STUDY ANGIOCORONARIO BY COMPUTERIZED TOMOGRAPHY CORONARY ANATOMY The coronary arterial anatomy normal finds constituted by the left coronary arteries and right. Lto left coronary artery, to his time, possesses a main trunk that divides in the downward coronary arteries previous and circunfleja. Between the variants and anomalies of the coronary circulation more frequent include the anomalous origin of the coronary artery in the coronary breast contralateral, the coronary aneurism, the coronary fistula, the syndrome of Bland-White-Garland. The atanimalia or estenosis coronary congenital and the bridge miocárdico. By his part, the coronary veins pass along the grooves auriculoventriculares and interventriculares until confluir in the coronary breast. CORONARY ARTERIES NORMAL ANATOMY The left coronary arteries and right originate of the breasts of Valsalva corresponding, just on of the aortic ring and under the union sinotubular. EI Coronary breast right is previous. The distance of the coronary arteries is epicárdico along the surface of the heart. The coronary arteries usually find surrounded by fat. His diameter depends on several factors as, for example, the sex of the individual, the presence of anatomical variants of the coronary circulation and the existence of hypertrophy or dilatation ventricular. LEFT CORONARY ARTERY LEFT MAIN TRUNK EI Left main trunk originates of the left coronary breast. His diameter (3-6 mm) and his length (0-20 mm) are variable. The left main trunk forks in the downward coronary arteries previous and circunfleja. Although until in the 15 % of the people gives origin to an intermediate bouquet or bisectriz. It estimates that in the 0.41 % of the cases the left main trunk does not develop and the downward coronary arteries previous and circunfleja originate directly of the left coronary breast. DOWNWARD CORONARY ARTERY PREVIOUS The downward coronary artery previous originates in the upper portion of the groove interventricular previous and passes until the ápex cardiac. In the majority of the patients the downward previous bordea the tip of the left ventricle and finishes in the inferior face of this; in some cases this artery does not reach the diaphragmatic face and finishes a bit before or just in the ápex cardiac. The downward coronary artery previous provides diagonal arteries and perforantes or septales. ARTERY CIRCUNFLEJA The artery circunfleja originates of the left main trunk, under the orejuela, and passes by the groove auriculoventricular left, irrigando the lateral wall of the left ventricle, part of the inferior face of this ventricle from small branches posterolaterales and part of the papillary muscle anterolateral from the obtuse branches marginales. In occasions observe branches for vascularizar the nodule sinoauricular. The artery circunfleja is used to to finish to level of the obtuse angle of the heart, distal to the origin of the first obtuse branch marginal. Artery circunfleja. To) Reconstruction with projection of maximum intensity (MIP) coronal oblicua. B) MIP sagital oblicua. C) MIP axial oblicua. D) volumetric Reconstruction. The artery circunfleja (Cx) passes along the groove auriculoventricular left and provides obtuse branches marginales (0M) that vascularizan the lateral wall of the left ventricle. In occasions gives origin to the artery of the nodule sinoauricular (tip of arrow). INTERMEDIATE BOUQUET OR BISECTRIZ The intermediate bouquet or bisectriz is an anatomical variant that originates directly of the left main trunk between the previous downward artery and circunfleja for irrigar the lateral wall of the left ventricle. The intermediate bouquet acts like analogous glass to a diagonal artery or to an obtuse branch marginal depending on his distance is previous or back along the lateral face of the left ventricle. RIGHT CORONARY ARTERY The coronary artery right is born of the coronary breast right, slightly underneath of the origin of the left coronary artery, and passes along the groove auriculoventricular right to the cardiac cross (convergence of the grooves auriculoventriculares and the interventricular inferior). In more than half of the cases, the first branch of the right coronary artery is the artery of the cone, that irriga the infundíbulo of the right ventricle. This artery forms the ring anastomótico of Vieussens to the anastomosarse with branches of the downward coronary artery previous; this ring possesses big clinical importance in cases of estenosis grave of the trunk or of the proximal segment of the downward previous. With frequency, the second branch is used to to be the artery of the nodule sinoauricular. In fact, this can be irrigado by branches of any coronary artery. More distalmente, the coronary artery right also contributes acute branches marginales for vascularizar the free wall of the right ventricle. To the height of the triangle of Koch, the coronary right is used to to give the artery of the nodule auriculoventricular. Finally, in cases of dominancia coronary right, the coronary artery right provides the back downward artery, or interventricular back, and the branches posterolaterales for irrigar the inferior face and the inferior third of the septum interventricular. DOMINANCIA CORONARY The pattern of dominancia coronary justifies the variations in the diameter and length of the coronary arteries and the quantity of myocardium vascularizado by each artery. It accepts that the artery that determines the dominancia is that that provides the vascularización of the nodule auriculoventricular and of the inferior face of the heart. Usually, the artery of the nodule auriculoventricular is very