Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Radiology and Endocrinology ANATOMY • Radiography • Ultrasound • CT • MRI FUNCTION • Radionuclide Imaging - Scintigraphy - PET Radionuclide Imaging • Images metabolic pathways • Pharmaceutical which mimics a component of a normal metabolic pathway is administered to the patient • Pharmaceutical radiolabelled so that its distribution in the patient can be visualised with a gamma camera Ideal Radionuclide • emits gamma radiation at suitable energy for detection with a gamma camera (60 - 400 kev, ideal 150 kev) • should not emit alpha or beta radiation • half life similar to length of test • cheap • readily available Ideal radiopharmaceutical • cheap and readily available • radionuclide easily incorporated without altering biological behaviour • radiopharmaceutical easy to prepare • localises only in organ of interest • t1/2 of elimination from body similar to duration of test Thyroid - radiography • Little role • Thyroid mass diagnosed incidentally on chest radiograph • Thoracic inlet views may demonstrate tracheal compression Thyroid - ultrasound • High resolution (5 - 10 MHz) • Confirms - mass is thyroid cystic or solid single or multiple • cannot distinguish solid carcinoma from solid dominant nodule • Not useful in hyperthyroidism Thyroid - CT/MRI • Not as good as US at resolving lesions within the thyroid • Best tests for assessing mediastinal disease • CT better than MRI for calcification • MRI better than CT for distinguishing between fibrosis and residual tumour Thyroid - scintigraphy 99m PERTECHNETATE Trapped but not organified Competes with iodide for uptake Cheap and readily available IODINE (123I or 131 I) Trapped and organified Better for retrosternal goitres Expensive, cyclotron generated RECENT (10 days) IODINE CONTRAST BLOCKS UPTAKE Thyroid scintigraphy 99m Tc 123 NaI ADMIN iv po/iv PATIENT PREP withdraw thyroid Rx avoid high Iodine foods IMAGING 15 min pi 1-2hr pi 24 hr po Hyperthyroidism RN uptake 1. Thyroid gland (>95%) Toxic nodular goitre Diffuse toxic goitre (Graves) Thyroiditis 2. Exogenous T3/4/iodine Iatrogenic Iodine - induced (XRay contrast, amiodarone) Thyroid nodules Risk of malignancy Overall 10% US - cystic 0.3 - 10% US - solid ???? RNI - cold 16% RNI - hot 4% First line investigation: Cytology +/- US RNI in thyroid disease • Investigation of hyperthyroidism • Location of ectopic thyroid tissue (congenital hypothyroidism, retrosternal goitre) • Little role in thyroid nodules ry 1 Hyperparathyroidism Adenomas Hyperplasia Carcinoma Type % Single Chief cell Clear cell 80 15 1 4 RN parathyroid imaging 99mTc / 201Tl subtraction scans 99mTc-MIBI early/late scans False positives: thyroid pathology False negatives: parathyroid hyperplasia Both good for ectopic parathyroids Parathyroid imaging • US not good at finding ectopic glands • CT Contrast Surgical artifacts • MRI Good for localisation and ectopic glands Imaging parathyroids Uncomplicated 1ry hyperparathyroidsim 90 -95% surgical success rate without imaging Recurrent/persistent hyperparathyroidism surgical success rate without imaging -50% with imaging - 90% (combined RNI + MRI) Adrenal glands Cortex aldosterone cortisol adrenal androgens Medulla adrenalin Adrenal glands • AXR - may show calcification • US - large masses only (unless neonatal) • CT - can detect small lesions - cannot distinguish metastases from non-functioning adenomas • MRI - small lesions - may distinguish mets from non-functioning adenomas Adrenal cortical RNI • Radiolabelled cholesterol esters (75 Seleno-methylnorcholesterol, 131 I - 6B iodomethyl-19-norcholesterol) • Image at 4 and 7 days • > 50% difference in activity between sides is abnormal RNI in Cushings syndrome ACTH-dependent CS pituitary/ectopic ACTH -independent CS bilat nodular hyperplasia adrenocortical adenoma bilat Adrenocortical carcinoma bilat bilat uni Cushings syndrome Diagnosis - biochemistry Localisation - CT/MRI for 1. Pituitary ACTH-dependent 2. Ectopic ACTH-dependant 3. ACTH - independant RNI not usually necessary RNI and Cushings syndrome Used for 1. Finding residual functioning adrenal remnants if recurrent disease after prior bilateral adrenalectomy 2. Somatostatin receptor scanning for ectopic ACTH from small bronchial carcinoid tumours Primary aldosteronism • small tumours may not be seen with CT/MRI • RNI + dexamethasone suppression can find tumours < 1cm • Adrenal visualisation before 5 days is abnormal (bilateral/unilateral) Adrenal medullary RNI Phaeochromocytoma Paraganglioma Neuroblastoma Ganglioneuroblastoma Ganglioneuroma Adrenal medullary RNI • Metaiodobenzylguanidine (MIBG) - localises in catecholamine storage vesicles of adrenergic nerve endings - 123 I or 131 I • somatostatin receptor imaging 111 In octreotide MIBG • • • • phaeochromocytomas (95% sensitivity) neuroblastoma (80 - 90% sens) carcinoid medullary thyroid carcinoma (MEN syndromes) Phaeochromocytomas 10% malignant bilateral extra- adrenal paediatric Phaeochromocytomas Diagnosis - biochemistry Localisation CT if > 2cm RNI to exclude - small tumours - bilateral adrenal - multifocal - metastases ‘Incidentalomas’ Incidental adrenal mass in patients undergoing abdominal imaging (2%) Q. Is it functioning? Is it benign or malignant? Functioning ‘incidentalomas’ Diagnosis Clinical features Biochmistry Confirmation RNI Non-functioning Non-functioning adenoma vs. metastasis • CT using attenuation values • MRI - chemical shift imaging Radiology and Endocrinology Localisation not Diagnosis IMAGING and the ENDOCRINE SYSTEM