Download Introduction to radiology

Introduction to radiology
Lecture no. 2
Prepared by
Dr. Salah Mhamad fateh
MBChB, DMRD, FIBMD( radiology)
Types of contrast media
1-Oral Contrast media;
Barium; used in barium study.
Gastrographin ; it is iodine based high osmolar
contrast agent .used in opacification of bowel
loops in the CT abdomen & in situations where
use of barium contraindicated
2- IV contrast
High osmolar CM(HOCM) e,g urographin.
Low osmolar CM(LOCM) e,g Omnipaque(
Iohexole)
Most of side effect of the contrast media related
to the osmolality
Side effect of IV contrast agents
IV contrast (including both HOCM LOCM ) are
among safest drugs used in the clinical
practice.
It is not known that LOCM decrease fatality ,
but if compared to HOCM, it has;
1. Less mild –moderate side effect
2. Less physiological & hemodynamic side
effects.
3. Less pain in arterial injection & less discomfort
during intra venues injection
Marjory of side effect are mild-moderate
but fatal reaction death can occur in 1:
160 000 of population
Fatal reaction to contrast media
Cause of death includes;
Cardiac arrest
Respiratory arrest
Pulmonary edema , brochospasm,
laryngeal edema , angioneurotic edema .
Coaguolpathy
Risky patient for developing adverse
reaction
Patient with asthma ,Hx of previous reaction to contrast media.
Infant , children & elderly.
Patient with Hx of heart or renal failure.
Dehydrated patient
Hx of Multiple meyloma , sickle cell anemia .
In above patients if examination is mandatory only
LOCM should be used & cautiously
MRI
( Magnetic resonance imaging)
The first MRI on a human was made in July 1977
MRI , closed type
CT scan
MRI, open type
T1
T2
Uses of MRI
Most commonly used for musculoskeletal
system as well as nervous system ( brain &
spinal cord) imaging .
for imaging heart , vessels (MR angiography )
Characterization of liver lesion as well as
abdominal& pelvic organs .
Advantage of MRI over CT
There is no ionizing radiation .
Image can be taken in any plain.
If compared to CT , it has better contrast
resolution & lesion characterization even
without use of contrast media.
MRI angiography can be done without giving
contrast media
Disadvantage of MRI
Take more time (often several minutes) .
Very sensitive to motion & production of
motion artifact.
Claustrophobia .
MRI Contraindications
Absolute ;
Pacemaker.
Cochlear implants.
Intra ocular metallic foreign bodies .
Aneurysmal clips
Relative contra indication;
Shell injury or metallic foreign body away from vital organ & major
vessels specially after more than 6 months post injury .
Pregnancy .
Claustrophobia .
Uncontrollable movement
MRI Contrast media
Most commonly used agent is gadolinium compound .
Tissues which take the contrast appear bright ( hyper
intense in T1) .
Is used for tumor characterization & in cases of contrast
enhanced MR angiography
MRI Contrast media
Usually safe & rarely fatal complication occur.
Can produce same side effect as IV contrast media
used in X-ray but as general is safer .
Contraindications;
As general same as IV iodinated contrast media
used in X-ray including , renal failure ,hepatic failure
, pregnancy , previous reaction to contrast media &
patient Hx of allergy
Ultrasound (US)
Gall stone (S) with acoustic shadows
(arrow heads)
cyst (C) with posterior acoustic
enhancement
Properties of US examination
There is no ionizing radiation , is available & cost effectiveness is low
At the energies & doses currently used in diagnostic US, no harmful
effect on any tissues have been demonstrated
Unlike other imaging modalities , there is no specific projections &
sections can be taken in any plain & is operator dependant .
Are capable of highly detailed information & very small lesion can be
demonstrated.
Recently small probes are developed & fine detail of particular organ
of interest can be obtained e.g trans rectal probe & trans vaginal
probes can be used for detecting detail image informations of
prostate & female pelvic organs respectively .
3D & 4D US has been developed recently & is used primarily in
obstetrical examination
Doppler US examinations
The principle is that when sound reflected from mobile structures
shows variation in frequency which is received by the transducer ,
this is called frequency shift.
this shift in frequency can be converted to audible sound (e,g
listening to fetal heart using Doppler probe ), color in color Doppler
or spectral waveform in spectral Doppler
Clinical use of Doppler US
To detect venous thrombosis .
Arterial stenosis or occlusion.
