The procedure of computed tomography of the limb bones with contrast injection

The article is expertly consulted by Master, Doctor Luu Thi Bich Ngoc - Doctor of Radiology - Department of Diagnostic Imaging and Nuclear Medicine - Vinmec Times City International General Hospital.

The technique of bone computed tomography with contrast injection is performed to diagnose diseases in the bones of the upper and lower extremities of patients such as bone and soft tissue tumors, acute or chronic osteomyelitis,...

Computed tomography of the extremities is performed by transverse sections covering the entire lesion or cutting the entire length of the bone, the length of the limb will then be injected with contrast to evaluate the enhancement. of the lesions (if any). Next, the radiologist uses specialized software to reconstruct bone images and software in the vertical, horizontal and 3D directions, helping the doctor confirm the diagnosis.

● Appoint people with bone and soft tissue tumors, acute or chronic osteomyelitis;
● Contraindications: The technique has no absolute contraindications. Relative contraindications for patients with a history of allergy to iodine contrast agents, people with liver failure, renal failure, bronchial asthma and pregnant women.

● Performers: Specialist doctors, radiology technicians and nurses;
● Medical supplies: Including water-soluble iodinated contrast agents, surgical instruments, syringes of all sizes, needles of all sizes, distilled water or physiological saline, skin antiseptic solutions, medicine boxes, emergency equipment for contrast drug accidents;
● Technical facilities: Computer tomography machine, specialized electric pump and film, film printer, image storage system;
● Patient: The doctor explains in detail about the technique; fast before 4 hours and can drink less than 50ml of water; give sedation if the patient is too excited, can't lie still;
Test card: There is a ticket to order computed tomography

metatarsal bones: The order from inside to outside is vertebrae I - vertebrae V, each with a base, body, and crest; Knuckle bones: Each leg has 3 bones, which are the proximal, middle and distal phalanges; except for finger I, there are only bones; The hip joint is the largest synovial joint in the body.

● Set machine parameters: Enter patient data information; cutting according to the spiral program with a cut thickness of 0.5m before injection, 1.25mm after injection; Kv 120; Pitch 0.6 – 1.375, mAs 150 - 250; ball rotation speed less than 1 second; FOV varies from patient to patient; injection rate 3-4 ml/s, dose 1.5 ml/kg body weight;
● Patient position: Lying on the back, the position of the extremities is similar to the position of angiography of the extremities. Next, the doctor places an intravenous needle in the upper limb opposite the side of the lesion. In some cases, the veins of the lower extremities, the subclavian veins, and the jugular veins can be placed;
● Shooting: Crop orientation in 2 vertical and horizontal planes; performing cross-sectional layers before contrast injection and after contrast injection, arteries and veins;
● Image rendering: Using specialized software such as MIP, VR,... to reconstruct the image of the limb bones in all directions, prioritizing exposure at the lesion site;
● Film printing: According to the bone window or according to the soft tissue window, depending on the doctor's instructions.

The obtained results show the anatomical structures of the limb system, helping the doctor to detect lesions and evaluate the nature of contrast enhancement if any.
The method of computed tomography of the extremities with contrast injection may have some errors such as the patient not keeping still during the CT scan, not revealing the clear image, so it needs to be done again. Others may experience contrast-related complications and will be managed according to standard protocols.
Measures to reduce the risk of complications when performing computed tomography of the limbs with contrast injection is that the patient strictly follows the instructions of the doctor before, during and after the CT scan.

Some common diseases in bones include:
● Osteoporosis: Due to abnormal deficiency in bone substance and bone structure degeneration in middle-aged people. This makes bones weak, more prone to fracture;
Vitreous bone disease: Due to a genetic disorder that causes a defect in the gene that produces collagen - a protein that makes bones strong and elastic. Patients with vitreous bone are prone to fractures and fractures; Paget's disease of bone: A bone disorder that causes abnormalities in certain bone tissues. Usually, the patient's bones will be thicker and larger;
Osteomalacia: Due to vitamin D deficiency, usually occurs in adults. A deficiency of vitamin D limits the ability of bones to absorb calcium and phosphorus, causing improper bone growth and fracture;
● Bone cancer : Usually does not originate from the bone, but mainly due to the metastasis of cancer cells from another organ;
Acromegaly: Bones grow oversized due to excess hormones in the body. This disease can lead to high blood pressure, type 2 diabetes, rheumatism, colon polyps,...;
Osteomyelitis : A sudden, acute or chronic bone infection.

The method of computed tomography of the extremities with contrast injection can diagnose the above diseases.
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Master, Doctor Luu Thi Bich Ngoc has 06 years of experience working in the field of diagnostic imaging, received formal training and graduated with a Master's degree from Hanoi Medical University. Dr. Ngoc has strengths in diagnosing breast, thyroid, liver cancers early. experience in doing ultrasound of tissue elastography for liver, breast, thyroid diseases... From 2019 until now, Dr. Ngoc has worked at Vinmec Times City International Hospital with a position at the department. Image analysation.
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