The reliability of digital non-contrast reconstructions of photon-counting detector CT scans in assessing belly organs | BMC Medical Imaging

Affected person inhabitants

The ultimate affected person cohort included 34 sufferers, of whom 19 have been identified with intraductal papillary mucinous neoplasms, 4 with mucinous cystic neoplasms, 4 with serous cystic neoplasms, 3 with adenocarcinomas, 1 with stable pseudopapillary neoplasm, 1 with cystic pancreatic neuroendocrine tumor, 1 with lymphoepithelial tumor, and 1 with unclassified PCN with out worrisome options. One affected person with serous cystic neoplasm had 2 follow-up CT scans.

The distinction materials routinely utilized in our CT laboratory was modified in the course of the investigated interval as a consequence of institutional components; subsequently, throughout contrast-enhanced CT examination, the Ultravist 370 distinction agent was used for 16 sufferers, whereas 19 sufferers acquired the Iomeron 350 distinction materials. Desk 2. summarizes the demographic information of the affected person cohort.

Comparability of the imply density values

The violin plots on the variations between the imply densities on the arterial section (HU_{VNC[arterial]}), portal section (HU_VNC[portal]), and venous section (HU_VNC[venous]) VNC reconstructions vs. densities on the actual unenhanced scans (HU_unenhanced) may be present in Further file 1 (Supplementary Figs. 3–6). The correlation plots on the affiliation between HU_VNC and HU_unenhanced in addition to the Bland-Altman plots illustrating the affiliation of HU_error with the organs’ common HU density may be present in Further file 1 (Supplementary Figs. 7–18 and Supplementary Figs. 19–22). All organs had a minimum of one distinction section that reached a robust correlation besides the spleen and kidneys. Furthermore, the correlation for the spleen within the portal venous section didn’t attain statistical significance.

Comparability of actual unenhanced with unenhanced VNC reconstructions

The HU_{VNC[unenhanced]} of the spleen, liver, and paraspinal muscle tissue have been considerably (p < 0.0001) larger, whereas these of the vertebrae have been considerably decrease (p < 0.0001) in comparison with the HU_unenhanced values (Desk 3). Nevertheless, the HU_error for the spleen and liver have been solely 2.35 ± 2.70 and 4.97 ± 2.94 HU, respectively. The HU_{VNC[unenhanced]} values confirmed very sturdy correlations with the HU_unenhanced values in all organs besides the kidneys (r = 0.78 and 0.73; p < 0.0001) and the spleen (r = 0.45; p = 0.0065) (Desk 4).

Evaluation of the vertebrae

In all postcontrast VNC reconstructions, probably the most marked HU_error was discovered within the vertebrae, the place the algorithm struggled to distinguish calcium from iodine which resulted in considerably (p < 0.0001) decrease density values on the VNC reconstructions (Desk 3). The HU_VNC values had very sturdy correlations with the HU_unenhanced (Desk 4). The HU_error additionally confirmed very sturdy correlations with the HU_postcontrast and HU_unenhanced (Desk 5).

Evaluation of the kidneys

There was no vital distinction between HU_unenhanced and HU_{VNC[unenhanced]} within the kidneys. Nevertheless, the distinction between HU_unenhanced and HU_VNC was vital (p < 0.0001) for each kidneys in all postcontrast phases (Desk 3) with a HU_error of -4.80 ± 4.05HU for the left and − 4.53 ± 4.75HU for the correct kidneys within the arterial section. The HU_error was markedly larger within the portal section and even larger within the venous section (Desk 3). Furthermore, the HU_VNC values had solely a average correlation with the HU_unenhanced values (Desk 4), and the HU_error additionally had a average affiliation with the HU_arterial and a weak to average correlation with the HU_venous (Desk 5).

Within the arterial section, 19/35 and 18/35 circumstances had a HU_error lower than ± 5 HU, and an extra 12/35 and 13/35 had a most HU_error of ± 10 HU. Within the portal venous section, these have been 9/35, 10/35, and eight/35, 6/35, respectively. Whereas within the venous section, 5/35 and 9/35 circumstances have been inside the vary of ± 5 HU, and an extra 11/35 and 6/35 had a most HU_error of ± 10 HU. The histograms illustrating the variety of sufferers in every class may be present in Further file 1 (Supplementary Fig. 23).

