[Whole body MR angiography. Physiologic presaturation++ of the inferior vena cava].

Whole-body MRA, performed with the time-of-flight (TOF) technique requires presaturation pulses adequately positioned and to eliminate the arterial and/or venous signal (FRODO technique: "Flow Respiratory artifact Obliteration with Directed Orthogonal pulses"). Additional presaturation pulses involve an increase in the radiofrequency dose absorbed by the patient, frequently over 0.4 watt x kg, which is the threshold absorption per kg. In the present paper, the possible saturation of caval system exploiting the modulation of apnea in whole-body MRA was investigated. Ten volunteers and 10 patients with different diseases were studied. All subjects underwent abdominal MRA with the TOF 2D (FA 18 degrees, TR 22 ms, TE 10 ms) technique. Images were acquired with three modulations of apnea: maximum inspiration, expiration, Müller maneuver. With respect to the anteroposterior diameter of inferior vena cava in inspiration, the inferior cava was reduced by 21.7% in expiration and by 35.7% in Müller maneuver. The lower caliber of vena cava allowed selective angiogram of the aorta. Expiration maneuvers are suggested as an alternative to caval flow saturation by the FRODO technique. As for expiration maneuvers, the volunteers and patients studied preferred to modulate the apnea in forcible expiration. Müller maneuver, through more effective (in 4 cases total caval collapse was obtained) is nonetheless more difficult.