| Haemoglobin | (11.5 - 16.5g/dl) | |
| RBC | (4.0 - 5.5 x1012/l) | |
| Reticulocytes | (less than 1%) | |
| PCV | (35 - 47%) | |
| MCV | (81 - 99fl) | |
| Platelets | (150 - 450 x109/l) | |
| White Cell Count | (4.0 - 11.0 x109/l) | |
| Neutrophils | (2.2 - 7.7 x109/l) | ~ 60 - 70% |
| Lymphocytes | (1 - 3.5 x 109/l) | ~ 25 - 35% |
| Monocytes | (1.6 - 1.8 x 108/l) | ~ 4 - 8% |
| Eosinophils | (less than 0.45 x 109/l) | ~ 1 - 4% |
Disappearance of the nucleus completes the formation of the young erythrocyte (reticulocyte) which is larger than the mature form and has a faintly bluish colour with Romanowsky stains and still contains fine reticular material.
The mature erythrocyte stains as an eosinophilic, circular biconcave disc with a diameter of 7.2 microns.
The presence of normoblasts in blood indicates excessive or abnormal blood formation or irritation of the bone marrow.
Excessive reticulocytes reflects increased erythropoiesis.
Haemoglobin is the oxygen transport system of blood and in the normal adult consists of four paired polypeptide chains, 2 alpha chains of 141 amino acids and 2 beta chains of 146 amino acids.
B12 and folate are required in the maturation of red blood cells, a deficiency state results in an increased proportion of immature blood cells in the circulation resulting in a macrocytic anaemia.
Iron is essential in the synthesis of haemoglobin and a deficiency results in over mature small red blood cells in the circulation and a microcytic anaemia.
Neutrophils have a high enzyme content and are actively phagocytic to infective organisms which they digest. The products of autodigestion are potent stimulants of fresh neutrophil formation by the bone marrow. Mature neutrophils account for about 70% of the total leucocytes in the peripheral blood of a healthy adult. Physiological factors which increase their number in the peripheral blood include exercise, emotional stress and pregnancy.
Immature granulocytes represented by metamyelocytes are found when the production of leucocytes is being stimulated by sever pyogenic infections. Appearance of myeloblasts reflects a serious disturbance of marrow function such as leukaemia.
Eosinophils are also phagocytic and their granules contain histamine and are concerned in processes involving foreign proteins such as hypersensitivity reactions.
Basophils are non phagocytic and have granules containing heparin and histamine.
Lymphocytes mainly derived from stem cells in lymphoid tissue though some are found in bone marrow. The immature form is the lymphoblast which resembles a myeloblast. Lymphocytes are mainly concerned with the formation and transport of antibodies. 'T' lymphocytes are concerned with cell mediated immunity and 'B' lymphocytes with humoral antibody synthesis.
Types of hypersensitivity reaction:
This is determined by the aggregation of erythrocytes into rouleaux which in turn is determined by the characteristics of the erythrocytes, the viscosity of the plasma and the electrostatic forces of the surrounding macromolecules
Erythrocytes usually repel each other due to a negative charge of the carboxyl group of N-acetylneuraminic acid located on the surface of the cell.
Absorbing force is provided by plasma macromolecules (acute phase reactants) many of which are positively charged and stick to the RBCs which then ® aggregates which have an increased combined weight relative to their surface area and settle to the bottom through the plasma
There is an increase in the concentration of acute phase reactants in situations of infection, malignancy or inflammatory conditions such as collagen vascular disease etc
Most commonly used in orthopaedic surgery to diagnose and then monitor the progression of or recovery from infection
The interval between the onset of symptoms and the return of the sedimentation rate to normal may be 3 - 4 months (the CRP will fluctuate more rapidly indicating response to treatment)
ESR will increase after an acute fracture but returns to normal after about one month
After THR the ESR will often remain slightly elevated for one year or so but if more than 40mm more than one year after THR suggests infection until proven otherwise.
Women tend to have a higher baseline ESR than men
Higher values occur in elderly patients, during pregnancy, and when taking certain medications such as heparin and oral contraceptives
Conditions that can lower the sedimentation rate include the administration of steroidal and non steroidal anti-inflammatories, the presence of sickle cell disease and haemolytic anaemia, haemoglobinopathy hereditary spherocytosis, polycythemia, hypofibrinogenaemia, deficiency of pyruvate kinase, etc
Sound waves are generated using a reverse piezo-electric effect when a signal is applied to a crystal and causes it to deform
The frequency at which the crystal vibrates is dependent on both the nature of the electrical stimulus applied and the characteristics of the crystal
The crystal is a transducer which transforms electrical stimulus into vibration and then acts as a receiver transforming reflected vibration into an electrical signal (about 1/1000 acts as a stimulus and 999/1000 as a receiver)
As the vibration travels from one substance into another with a different density some sound energy is reflected and recorded, the bigger the change in sound transmission the greater the reflection (sound transmission is best in liquid and worst in air)
Tissue penetration is better with lower frequencies but spatial resolution is better with higher frequencies
At least 48 hours should ordinarily be allowed before repeat examination
Patients should be well hydrated prior to the study and maintain a normal diet up to two hours prior to the study
Should discontinue neuroleptic drugs at least 48 hours prior to the study
During the procedure keep the patients head elevated above the highest level of the spine and do not lower the head of the bed more than 15o in order to move contrast cranially
Inject contrast slowly over 1 - 2 minutes, avoid intracranial entry of contrast and after the procedure raise the head of bed 15o - 45o and maintain patient in a semi sitting position for the first few hours
Recommend to maintain close supervision of the patient for at least 12 hours post myelogram and after 8 hours the patient may be lowered to the horizontal position for a further 16 hours and encourage oral fluids throughout
These reactions generally occur 3 - 8 hours after the study and almost all occur within 24 hours of the study.