Evaluation of the paraspinal and iliopsoas muscle tissue

The HU_error dominantly resulted in optimistic values for the paraspinal muscle tissue and the distinction between HU_unenhanced and HU_VNC was vital in all phases. In the meantime, the HU_error of the iliopsoas muscle tissue persistently resulted in unfavourable values however the distinction reached significance in solely the portal and venous phases (Desk 3). The HU_VNC values had very sturdy correlations with the HU_unenhanced values in each phases for the paraspinal muscle tissue, whereas the iliopsoas muscle tissue confirmed sturdy to very sturdy correlations (Desk 4). The HU_error within the paraspinal muscle tissue confirmed weak to average correlations with the HU_arterial, HU_portal, and HU_venous values, whereas within the iliopsoas muscle tissue, a big correlation was solely discovered within the venous section (Desk 5). In each three phases, the HU_error had weak however vital correlations with HU_unenhanced values for all muscle tissue besides the left iliopsoas within the venous section and proper iliopsoas within the portal section (Desk 5).

The HU_error was inside the vary of a most of ± 15 HU values in all phases for all muscle tissue. For the paraspinal muscle tissue, 10/35 circumstances have been inside the vary of ± 5 HU within the arterial section, 15/35 have been inside this vary within the portal venous section, whereas within the venous section, it was 17/35 circumstances. The iliopsoas muscle tissue confirmed higher outcomes, 30/35 and 29/35 circumstances have been inside the vary of ± 5 HU within the arterial section, 29/35 have been inside this vary within the portal venous section, whereas within the venous section, it was 28/35 and 26/35 circumstances for the correct and left muscle tissue, respectively. The histograms illustrating the variety of sufferers in every class may be present in Further file 1 (Supplementary Fig. 23).

Evaluation of the pancreas and PCNs

The evaluation of the pancreas revealed no vital variations between HU_unenhanced and HU_{VNC[arterial]} (Desk 3). The HU_VNC values confirmed very sturdy correlations with the HU_unenhanced values in all phases (Desk 4). Furthermore, no correlation was discovered between HU_error and both HU_unenhanced, HU_arterial, HU_portal, or HU_venous (Desk 5).

Within the arterial section, the HU_error values have been inside the vary of ± 5 HU in 29/53 circumstances, whereas all however one circumstances have been inside the vary of ± 10 HU. Within the portal venous section, 20/35 circumstances had a most HU_error of ± 5 HU, whereas an extra 12/35 have been inside the vary of ± 10 HU. Comparable outcomes have been discovered within the venous section with 26/35 circumstances inside the vary of ± 5 HU and an extra 8/35 circumstances inside the vary of ± 10 HU. The PCNs confirmed one of the best outcomes on the arterial section, the place the HU_error was inside the vary of ± 5 HU in 18/35 circumstances, and an extra 11/35 had a most HU_error of ± 10 HU. The worst HU_error outcomes have been noticed within the portal section, the place 7/35 circumstances have been out of the vary of ± 15 HU. The histograms illustrating the variety of sufferers in every class may be present in Further file 1 (Supplementary Fig. 23).

The evaluation of the PCNs revealed vital variations between HU_unenhanced and each HU_{VNC[arterial]}, HU_VNC[portal], and HU_VNC[venous], nevertheless, the distinction within the arterial section was solely − 3.81 ± 5.76 HU (Desk 3). The HU_{VNC[arterial]} had a really sturdy, whereas the HU_VNC[venous] and the HU_portal−VNC had sturdy correlations with the HU_unenhanced (Desk 4). The HU_error confirmed a big correlation solely with the HU_arterial values, no correlation was discovered with HU_unenhanced in both section (Desk 5).

Evaluation of the spleen

Within the spleen, vital variations have been detected between HU_unenhanced and HU_VNC in all phases, though the HU_error was just one.64 ± 2.66 HU within the arterial section (Desk 3). The HU_VNC had solely a average correlation with the HU_unenhanced on the arterial and venous phases, whereas no correlation was discovered within the portal section (Desk 4). Furthermore, the HU_error additionally had vital, sturdy correlations with HU_arterial and HU_portal, and a average correlation with HU_venous (Desk 5).

Within the arterial section, 23/35 circumstances had a HU_error lower than ± 5 HU, and all of the circumstances have been inside the vary of ± 10 HU. Within the portal venous section, 23/35 have been inside the vary of ± 5 HU, an extra 9/35 had a most HU_error of ± 10 HU, whereas the remaining 3/35 had a most HU_error of ± 15 HU. Within the venous section, 33/35 circumstances have been inside the vary of ± 5 HU, and the remaining 2/35 circumstances had a most HU_error of ± 10 HU. The histograms illustrating the variety of sufferers in every class may be present in Further file 1 (Supplementary Fig. 23).

