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; Less mild –moderate side effect Less physiological & hemodynamic side effects. 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

( Magnetic resonance imaging) 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)

cyst (C) with posterior acoustic enhancement Gall stone (S) with acoustic shadows (arrow heads)

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

Radio isotope (radioactive isotope ); 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 non-diagnostic, 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 360-degree 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 PET images show abnormal FDG uptake in upper chest 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 contrast-enhanced CT scan, both lymph nodes were considered suspicious for metastases. Figure 5c. 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. (a) Coronal and (b) transaxial PET images show abnormal FDG uptake in upper chest. (c) Nonenhanced CT scan shows slightly enlarged lymph nodes (15 × 10 mm and 13 × 9 mm) in the anterior superior mediastinum. On concurrent contrast-enhanced CT scan, both lymph nodes were considered suspicious for metastases. (d) 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

PET/CT image shows abnormal FDG uptake in one of these lymph nodes 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. Figure 5d. 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. (a) Coronal and (b) transaxial PET images show abnormal FDG uptake in upper chest. (c) Nonenhanced CT scan shows slightly enlarged lymph nodes (15 × 10 mm and 13 × 9 mm) in the anterior superior mediastinum. On concurrent contrast-enhanced CT scan, both lymph nodes were considered suspicious for metastases. (d) 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 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.