small. Especially to be detected by TC, and originates of the same artery that the back downward artery and the branches posterolateraIes. Therefore, in TC employ these two last arteries to define it dominancia. EI Dominant coronary system can be right or left or can exist codominancia. In the dominancia right, the back downward artery and the branches posterolaterales that irrigan the backside or inferior of the septum interventricular and the cardiac cross originate of the right coronary artery. In the coronary system of dominancia left, the back downward artery and the branches posterolaterales originate of the artery circunfleja, by what the coronary right is used to to be of very small calibrate and frequently finishes his route before arriving to the inferior face of the heart. If the system is codominante (also known like circulation swung), the back downward artery and the branches posterolaterales originate of the right coronary arteries and circunfleja, respectively; also it considers system codominante if they exist two downward arteries back an originated of the right coronary artery and another of the circunfleja. NOMENCLATURE OF THE CORONARY SEGMENTS To appoint and identify the coronary segments use distinct classifications. THE most extended model in TC cardiac is the proposed by the American Heart Association (AHA), that divides the vascularización coronary in 15 segments. The coronary artery right divides in the segments: 1, proximal, 2. Half, and 3, distal. The segment 4 is the back downward artery. The coronary artery left divides in the following segments: 5, left main trunk; 6, downward previous proximal; 7, downward previous average; 8, downward previous discal; 9, first diagonal branch; 10, second diagonal branch; 11, circunfleja proximal; 12. First obtuse branch marginal; 13, circunfleja discal; 14, first branch posterolateral left; 15, back downward artery if it originates of the artery circunfleja. CORONARY VEINS The coronary veins pass beside the coronary arteries, along the grooves auriculoventriculares and interventriculares until confluir in the coronary breast. The coronary breast finds in the backside of the groove auriculoventricular right and ends in the right auricula, at the side of the vein digs inferior. In the coronary breast end, by the left, the coronary vein elder, the vein oblicua of the left auricula and the back vein of the left ventricle, and by the right, the coronary vein minor and the vein interventricular posterior.la coronary vein elder or cardiac vein magna originates in the ápex cardiac, visits the groove interventricular previous beside the downward coronary artery previous, collecting the blood of the previous surface of the ventricles, and passes along the groove auriculoventricular left June to the artery circunfleja, until ending in the coronary breast. The cardiac vein magna is composed by the vein interventricular previous and marginal left, that collect the blood of the previous part of the ventricles, the septum interventricular, the lateral face of the left ventricle and the left auricula. The back vein of the left ventricle locates in the half part of the back face of the left ventricle and ends in the coronary breast. The coronary vein minor or cardiac vein minor originates in the right edge of the heart, passes along the groove auriculoventricular right and ends in the terminal portion of the coronary breast. In his route collects the blood of the veins marginales of the right ventricle. The vein interventricular back or cardiac vein average passes to the long dcl groove interventricular back until ending in the coronary breast together with the lower coronary vein. In addition to the venous system that drains in the coronary breast, exists a system of venous drainage that drains directly in the cardiac cavities, like the previous coronary veins and the minimum cardiac veins of Tebesio. The previous coronary Veins or previous cardiac veins collect the blood of the previous part of the right ventricle and end directly in the right auricula. The minimum cardiac veins of Tebesio are internal, do not appear in the surface of the heart and end in the cavity in which they find . Fundamental concepts of the computerized tomography DEFINITION OF PITCH The pitch is an important parameter that characterises to the helicoidal acquisition. It defines like the relation between the advance of the table by rotation the total width of the do of colimación. The total width of the do of colimación in a team multicorte is determined by the number of detectors and the thickness of colimación. For example, in a team of 64 courts with a colimación of 0.625 mm, the width toral of the do of colimación is of 40 mm. If the advance of the table is of 10 mm by rotation, the pitch of said acquisition is of 0.25. The selection of the pitch involves a balance between the acquisition of the data and to dose of radiation administered. A pitch lower of 1 indicate solapamiento dc the data during the acquisition and comports to go back to irradiar segments already purchased, translating in dose of radiation relatively high. By the contrary, an acquisition with a pitch greater of 1 is a faster acquisition and in which it does not administer so much radiation, but comports the danger that the acquisition was so fast that do not obtain all the necessary data to reconstruct the image. In the field of the TC cardiac the aim is to study anatomical structures of very small calibrate and minimise them artefacts by movement, by what in the acquisitions made with instrument of TCMD of 64 conventional courts the pitch that generally uses is of 0,2-0,4. In some teams