Radiopharmaceutics (2) Flashcards
1
Q
Diagnostic applications respiratory system
A
- Lung perfusion imaging performed by IV injection of 99Tc MAA (Macroaggregates of albumin typically 30-50um)
- Particles lodge in the terminal arterio-capillary bed
- Images which show area’s of reduced uptake could be caused by PE (Also inflammation, neoplasm, chronic obstructive pulmonary disease)
2
Q
Diagnostic applications
Respiratory system
A
- Lung ventilation carried out in conjugation with perfusion
- Radioactive gases such as 81mKr may be used- radioactive gas- Half-life of 31 seconds- have to produce Krypton using a generator
- Don’t have to worry about removal
- Have to buy everyday
- Because it is a different isotope to Tc you can perform ventilation and perfusion imaging as detectors can distinguish between Kr and Tc- cant do with technegas
- More readily available is 99Tc technegas
- Very readily available
- Equipment is expensive
- Vent and perfusion scans compared- mismatch is indicative of PE
3
Q
Example studies
A
- Inject 100 MBq of Tc-99m- MAA
- Albumin is trapped in the pulmonary capillaries to assess blood supply
- Also, breathe in Krypton-81m gas
- Scan straight away
- 20-minute acquisition
- Patches on perfusion would be suggestive of PE
4
Q
Normal lung scan
A
5
Q
Lung scan showing pulmonary embolus
A
6
Q
Musculoskeletal system
A
- A most common indication for the bone scan is to assess bone metastases usually 2o to Ca breast and prostate
- Medronate or oxidronate is injected and the patient scanned 2-3 hours later-
- Uptake is enhanced in active areas of bone growth- abnormal uptake seen as hot spots- cancers
- The bone scan also used for diagnosis of Paget’s Osteomyelitis and stress fractures
7
Q
Normal bone scan
A
Normal bone scan- whole body 34 year old patient
Uptake high in long bones due to growth
8
Q
Normal bone scan paediatric aged 14 years
A
Normal scan showing metastases
9
Q
Whole body scan with widespread metastases- prostate 59 years
A
Whole body scan with metastases- lung carcinoma
10
Q
CV system
A
- NICE guidelines 2003 state that MPI scintigraphy using SPECT recommended for use in diagnosis and management of coronary artery disease
- Patients undergo MPI in 2 parts
- Heart stressed by exercise or pharmacologically using adenosine or dobutamine
- Heart imaged at rest
- Comparison of 2 studies provides the diagnosis
- MUGA (Multigated acquisition) scan provides data of LVEF- radiolabeled red blood cells and images the heart pumping to see how effectively the heart pumps the blood
11
Q
MPI (Myocardial perfusion imaging) slices
A
- We have to take a 3D image of the heart
- If infarct was at the back and we took a 2D picture we wouldn’t see it as the uptake at the front of the heart would mask
- We take multiple slices of the different parts of the heart to see the perfusion of the different part of the heart muscle
- Long axis slices should be in a horse shoe shape
12
Q
Example studies
A
- Inject 600 MBq of Tc99m- tetrofosmin
- If there is uptake of blood supply to the heart then tetrofosmin will be taken up
- Sticks to mitochondria in heart muscle
13
Q
Normal MPI v MPI showing ischaemia
A
MPI showing fixed defects
14
Q
Example studies
A
- Inject stannous agent (tin) to prepare blood- otherwise, blood won’t stain
- Inject 800 MBq of Tc99m-O4-
- TcO4- sticks to stannous labelling the blood
- Attach the patient to an ECG
- Scan straight away
- 30 minute acquisition
15
Q
CNS
A
- NM studies increasingly important in diagnosisof neurological disorders especially Alzheimer’s or Parkinson’s
- First radiopharmaceutical was HMPAO Ceretac- this became the gold standard for cerebral blood flow imaging
- 123Ioflupane DaTSCAN used to differentiate essential tremor from Parkinsonian syndrome in patients where diagnosis uncertain and DLB from Alzheimer’s disease
16
Q
Example studies- 3D tomographic brain scan for Parkinson’s disease
A
- Inject 185 MBq of I-123-Ioflupane (DaTSCAN)
- Accumulates in the striata of the brain, used to co-ordinate movement
- Scan 3 hours later
- 30 minute acquisition, claustrophobic
17
Q
Normal DaTSCAN
A
Abnormal DaTSCAN
Normal= comma
Abnormal = Full stop
18
Q
GI-tract
A
- Salivary activity and secretion can be monitored using pertechnetate
- Tc-colloid mixed with food or drink used for gastric emptying studies- pancake or scrambled egg
- Oesophageal transit measured using Tc-colloid in tomato soup
- GI bleeding assessed using Tc labelled RBC- if RBC appear in stomach= bleed
19
Q
Hepatic system
A
- NM studies for investigating the liver have declined as other scanning methods especially US and CT have become more prominent
- T-BIDA used for imaging the biliary system and evaluating it’s function
- Abnormal transit occurs in biliary atresia, acute cholecystitis and obstructive jaundice
20
Q
Renal system
A
- 3 types of renal investigation
- Study of GFR using 51Cr EDTA
- Renal perfusion using MAG 3
- Renal parenchymal function using DMSA
- With the addition of furosemide or captopril these studies are used to identify renal vascular HTN and renal obstruction
21
Q
Example studies- dynamic scan renogram to see if kidney are functioning
A
- inject 80 MBq of Tc99m-MAG3
- Absorbed and excreted by kidneys to bladder
- Scan immediately
- 20 minute acquisition
22
Q
MAG-3 normal
A
23
Q
MAG-3 showing obstruction v kidney transplant
A
24
Q
Normal DMSA scan
A
25
Q
Infection and inflammation
A
- White blood cells can be labelled using 99mTc or 111In
- following re-injection WBC migrate to sites of infection and inflammation
- Useful for diagnosis of infection of unknown origin
- Also used in assessment of Crohns and UC- lots of WBC in the GIT
- Tc labelled Abs and Ab fragments e.g. Tc-sulesomab (Leukoscan)
26
Q
Imaging in Oncology
A
- Thyroid Ca diagnosed as a solitary “Cold” node on a Tc scan- confirmed by US and biopsy
- Nanocolloid in sentinel node imaging- breast and melanoma
- Octrescan used in somatostatin receptor tumours e.g. carcinoid
- FDG-PET scan used in lung cancer
27
Q
68-Gallium PET imaging new gold standard for imaging NET
A
28
Q
SLN imaging in melanoma
A