To assess Vasculature & tumor blood flow.
In obstetric to determine fetal blood flow through umbilical artery &
to assess placental insufficiency & fetal distress.
With Doppler echocardiography it is possible to demonstrate
regurgitation through incompetent valve & pressure gradient can be
calculated across the valves
Isotope scan
Isotope ; those element that has same atomic no. (protons) , but they
are differ from each other in atomic mass (no. of neutrons).
Radio isotope (radioactive isotope );
is one with unstable nucleus which emits characteristic radiation
during its decay to a stable form
Technetium-99m is a meta stable nuclear isomer of technetium-99,
symbolized as 99mTc, this emit Gamma ray when disintegrate &
convert to stable form technetium-99 .
Radionuclide image depend on the fact that certain substance
concentrate selectively in different parts in the body & radionuclide
can be tagged to these substance (radiotracer )to direct them to
those specific sites e,g TC 99mm labeled with phosphate to image
bone , with macroaggregates of albumin to image lung perfusion
Medically used radioactive isotope
Should have short physical & biological half life .
The radio pharmaceuticals should have no undesirable biological
effects & should rapidly eliminated from the body after completion of
investigation.
In isotope scan , the patient become the source of
radiation & emit radiation from patients body
detected by gamma camera & computer aided
image will produces
gamma camera
SPECT( single photon emission
tomography)
Is isotope based imaging technique , its relation to
conventional isotope scan, is similar to relation of
conventional X-ray to CT scan.
Because SPECT permits accurate localization in 3D space, it can be
used to provide information about localized function in internal
organs, such as functional cardiac or brain imaging
SPECT( single photon emission tomography)
Because SPECT acquisition is very similar to planar gamma camera
imaging, the same radiopharmaceuticals may be used. If a patient is
examined in another type of nuclear medicine scan but the images are nondiagnostic, it may be possible to proceed straight to SPECT by moving the
patient to a SPECT instrument, or even by simply reconfiguring the camera
for SPECT image acquisition while the patient remains on the table
To acquire SPECT images, the gamma camera is rotated around the
patient. Projections are acquired at defined points during the
rotation, typically every 3–6 degrees. In most cases, a full 360degree rotation is used to obtain an optimal reconstruction.
PET scan (Positron Emission Tomography)
Uses short lived positrons emitting isotope
The most commonly used agent is F-18 fluoro-deoxyclocose (FDG).
This is analog to glucose & is taken by the cells in proportion to
glucose metabolism which is increased in tumor cells .
Because muscle activity result in in the uptake of FDG, the patient
should rest quietly in the interval between injection of the injection
FDG scan.
The images should be interpreted carefully as non cancerous
conditions may show uptake resembling cancer
FDG PET is a strictly functional modality and lacks
anatomic landmarks for precise morphologic orientation.
Co registration of PET scans (functional and
morphologic information) with computed tomographic
(CT) scans (anatomic information) using a combined
PET-CT scanner( fusion image) improves the overall
sensitivity and specificity of information provided by PET
or CT alone
Case
Transaxial images in a 44-year-old man with history of nasopharyngeal
carcinoma in 2000, which was treated with radiation therapy. In
March 2002, clinical examination findings were negative. PET was
ordered for evaluation of potentially recurrent or metastatic disease.
transaxial PET images show abnormal FDG uptake in upper chest
Nonenhanced CT scan shows slightly enlarged lymph nodes (15 × 10 mm and
13 × 9 mm) in the anterior superior mediastinum. On concurrent contrastenhanced CT scan, both lymph nodes were considered suspicious for
metastases.
Schöder H et al. Radiology 2004;231:65-72
©2004 by Radiological Society of North America
PET/CT image shows abnormal FDG uptake in one of these lymph nodes.
Biopsy demonstrated malignant cells. The patient underwent chemotherapy
followed by resection of paratracheal nodes.
Schöder H et al. Radiology 2004;231:65-72
©2004 by Radiological Society of North America
FDG is not specific for neoplastic processes; it
accumulates physiologically in various normal organs,
Normal distribution of FDG. PET and PET-CT fusion images demonstrate the
physiologic accumulation of FDG in the cerebral-cerebellar cortex at the base of the
skull and in the myocardium, liver, kidneys, renal pelvis, bone marrow, and urinary
bladder. Note also the minimal uptake in the mediastinum and bilaterally in the lower
cervical and psoas muscles.