the pitch selects manually when scheduling The exploration and keeps fixed during all the acquisition. In these cases, the selection of the pitch is used to to make in function of the cardiac frequency of the patients, by what, unfortunately, if the cardiac frequency modifies during the study, the acquisition of the data can result erroneous. This is one of the reasons to avoid in the possible that exist variability of the heart rate. Therefore, the pitch exerts an important paper in the optimisation of the resolution of the images and constitutes, besides, one of the main determinants of the dose of final radiation administered. As it has mentioned , since the dose of radiation is inversamente proportional to the pitch, the utilisation of a pitch low for cardiac studies by TC will translate in dose of radiation relatively high. The new volumetric teams with greater number of rows of detectors suppose a big advance in this sense, since they can cover the cardiac volume in scarce beats. SPACE RESOLUTION The space resolution defines like the minimum distance that allows to identify two points like separate in the space and expresses in millimetres (mm). What more jumps was the space resolution, lower is the minimum distance detectable and, therefore, greater is the anatomical detail with which will be able to study the distinct structures. The space resolution depends fundamentally of the size of the detectors and of the interval or increase of reconstruction of the images. SIZE OF THE DETECTOR The size of the detector affects to the space resolution of the image so much in the plane of study (in-plane) as in the longitudinal axis of the patient (axis z. through-plane). In the plane of study (in -plane) the space resolution is determined by the number of active detectors in each row of detectors and by the width of each detector. In the plane of the image, the space resolution depends of the field of vision and of the matrix of reconstruction: the size of the pixel is the relation between these two parameters. For a conventional matrix of 512 X 512 pixels and a field of vision of 25 cm, the size of pixel is of 0.5 mm. The resolution through the plane, that is to say, the resolution along the axis z of the patient, is determined by the thickness of court and finds limited by the geometry of the detectors. This resolution is the one who more has evolved in the last decades, happening of 1-1,25 mm in the first teams of TCMD of 4 courts to 0,5-0,625 mm in the teams of TCMD of 64 conventional courts. This has supposed the introduction of the concept of images isotrópicas. That is to say, images that possess the same dimensions of width, height and depth and that, therefore, can reconstruct in any plane of the space without deterioration of the quality. INTERVAL OF RECONSTRUCTION The interval or increase of reconstruction defines the degree of solapamiento that exists in the axial images reconstructed. Since the solapamiento makes once obtained the data, the interval of reconstruction does not influence in the own acquisition of the study, in his length or in the dose of radiation administered. The interval or increase of reconstruction influences only in the space resolution of the longitudinal axis of the patient (axis z). The solapamiento of the images allows to increase his space resolution, what results of utility to the pos-process the volume, since the images possess greater anatomical detail. The inconvenient elder to modify the interval of reconstruction is, however, that goes to affect directly to the number of resultant images, by what has to look for a balance between the profit diagnostic of a determinate percentage of solapamiento and the number of images that goes to generate. CLINICAL APPLICATION The space resolution is one of the big qualities of the TC. A high space resolution is especially important to be able to delineate with detail The coronary anatomy, detect and characterise the coronary illness value the degree of estenosis. The space resolution earns particular importance in cases of extensive calcification or stent, in which the artefacts hamper a correct visualisation of the light. The space resolution isotrópica current of the teams of TC is of roughly 0,5 mm. This resolution still is distant of the own of the coronariografía conventional, in which the space resolution is of 0,16 mm. Therefore, although the TC allows to obtain images with a relatively fine thickness, the information obtained by means of these teams still can not consider totally equiparable to the one of the coronariografía conventional. TEMPORARY RESOLUTION In the clinical practice is not infrequent to find coronary segments no valorables. In the majority of the cases is due to that the temporary resolution of the current teams is limited, what prevents to purchase the images with the sufficient rapidity as to avoid the artefacts owed to the cardiac movement. Numerous studies made to know the pattern of movement of the coronary arteries have showed that the phases of the cycle in which it exists minimum trip of the coronary arteries is at the end dela systole and during the half of the diastole. The half length of these phases is of 120 ms (rank, 66-333 ms), by what the temporary resolution of the teams TCMD of 64 conventional courts (165 ms) many times results insufficient to obtain studies without artefacts. The temporary resolution in TC is determined by the time of exhibition required to obtain the necessary data that allow to reconstruct an image. That is to say, the temporary resolution, expressed in milliseconds (ms), is the time of necessary acquisition to be able to obtain the minimum of