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NRAO Very Long Baseline Array (VLBA) observations of NGC 4278, NGC 4374(M84), NGC 6166, and M87 (NGC 4486) have been made at 43 GHz in an effort toimage the jet collimation region. This is the first attempt to image the firstthree sources at 43 GHz using Very Long Baseline Interferometry (VLBI)techniques. These three sources were chosen because their estimated black holemass and distance implied a Schwarzschild radius with large angular size,giving hope that the jet collimation regions could be studied. Phasereferencing was utilize for the three sources because of their expected lowflux densities. M87 was chosen as the calibrator for NGC 4374 because itsatisfied the phase referencing requirements: nearby to the source andsufficiently strong. Having observed M87 for a long integration time, we havedetected its sub-parsec jet, allowing us to confirm previous high resolutionobservations made by Junor, Biretta & Livio, who have indicated that a wideopening angle was seen near the base of the jet. Phase referencing successfullyimproved our image sensitivity, yielding detections and providing accuratepositions for NGC 4278, NGC 4374 and NGC 6166. These sources are pointdominated, but show suggestions of extended structure in the direction of thelarge-scale jets. However, higher sensitivity will be required to study theirsub-parsec jet structure

An Attempt to Probe the Radio Jet Collimation Regions in NGC 4278, NGC 4374 (M84), and NGC 6166