Evaluation of the liver

The liver confirmed larger HU_{VNC[arterial]} in comparison with HU_unenhanced, nevertheless, the HU_error was solely 4.64 ± 2.85 HU. For the portal and venous phases, the HU_error values have been even decrease, solely 2.12 ± 2.60 HU, and a couple of.50 ± 2.22 HU, respectively. The HU_VNC values confirmed a really sturdy correlation with the HU_unenhanced in all phases (Desk 4). In the meantime, the HU_error had no vital correlation with HU_unenhanced in both section, and it confirmed solely a average correlation with HU_portal and a weak correlation with HU_venous (Desk 5).

The HU_error values have been inside a most of ± 10 HU in all circumstances in all distinction phases. Within the arterial section, 17/35 circumstances had a HU_error lower than ± 5 HU, within the portal venous section, it was 31/35, whereas one of the best outcomes have been discovered within the venous section, the place 32/35 circumstances have been inside the vary of ± 5 HU. The histograms illustrating the variety of sufferers in every class may be present in Further file 1 (Supplementary Fig. 23).

Intraclass correlation coefficient evaluation

The outcomes of ICC evaluation confirmed that the majority organs had a minimum of one postcontrast section VNC reconstruction that confirmed good-to-excellent reproducibility based mostly on the decrease worth of the 95% confidence interval. Besides the vertebrae, spleen, and kidneys which persistently resulted in poor ICC values, and the paraspinal muscle tissue that confirmed glorious ICC values however with large confidence intervals. The outcomes of the ICC evaluation may be present in Desk 6.

Within the arterial section, the ICC evaluation confirmed glorious reliability for the pancreatic parenchyma with an ICC of 0.90 [0.80–0.95]. Good reliability was discovered for PCNs with ICC of 0.76 [0.43–0.89]) and for iliopsoas muscle tissue with ICCs of 0.79 [0.59–0.89], and 0.75 [0.56–0.87]). Nevertheless, the remaining organs confirmed large confidence intervals. Within the portal venous section, solely the liver confirmed glorious reliability with an ICC of 0.93 [0.70–0.97], different organs both had low ICC values or large 95% confidence intervals. Whereas within the venous section, solely the liver and pancreas confirmed good reproducibility with ICC of 0.93 [0.46–0.98], and 0.92 [0.42–0.98], respectively.

Bland-Altman plots additional supported the outcomes of the ICC evaluation (Supplementary Figs. 19–22 of Further file 1). All circumstances have been distributed round a HU_error near zero, with virtually all measurements inside ± 1.96 SD; aside from vertebrae, kidneys, and spleen, which confirmed an enormous HU_error, which was considerably affected by the imply of the measurements.

Comparability of picture high quality

Subjective analysis of picture high quality

Through the subjective evaluation of the 35 CT examinations, the skilled radiologist discovered that the VNC reconstructions have been smoother and extra blurred in comparison with the actual unenhanced scans. The skilled radiologist reported the presence of kidney stones in 10 circumstances, whereas, 5 had pancreas calcification, 3 had PCNs with mural calcification, and a couple of had PCNs with central calcification. The dimensions of the kidney stones was between 1.9 and 6.9 mm, the pancreatic calcifications evaluated had sizes between 1.9 and three.5 mm, the mural calcifications had sizes between 2.0 and a couple of.5 mm, whereas the 2 central calcifications had sizes of two.0 and 6.5 mm on the actual unenhanced scans. Evaluating the measured diameters of those 20 lesions on the actual unenhanced scans vs. VNC reconstructions, the unenhanced section VNC yielded acceptable outcomes with no vital distinction (2.98 ± 1.41 mm vs. 2.48 ± 1.19 mm, p = 0.067), whereas the arterial, portal, and venous section VNC reconstructions confirmed considerably decrease measured diameters with 1.64 ± 1.54 mm, 1.65 ± 1.33 mm, and 1.57 ± 1.50 mm every with p < 0.001, respectively.

The skilled radiologist rated the picture high quality on the premise of the radiological assessability of the calcifications in line with a 5-point scale. If a couple of calcification or a couple of kidney stone was introduced, the one with the worst assessability on VNC was reported. Subsequently, 20 lesions have been evaluated on this subanalysis. Because of this, the VNC reconstructed from the actual unenhanced scans confirmed acceptable picture high quality with a median level of 4.3/5.0. From the postcontrast section VNC reconstructions, the arterial section had the best picture high quality with a median level of two.65/5.0, adopted by the portal venous section VNC with 2.45/5.0 factors on common, whereas the venous section VNC confirmed the worst picture high quality with common factors of two.4/5.0. A complete variety of 7/20 lesions resulted in full subtraction in both of the postcontrast section VNC reconstructions. Though not one of the calcifications have been absolutely subtracted from the VNC reconstructions generated from the unenhanced section scans, the variety of absolutely subtracted calcifications was 6/20 on the arterial section VNCs, 4/20 on the portal venous section VNCs, and seven/20 on the venous section VNCs.

