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DIAGNOSTIC IMAGING |
This Services is located at the ground floor. The Services has a crucial and vital role in the work-up of patients by providing radiological input to complement and in some instances to confirm the clinical diagnosis and in other occasions to add further information with regards to the illness of patients which may be so subtle to be elicited by the clinicians. In other instances, radiological examination is utilized to assess the status of patient, following the treatment.
Services that can be provided by DIS includes:
- Plain radiography/ plain X-ray
- X-ray mammography
- Ultrasonography; including Doppler study
- Fluoroscopy
- Contrast radiography e.g. intravenous urography(IVU)
- Computed topographic scanning (CT scan)
- Mobile radiography
- C-arm; operating theatre radiographic facility
Plain Radiography
Examples include chest radiography (CXR), skull radiograph (SXR) and radiographs of the extremities/ limbs. In most instances, this is the first radiographic examination that would be requested by the clinician. The information that can be obtained may confirm the clinical diagnosis, provide insight into the extent of the disease, help the clinician in instituting the proper mode of treatment and dictate the subsequent imaging modality or any combination of the other imaging modalities available.
Ultrasonography (US)
This imaging modality utilizes the high frequency sound waves (not X-radiation) usually in the range of 3 MHz to 15 MHz. Thus these sound waves are not audible to human being as this frequency range is beyond our audible range. The ultrasound is generated from a special gadget which is a vital component of an ultrasound unit. This gadget is known as an ultrasound (US) transducer or probe. The probe contains a special component which vibrates and produces ultrasound when it is subjected to an electrical voltage. This material is known as a piezoelectric element. When the ultrasound is produced by the transducer, it will penetrate into the tissues and some of the ultrasound waves will be reflected towards the probe when these sound waves reaches an interface such as muscle and blood vessels. The reflected sounds return to the probe and these sound waves are converted into electrical signals and then transmitted into the computer system of the US unit. The electrical signals are then converted into shades of grey ranging from black to white, depending on the intensity of the electrical signals. Arrangements of these tiny dots of various shades of grey will form what is known as an ultrasonographic image. The intensity of the electrical signals is proportional to the intensity/ amount of the reflected sound waves i.e. echoes. This is why, US examination is also known as echography e.g. echocardiography i.e. ultrasonographic examination of the heart. Ultrasonography is a versatile imaging tool; however it is very operator dependent unlike the other imaging modalities. Thus the expertise and experience of the operator is very important to utilize this examination for maximum benefit. US can be utilized as diagnostic tool, guiding for intervention such as biopsy and drainage or both. It is a relatively very safe imaging modality as no X-radiation is involved. In some disease entity, such as looking for the presence of gallstones or renal stones, US is now the first imaging and the imaging procedure of choice compared to plain radiography.
Mammography(Conventional X-ray Mammography)
Mammography is an imaging procedure for the breast. Breast in medical terms is known as mammary gland.An X-ray mammographic unit is a system which is specifically design for the sole examination of the breasts. There are specific differences in the components of the X-ray mammographic unit which allows the optimum parameters and comfort for the patient undergoing this examination.
One of the objectives of doing this examination is for screening the breast for possible abnormalities and more importantly in detecting early breast cancers which might not be felt by the patient or the attending doctor. The other objective is to try to provide further information with regards to specific complaints by the patient or abnormalities noted by the examining doctor. The information obtained will provide further clues as to the nature of the abnormality i.e. whether the lesion is likely to be cancerous, less likely or unlikely. X-ray mammography is also utilize as a follow up examination for known case of breast cancer who had undergone treatment so as to allow the attending doctor to know whether the patient has respond to treatment and also to assess the disease progression.