data that allow to reconstruct an image. This minimum of necessary data to reconstruct an image designates partial-scan. The factors that determine the temporary resolution in TCMD are the time of rotation of the gantry and the method of reconstruction of the image. TIME OF ROTATION OF THE GANTRY The time of rotation of the gantry defines like the necessary time to make a complete rotation (360°) of the tube and the detectors around the patient. The times of rotation of the teams have improved of substantial form from the 2 seconds of the first teams of TC until the 330 ms of the teams of TCMD conventional of 64 courts or the 250-280 ms of the teams of TC of double source my current. The algorithm of specific reconstruction employee in TC cardiac designed to increase Lto temporary resolution using the minimum quantity of data knows like half-scan. This algorithm requires roughly the half of the rotation of the gantry to reconstruct an image. Therefore, the temporary resolution of the teams equates roughly to the half of his time of rotation in the centre of field of vision. Of this way, if the time of rotation of a team TCMD of 64 courts is of 330 ms, The temporary resolution of this team is roughly of 165 ms. The real temporary resolution is slightly inferior, since technically it requires purchase the half of the rotation in addition to the angle of disposal of the detectors (generally 30-60°). Because of this, what faster rote the gantry, higher will be the temporary resolution of the team, by what will require less time to purchase the data that will reconstruct an image and will reduce the artefacts. A high temporary resolution is critical to diminish or delete the artefacts related with the cardiac movement. One of the solutions that has allowed to increase the temporary resolution in TC cardiac has been the development of the teams TC of double source, composed by two tubes of X-rays oriented almost perpendicularmente one with regard to the another. This disposal of the tubes of X-rays allows that the 180° of rotation (half-scan) necessary to obtain the data that reconstruct the image can generate of simultaneous way with 90° of rotation of each tube. METHODS OF RECONSTRUCTION The algorithms of reconstruction of the images in ‘TC cardiac are complex and base in the combination of the reconstruction half-scan (data from roughly the half of the rotation of the gantry) and in inherent specific algorithms to the technology multicorte. They exist two methods of main reconstruction: the reconstruction partial-scan and the reconstruction multisegmento. RECONSTRUCTION PARTIAL-SCAN The interpolation of the data purchased during a partial rotation allows to obtain the minimum of necessary data to reconstruct an image in each beat. This type of reconstruction knows like partial-scan. In this type of reconstruction, the temporary resolution depends of the time of rotation of the gantry. When it chooses this type of reconstruction, the data that go to conform the volume of study collect to way of successive blocks of axial images that are reconstructed in consecutive cardiac beats. In function of the number of rows of detectors of the team, the number of axial courts that will compose each group of images will be variable, by what will require more or less beats to cover all the volume of the heart. To equality of parameters of acquisition, what elder was the number of detectors, lower will be the number of necessary beats to cover the rank of study. RECONSTRUCTION MULTISEGMENTO In an attempt to compensate the limited temporary resolution of the teams of TC have developed algorithms of specific reconstruction. These algorithms engloban inside the term reconstruction multisegmento and base in using the data obtained in several cardiac cycles (segments) to make the reconstruction partial-scan, in place to take all the data of an only cardiac cycle every time. The reconstruction multisegmento can make in cases of acquisition with synchronisation electrocardiográfica retrospective and his success will depend to a large extent that the heart rate of the patient was to regulate. The reconstruction multisegmento bases in groups of data obtained of several cardiac cycles, so that it is the combination of the data of two, three or more consecutive cardiac beats the one who will contribute to achieve the minimum of necessary data to reconstruct an image (partial-scan,). With this boarding, in theory, is possible to improve the temporary resolution of significant way (2 X number of cardiac cycles/included segments), although with frequency at the expense of images of worse definition, greater length of the study and greater dose of radiation. In such a way, one of the greater problems of the reconstruction multisegmento is that although it possesses greater temporary resolution, the resultant images of this type of reconstruction can have worse quality that the obtained with the traditional reconstruction of an only segment, to achieve an image nítida with the reconstruction multisegmento is necessary that in each beat the data find exactly in the same phase of the cardiac cycle. Often, however. The heart rate of the patients is not entirely regulate along the exploration and the anatomical structures can find in positions slightly different in each beat. When combining the information of distinct beats, therefore, the final image can present little definition. On the other hand, in accordance with the technical foundation of this type of reconstruction, what elder was the number of beats that wish include for the reconstruction and minor was the cardiac frequency of the patient, has to choose a