Histogram analysis in the differentiation between adrenal adenomas and pheochromocytomas: the value of a single measurement

Teixeira, Ana P.; Haddad Jr., William; Barreto, Luan Oliveira; Secaf, André; Mermejo, Livia M.; Lucchesi, Fabiano R.; Tucci Jr., Silvio; Elias Junior, Jorge; Molina, Carlos A. F.; Muglia, Valdair F.

doi:10.1590/0100-3984.2022.0067

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Original Article • Radiol Bras 56 (2) • Mar-Apr 2023 • https://doi.org/10.1590/0100-3984.2022.0067 copy

Histogram analysis in the differentiation between adrenal adenomas and pheochromocytomas: the value of a single measurement

Análise por histograma para diferenciação entre adenomas da adrenal e feocromocitomas: o valor de uma medida única

Authorship SCIMAGO INSTITUTIONS RANKINGS

Abstract

Objective:

To assess the diagnostic accuracy of histogram analysis on unenhanced computed tomography (CT) for differentiating between adrenal adenomas and pheochromocytomas (PCCs).

Materials and Methods:

We retrospectively identified patients with proven PCCs who had undergone CT examinations between January 2009 and July 2019 at one of two institutions. For each PCC, we selected one or two adenomas diagnosed within two weeks of the date of diagnosis of the PCC. For each lesion, two readers scored the size, determined the mean attenuation, and generated a voxel histogram. The 10th percentile (P10) was obtained from the conventional histogram analysis, as well as being calculated with the following formula: P10 = mean attenuation – (1.282 × standard deviation). The mean attenuation threshold, histogram analysis (observed) P10, and calculated P10 (calcP10) were compared in terms of their diagnostic accuracy.

Results:

We included 52 adenomas and 29 PCCs. The sensitivity, specificity, and accuracy of the mean attenuation threshold were 75.0%, 100.0%, and 82.5%, respectively, for reader 1, whereas they were 71.5%, 100.0%, and 81.5%, respectively, for reader 2. The sensitivity, specificity, and accuracy of the observed P10 and calcP10 were equal for both readers: 90.4%, 96.5%, and 92.6%, respectively, for reader 1; and 92.3%, 93.1%, and 92.6%, respectively, for reader 2. The increase in sensitivity was significant for both readers (p = 0.009 and p = 0.005, respectively).

Conclusion:

For differentiating between adenomas and PCCs, the histogram analysis (observed P10 and calcP10) appears to outperform the mean attenuation threshold as a diagnostic criterion.

Keywords:
Adrenal glands; Adrenocortical adenoma; Adrenal gland neoplasms; Incidental findings; Pheochromocytoma; Tomography, X-ray computed

Variable	Adenomas (n = 52)	Pheochromocytomas (n = 29)	P
Age (years)*	60.0 ± 15.2 (9–87)	47.9 ± 16.7 (15–74)	0.001
Sex^†
Female	36 (69.2)	20 (69.0)	0.98
Male	16 (30.8)	9 (31.0)	0.98
Laterality^†
Right	25 (48.1)	13 (44.8)	0.77
Left	27 (51.9)	16 (55.2)	0.77
Reference standard^†
Follow-up	48 (92.3)	–	–
Surgery/pathology	4 (7.7)	29 (100.0)	–

Parameter	Reader	Adenomas (n = 52)	Pheochromocytomas (n = 29)	P
Size (cm), mean ± SD (range)	1	2.53 ± 1.43 (1.2 to 11)	5.32 ± 3.32 (1.4 to 16.0)	< 0.0001
Size (cm), mean ± SD (range)	2	2.42 ± 1.44 (1.0 to 10.6)	5.03 ± 3.12 (1.3 to 14.9)	< 0.0001
Mean attenuation (HU), mean ± SD (range)	1	4.84 ± 15.44 (–27 to 44)	36.58 ± 8.31 (11 to 47)	< 0.0001
Mean attenuation (HU), mean ± SD (range)	2	5.83 ± 14.81 (–29 to 49)	36.63 ± 8.27 (12 to 49)	< 0.0001
calcP10 (HU), mean ± SD (range)	1	–23.04 ± 16.67 (–54 to 27)	14.55 ± 10.32 (–14 to 34)	< 0.0001
calcP10 (HU), mean ± SD (range)	2	–24.83 ± 17.06 (–64 to 34)	13.32 ± 10.25 (–19 to 30)	< 0.0001
Observed P10 (HU), mean ± SD (range)	1	–23.11 ± 16.51 (–51 to 28)	14.58 ± 10.4 (–15 to 35)	0.01
Observed P10 (HU), mean ± SD (range)	2	–24.96 ± 17.0 (–59 to 35)	13.31 ± 10.61 (–20 to 31)	0.001
Calcifications, n (%)	1	1 (1.9)	5 (17.2)	0.01
Calcifications, n (%)	2	1 (1.9)	4 (13.8)	0.03
Homogeneity, n (%)	1
	Homogeneous	43 (82.7)	7 (24.1)	< 0.0001
	Heterogeneous	9 (17.3)	22 (75.9)	< 0.0001
	2
	Homogeneous	42 (80.8)	7 (24.1)	< 0.0001
	Heterogeneous	10 (19.2)	22 (75.9)	< 0.0001
Normality, n (%)	1	45 (86.5)	26 (89.7)	0.67
Normality, n (%)	2	45 (86.5)	24 (82.8)	0.65

	Reader 1					Reader 2
Method	Sensitivity	Specificity	PPV	NPV	Accuracy	Sensitivity	Specificity	PPV	NPV	Accuracy
Mean attenuation criterion
%	75.0	100.0	100.0	63.2	82.5	71.1	100.0	100.0	65.9	81.5
95% CI	(61.0–85.9)	(88.0–100.0)	—	(51.7–73.3)	(72.5–90.0)	(52.9–86.9)	(88.0–100.0)	—	(54.8–74.8)	(71.3–89.2)
Observed P10
%	90.4	96.5	97.9	84.8	92.6	92.3	93.1	96.0	87.1	92.6
95% CI	(79.0–96.8)	(82.2–99.9)	(87.2–99.9)	(70.8–92.8)	(84.6–97.2)	(81.5–97.9)	(77.2–99.1)	(86.3–98.9)	(72.4–94.6)	(84.6–97.2)
CalcP10
%	90.4	96.5	97.9	84.8	92.6	92.3	93.1	96.0	87.1	92.6
95% CI	(79.0–96.8)	(82.2–99.9)	(87.2–99.9)	(70.8–92.8)	(84.6–97.2)	(81.5–97.9)	(77.2–99.1)	(86.3–98.9)	(72.4–94.6)	(84.6–97.3)

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[1] Correspondence: Dr. Valdair F. Muglia. Hospital das Clínicas – FMRP-USP. Avenida Bandeirantes, 3900, Monte Alegre. Ribeirão Preto, SP, Brazil, 14049-900. Email: fmuglia@fmrp.usp.br.