Fig. 2
Artifact examples in earlier prototypes (a-g) and final T1MES phantom (i, j). Four earlier prototypes (models A—D) were rejected before the final model. a Coronal image of the earlier A-model (aqueous fill) showing bright artifacts around the tubes resulting from bSSFP going off-resonance that would have led to variations in T1 values by MOLLI and similar sequences. b Transverse image of A-model showing the characteristic ‘cat’s head’ artifact of air-bubbles trapped in the paramagnetically doped aqueous tubes. Significant off-resonance artifact is also noticeable in the central tubes. c Another coronal image through A-model but with larger gaps between tubes showing the combined effect of motion artifact (due to the aqueous fill) and B 0 distortion. d Transverse image of C-model attempting to use narrower tubes to pack 12 instead of 9, but significant Gibbs artifact can be seen in each tube. e Transverse image of C-model showing three small dark circular artifacts (12, 3 and 9 o’clock positions) caused by glue used to stabilize the tube arrangement. We subsequently switched to silicone-based glues that were less likely to trap air bubbles and were artifact-free. f Severe stabilisation artifact appearing as a thick dark band around the border of a D-model—here the phantom was scanned immediately after being received from the courier company and the bottle was still very cold from the transportation. Additionally susceptibility artifacts can be seen as thin linear bands spoiling some of the tubes (9 and 3 o’clock). g Significant image intensity inhomogeneity during a D-model test session on a GE scanner caused by accidental omission of the folded blanket, intended to separate the phantom bottle from the anterior chest coil. h Curved tube artifact and dark rings arising from ink printed onto the sides of digestive tubes (images courtesy of K. E. Keenan and NIST). i Coronal bSSFP localiser image and (j) typical T1 map of a final 3 T T1MES phantom obtained by MOLLI using a bSSFP readout on a Siemens 3 T Skyra scanner. bSSFP = balanced steady-state free precession; MOLLI = modified Look-Locker inversion recovery. Other abbreviation as in Fig. 1