Utility of the inversion scout sequence (TI scout) in diagnosing myocardial amyloid infiltration

Abstract

To evaluate the utility of inversion scout (TI-scout) obtained during cardiac magnetic resonance imaging (CMR) in diagnosing myocardial amyloid infiltration. A retrospective analysis of CMR exams in 39 patients (24 males, age range 29-77 years) was performed. Imaging was performed on a 1.5T system, and included steady state cine, post contrast TI-scout and delayed enhancement images. Evaluations included studies in 13 patients with myocardial amyloidosis and 26 patients without myocardial amyloidosis. To characterize abnormal nulling, the time to myocardial nulling on the TI scout was compared to the null times of the blood pool and spleen for each scan. The sensitivity and specificity of different tissue nulling abnormalities for myocardial amyloidosis were computed. The null times of tissues in 18/26 (69%) patients in the non-amyloid group followed a consistent order with the blood pool null time preceding the myocardial nulling which was equal to that of splenic nulling (Type 1 pattern). This order differed in all 13 patients with myocardial amyloidosis described as three non-mutually exclusive nulling categories: 10 patients had myocardial null time preceding or coincident with blood pool (Type 2 pattern); in 11 patients myocardial null time was non-coincident with splenic nulling (Type 3 pattern); and in 8 patients myocardial null time was non-coincident with both blood pool AND splenic nulling (Type 4 pattern). While no patient exhibited Type 4 nulling pattern in the non-amyloid group, 1/26 patient had a Type 2 and 7/26 patients had a Type 3 nulling pattern. A sensitivity of 100% was obtained when either Type 2 OR Type 3 nulling was present while a specificity of 100% was obtained when both Type 2 AND Type 3 nulling were present together (Type 4 pattern). Our study demonstrates that the pattern of nulling on the TI scout sequence CMR has potential diagnostic utility for the presence of myocardial amyloidosis. The temporal pattern of myocardial, blood pool and splenic nulling needs to be carefully evaluated on the TI scout sequence and could prove useful in other infiltrative cardiomyopathies.

Fig. 1

Four-chamber (top left) and vertical long axis two chamber (top right) true-FISP phase sensitive inversion recovery (PSIR) CMR image obtained after 10 min of intravenous gadolinium injection shows normal homogenous nulling of the myocardium in a patient from the control group. 10 min post contrast two-chamber short axis PSIR image (bottom) in a biopsy proven case of myocardial amyloidosis shows global subendocardial hyperenhancement (arrows)

Fig. 2

Type 1 (normal) nulling pattern: sequential TI scout two chamber short axis images are shown at different inversion times. Notice the temporal sequence of nulling of the blood pool, (Bl) at 230 ms, followed by myocardium (m) and spleen (Sp) (252 ms). The myocardium and spleen normally show coincidental nulling

Fig. 3

Type 2 nulling pattern: sequential TI scout two chamber short axis images are shown at different inversion times. Notice that the nulling of the myocardium (m) (275 ms) precedes the nulling of the blood pool (Bl) and spleen (Sp) at 315 ms

Fig. 4

Type 3 nulling pattern: sequential TI scout two chamber short axis images are shown at different inversion times. Notice that the blood pool (Bl) and the myocardial (m) nulling occurs earlier at 200 ms than the splenic (Sp) nulling (240 ms)

Fig. 5

Type 4 nulling pattern: sequential TI scout two chamber short axis images are shown at different inversion times. Notice that the myocardial (m) nulling is patchy but occurs earlier (197–217 ms) than the blood pool (Bl) nulling (260 ms) which is not coincident with the splenic (Sp) nulling (302 ms)

Fig. 6

Graphical representation of temporal nulling patterns on a TI scout sequence obtained by plotting the mean signal of the region of interest (ROI) in each image of the sequence with ROI placed over myocardium, blood pool and spleen: In Type 1 nulling pattern the blood pool (dashed line) nulls earlier than myocardium (solid line) and spleen (dotted line). Both myocardium and spleen null together. In Type 2 Nulling pattern, myocardial nulling precedes blood pool and splenic nulling. In Type 3 nulling pattern the splenic nulling is non-coincident with either the blood pool or myocardium and in Type 4 nulling all three null at different times

Fig. 7

Sensitivity and specificity for different nulling types (n=39)