| Abstract: |
Sonography is perhaps the first modality available, cheap non time consuming, non-invasive, most definitive method for distinguishing cystic from solid lesions, capable of establishing the presence of multiple small nodules in the gland, presence of calcifications together with other multiple Sonographic finding raising possibility of malignant thyroid lesions. The disadvantage of this technique is its limited penetration in some anatomic locations, such as retrosternal and substernal areas and limited field of view for assessing large masses and retrosternal extension.Color Doppler imaging is an adjuvant modality together with US done at the same setting that combination of both have proved to be extremely helpful in raising rates of sensitivity, specificity and accuracy in differentiation between benign and malignant natures and also provide to be extremely helpful in reduction of performance of scintigraphy and fine needle aspiration biopsy.The evaluation of the thyroid diseases requires the evaluation of both anatomy and function and tissue characterization as well so the traditional approach to the investigation of thyroid gland masses is by Ultrasound followed by Scintigraphy. The radionuclide study effectively defines the functional status of an enlarged gland and palpable nodule. Scintigraphy can eliminate the need of fine needle aspiration biopsy (FNAB) radionuclide scanning is very useful in the demonstration of retrosternal extension of thyroid swelling. However the spatial resolution of this technique is limited so that multiple nodules may be present when Scintigraphy indicates a single nodule.Histologic specificity of solid thyroid masses can be attained with percutaneous biopsy and can preclude the need of any imaging study. FNAB is a simple, safe and cost-effective screening test for thyroid malignant masses with no contra-indications. Its major values is in the detection of clinically and Radiologically unsuspected malignancy as FNAB diagnosis of malignancy is highly significant and should lead to recommendation of thyroidectomy, it can also be effectively used in the management, diagnosis and treatment of thyroid lesions, where close co-operation between the clinician and cytopathologist exists however FNAB is of limited values in the diagnosis of follicular carcinomas also when the cytologic diagnosis is benign, the risk of malignancy is low but not zero.CT has subsidiary role in thyroid disease however it overcomes limitations enumerated for Sonography. CT is of great values in evaluation of huge thyroid masses, detection of extent and effect on surrounding structures, planning for surgery, detection of lymphadenopathies especially lower deep cervical and mediastinal, and lastly evaluation of retrosternal extensions. However, CT is contraindicated in patients with toxic manifestations, streak artifacts from shoulder girdle, need for contrast material and exposure to ionizing radiation are undesirable feature, furthermore it may be very difficult to evaluate structures in the neck for possible recurrence of tumors in patient who have had surgery for thyroid malignancy interpretation of the finding discovered by palpation in the post-operative neck may be confused by scar tissues, deformity or displaced normal structures. CT scanning may reveal the high iodine content of a palpable lesion thereby indicating its thyroid nature.Because MR imaging cannot distinguish benign from malignant tumours or determine functional status, it has little role in the evaluation of most patients with thyroid nodule or goiters, it is superior than CT in availability of multiplaner imaging modalities and no need for use of iodinated contrast materials, it is properly less specific than Sonography for establishing the cystic nature of a nodule, however early experience does suggest three specific indications for MR imaging in thyroid lesions:1) Depiction of the overall extent of the mass and involvement of the surrounding muscles by invasive tumor of the thyroid2) Assessment of substernal goiters3) Identification of sites of recurrence of thyroid carcinomas.Also if there is concern regarding the presence of a simple non functioning nodule on a radionuclide scan, MRI and CT may also be useful for assessing the possibility of multiple smaller nodules in the thyroid.The cost-benefit ratio must be considered carefully in using CT & MRI in the diagnosis of thyroid gland swelling, and therefore CT & MRI are not necessary when adequate information are available with other less expensive technique and from previous results and finding of CT and MRI in benign and malignant thyroid gland swelling, we found that CT and MRI of the thyroid supplements but not replace other diagnostic methods by providing little additional information about nature of the disease.
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