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Scientific Reports logoLink to Scientific Reports
. 2026 Apr 8;16:11639. doi: 10.1038/s41598-026-39523-2

A geometric function theoretic approach to MRI distortion correction using Miller Ross Poisson series

S Manoj 1, B Srutha Keerthi 1,✉
PMCID: PMC13061884  PMID: 41951664

Abstract

This study focuses on the newly introduced subclass of Sakaguchi-type function associated with the Miller–Ross-type Poisson distribution series. Using the proposed operator, we derive several coefficient bound, inverse function estimates, initial logarithmic coefficient results and Feketo-Szego type inequalities. Furthermore, growth, distortion, convex combination properties, subordination outcomes, and partial sum results are derived for the defined class. Application part demonstrates how the obtained coefficient bounds can be employed to design an analytic correction operator for improving the quality of distorted Magnetic Resonance Imaging (MRI) scans. Numerical experiments on real datasets validate the effectiveness of the proposed model, showing significant improvement in terms of MSE, PSNR, and SSIM. These results highlight the interplay between geometric function theory and practical imaging problems, thereby providing a new perspective on the use of analytic function subclasses in applied sciences.

Keywords: Analytic functions, Univalent function, Starlike function, Subordination, Fekete-Szego inequality, Miller-Ross distribution series, Geometric properties.

Subject terms: Engineering, Mathematics and computing

Introduction and preliminaries

Let Inline graphic be the class of analytic functions Inline graphic inside open unit disc Inline graphic with Montel’s normalization Inline graphic and is of the form

graphic file with name d33e177.gif 1.1

Let class Inline graphic is the class of all univalent function in Class Inline graphic it is denoted by Inline graphic. If for every point in class Inline graphic domain Inline graphic of the complex plane Inline graphic is said to be starlike with respect to a point Inline graphic. If the line segment joining Inline graphic, to any pointInline graphic lies in Inline graphic itself. It is denoted by Inline graphic. A function Inline graphic is said to be starlike if,

graphic file with name d33e233.gif 1.2

Miller and Ross2 was introduced the function Inline graphic,as a solution of fractional order initial value problem which is called the Miller-Ross function.

where Inline graphic is the incomplete gamma function. Using the properties of the gamma functions, the Miller–Ross function can easily be written as:

graphic file with name d33e252.gif 1.3

which can also be stated as:

graphic file with name d33e257.gif 1.4

where Inline graphic is the Mittag-Leffler function of two parameters. Some special values of the Miller–Ross functions can be given as follows:

graphic file with name d33e266.gif 1.5
graphic file with name d33e270.gif 1.6
graphic file with name d33e275.gif 1.7

The Probability mass function of the Miller–Ross-type Poisson distribution is given by:

graphic file with name d33e280.gif 1.8

where Inline graphic and Inline graphic is the Miller–Ross function given in 1.411,16. The normalized form of the Miller–Ross-type Poisson distribution is given by:

graphic file with name d33e303.gif 1.9

We consider the linear operator

graphic file with name d33e308.gif 1.10

as below:

graphic file with name d33e313.gif 1.11
graphic file with name d33e317.gif 1.12

where

graphic file with name d33e322.gif 1.13

and the symbol Inline graphic specifies the Hadamard product (convolution) of two series.

Definition We introduced a new subclass of analytic functions using operator as follows:

graphic file with name d33e335.gif 1.14

where Inline graphic

Note that Inline graphic maps Inline graphic conformally onto a symmetrical disc with respect to the real axis, which is centered at Inline graphic Inline graphic, and with a radius Inline graphic Inline graphic.

Note

(1) For Inline graphic in the class Inline graphic, we get the class Inline graphic, and their geometric properties were studied by Murugusundaramoorthy and et.al.

(2) For Inline graphic in the class Inline graphic, we get the class Inline graphicwas studied by Sheza M. El-Deeb and et.al.

