Introduction to Diagnostic Radiology Imaging

BY Dr Riaz Mohammad

Definition of Radiology

• Radiology is a medical specialty using medical imaging technologies to diagnose and treat patients.

Diagnostic imaging Modalities • Plain x-rays• Fluoroscopy• Mammography• Nuclear Medicine,conventional,Spect/Pet• Ultrasound• CT Scan• MRI• Angiography

Which of these modalities useionizing radiation?

X-Rays is a form of electromagnetic radiation.X-Rays is a form of electromagnetic radiation.Thay are Thay are produced when high energetic electrons interact with matter. produced when high energetic electrons interact with matter. Kinetic energy of electron are converted in to electromagnetic Kinetic energy of electron are converted in to electromagnetic energy by atomic interactionenergy by atomic interaction

The figure shows a modern X-ray tube and housing assembly. The figure shows a modern X-ray tube and housing assembly.

Typical operation conditions are: Typical operation conditions are:

Acceleration Voltage: 20 to 150 kV Acceleration Voltage: 20 to 150 kV

Electron Current: 1 to 5 mA (for continuous operation) Electron Current: 1 to 5 mA (for continuous operation)

Electron Current: 0.1 to 1.0 A (for short exposures) Electron Current: 0.1 to 1.0 A (for short exposures)

Plane Radiograph• X-rays are absorbed to variable extent as they pass through the body. The

visibility of normal and disease depend on this differential absorption. With conventional radiography there are five different densities, gas,fat,all other soft tissues, calcifications and metallic density. X-ray pass through are least absorbed and cause the most blackening of the radiograph, calcium absorb most so bone and other calcified structures appear virtually white

• Soft tissues with the exception of fat have similar density and appear same shade of grey. Fat absorb slightly fewer x-rays and appear blacker than the other soft tissues. White coloration is called opacity and black coloration is called lucency.

• Projection are usually describe by path of x-ray beam. Thus the term PA(Poster anterior) view designate that the x-ray beam pass from back to front, the standard projection for the chest. Ap (ante posterior) view means that the beam is passing from front to back. The image on an x-ray film is two dimensional.All the structures along the path of the beam are projected

on the same portion of the film overlapping each other. Therefore, it is often necessary to take at least two views to gain information about the third dimension.

Three things can happen

• X-rays can:– Pass all the way through the body– Be deflected or scattered– Be absorbed

Where on this imagehave x-rays passedthrough the bodyto the greatest degree?

5 Basic Radiographic Densities

• Air• Fat• Soft tissue/fluid• Mineral• Metal

1.

2.

3.

4.

5.

Name these radiographic densities.

Plain x-ray's Indications

• X-ray chest. Chest trauma,Infection,Tumour• X-ray abdomen. Acute abdomen,eg Renal

Colic,Obstruction,tumour and infection• Bone x-ray.Bone fracture,Infection and

tumours.

AP and PA chest positions

                              

Chest PA view Chest AP view

Lung Mass: Solid Tissue

Lung Mass: Cavitation

Ultrasound• Is a very high frequency sound directed in to the body from a transducer

placed in contact with the skin. In order to make a good acoustic contact, the skin is smeared with a gel like substance. As the sound travel through the body, it is reflected by the tissue interfaces, which is pick up by the same transducer and convert it to an electrical signal. Machine process the data and form a grey scale image.

• Not invasive, cheap and available in almost every hospital.• No ionizing radiation• Safe for pregnant patient• Operator dependent• There is organ limitation( It can not penetrate air or bone so we can not

use with lung or brain for instance) • Fluid is a good conductor of sound, therefore, ultrasound, is particularly

good imaging modality for diagnosing cyst and other fluid filled structures like urinary bladder and biliary system and demonstrating the fetus in its amniotic sac.

www.upei.ca/~vetrad

Ultrasound

Ultrasound– Ultrasound is often used to determine

weather the structure is solid or cystic– Cyst and other fluid filled structure

produce a large echo from their but no echo from the fluid contained with in them. Also more echo than usual are received from behind the fluid filled structures, an effect called acoustic enhancement. Conversely with calcified structures, e.g. gall stone, there is great reduction in the sound that will pass through, so a band of reduced echoes, referred to as an acoustic shadow is seen behind the stones.

