2006/21251.
Teh, J. and Whitely, G. (2007), MRI of soft tissue masses of the hand and wrist. The British Journal of Radiology, vol.80, pp. 47-63. Retrieved on November 27, 2010 from: doi:10.1259?bjr?53596176
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