pitch lower so as to that it do not exist loss of data. As it has mentioned previously, a pitch low carries to prolong the length of the exploration and increase it dose of radiation. In this sense, have developed specific algorithms that adapt to the cardiac frequency so as to limit the dose of radiation administered: if the cardiac frequency is slow, uses the information of an only cardiac cycle to reconstruct the image (reconstruction monosegmento), whereas if the cardiac frequency is fast, can employ until 3 beats or more. Finally, by mechanical questions, so that the reconstruction divided work properly has to exist a perfect synchronisation between the cardiac frequency of the patient the rotation of the gantry. It is necessary that all the subsegmentos obtained can range properly to reconstruct the final image. CLINICAL APPLICATION The coronary arteries remain in state quiescente in moments very concrete of the end of the systole and of the half of the diastole. The length of these phases varies with the cardiac frequency Although the length of the TV systole keeps practically constant (100- 150 ms). It exists a reverse relation between the length of the diastole and the cardiac frequency. The slow cardiac frequencies involve long diastoles, whereas high cardiac frequencies comport short diastoles. Of this way, in patients with slow cardiac frequencies the length of the diastole is proportionally a lot greater that the length of the systole, whereas in patients with fast cardiac frequencies, the length of the systole and the length of diastole can be equiparables. Likewise, since the temporary resolution of the teams of TCMD of 64 conventional courts is limited (some 165 ms in teams with time of rotation of 330 ms) to visualise the coronary arteries prefers purchase the studies during the diastole. In patients with cardiac frequency minor of70 beats by minute the window of acquisition with minimum cardiac movement can last until 250 ms, By what is usual practice control pharmacologically the cardiac frequency before the exploration by means of the administration of drugs bloqueantes. When reducing the cardiac frequency prolongs the diastole and therefore it exists greater probability to obtain images of the coronary arteries without artefacts of movement. RESOLUTION OF CONTRAST And RELATION CONTRAST-NOISE Unlike other technicians of image like the magnetic resonance, the resolution of contrast of the TC is not high because they do not exist big differences in the mitigation of the distinct fabrics. To increase the resolution of contrast in TC is necessary to administer intravenous iodized contrast. The iodized contrast allows to differentiate the coronary arteries of the adjacent myocardium. The parameters that more influence in the mitigation of the contrast are some characteristics of the patient. Like the corporal habit or the cardiac cost; parameters related with the handle of the contrast, like the length of the injection, the speed of injection, the moment of the acquisition and the concentration of the contrast , and appearances related with the type of acquisition and the team of TC. A way to increase the resolution of the contrast in the studies angiograficos is to modify the kilovoltaje, what will allow to increase the enhance of the vascular structures. Between the technical advance in resolution of contrast stand out the technicians of double energy with his capacity to differentiate the distinct structures in function of his behaviour with different kilovoltaje, of equal way the high space resolution that requires the TC translates in the need to employ a thickness of fine courts, with the consequent increase of the noise of the image. A way to reduce the noise is to increase the dose of radiation administered; also it can reduce the noise increasing the thickness of court when reconstructing the data. SYNCHRONISATION ELECTROCARDIOGRÁFICA The computerized tomography (TC) cardiac requires a space resolution, temporary and a relation contrast-noise elevated. The TC cardiac also precise synchronise the acquisition and reconstruction of the data with the register electrocardiográfico of the patient. The synchronisation electrocardiografía makes to increase the temporary resolution, purchase and reconstruct the studies in the phase of the cardiac cycle wished, with what avoid big part of the artefacts owed to the cardiac beat and to the coronary movement. Synchronise the acquisition and reconstruction of data with the electrocardiograma (ECG), therefore, is indispensable to obtain studies that allow to value the coronary anatomy, detect estenosis along his distance and characterise the vascular wall. The method of synchronisation ECG possesses a direct implication in the performance of the study, the quality of image. The type of exploration that goes to be able to make and, especially, in the dose of final radiation administered. In general, they exist two technicians of synchronisation ECG: the retrospective and the prospectiva. An important difference between the methods of retrospective synchronisation and prospectiva is that they comport a type of different acquisition. The synchronisation ECG retrospective uses for acquisitions spirals or helicoidal, whereas the synchronisation ECG prospectiva employs in sequential or axial acquisitions. ABSOLUTE And RELATIVE DELAY The periods of the cardiac cycle in that the coronary arteries present movement and minimum trip are very concrete. To avoid artefacts, the acquisition of the data has to adjust to these specific phases of the cycle. This achieves with the synchronisation ECG, that allows to choose the moment in that