Supporting lemma

Lemma 1

6,7 Let

graphic file with name d33e415.gif 2.1

be in the class Inline graphic of functions of the positive real part in Inline graphic, then

graphic file with name d33e428.gif 2.2

and for any complex number Inline graphic

graphic file with name d33e437.gif 2.3

In particular, if Inline graphic is a real parameter, then

graphic file with name d33e446.gif 2.4

Coefficient inequalities for Inline graphic

Theorem 1

Let Inline graphic be assigned to the class Inline graphic. Then,

graphic file with name d33e468.gif 3.1
graphic file with name d33e472.gif 3.2

Further, for a complex number Inline graphic

graphic file with name d33e480.gif 3.3

where

graphic file with name d33e486.gif 3.4
graphic file with name d33e490.gif 3.5
graphic file with name d33e494.gif 3.6
graphic file with name d33e498.gif 3.7

Proof

We consider the subordination

graphic file with name d33e506.gif 3.8

It can be written as :

graphic file with name d33e511.gif 3.9

Let

graphic file with name d33e516.gif 3.10
graphic file with name d33e520.gif 3.11
graphic file with name d33e524.gif 3.12

Comparing the coefficient of 3.10 and 3.11, we get

graphic file with name d33e536.gif 3.13
graphic file with name d33e540.gif 3.14
graphic file with name d33e544.gif 3.15
graphic file with name d33e548.gif 3.16

Substitute the value of Inline graphic and Inline graphic, we get

graphic file with name d33e562.gif 3.17

where

graphic file with name d33e567.gif 3.18

Applying 1.1to the above 3.6, we get the result. Inline graphic

Theorem 2

Let Inline graphic be the class Inline graphic. Then for a real parameter Inline graphic

graphic file with name d33e596.gif 3.19

where Inline graphic.

Coefficient inequalities for Inline graphic

With the help of the8 Koebe one-quarter theorem every univalent function Inline graphic has an inverse Inline graphic that satisfies the conditions Inline graphic and Inline graphic that the image of Inline graphic contains a disk of radius Inline graphic

Theorem 3

If Inline graphic and Inline graphic is the inverse function of Inline graphic with Inline graphic, the Koebe domain of the class Inline graphic, then

graphic file with name d33e666.gif 4.1
graphic file with name d33e670.gif 4.2

and for any complex number Inline graphic, we have

graphic file with name d33e679.gif 4.3

where Inline graphic.

Proof

As

graphic file with name d33e692.gif 4.4

is the inverse function of Inline graphic

graphic file with name d33e700.gif 4.5

From 1.1 and 4.5

graphic file with name d33e710.gif 4.6

From Equations 4.5 and 4.6, we can obtain

graphic file with name d33e722.gif 4.7

By equating the corresponding coefficients of 4.7, we have

graphic file with name d33e730.gif 4.8
graphic file with name d33e734.gif 4.9

Substitute the value of Inline graphic in equation4.8,

graphic file with name d33e747.gif 4.10
graphic file with name d33e751.gif 4.11

To find Inline graphic, from 4.9, we take Inline graphic in 4.8. then equation becomes,

graphic file with name d33e771.gif 4.12

thus

graphic file with name d33e776.gif 4.13

where

graphic file with name d33e781.gif 4.14

For any complex number Inline graphic,

graphic file with name d33e791.gif 4.15
graphic file with name d33e795.gif 4.16
graphic file with name d33e799.gif 4.17

Hence the proof.

