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8 Cards in this Set
- Front
- Back
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instrumentation
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-high frequency td 7-15 Mhz
-provide up to 5cm penetration -high definition with resolution 0.7-1mm -high degree spatial resolution -linear array preferred over sector because of the wider near field of view & ability to combine high frequency gray scale and color doppler images -one of the most vascular organs of the body |
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Technique
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-patient examined in the supine position with the neck exteded
-TRV & longitudinal images in right and left lobes -isthmus -lateral -should include lateral out to the carotid and internal jugular vein to medial trachea -TRV -Superior - inferior -measuremenet midpole long, AP, TRV midpole -Isthmus AP measurement -worksheet and diagram necessary |
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Anatomy
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-Anteroinferior part of the neck in a space outlined by muscle, trachea, esophagus, carotid, and IJV
-RT & LT lobe connected by the isthmus (sturcture draping over the anterior tracheal wall at the level-mid or lower 3rd of the thyroid gland) -10-40% of patients have small thyroid (Pyramidal) -Size & shape vary tall patient have elongated glands on SAG scans -shorter patients have more oval shaped glands |
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Volume
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-Lenth x width x height x .52 for each lobe
-useful for goiter size determination and to asserss for surgical intervention -permit calculation of the dose of Iodine- 131 needed for treating Thyrotoxicosis -Eval the response to suppression treatments |
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Thyroid Parenchyma
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-HOMOGENEOUS- MEDIUM TO HIGH LEVEL ECHOGENICITY MAKING DETECTION OF FOCAL, CYSTIC, OR HYPOECHOIC LESIONS RELATIVELY EASY
-Thin hyperechoic line that bounds the thyroid lobes is the capsule -capsule may becom calcified in patients with uremia or disorders of calcium metabolism |
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Vasculature
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-Superior thyroid artery & vein- Upper pole each lobe
-Inferior thyroid vein- lower pole -Inferior thyroid artery-posterior lower third of each lobe -mean diamety of arteries 1-2mm -lower veins can be up to 8mm in diameter -peak systolic velocity 20-40cm/sec in major thyroid arteries -15-30cm/sec in the intraparenchymal arteries -HIGHEST VELOCITIES FOUND IN BLOOD VESSELS SUPPLYING SUPERFICIAL ORGANS |
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muscles
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-sternohyoid and omohyoid muscles are seen as thin, hypoechoic bands anterior to the thyroid gland
-Sternocleidomastoid muscle is seen as larger oval band that lies lateral to the thyroid gland -Longus colli muscle is located posterior to each lobe, in close contatct with the prevertebal space IMPORTANT LANDMARK -The recurrent larygeal nerve & the inferior thyroid artery pass in the angel between the trachea esophagus & thyroid lobe -On longitudinal scans visualized between thyroid lobe & esophagus on left and thyroid lobe and longus colli muscle on the right -The esophagus, primaryly a midline structure, may be found laterally and is usually on the left side -Identified by the target apperance of bowel in the TRV plane and by its peristaltic movement when the patient swallows |
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Congenital Thyroid Abnormalities
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-agenesis of one lobe or whole gland
-varying degrees of hyperplasia & ectopia -Ultrasound can be used to establis diagnosis of HYPERPLASIA BY DEMONSTRATING A DIMINUTIVELY SIZED GLAND -Higher frequency ultrasound is used to study congenital hypothyroidism -Radionuclide scan are more commonly used to detect ectopic thyroid tissue i.e. in a lingual or suprahyoid position |