Computed Tomographic Scan(CT Scan)
This examination utilizes X-rays basically similar to plain radiography. However, the X-rays that exit from the patient's body do not 'interact' with the radiographic film as in plain (conventional) radiography. In CT scan, the X-rays that exit from the patient will 'interact' with special detectors which convert the X-rays into electrical signals and subsequently being channeled to the computer system. The computer system will then 'processed' the signals and finally will reconstruct an image of the body part that is being examined. Thus the images that we seen in a CT scan examination are computer constructed images. There are many benefit and advantages of CT scan compared to the plain (conventional) radiography which include, allowing image manipulation, reconstruction, 'clearer' image of body parts and more importantly allows visualization of body parts that are no visible in the plain radiograph.
The newer CT scanner allows further benefical capabilities which provide informations that immensly surpass the capability of plain radiography. At PdSH, the CT scanner is of the helical type which means it has a volume data acquisition i.e. scanning is being performed while patient is gradually moved into or out of the gantry. The advantage of helical CT is it allows faster scanning and a better multi planar image reconstruction compared to the conventional computrd tomography. Patient who's undergoing a CT examination may be required to ingest radiographic contrast medium prior to the examination. In addition, patient may also be given intravenous contrast medium. This is to further enhance and characterize the abnormality. Sometime contrast medium may need to be given through other routes such as per rectal, insertion of tampoon pervaginal and also into the thecal space for spinal and intracranial lesion. However intrathecal contrast injection has significantly decrease with the availability of magnetic resonance imaging (MRI). CT can also be utilized as a guiding modality for certain interventional procedures such as biopsy or therapeutic procedure such as insertion of drainage tubes.
Fluoroscopy (X-ray Conventional Fluoroscopy)
This imaging technique allows real time visualization, by means of image intensfier and TV moniter the target organ that is being examined. This imaging technique usually utilizes the usage of special radiographic contrast medium to delineate the structure of interest. The examination is usually carried out with the radiologist and an assistant inside the examination with the patient. Therefore the radiologist and other persons (excluding the patient) within the room need to put on proctective lead gown and other radiation protective harness during a fluoroscopic examination.
By performing this examination, the radiologist could evaluate and detect presence of abnormality and document this abnormality by taking appropriate radiographs. The introduction of radiographic contrast medium can be performed through various routes depending on the organ or structure of interest. Some of the routes include per oral (through the mouth), per rectal (through the anal opening), per urethral (through the urethra i.e. urinary passageway) and other openings which might occur as a result of the disease process, trauma or being surgically created. Examples of fluoroscopic examination includes barium swallow, barium meal, barium meal follow through, barium emema, loopogram, micturating cysto urethrogram, nephrostomogram, sinogram and fistulogram. The contrast medium used is usaually a positive contrast medium such as barium suspension, gastrografin or other iodine contining water solible contrast medium. Fluoroscopy is also utilized in performing other image guided procedures diagnostic, therapeutic or both. This include endoscopic retrograde cholangio-pancreaticography (ERCP), pacemaker insertion, nephrostomy, hystrosalphingography (HSG), or tissue biopsy such as pulmonary (lung) masses.
CPortable/Mobile Radiography (Portable X-ray)
This radiographic facility is provided specifically for the ill patient who is too ill to come to the DID for plain radiographic examination. The radiograph obtained is usually not as 'good' as those that is being performed in the DID. There are various reasons for the compromise of the radiographic quality. This includes lower output of the mobile radiographic unit i.e. kV and mA, poor patient compliance and also shorter focus film distance. However the main purpose of mobile radiography is to demonstrate gross abnormality in the critically patient. Thus appropriate radiograph may be performed in DID when the patient's condition improved. Therefore as far as possible radiography of patient is best performed in DID where better radiographic unit is available.
Mobile C-arm Fluoroscopy
This floroscopic unit is usually utilized in the operating theatre (OT), to assist the surgeon who's performing certain procedures such as operative cholangiogram, insertion of certain surgical or orthopedic gadgets into the patient or in guiding the surgeon to identify certain bony landmark during surgery such as spinal surgery. The radiographs is the being processed for hard copy documentation when the need arises.
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