Initial logarithmic coefficient bounds and Fekete-Szegö problem for Inline graphic

9,10 If the function Inline graphic is analytic in Inline graphic, such that Inline graphic for all Inline graphic, then the well-known logarithmic coefficients Inline graphic, Inline graphic, of Inline graphic are given by

graphic file with name d33e847.gif 5.1

Theorem 4

Let Inline graphic with the logarithmic coefficients given by 5.1. Then,

graphic file with name d33e862.gif 5.2
graphic file with name d33e866.gif 5.3

and for Inline graphic we have

graphic file with name d33e875.gif 5.4

Proof

If Inline graphic has the form 1.14, equating the first two coefficients of the relation (5.1), we obtain

graphic file with name d33e890.gif 5.5
graphic file with name d33e894.gif 5.6

Replacing Inline graphic and Inline graphic in the above equalities 3.13 and 3.14, we obtain

graphic file with name d33e914.gif 5.7
graphic file with name d33e918.gif 5.8
graphic file with name d33e922.gif 5.9

Using the equation2.2,

graphic file with name d33e930.gif 5.10

and using the equation2.3,

graphic file with name d33e939.gif 5.11

We have

graphic file with name d33e944.gif 5.12
graphic file with name d33e948.gif 5.13

and in view of 2.3, we obtain the desired result. Inline graphic

Characterization properties

In this section we investigate the convex combination growth and distortion bounds and necessary and sufficient condition for the newly defined class

Theorem 5

Let Inline graphic be assigned to the class Inline graphic if it fulfills the inequality

graphic file with name d33e975.gif 6.1

equivalently, we may write

graphic file with name d33e981.gif 6.2

where

graphic file with name d33e986.gif 6.3

and Inline graphic as given in 1.13. Inequality 6.1is sharp.

Proof. Assume that inequality 6.1 holds, and Inline graphic. Then, one can put 1.14 in the form of a Schwarz function Inline graphic as

graphic file with name d33e1024.gif 6.4

It must satisfy the condition

graphic file with name d33e1030.gif 6.5

Then, we have

graphic file with name d33e1035.gif 6.6
graphic file with name d33e1039.gif 6.7

Hence, Inline graphic.

Now, for the function

graphic file with name d33e1050.gif 6.8

such that Inline graphic, we have

graphic file with name d33e1059.gif 6.9
graphic file with name d33e1063.gif 6.10
graphic file with name d33e1067.gif 6.11

Thus, Inline graphic, and the approximation 6.1is sharp. Inline graphic

A function Inline graphic defined by 1.1 and belonging to the class Inline graphic is said to be in the class Inline graphic if it also satisfies the coefficient inequality 6.1. Using the technique of proof of distortion theorems given by Silverman12, we state the following results without proof.

Theorem 6

If a function Inline graphic, then

graphic file with name d33e1116.gif 6.12

The result is sharp for the function defined as:

graphic file with name d33e1122.gif 6.13

Theorem 7

If a function Inline graphic, then

graphic file with name d33e1134.gif 6.14

The result is sharp for the extreme function defined in 6.5.

Theorem 8

Let Inline graphic and have the form

graphic file with name d33e1150.gif 6.15

Then, Inline graphic, where

graphic file with name d33e1159.gif 6.16

Proof

Consider Inline graphic. Then, we can write

graphic file with name d33e1172.gif 6.17

Further,

graphic file with name d33e1177.gif 6.18
graphic file with name d33e1181.gif 6.19

Therefore,

graphic file with name d33e1186.gif 6.20
graphic file with name d33e1190.gif 6.21
graphic file with name d33e1194.gif 6.22

Thus, Inline graphic. Inline graphic

Theorem 9

Let Inline graphic for Inline graphic. Then, the arithmetic mean G of Inline graphic is given by

graphic file with name d33e1226.gif 6.23

and also belongs to class Inline graphic.