Symptoms are usually mild or moderate in degree, lasting for a few hours and usually disappearing within 24 hours. Rarely symptoms may persist for days and be severe
Back ache, pain in the arms, neck stiffness, weakness, numbness and paraesthesia or sciatic type pain have occurred less frequently often in the form of transient exacerbation of pre-existing symptomatology
Isotopes in common use are Tc99m MDP (methylene diphosphonate) and Tc99m EHDP (ethyl hydroxy-diphosphonate)
Tc99 is the degradation product of Molybdenum99
Tc99 is bound in the generator to aluminium hydroxide and the technitium is washed off with saline to form pertechnate (TcO4) which can be bound to diphosphonate for bone scanning (generators received weekly from Lucas Heights)
Diphosphonates are the most commonly used ligands and are phosphate-carbon-phosphate compounds which are rapidly cleared from the blood producing high bone to soft tissue ratios and marked accumulation within areas of bony pathology within 2 - 3 hours of injection.
T1/2 is 6 hours for the Tc99 but the biological T1/2 is less due to renal excretion
Abnormality can be indicated by an increase in the blood supply to a region as indicated by rapid sequential images after injection of the isotope indicating arterial blood flow (Phase 1). Phase 2 follows immediately and is designed to image the static blood pool and relative vascularity of a lesion. Phase 3, delayed images are taken after 2 - 3 hours and indicate increased bone turnover.
Arterial phase scans may be of use in the assessment of RSD and arterio-venous malformations etc.
Occasionally the patient may be re-scaned at 24 hours, particularly for pelvic pathology in an attemp to reduce activity in the overlying bladder.
Gallium has similar phases but takes longer for cellular uptake therefore scan initially at 6 hours and then at 48 hours (taken up by cells with a high transferrin content, particularly WBCs, tumour cells particularly lymphoma and lung)
T1/2 of Gallium is 72 hours
Indium111 labelled WBC scan performed by taking 80 - 90ml of venous blood ® separate the leucocytes, label the leucocytes in vitro with In111 by incubating the cells in In111 oxide for 10 - 20 minutes at room temperature and replace WBCs in the patient ® scan 18 - 24 hours later (the whole process takes ~ 3 hours to label the cells)
Can be coupled with computer tomography (SPECT; Single Photon Emission Computer Tomography)
Once exposed to a magnetic field they align within the field in one of two positions either parallel (low energy state) or anti-parallel (high energy state)
In addition to spinning the nuclei precess or wobble a few degrees off axis, the frequency of precession is known as the resonance frequency and is proportional to the strength of the magnetic field applied
It is the hydrogen nucleus, which accounts for 2/3 of the atoms in the body and is a single proton that is used for clinical magnetic resonance imaging.
If radiofrequency energy is applied at the proper frequency (resonant frequency) the protons can be caused to realign from their original orientation within the magnetic field. When the radiofrequency is turned off the protons return to their original position and a small amount of energy is given off, which is detected by the receiving coil.
The intensity of the voltage (spin density) is related to the concentration of nuclei in the site being imaged
The time it takes for the voltage to decay or relaxation to occur is expressed by the T1 and T2 relaxation times
T1 relaxation (longitudinal or spin lattice) is the time taken for 63% of longitudinal magnetisation to recover following a RF pulse.
T1 weighted images are good for identifying the anatomy with good tissue plane differentiation and water has a low signal intensity, fat has a high signal intensity
T2 relaxation (transverse or spin-spin) is due to randomly varying inhomogenicities in the magnetic field created by adjacent nuclei and equals the time necessary to reduce transverse magnetisation to 37% of original value following the RF pulse
T2 weighted images assist in distinguishing normal and abnormal soft tissues and water appears white with high signal intensity
By varying the conditions under which the radiofrequency pulses are applied can emphasise the spin density resulting in a T1 or T2 weighted image
TR is the repetition time between radiofrequency pulses and the echo time. The longer the delay the more the image depends on proton density, and the shorter the delay the more T1 weighted the image will become
TE is the time between application of the RF pulse and the recording time
Application of the radiofrequency results in the protons flipping 90 - 180o in the magnetic field and it is the characteristics of the tissue that governs the rate of regaining alignment in the axis of the magnetic field. Application of a second radiofrequency pulse when the orientation of the protons is out of phase gives further information about the characteristics of the tissue.
Blood flow results in a signal void as do substances with a low proton density
Gadolinium-diethylenetriamine penta-acetic acid (Gadolinium DPTA) contain paramagnetic moieties which create local magnetic fields leading to quicker relaxation of adjacent tissues and its effect is seen indirectly by its effect on adjacent tissues (shortens the T1 relaxation time of vascular tissue)
Surface coils are small RF receivers wrapped around or placed on body parts which result in better signal to noise ratios
Best test for vascularity of bone with changes evident with avascularity of the marrow well before other investigations will alter.