they purchase or reconstruct the images. In TC cardiac the cycle extends from a wave R to the following wave R of the ECG (interval R-R). The acquisition or reconstruction of the data can make of absolute or relative form to said wave R. EI Method of the absolute delay involves a fixed delay before or after the wave R of the ECG, during which synchronises the acquisition or initiates the reconstruction of the data. The relative delay is the method that employs at present with greater frequency and does reference to a delay of relative time to the wave R precedent to initiate the acquisition or reconstruction of the data. This relative delay determines for each cardiac cycle in accordance with the length of the interval R- W. With independence of the type of delay chosen, the suitable selection of the window of acquisition or reconstruction will be the one who guarantee the success of the exploration. WAYS OF SYNCHRONISATION The two strategies of synchronisation for the acquisition of data of TC cardiac are the prospectiva and the retrospective. SYNCHRONISATION ELECTROCARDIOGRÁFICA RETROSPECTIVE As his name indicates this type of synchronisation involves a continuous helicoidal acquisition of the data of all the cardiac cycle and his back reconstruction, retrospective, in the phase of the cardiac cycle wished. Given the nature of the acquisition by means of synchronisation ECG retrospective, the images can reconstruct in any phase of the cardiac cycle; that is to say, will be able to study so much in the systole as in the diastole, what provides flexibility to the hour to evaluate the coronary arteries. Even with optimum cardiac frequencies the reconstruction of the data of an only phase (Diastole, Systole) can result insufficient to analyse the complete coronary tree. Also it can occur that even treating of the optimum phase to value the majority of the segments, an only reconstruction was insufficient to analyse the whole of the coronary segments. Therefore, it is necessary to resort to additional reconstructions to be able to interpret the coronary vascular system complete. In teams of TC multidetector of 64 courts recommends make distinct reconstructions in function of the cardiac frequency: during the 50 and 60 % of the interval R-R if the cardiac frequency is lower of 60 beats by minutes The greater limitation of the synchronisation ECG retrospective is the high dose of radiation that administers during the exploration. This is due to 2 fundamental questions. To obtain studies with retrospective synchronisation and guarantee a complete coverage of the cardiac volume without loss of information , is necessary that the data purchase with a slow movement of the table, that is to say , a pitch low. This involves overexposure to the radiation, since during the study each concrete area of the heart purchases more than once. SYNCHRONISATION ELECTROCARDIOGRÁFICA PROSPECTIVA The synchronisation ECG prospectiva was the method of synchronisation employed in the starts of the TC cardiac and is the way of synchronisation that usually uses to quantify the coronary calcification. Because of the limitations in the space and temporary resolution and anatomical coverage of the ancient teams of TC the synchronisation prospectiva did not allow to obtain images diagnose of the vascularización coronary by what initially descartó his employment for studies coronarioangiografia by TC. At present thanks to the development of the teams of TCMD and to the advances of the space and temporary resolution and like consequence of the high dose of radiation related with the retrospective synchronisation has restarted the synchronisation prospectiva. The sequential acquisition with synchronisation prospectiva involves to purchase the studies in a very concrete phase of the cardiac cycle. The rest of the cycle desestima so as to minimise the dose of radiation administered this requires to know with accuracy and of in front of hand the phase of the cardiac cycle optima in each patient that allow to visualise the coronary arteries without artefact of movement. Another advantage of the synchronisation prospectiva in front of the retrospective is that they reduce the artefacts in case of extensive coronary calcification or stent, since it does not exist on acquisition of data. CLINICAL INDICATIONS AND SELECTION OF THE PATIENT The coronarioangiografia by TC has to be made in patients with probability pretest drop or intermediate of coronary illness and atypical thoracic pain and/or in the context of an electrocardiograma of exercise or a proof of detection of isquemia makes a mistake. The quality of the exploration is better in patients with cardiac frequency drop (<65 lat./min), cardiac rhythm regulate. The patients have to find in a situation hemodinámica stable and be able to cooperate with the breath, not to move during the exploration and bear the length of the apnoea that is used to to be of 6 to 8 seconds. The patients with grave arrhythmia, unsteadiness hemodinámica, chronic renal insufficiency and patient with obesity mórbida do not describe to make the study. In the selection of the patient also can consider the calsificación coronary, very related, in general with the cardiovascular risk of the patient. When the risk is high is more likely to find calsificación coronary extensive. In a lot of centres is usual practice make an initial acquisition to quantify the coronary calcification so as to stratify better the cardiovascular risk. In some centres uses the total quantity of coronary calcium like decisive element to the hour to proceed or no with the study. The extensive coronary calcification difficulty the