US Indications:

• OB/GYN.Evaluation of Ist,secnd and third trimester pregnancy

• Congenital Anamolies.• Evaluation of placenta previa and haemorrhages• Evaluation of gyenacological diseases.• Abdominal indications. • Muscuskeletal indicaions• Neonatal brain ultrasound.

UltrasoundAdvantages1. No ionizing radiation2. Applicable to any plane3. Cost-effective4. Portable5. Real-time imaging

Disadvantages1.Operator dependent2. Can not penetrate every structure like bone and air containing

organs

Ultrasound

2D vs 3D

3-4 D U/S images

Computed Tomography• Computerized (or computed) tomography, and often formerly referred to as

computerized axial tomography is an X-ray procedure that combines many X-ray images with the aid of a computer to generate cross-sectional views and, if needed, three-dimensional images of the internal organs and structures of the body. Computerized tomography is more commonly known by its abbreviated names, CT scan or CAT scan. A CT scan is used to define normal and abnormal structures in the body and/or assist in procedures by helping to accurately guide the placement of instruments or treatment planning. There is more sensitive x-ray detection system and the image consist of sections (slice) through the body and the data is manipulated by computer.

• CT has a very small difference in x-ray absorption value compared with conventional radiography, the range of densities recorded is increase approximately 10 fold. So gradation of densities with in the soft tissues can be recognized e.g brain substance from CSF and tumor from normal tissues. Even grey and white matter of brain can be differentiated.

• The major risk behind the CT is ,that 1 brain CT scan radiation is 200 X-ray and 1 pelvis CT is 400 x-ray which means do not request Ct scan unless it is needed and we can not do it for pregnant women unless it is necessary.

CT scan

X-ray Computed Tomography

CT angiography

• Rapid intravenous injection of contrast media result in significant opacification of blood vessels, which with multiplanner or 3D reconstruction, can be can be exploited to produce an angiogram. CT angiography along with MRA is gradually replacing conventional angiography

Angiography images

MRI

MRI(magnetic resonance imaging) To perform the test, the patient is put in the MR scanner which form a strong magnetic field around the area to be imaged Hydrogen atom(protons) in water molecules and lipids are excited with radio waves by radiofrequency coil which after a while return to the equilibrium state produce radiofrequency signal. Radiofrequency coils are switched off and an to change the direction of magnetic field. When ever molecules spin around they produce a light radio waves. MRI machine detect this change and convert it to an MR image. MRI contrast agent. Gadolinium DTPA( Ethylene Triamine Penta acetic acid) is used as contrast agent. It is used with TW images only.

MRIAdvantages of MRI

• Best for soft tissue imaging• There is no ionizing radiation• Procedure of choice for MSK• It can be done for pregnant

women with caution.• Multiplanner so image can be

taken in any plan with out changing the position of the patient.

• MR angiogram can be perform wit out introducing contrast media

Disadvantages

• Expensive and time consuming• Patient fear it and dislike it because

it is a narrow place(claustrophobia) . Now a days open MRI system has over come this problem

• Since it is magnetic no metal can be allowed

• Patient has to keep still during the producer.

MRI continueAxial sagittal

Contraindications of MRI if there is

• Cardiac pace maker• Intracranial vascular clips• Neurostimulators of any kind• Intraocular metallic foreign body• Ossicular implants• Any metallic implants, rods, metal plates and pins. • Heart failure• Surgical clips on arteries and wire sutures

MRAngiographyMRA

• Unlike CT angiography, MRA can done with out contrast. But in contrast enhanced MRA, contrast is often used to make blood vessel show up more clearly.

Images

Very important to know different planes

Fluoroscopy

• Utilizes X-Rays• Real-time imaging• Utilizes image intensifier • May involves use of contrast agents

FluoroscopyMechanism: Continuous

below patient, amp- lified by intensifier above patient; shown on high-resolution television screen

Provides real time moving image of internal structure.

