Radiology and Endocrinology

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  • 1. Radiology and Endocrinology
    • ANATOMY
  • Radiography
  • Ultrasound
  • CT
  • MRI
  • FUNCTION
  • Radionuclide Imaging
  • - Scintigraphy
  • - PET

2. 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

3. 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

4. Ideal radiopharmaceutical

  • cheap and readily available
  • radionuclide easily incorporated without altering biological behaviour
  • radiopharmaceutical easy to prepare
  • localises only in organ of interest
  • t 1/2of elimination from body similar to duration of test

5. Thyroid - radiography

  • Little role
  • Thyroid mass diagnosed incidentally on chest radiograph
  • Thoracic inlet views may demonstrate tracheal compression

6. 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

7. 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

8. Thyroid - scintigraphy

  • 99mPERTECHNETATE
  • Trapped but not organified
  • Competes with iodide for uptake
  • Cheap and readily available
  • IODINE ( 123 I or131I)
  • Trapped and organified
  • Better for retrosternal goitres
  • Expensive, cyclotron generated
  • RECENT (10 days) IODINE CONTRAST BLOCKS UPTAKE

9. Thyroid scintigraphy

  • 99mTc 123NaI
  • ADMIN iv po/iv
  • PATIENT withdraw thyroid Rx
  • PREP avoid high Iodine foods
  • IMAGING 15 min pi 1-2hr pi
  • 24 hr po

10. 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)

11. 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

12. RNI in thyroid disease

  • Investigation of hyperthyroidism
  • Location of ectopic thyroid tissue (congenital hypothyroidism, retrosternal goitre)
  • Little role in thyroid nodules

13. 1 ryHyperparathyroidism

  • Type %
  • Adenomas Single 80
  • Hyperplasia Chief cell 15
  • Clear cell 1
  • Carcinoma 4

14. RN parathyroid imaging

  • 99m Tc /201 Tl 99m Tc-MIBI
  • subtraction scans early/late scans
  • False positives: thyroid pathology
  • False negatives: parathyroid hyperplasia
  • Both good for ectopic parathyroids

15. Parathyroid imaging

  • US not good at finding ectopic glands
  • CT Contrast
  • Surgical artifacts
  • MRI Good for localisation and ectopicglands

16. Imaging parathyroids

  • Uncomplicated 1 ryhyperparathyroidsim
  • 90 -95% surgical success rate without imaging
  • Recurrent/persistent hyperparathyroidism
  • surgical success rate without imaging -50%
  • withimaging - 90%
  • (combined RNI + MRI)

17. Adrenal glands

  • Cortex aldosterone
  • cortisol
  • adrenal androgens
  • Medulla adrenalin

18. Adrenal glands

  • AXR - may show calcification
  • US- large masses only (unless neonatal)
  • CT- can detect small lesions
  • -cannot distinguish metastasesfrom non-functioning adenomas
  • MRI - small lesions
  • - may distinguish mets from
  • non-functioning adenomas

19. Adrenal cortical RNI

  • Radiolabelled cholesterol esters
  • ( 75Seleno-methylnorcholesterol,
  • 131I - 6B iodomethyl-19-norcholesterol)
  • Image at 4 and 7 days
  • > 50% difference in activity between sides is abnormal

20. RNI in Cushings syndrome

  • ACTH-dependent CS bilat
  • pituitary/ectopic
  • ACTH -independent CS
  • bilat nodular hyperplasia bilat
  • adrenocortical adenoma uni
  • Adrenocortical carcinoma bilat

21. Cushings syndrome

  • Diagnosis- biochemistry
  • Localisation- CT/MRI
  • for
  • 1. Pituitary ACTH-dependent
  • 2. Ectopic ACTH-dependant
  • 3. ACTH - independant
  • RNI not usually necessary

22. RNI and Cushings syndrome

  • Used for
  • 1. Findingresidual functioning adrenal remnantsif recurrent disease after prior bilateral adrenalectomy
  • 2. Somatostatin receptor scanning forectopic ACTHfrom small bronchial carcinoid tumours

23. 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)

24. Adrenal medullary RNI

  • Phaeochromocytoma
  • Paraganglioma
  • Neuroblastoma
  • Ganglioneuroblastoma
  • Ganglioneuroma

25. Adrenal medullary RNI

  • Metaiodobenzylguanidine (MIBG)
  • - localises in catecholamine storagevesicles of adrenergic nerve endings
  • -123Ior131I
  • somatostatin receptor imaging
  • 111In octreotide

26. MIBG

  • phaeochromocytomas(95% sensitivity)
  • neuroblastoma(80 - 90% sens)
  • carcinoid
  • medullary thyroid carcinoma
  • (MEN syndromes)

27. Phaeochromocytomas

  • 10% malignant
  • bilateral
  • extra- adrenal
  • paediatric

28. Phaeochromocytomas

  • Diagnosis- biochemistry
  • Localisation
  • CT if > 2cm
  • RNI to exclude- small tumours
  • - bilateral adrenal
  • - multifocal
  • - metastases

29. Incidentalomas

  • Incidental adrenal mass in patients undergoing abdominal imaging (2%)
  • Q. Is it functioning?
  • Is it benign or malignant?

30. Functioning incidentalomas

  • Diagnosis
  • Clinical features
  • Biochmistry
  • Confirmation
  • RNI

31. Non-functioning

  • Non-functioning adenoma vs. metastasis
  • CT using attenuation values
  • MRI - chemical shift imaging

32. Radiology and Endocrinology

  • Localisation
  • not
  • Diagnosis

33. IMAGING and the ENDOCRINE SYSTEM