Proof

Let

graphic file with name d33e1240.gif 6.24
graphic file with name d33e1244.gif 6.25
graphic file with name d33e1248.gif 6.26

To show Inline graphic, it is sufficient to show that

graphic file with name d33e1257.gif 6.27

Consider

graphic file with name d33e1262.gif 6.28
graphic file with name d33e1266.gif 6.29
graphic file with name d33e1271.gif 6.30

which gets Inline graphic. Inline graphic

Subordination results

Definition (Subordinating factor sequence)13.A sequence Inline graphic of complex numbers is said to be a subordinating sequence if, whenever Inline graphic, Inline graphic is regular, univalent, and convex in U, we have

graphic file with name d33e1309.gif 7.1

Lemma 2

The sequence Inline graphic is a subordinating factor sequence if and only if

graphic file with name d33e1321.gif 7.2

Theorem 10

Let Inline graphic and Inline graphic be any function in the usual class of convex functions C, then

graphic file with name d33e1340.gif 7.3

and

graphic file with name d33e1345.gif 7.4

where

graphic file with name d33e1351.gif 7.5
graphic file with name d33e1355.gif 7.6

The constant factorInline graphic in equation7.3 cannot be replaced by a larger number.

Proof

Let Inline graphic and suppose that Inline graphic. Then,

graphic file with name d33e1380.gif 7.7

Thus, the subordination result holds if

graphic file with name d33e1385.gif 7.8

is a subordinating factor sequence, with Inline graphic.

graphic file with name d33e1395.gif 7.9

By noting the fact that Inline graphic is an increasing function for Inline graphic, and in particular

graphic file with name d33e1408.gif 7.10

then for Inline graphic, we have

graphic file with name d33e1417.gif 7.11
graphic file with name d33e1422.gif 7.12
graphic file with name d33e1426.gif 7.13
graphic file with name d33e1430.gif 7.14
graphic file with name d33e1434.gif 7.15

where we have also made use of assertion 6.1 of Theorem 5. This evidently proves inequality 7.3 and hence also the subordination result 6.1 asserted by 7.3.

Inequality 7.4 follows from 7.3 by taking

graphic file with name d33e1460.gif 7.16

Next, we consider the function

graphic file with name d33e1465.gif 7.17

Clearly, Inline graphic. For this function, (52) becomes

graphic file with name d33e1475.gif 7.18

It is easily verified that

graphic file with name d33e1480.gif 7.19

The constant Inline graphic cannot be replaced by any larger one. Inline graphic

Partial sums

In 1997, Silverman14 investigated partial sums results for the classes of starlike and convex functions Inline graphic given by 1.1 and established through

graphic file with name d33e1507.gif 8.1
graphic file with name d33e1511.gif 8.2

Many authors have investigated partial sums for different subclasses; Recently Rosy.T and et.al were studied partial sum of starlike function based on Ruscheweyh domain15

Theorem 11

If Inline graphic of the form 1.1 satisfies condition 6.5, then

graphic file with name d33e1533.gif 8.3

and

graphic file with name d33e1538.gif 8.4

where

graphic file with name d33e1544.gif 8.5

Proof

Now we set,

graphic file with name d33e1552.gif 8.6
graphic file with name d33e1556.gif 8.7
graphic file with name d33e1560.gif 8.8

After doing some calculation we get,

graphic file with name d33e1565.gif 8.9
graphic file with name d33e1569.gif 8.10

By using the triangle inequalities with Inline graphic, we get the following inequality:

graphic file with name d33e1578.gif 8.11
graphic file with name d33e1583.gif 8.12

if and only if

graphic file with name d33e1588.gif 8.13
graphic file with name d33e1592.gif 8.14

To prove the inequality in (8.3), it sufficent to show that the left-hand side of (8.15) is bounded above by the following sum:

graphic file with name d33e1597.gif 8.15

which is equivalent to

graphic file with name d33e1602.gif 8.16

To prove inequality (8.4), we take

graphic file with name d33e1607.gif 8.17
graphic file with name d33e1611.gif 8.18
graphic file with name d33e1616.gif 8.19

where

graphic file with name d33e1621.gif 8.20
graphic file with name d33e1625.gif 8.21
graphic file with name d33e1629.gif 8.22

which completes the proof of Theorem 11. Inline graphic

Theorem 12

If Inline graphic of the form 1.1 satisfies condition 6.1, then

graphic file with name d33e1651.gif 8.23

and

graphic file with name d33e1656.gif 8.24

where Inline graphic is given by equation8.5 so we have completed the proof.

