Patient head-first position

Most manufacturers assume that the patient will be in the head-first position, and the preset protocols are designed accordingly. A head-first position has the following disadvantages ... 

A disadvantage of the foot-first position is that most CT tables need to be extended for patients to be positioned comfortably without their legs dangling the extension may prevent the table from being lowered far enough, and alterations are necessary if a head-first position is required (e.g. for additional head CT). The patient s direction must, without fail, be entered correctly in the examination protocol, since the left side may otherwise be taken for the right and some scanners do not allow later correction of the side identifiers. 

Maintenance of an adequate oxygen supply is the first priority. A systolic blood pressure of 80 mmHg can be tolerated in a young person but a level below 90 mmHg will imperil the brain or kidney of the elderly. Expansion of the venous capacitance bed is the usual cause of shock in acute poisoning and blood pressure may be restored by placing the patient in the head-down position to encourage venous return to the heart, or by the use of a colloid... 

Drugs injected directly into the cerebrospinal fluid have a tendency to produce unpredictable effects, their spread being influenced not only by the volume administered, but also by the concentration of the drug, its specific gravity in relation to that of cerebrospinal fluid, the positioning of the patient (head-up or head-down), and on the speed of injection of bolus doses. Truncal muscle spasms can also increase the spread of drug within the cerebrospinal fluid. All these parameters need to be taken into consideration. Standardization is required as a first step. Rapid bolus injection in particular can produce unexpectedly severe adverse effects. 

In the DICOM system, these CS definitions are independent of the scanning position. However, this requires defining the patient position relative to the image acquisition equipment. The previous CS assumes that the patient is head-up (supine) and head first into the scanner. If the patient is scanned in another orientation or scanning is obhque to one of the anatomical axes, the patient orientation must be defined during acquisition. In DICOM, this orientation is stored with each image as the direction cosine of the patient relative to instrument. Finally, the image position specifies the location of the center of the first pixel in each direction. 

Retinoids have also been studied for their potential in the treatment of oral leucoplakia [243], the prevention of cancers [244,245], and in the treatment of a leukaemia other than APL [246]. In one study, 13-c/s-retinoic acid was found effective for treatment of oral leucoplakia with 16 out of 24 patients responding positively to the treatment [243]. An average of 63% reduction of skin cancers was observed in 5 patients treated with 13-cis-RA (2 mg/kg daily) over a period of 2 years [244]. After discontinuance of therapy, tumour incidence increased 8.5-fold relative to the frequency during treatment. Similarily, 13-ew-RA treatment at 50-100 mg m day was effective in the prevention of second primary tumours in patients with squamous-cell carcinoma of the head and neck [245], although the retinoid was ineffective in preventing recurrences of the original tumour. Recently, the first effective response to oral RA therapy from a patient with a blast crisis of chronic myelogenous leukaemia (CML-BC) was reported [246]. 

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