Through the subjective studying of the scans, the radiologist discovered that the Liver-VNC algorithm was much less dependable in sufferers with persistent pancreatitis. Throughout iodine subtraction the algorithm struggled to distinguish calcifications from the iodine distinction materials, reducing the density values of small calcifications and blurring their borders (Fig. 2). In kidneys, particular consideration must be paid to the density values of stones which can even be diminished on the VNC reconstructions (Fig. 3). From the kidneys that confirmed marked distinction enhancement, the algorithm didn’t subtract the iodine distinction which remained detectable within the renal cortex even on VNC reconstructions (Fig. 4). In the meantime, the algorithm markedly diminished the densities of these kidneys that confirmed much less pronounced distinction enhancement (Fig. 5). Moreover, in circumstances the place the spleen had marked placing wave-like distinction enhancement, the Liver-VNC algorithm markedly decreased the density values of the extremely enhancing areas (Fig. 6).

Illustration of the limitation of the Liver-VNC algorithm in pancreatic calcifications. Pancreatic calcifications on the unenhanced section CT scan of a affected person with persistent pancreatitis (A). The algorithm blurred the margins and decreased the dimensions of the calcifications (arrow) in the course of the reconstruction of the digital non-contrast photos from the unenhanced section (B) arterial section (C), portal section (D), and venous section (E) postcontrast CT scans

Illustration of the limitation of the Liver-VNC algorithm in kidney stones. The distinction within the density of a kidney stone between the actual unenhanced section CT sequence (A) and the digital non-contrast reconstructions generated from the arterial section (B), portal section (C), and venous section (D) sequence

Illustration of the failure of the Liver-VNC algorithm for iodine distinction subtraction from kidneys. The left kidney on an arterial section CT scan (A), and the distinction between the actual unenhanced section CT scans (B) and the digital non-contrast reconstruction (C)

Illustration of the extreme lower in density values throughout iodine distinction extraction from kidneys by the Liver-VNC algorithm. The distinction within the density of the kidney between the actual unenhanced section CT scans (A) and the digital non-contrast reconstructions of arterial section (B), portal section (C), and venous section (D) scans. The algorithm decreased the imply densities

Illustration of the failure of the Liver-VNC algorithm for iodine distinction subtraction from the spleen. The placing wave-like distinction enhancement sample of the spleen on the arterial section (A) scan. The distinction within the density of the spleen on the actual unenhanced section CT scans (B) and the digital non-contrast reconstructions generated from the arterial section (C)

Quantitative analysis of picture high quality

The subjective impression of smoother photos for VNC reconstructions in comparison with the actual unenhanced scans was supported by the outcomes of the quantitative evaluation of picture noise by calculating the CNR. The CNR_{VNC[unenhanced]} was discovered to be considerably decrease in comparison with the CNR_unenhanced values for the kidneys (p = 0.016), pancreas (p = 0.041), vertebrae (p < 0.0001), iliopsoas muscle tissue (p = 0.013), and PCNs (p = 0.03). The CNR resulted in considerably decrease values on the portal venous section and venous section VNC reconstructions in comparison with the actual unenhanced scans for all organs. On the arterial section, solely the vertebrae confirmed considerably decrease CNR_{VNC[arterial]} values (Desk 7).

The comparability of the SNR between VNC reconstructions and actual unenhanced scans confirmed heterogeneous outcomes for the completely different organs on completely different phases (Desk 8). The SNR_{VNC[unenhanced]} have been considerably larger for the spleen (p < 0.0001), kidneys (p < 0.0001, p < 0.0001), liver (p < 0.0001), pancreas (p < 0.0001), paraspinal muscle tissue (p < 0.0001), and iliopsoas muscle tissue (p < 0.0001) in comparison with the SNR_unenhanced, whereas no vital distinction was discovered within the vertebrae and PCNs. For all postcontrast phases, the muscle tissue confirmed considerably larger SNR_VNC values, whereas the kidneys and PCNs had considerably decrease SNR_VNC values in comparison with SNR_unenhanced.