Proof

The proof of Theorem 12 is similar to that of Theorem 11. Inline graphic

Application

Introduction

Magnetic Resonance Imaging (MRI) is the one of the most wiedely used medical imaging modalities due to its ability to provide high resolution, non invasive of soft tissue. It plays a crucial role in the diagnosis and monitoring of neurological, cardiovascular and musculoskeletal disorders. Despite these advantages, MRI images frequently suffer from intensity inhomogeneity and nonlinear signal distortions caused by nonuniform magnetic fields, coil sensitivity variations and hardware imperfections. These effects appear as gradual intensity drifts or nonlinear intensity wrapping across the image, leading to reduced contrast and loss of diagnostically important structural information.

Various proposals have been made to correct for the intensity inhomogeneity of the images obtained by MRI. They range from polynomial fitting models, bias field correction approaches, homomorphic filtering techniques, and surface coil normalisation. While the approaches have the ability of reducing the intensity inconsistencies of the images to some degree, they tend to remain rather experience-dependent. As a result, over-correction of the images as well as the instability of the images often become evident.

From the mathematical viewpoint, the intensity distortion problem of the MRI can be formulated as a nonlinear transformation of the analytical intensity distribution. It seems that the application of transformation operators with defined analytical structures and specified geometric characteristics could be useful here. Specifically, the class of analytical functions with bounded coefficients and specified geometry may serve as a basis for designing the intensity correction transformation operators.

Motivated by this viewpoint, we apply the theoretical results established in the above section, where coefficient bounds were derived for a subclass of Sakaguchi-type analytic functions associated with the Miller–Ross-type Poisson distribution series. The boundedness and subordination properties of this subclass ensure controlled growth, stability under transformation, and preservation of essential geometric features. These characteristics are especially desirable in MRI image enhancement, where uncontrolled amplification may distort anatomical boundaries.

Using Theorem 1, we construct a mathematically constrained correction operator that acts on MRI intensity values as an analytic transformation. The resulting framework provides a direct bridge between geometric function theory and practical MRI image enhancement. Unlike conventional heuristic approaches, the proposed method is supported by explicit coefficient bounds and analytic stability guarantees, offering a principled mechanism for correcting intensity inhomogeneity while preserving structural details.

18–20Recent years have witnessed significant research efforts aimed at improving magnetic resonance imaging (MRI) quality by correcting intensity inhomogeneity and nonlinear signal distortions arising from magnetic field nonuniformity, coil sensitivity variations, and hardware imperfections. Early systematic evaluations of bias field correction techniques demonstrated that widely used methods integrated into software packages such as SPM, FSL, and FreeSurfer exhibit varying levels of performance and stability, particularly under high noise and strong inhomogeneity conditions. These studies highlighted the limitations of conventional heuristic correction models and emphasized the need for more robust and theoretically justified approaches21–26.Subsequent developments introduced multi-scale and learning-based correction strategies to address these challenges.

Deep learning frameworks such as InhomoNet employed multi-scale feature extraction and specialized loss functions to achieve improved bias field correction compared with traditional polynomial or filtering-based techniques. More recent approaches have focused on implicit and unsupervised learning paradigms, enabling bias field estimation and correction without the requirement of ground-truth bias information, thereby improving generalizability across different MRI modalities and acquisition protocols. Clinical investigations have also demonstrated that effective post-processing bias field correction can significantly enhance quantitative MRI analysis, including segmentation accuracy and biomarker reliability in applications such as breast and brain MRI.

