Radiology and Endocrinology

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Radiology and Endocrinology

• ANATOMY
• Radiography
• Ultrasound
• CT
• MRI

• FUNCTION
• Radionuclide Imaging
• - Scintigraphy
• - PET

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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

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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

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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

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Thyroid - radiography

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

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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

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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

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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

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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

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Hyperthyroidism

• RN uptake
• 1. Thyroid gland (gt95)
• Toxic nodular goitre
• Diffuse toxic goitre (Graves)
• Thyroiditis
• 2. Exogenous T3/4/iodine
• Iatrogenic
• Iodine - induced
• (XRay contrast, amiodarone)

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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

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RNI in thyroid disease

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

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1ry Hyperparathyroidism

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

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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

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Parathyroid imaging

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

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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)

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Adrenal glands

• Cortex aldosterone
• cortisol
• adrenal androgens
• Medulla adrenalin

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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

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Adrenal cortical RNI

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

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RNI in Cushings syndrome

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

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Cushings syndrome

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

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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

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Primary aldosteronism

• small tumours may not be seen with CT/MRI
• RNI dexamethasone suppression can find tumours
  lt 1cm
• Adrenal visualisation before 5 days is abnormal
  (bilateral/unilateral)

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Adrenal medullary RNI

• Phaeochromocytoma
• Paraganglioma
• Neuroblastoma
• Ganglioneuroblastoma
• Ganglioneuroma

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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

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MIBG

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

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Phaeochromocytomas

• 10 malignant
• bilateral
• extra- adrenal
• paediatric

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Phaeochromocytomas

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

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Incidentalomas

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

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Functioning incidentalomas

• Diagnosis
• Clinical features
• Biochmistry
• Confirmation
• RNI

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Non-functioning

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

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Radiology and Endocrinology

• Localisation
• not
• Diagnosis

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IMAGING and theENDOCRINE SYSTEM