Quantitation in Dextrocardia on myocardial perfusion imaging: How to perform quantitative analysis using Cedars-Sinai software

Abstract

Dextrocardia, although a rare cardiac abnormality, carries the same risk for cardiac events as other people. SPECT Myocardial perfusion imaging is a potentially helpful diagnostic tool in patients with dextrocardia. Because of swapping of lateral and septal walls on SPECT slices, although visual analysis is possible, quantitation is substantially limited. Here, we introduce a simple practical method to make quantitative analysis feasible and accurate.

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Nuclear Medicine Rev iew 2018, 21, 1: 50–52
DOI: 10.5603/NMR.a2018.0010
Copyright © 2018 Via Medica
ISSN 1506–9680
Clinical
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www .journals.viamedica.pl/nuclear_medicine_review
Correspondence to: Mohsen Qutbi, Department of Nuclear Medicine,
Taleghani Hospital, Yaman St., Velenjak, Tehran, Iran; mobile phone:
00989197975902, Nuclear medicine department phone: 00982123031250,
fax: 00982122432596, e-mail: mohsen.qutbi@gmail.com,
mohsen.qutbi@sbmu.ac.ir
Quantitation in Dextrocardia on myocardial
perfusion imaging: how to perform
quantitative analysis using Cedars-Sinai
software
Mohsen Qutbi1, Mehdi Soltanshahi1, Mojtaba Ansari2, Hoda Hashemi2, Babak Shafiei1, Isa Neshandar Asli1
1Department of Nuclear Medicine, Taleghani Educational Hospital, School of Medicine, Shahid Beheshti University of Medical Sciences,
Tehran, Iran
2Department of Nuclear Medicine, Imam Hosein Educational Hospital, School of Medicine, Shahid Beheshti University of Medical
Sciences, Tehran, Iran
[Received 28 VIII 2017; Accepted 1 III 2018]
Abstract
Dextrocardia, although a rare cardiac abnormality, carries the same risk for cardiac events as other people. SPECT Myocardial
perfusion imaging is a potentially helpful diagnostic tool in patients with dextrocardia. Due to swapping of lateral and septal
walls on SPECT slices, although visual analysis is possible, quantitation is substantially limited. Here, we introduce a simple
practical method to make quantitative analysis feasible and accurate.
KEY words: dextrocardia; SPECT myocardial perfusion imaging; quantitation; Cedars-Sinai software.
Nucl Med Rev 2018; 21, 1: 50–52
Case report
A 50-year-old male patient with known history of dextrocardia
with situs inversus presented for cardiac evaluation. A dipyrida-
mole gated SPECT myocardial perfusion imaging (G-SPECT MPI)
was performed with same-day stress-rest protocol. As we knew that
the patient had dextrocardia, we modied the acquisition protocol.
The patient was positioned supine and imaging was acquired
from left anterior oblique (LAO) to right posterior oblique (RPO)
views. Other acquisition parameters were as routine (e.g., orienta-
tion: feet-in, number of projections: 32 and number of frames for
gating: 8). First, Images were reconstructed and processed with
routine protocol, then, with modied protocol (Figure 1). In modi-
ed protocol, we changed orientation of images from “Feet-in”
to “Head-in”. Analysis for gating was also performed with both
protocols (Figure 2).
Discussion
Dextrocardia is a rare congenital abnormality of the heart with
incidence of less than 0.01% [1]. The heart is positioned on the
right side and the axis of left ventricle (LV) is directed toward the
left side. In dextrocardia with situs inversus or mirror-image dextro-
cardia, the LV is positioned posterior and left to the right ventricle
(RV). The position of other organs including visceral organs (e.g.,
liver, stomach and etc.) is also reversed [1].
It has been shown that the risk of coronary artery disease
in patients with dextrocardia is the same as that in general
population [2, 3]. SPECT MPI is a potentially helpful modality for
cardiac assessment in these patients, although some modica-
tions in acquisition protocol are required. Otherwise, perfusion
abnormalities in LV myocardium will occur. The acquisition arc
ranges from LAO to RPO. When images are reconstructed as rou-
tine, tomographic slices are visualized mirrored in a way that
interventricular septum and lateral free wall are swapped and RV
is located on the right side of image. Quantitative analysis usu-
ally reveals perfusion defect and motion abnormality in lateral
segments of polar map, because septal wall of patients are
compared to lateral wall in normal database. Therefore, quanti-
tative analysis is not helpful in these situations and images are
interpreted solely visually.

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Mohsen Qutbi et al., Quantitation in Dextrocardia
Clinical
vignette
Figure 1. SPECT slices with routine processing (upper panel) and with modified processing (lower panel); on images with routine processing,
lateral and septal walls are swapped. Lateral free wall and true interventricular septum are visually normal. Here, on semiquantitative analysis, no
score is given to lateral segments on perfusion polar map. Prominent activity of septal wall (true interventricular septum) compared to lateral wall
(lateral free wall) can be a reason. Severe perfusion abnormality of inferior wall is compatible with previous myocardial infarction

Nuclear Medicine Review 2018, Vol. 21, No. 1
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Clinical
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In order to make the quantitation feasible and accurate,
a simple practical method is to change the orientation of images.
When images are processed with modied protocol (changing
of orientation from “Feet-in” to “Head-in”), the images are again
mirrored, therefore lateral and septal walls are in their correct
position on tomographic slices. Contours of LV walls are drawn
erroneously as basal part of septal wall (true lateral free wall)
is cut off. Because by default, septal wall is shorter than lateral
wall. True septal walls have normally less motion compared to
true lateral walls. As in this case, the true interventricular septum
is compared to the lateral free wall of normal population included
in normal database. Therefore, motion abnormality will be evident
in lateral segments on the polar map. Contrary to motion, thicken-
ing does not show similar abnormality as the degree of thickening
is almost homogeneous circumferentially in LV walls. Because
the basal portion of septal wall (lateral free wall) is cut off from LV
myocardial wall contours, LV volumes, particularly end-diastolic LV
volume will be signicantly underestimated in routine processing.
Therefore, a more accurate estimation of ejection fraction (EF) can
be achieved with modied processing.
Conflict of interest
No conict of interests is declared.
References
1. Evans WN, Acherman RJ, Collazos JC, et al. Dextrocardia: practical clinical
points and comments on terminology. Pediatr Cardiol. 2010; 31(1): 1–6, doi:
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mirror-image heart (“situs inversus”). Int J Cardiol. 1988; 20(2): 273–275,
doi: 10.1016/0167-5273(88)90272-0, indexed in Pubmed: 3209258.
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Figure 2. Results of LV systolic function indices and polar maps of wall motion and thickening of gated study with routine processing (A) and with
modified processing (B); processing with routine protocol reveals wall motion abnormality on lateral wall (lateral segments on the polar map) which
is normalized with modified processing. The measurement of ejection fraction (EF) and end-diastolic LV volume are also underestimated (44% vs.
50% and 96 mL vs. 116 mL respectively)