Imaging reversed vs xray Uses: Barium swallow to evaluate esophagus, small and large intestines, vessel catheter guidance

X-ray beams from

FluoroscopyAdvantages Disadv

• Widely Available• Inexpensive• Functional and

Anatomic• No sedation required

• High radiation dose ingestion/injection of contrast

• Patient cooperation• Time consuming

Gastrointestional Fluoroscopy

• Esophogram /Barium Swallow• Modified Barium Swallow• Small Bowel Series• Enteroclysis• Contrast Enema

Barium swallow spot films

Single ContrastBarium Enema

Double ContrastBarium Enema

Single Contrast vs Double Contrast

Single ContrastBarium Enema

Double ContrastBarium Enema

Contrast Enemas

Hysterosalpingogram

• Used to evaluate endometrial canal and fallopian tubes

• Infertility and uterine anomalies• Dye injected into cervical os under fluoro• Injection continued with goal to opacify the

fallopian tubes and spill contrast into peritoneum

Musculoskeletal Fluoroscopy

• Fracture/Dislocation reduction• Hardware placement in the OR• Flexion/Extension views of c-spine• Arthrography

– May be performed in conjunction with MRI or CT

Conventional Angiography

• Contrast is rapidly injected in to the blood vessel and a series of images are taken rapidly to follow the flow of contrast in the blood vessel. Angiography is indicated to diagnose vascular pathology.

Nuclear Medicine (Scintigraphy)

Bone Scan

Procedure of radioisotope study • Radioisotopes are substances which contain

atomic nuclei that emit alpha, beta and gamma radiation. If any of these substances are taken into our body they emit radiation giving us a method of locating where it is. The selected radioisotope is attached to a convenient chemical compound that is administered to the body. It then makes its way through the system leaving a trail of radiation permitting us to trace its path. It will concentrate the activity in a particular organ of the body allowing detail imaging of the structure. The gamma camera detects signals which then build up a picture of the distributed radioisotope in the body. Gamma emitters are only used.

Radionuclide study Indications:

• Detection of bone infections, tumor and fractures.

• Thyroid diseases• Cardiac Imaging e.g. perfusion images.• Brain images. Tumor and infections.

How nuclear medicine detects problems within different areas in our organ

• In order to investigate a body organ. A suitable radioactive tracer having a particular affinity for that organ is injected into the blood stream this is up taken by the organ of interest which is then assessed by imaging with the gamma camera. The image beside explains how whole process works.

SPECT

• Single-photon emission computed tomography (SPECT) is a nuclear medicine tomographic imaging technique using gamma rays. It is very similar to conventional nuclear medicine planar imaging using a gamma camera However, it is able to provide true 3D information which is then presented as cross sectional image.

SPECT SCANNER

PET Scanner• A PET scan uses a small amount of radioactive material

(tracer). The tracer is given through a vein (IV), most often on the inside of your elbow. The tracer travels through your blood and collects in organs and tissues. This helps the radiologist see certain areas of concern more clearly

• A PET scan shows how organs and tissues ar

PET/CT • In many centers, nuclear medicine images can be

superimposed with computed tomography (CT) or magnetic resonance imaging (MRI) to produce special views, a practice known as image fusion or co-registration. These views allow the information from two different exams to be correlated and interpreted on one image, leading to more precise information and accurate diagnoses. In addition, manufacturers are now making single photon emission computed tomography/computed tomography (SPECT/CT) and positron emission tomography/computed tomography (PET/CT) units that are able to perform both imaging exams at the same time. An emerging imaging technology, but not readily available at this time is PET/MRI.

PET/ CT

PET SCAN

Mammography

• Mammography is the process of using low-energy X-rays (usually around 30 kVp) to examine the human breast and is used as a diagnostic and a screening tool. The goal of mammography is the early detection of breast cancer, typically through detection of characteristic masses and/or microcalcifications.

Diagnostic Mammogram

• For woman presenting with clinical evidence of breast disease, palpable mass or other symptom

• Uses specific projections to – Rule out cancer – Demonstrate suspicious area seen on screening

mammogram

Compression Device• Compression

decreases thickness of breast, magnification and scatter

• Increases contrast• Reduces motion

unsharpness• Reduces dosage

Routine mammography projections

Craniocaudal (CC)

Mediolateral oblique (MLO)

CC view ( lesion)

The End