visualisation of the vascular light, by what the coronary segments do not are used to to be valorables. PREPARATION OF THE PATIENT VENOUS ACCESS The venous access more convenient for the CTC is the vein antecubital right. This vein is used to to be of sufficient size to be able to enter a catéter of 18-20 G that allows to inject the contrast to a high flow. It prefers the road of the right side by the route to the heart is shorter with which can take advantage of better the contrast. CONTROL OF THE CARDIAC FREQUENCY One of the appearances that more conditions the quality of the exploration is the cardiac frequency the CTC requires that the cardiac frequency was slow and the stable cardiac rhythm, to a large extent because of which the temporary resolution of teams of TCMD is limited. The most common way to establish and control the cardiac frequency is by means of the administration of drugs. To achieve a cardiac frequency optima (<65 lat./min) The most common is to use drugs bloqueantes, although they also can employ other drugs like the antagonists of the channels of calcium. PLACING AND TRAINING OF THE PATIENT The patient plants of cubito supino, in the position (first feet) or (first head) as it prefer . To avoid artefacts is preferable that the route of the wires of the electrodes on the surface of the patient was the possible minimum. Since the acquisition goes to make with synchronisation SG the electrodes have to plant properly and very adhered to the torso of the patient. It is necessary that the wave “R “of the SG differentiate of the rest of the outline. If the electrodes connect of wrong form will not be able to obtain a good register of the SG with which synchronise the acquisition. If it does not exist good contact with the skin of the individual, the electrodes can despegarse during the exploration, with the consequent loss of data. To avoid artefacts the arms of the patient have to elevate above the shoulders. During the preparation of the patient, the arms have to find relaxed and has to evaluate only just before the exploration to avoid that by the tiredness or pain the patient move them and despeguen the electrodes. On the other hand it is important to train the breath of the patient. It has to him explain how has to make the inspiration so that it was similar in all the acquisitions and can adjust properly the ranks of the exploration. The ideal is to make the procedure with apnoeas that approximate to the length of the acquisition. ADMINISTRATION OF NITROGLYCERINE The gliceriltrinitrato, also known like nitroglycerine, is a glass dilatador arterial and venous powerful. In TC cardiac employs to dilate the coronary arteries and visualise the segments and branches of lower size. This drug can increase the diameter luminal until a 20-25 % and his employment can help to differentiate an estenosis coronary real of a glass espasmo transitory. ACQUISITION OF THE STUDY: TOPOGRAMA The cardiac study begins with the acquisition of the topograma. According to the team of TCMD can be an only frontal projection or 2 projections (frontal and lateral). The topograma uses to adjust the rank of exploration, by what has to make in inspiration, such as it has to purchase the cardiac study. When scheduling the exploration, the rank has to adjust to the type of protocol that wishes make to value the vascularización coronary the rank initiates of 1 to 2 cm underneath of the carina and extends until the inferior cardiac flange, under the diaphragm. CORONARIOGRAFIA BY COMPUTERIZED TOMOGRAPHY To obtain the maximum performance of the exploration, the parameters and protocols of CTC, have to individualizar in each patient. In effect, the technician of acquisition fulfils an important paper in the information that will be able to obtain of each study and in the dose of radiation that finally will receive the patient. PARAMETERS AND TECHNICAL OF ACQUISITION The intensity of the current and the potential of the tube can modify of manual or automatic form and have to adjust to the characteristic antropomórficas of the patient. The intensity of current relates of linear way with the dose of radiation; the dose of radiation, instead is proportional to the square of the potential of the tubo.es say reduce the potential of the tube involves to reduce much more the dose of radiation that what supposes to modify the intensity of current. In the majority of the cases, in a team of TCMD of 64 courts the intensity of current that is used to to use is of some 700-800 but. In teams but advanced the current of the tube is used to to be lower. Regarding the potential of the tube, the normal is to use 120 kV, although whenever it was possible, especially in patients with index of corporal mass (IMC) <30 kg/m2 that do not present extensive coronary calcification, stent coronary or other metallic elements that hamper the coronary assessment, recommends employ 100 kV. The population pediátrica also requires that the potential of the tube adjust to 80 or 100 kV. FIELD OF VISION (FIELD OF VIEW) The images of TC are composed by a matrix of 512 x 512 pixels. A simple way to increase the information contained in each pixel and, therefore, to increase the space solution, is to adjust the field of vision the maximum possible to the heart for this purpose, usually uses a field of vision of some 18 to 20 cm to reconstruct the images. Besides, it is used to make an additional reconstruction in the included thoracic cavity in the rank of the exploration with a field of vision expanded (35 40 cm) to be able to value the cardiac extra findings. THICKNESS OF COURT. Because of his small size the assessment of the coronary