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
( 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
t1/2 of 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
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

9. Thyroid scintigraphy 99m Tc 123 NaI 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 %
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. 1ry Hyperparathyroidism
Type %
Adenomas Single 80
Hyperplasia Chief cell 15
Clear cell 1
Carcinoma

14. RN parathyroid imaging
99mTc / 201Tl 99mTc-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 ectopic glands

16. 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)

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 metastases from non-functioning adenomas
MRI - small lesions
- may distinguish mets from
non-functioning adenomas

19. 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

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. Finding residual functioning adrenal remnants if recurrent disease after prior bilateral adrenalectomy
2. Somatostatin receptor scanning for ectopic ACTH from 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 storage vesicles of adrenergic nerve endings
- 123 I or 131 I
somatostatin receptor imaging
111 In octreotide

26. MIBG phaeochromocytomas (95% sensitivity)
neuroblastoma ( % 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