Helical CT Scan in Comparison to MRI Scans

Helical CT Scan in equivalence to drawing cardic rapport imaging ScansIntroductionHelical CT is as well known as spiraling CT the two terms atomic number 18 interchangeable (Kalender, 1994). nigh(prenominal) magnetized resonance imaging and helical CT have been introduced into clinical practice forwards of any try for cost- potent improvement in clinical c ar. both technologies ar still evolving. For case vascular 3D imaging is a newly expanding indication within CT. Although helical CT is replacing schematic CT the question arises as to whether it go out replace charismatic resonance imaging.1) EquipmentHelical CT began in the 1990s. It is a fast technique data is collected perpetually at less than one second for a 10 mm slice. It is called helical because the unhurried exits continuously though the machine whilst the X-ray supply rotates around them. Slip ring technology enables the creasener, mounted on a gantry, to continue rotating in the real(prenominal ) direction around the persevering even still maintain its power supply and x-Ray capability. Because it is so speedily breathing does non affect the quality of the final image and it is an sharp way to view the lungs and liver. Because of the continuous rotation helical CT enables patient translation and the acquisition of data to take place at the same time. Helical CT requires completely different equipment to convention CT necessitating the substitution of the entire unit non just an upgrade. A multislice CT scanner is along the same principle as a helical scanner but is even faster still and contains more detection elements. Although the genuine data acquisition is so much faster with multislice the time un vacateable to process the image is lengthy (so patient through put will be no faster). The amount of data storage space indispensable for multislice images is incredibly vast and may overload the capability of the existing PACS administration within the hospital. The equipment for magnetic resonance imaging consists of a large, heavy magnet which creates the magnetic field. magnetised shielding of the room is necessary together with stringent safety precautions to avoid accidents for instance with flying metal objects within the room. The scanning tube-shaped structure where the patient must lie is relatively enclosed and this can create line of works with claustrophobia. The equipment is also very noisy which may unnerve the patient. magnetic resonance imaging requires more immense software for viewing the images than does CT. Some magnetic resonance imaging machinery is more open permitting greater patient access even to the extent of allowing simultaneous performance (Gould and Darzi, 1997).2) Techniquesmagnetic resonance imaging involves the person being placed in a large magnet the magnetic field of which causes all the protons (the nuclei of heat content atoms) in the body to linage up and oscillate at a certain frequency (preci sion frequency). Radiofrequency pulses are emitted from the machinery at the same frequency as the precision frequency make the protons to come out of alignment for a brief time and later on realign emitting energy in the process. The radiofrequency of these emissions is specific to the type of issue (since it reflects the hydrogen content) and is then computed to form an image. patient movement is a major problem with the MRI technique since data acquisition is quite slow and so it is not as good as helical CT for move organs such as the lungs and liver. MRI scans are more costly to produce that helical CT. The major advantages of MRI over helical CT are that MRI involves no x-Ray exposure and certain structures depict better images with MRI such as the brain and musculoskeletal system. MRI is definitely the best test for acoustic neuroma (Renowden and Anslow 1993). CT is better than MRI for imaging brain harm and is better in the belly for the gut (on account of it being a moving structure) whereas MRI is better in the pelvis. Helical CT is finding a place in the diagnosing of pulmonary embolism (Roy 2005). The disadvantages of CT are the x-Ray dose and the nephrotoxicity of some contrast agents.In 1993 the Royal College of Radiologist deallines recommended MRI be utilize for investigations on the brain, musculoskeletal system, oncology and paediatrics, the 1995 version of the guidelines recommended back pain beyond sextette weeks be investigated by MRI. The Royal College of Radiologists document on oncology (1999) provides graded evidence based recommendation of which scanning humour to use according to tumor site.3) StaffStaff training is necessary for both modalities of scanning. MRI staffing be are higher than with CT. Because MRI scans are in such withdraw and scanning time long it is often necessary to run the machines in the evenings and at weekends (Moore Golding, 1992). Multislice CT can involve increased radiologist workload.4) Pati entPatients with metal implants or pacemakers or who are claustrophobic are unfit for MRI. Mechanical ventilation is a relative contraindication. Patients with acute major distress including head injury are unlikely to be suitable for MRI because of the duration of scanning. The increased x-Ray dose to patients (and to the community) of the later generation CT scanners is of concern ( guinea pig Radiological Protection Board, 1990). For this reason MRI is the preferred modality for children and fetuses (Duncan 1996). Patients requiring interventional procedures may be suitable for a CT fluoroscopy (Wagner 2001).5) Quality of resultsMRI is preferred for the brain and spine (where it is of overriding advantage), orthopaedics and the pelvis. MRI produces very accurate images of soft tissues but imaging time is longer and artefacts are caused by patient movement. It is likely it has reduced the number of knee arthroscopies (Stoner, 1995) and it is anticipate to reduce the number of i nvasive radiological investigations such as angiograms. MRI may develop a clinical role as canvas the actual function of the brain in neuropsychiatry (Callicott and Weinberger1999). CT is preferable for bone. In brain trauma, subarachnoid haemorrhage and acute cerebrovascular disease MRI is not as good as CT. coiling CT is used for the lungs and abdomen and pelvis. It is valuable in detecting small lesions. It is helpful in trauma patients since the procedure is so quick. Spiral CT does lose a splintering of resolution as compared with conventional CT and so for structures that are not moving conventional CT or MRI has the advantage.6) tollCost considerations include those of initial purchase (or lease) set up and also political campaign be. Assistance in the procurement process is available from the Diagnostic medical examination Equipment team which is working closely with the segment of Health in the optimising of shelter for money in the replacement of all MRI and CT sca nners that are pre-1997. A 16 multislice CT scanner costs approximately d 000 whereas an MRI scanner is more at 800 000 running costs are also more with MRI ( frank, 2003). Bowens and Smith (writing in 1999) affirm the costs of an MRI scanner are from 400 000 for a 0.5T and 750 000 for a 1.5T. They state the service contracts are around 50 000 per year and that to lease a machine costs about 120 000 per year. MRI may be more expensive to install since the magnet is large and heavy. The site may be unsuitable with regard to load bearing or access. In any case expense will be incurred in magnetic shielding. MRI is a relatively expensive imaging modality. Fletcher (1999) has analysed costs of getting and operating MRI in the NHS over a seven-year machine lifespan. Its staffing, upgrade, upkeep and running costs are all high. The cost of an MRI scan varies from 30 to 180 (Bowens and Smith, 1999).In evaluating costs it is necessary to look at the whole picture. The running costs of i solated MRI machines will be higher than where machines are grouped together. Smaller MRI scanners just for union scanning use may prove cost effective (Marti-Bonmati Kormano, 1997). If a more expensive scanning modality saves on the costs of surgery then overall there may be economic gain. For instance MRI may avoid knee joint surgery (Bui-Mansfield 1997). It is substantial to ensure that it is actually replacing other investigations or surgery and not just adding to them (Hailey Marshall, 1995). Overall the cost effectiveness will depend on how appropriately the imaging modality is used.Regarding CT the X- Ray tubes are expensive. A helical scanner is likely to need one x-Ray tube replacement per year (possibly more frequently in the case of a multislice scanner) and this will cost approximately 30000-40000 (Conall and Hanlon, 2002). Berry (1999) performed a systematic reexamination finding little clinical or economic impact of spiral CT.ConclusionAlthough there has been away from MRI to helical CT in some clinical situations units will need access to both types of scan. Cooperation among different units is important in order to provide a all-around(prenominal) service to the population. It is likely that some patients such as orthopaedic outpatients should move to another unit for the scan. Computerised reporting makes off site scanning realistically closer. Choice of scanning modality is likely to ultimately depend upon collaborationism with local units to develop a hub and spoke approach to providing cost effective services which are also effective and convenient for patients.ReferencesBookFishman EK Jeffrey RB Spiral CT. Principles, Techniques and Clinical Applications. 2nd edition. 1998 Philadelphia. Lippincourt Raven.ArticlesBerry E et al A systematic literature review of spiral and electron beam computed mental imagery with particular reference to clinical applications in hepatic lesions, pulmonary embolus and coronary artery disease. Health Technology Assessment, 1999 3(18)Bui-Mansfield LT et al Potential cost nest egg of MR imaging obtained before arthroscopy of the knee evaluation of 50 consecutive patients. 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London RCR, (3rd edition) 1993, (4th edition) 1998, (5th edition) 2003.Stoner DW. The knee. In Seminars in Roentgenology 1995 30 277-93Wagner LK. CT fluoroscopy another emanation with additional challenges in radiation management. Radiology 2001 216 9-10ReportsBowens A Smith I Magnetic resonance imaging current provision and future demands. Nuffield Portfolio programme Report No3. Northern and Yorkshire RD Portfolio programme at the Nuffield Institute for Health. December 1999. ready(prenominal) at http//www.nuffield.leeds.ac.uk/downloads/portfolio/mri.pdfRoyal College of radiologists Making the Best mapping of a Department of Clinical Radiology Guidelines for Doctors. Fifth Edition 2003 BFCR(03)3 Making the Best Use of a Department of Clinical Radiology Guidelines for Doctors. Fifth EditionWebsitesBritish Association of MR Radiographers http//www.bamrr.net/Departm ent of Health www.dh.gov.ukDiagnostic Medical Equipment team http//www.pasa.doh.gov.uk/dme/radiology/mr.stm