arteries requires to reconstruct the images with the minimum thickness of court that provide the best relation contrast-noise. In some teams this involves to use a thickness of court slightly upper to the thickness of colimación. To increase the space resolution, recommends , solapar the reconstruction in a 40 or 50 % of the thickness of the cut selected. For example, if it chooses a thickness of cut of 0,75 mm, recommends a solapamiento of 0,4 mm. In cases that the noise of the image was high, for example, in patients very obese can employ a thickness of court thicker ( 1-1,2 mm ) to reconstruct the study. FILTER OF RECONSTRUCTION The filters of reconstruction that use in CTC ah been generally, specifically designed to maintain a balance between the anatomical detail and the noise of the image. Usually they employ filters with vencionales of soft parts that allow to value the light and differentiate the components of the wall of the glass in the case of STENT or extensive coronary calcification is preferable to use specific filters that reinforce the edges. Although incrementan slightly the noise of the image, these filters allow to reduce the artefact by hardening of the do of ray caused by the metal that composes the endoprotesis or the calcification, by what facilitate the visualisation of the vascular light. GLOBAL ASSESSMENT OF THE STUDY The quality of the images obtained in the processing depend directly of the quality of the data purchased during the exploration after applying distinct algorithms, the processing can help to visualise better the structures or do easier the interpretation of the study. However, if the quality of the data obtained during the exploration is bad, for example by a high cardiac frequency, variability of cardiac rhythm, arrhythmia and excess of noise, the images that will obtain after being processed also will be low quality. The most employed technicians in CTC are the reconstruction multiplanal (MPR), reconstruction planal curve (CPR), the projection of maximum intensity (MIP) and the volumetric reconstruction (VR). Each technician of processing presents advantages and contributes more information that others in front of concrete findings, by what the ideal is individualizar the processing to each case and combine all the technicians to make the diagnose final. RECONSTRUCTION MULTIPLANAL The reconstructions multiplanares constitute the base of the processing in TC cardiac. The parameters and planes of study are used to to accommodate to each case. The thickness of court that use has to be the finest that allows to identify the structure of interest with the maximum anatomical detail and the minimum noise. Due to the fact that the reconstruction multiplanal allows to study the vascular anatomy in any plane of the space results of big utility to value with details any type of injury. The reconstructions of greater interest are the purchased in a parallel plane to the groove interventricular previous, used to study the downward coronary artery previous, and the obtained in a parallel plane to the grooves auriculoventriculares, employed to value the right coronary arteries and circunfleja. Also it can make a projection oblicua previous left with angulación discharge (spider) to study the left main trunk and the left coronary artery. The reconstructions multiplanares also allow rotar an image on a central point fix this results of interest, as for example, to value a concrete coronary injury, since it allows to establish the morphology of the plate and the degree of estenosis produced. RECONSTRUCTION PLANAL CURVE It is a variant of the reconstruction multiplanar conventional and developed to be able to study long distances of structures with routes curvos or tortuous. To create a planar reconstruction curve have to join in a plane the points that represent the centre of the light of a glass. The plane can obtain marking manually the centre of the glass of interest in distinct images. The images that obtain show the artery elongada in an only plane. PROJECTION OF MAXIMUM INTENSITY The reconstruction with technician of projection of maximum intensity (MIP) are used to to value of conjoint form with the reconstructions multiplanares. The reconstruction MIP sample in a plane the pixels of maximum mitigation of a volume or determinate thickness, this type of reconstruction uses a lot in studies angiograficos, since it allows to visualise the vascularización arterial of selective way and facilitates the assessment of arteries of small calibrate. The reconstruction MIP is a good technician of processing for studies little contrasted or when it exists a lot of noise in the images, due to the fact that this type of reconstruction tends to enhance the vascular structures and to reduce the perception of the noise. VOLUMETRIC RECONSTRUCTION This type of reconstruction is of big utility to show the three-dimensional morphology of the heart and the anatomical relations between the distinct structures mediastínicas. The volumetric reconstruction, roots in algorithms based in the mitigation of the vóxeles that conform the image; to each voxel assigns him a colour in function of the elements and ranks of units hounsfield that possesses. In the case of the coronary arteries this type of reconstruction stand out to define the coronary anatomy in case of anomalies, establish the origin, distance and anastomosis distal of the injertos aortocoronarios, shows the anatomical relations between the heart and the big glasses in the complex congenital cardiopathies and serve to schedule the surgical treatment especially in patients that go to be subjected to a second intervention.