Parallel to these advances in medical image processing, mathematically rigorous frameworks have increasingly been explored for image enhancement and signal correction. In particular, recent studies have demonstrated that coefficient-based constructions from geometric function theory, such as those involving26–28Hankel determinants and subclasses of starlike and convex functions, can be effectively employed to design image enhancement algorithms with improved stability and structural preservation. These analytic approaches offer inherent mathematical constraints that regulate intensity transformation and contrast amplification, thereby reducing overcorrection and artifact introduction.

Motivated by these developments, the present work integrates geometric function theory with MRI image enhancement by exploiting coefficient bounds derived for a subclass of Sakaguchi-type functions associated with the Miller–Ross-type Poisson distribution series. Unlike purely data-driven or heuristic correction methods, the proposed approach provides a mathematically constrained intensity transformation framework, ensuring analytic stability while enhancing MRI image quality. This establishes a meaningful bridge between abstract analytic function theory and practical medical imaging applications.

Experiment setup

To validate the applicability of the proposed framework, a controlled simulation study was performed. An MRI slice was chosen as the reference image and normalised to the intensity range [0,1]. To simulate realistic distortions, a polynomial-based intensity warping was applied, defined as:

graphic file with name d33e1722.gif 9.1

where I is the normalized reference image intensity and Inline graphic are distortion parameters. In this study, the chosen values were Inline graphic, which produce noticeable nonlinear intensity shifts while preserving the global image structure. This emulates the type of distortions encountered in clinical MRI due to field inhomogeneity and hardware nonlinearity.

The correction was then applied using an analytic transformation derived from Theorem 1:

graphic file with name d33e1740.gif 9.2

where Inline graphic and Inline graphic are correction coefficients constrained by the coefficient bounds of the class :

graphic file with name d33e1753.gif 9.3

Here, Inline graphic and Inline graphic are functions of the Miller–Ross parameters, while R, S, t are the Janowski domain parameters. This ensures that the correction transformation remains analytic and univalent in the unit disc, preventing overcorrection and ensuring stability.

The corrected image was then compared with both the distorted and the original reference images for qualitative and quantitative evaluation.

Algorithm part

  1. Take the input image.

  2. If the image is RGB, convert it to grayscale. Normalise its intensity range to [0,1].

  3. Stimulate distortion by adding nonlinear intensity components by using the equation 9.1.

  4. Calculate the coefficient bounds of Inline graphic and Inline graphic.

  5. Apply the fractional polynomial correction to the image by using the equation 9.2.

  6. Evaluate the quality metrics such as MSE, PSNR, SSIM, NIQE and BRIQUE.

  7. Display the values.

The proposed MRI image enchancement framework follows a structured and analytically guided image processing pipeline, as illustrated in Figure1. The pipeline begins with the acquisition of an input MRI image, If the input image is in RGB format, it is first converted into a grayscale image to ensure intensity based processing. The grayscale image is then normalized to the range[0,1], which improves numerical stability and enables consistent application of nonlinear transformation.

Fig. 1.

Fig. 1

flowchart of the proposed method.

To modelise realistic MRI intensity inhomogeneity and nonlinear signal distortion, an artifical distortion model is applied to the normalized image using the nonlinear intensity transformation given in equation9.1. Subsequently, the analytically derived coefficient bounds Inline graphic and Inline graphic obtained from the theorem 1 for the considered subclass of Sakaguchi-type function associated the Miller Ross type Poisson distribution series are computed. These coefficient ensure that the correction operator satisfies theoretical stability and boundedness conditions.

Using the computed coefficients, an analytic correction operator defined in equation9.2 is applied to the distorted image.

Dataset

In this study, we utilise imaging data from The Cancer Genome Atlas Lung Adenocarcinoma (TCGA-LUAD) collection, a publicly accessible dataset hosted by The Cancer Imaging Archive (TCIA). The TCGA-LUAD dataset forms a key component of The Cancer Genome Atlas (TCGA) initiative, which systematically catalogues and analyses genomic alterations responsible for cancer development, thereby facilitating advancements in diagnosis and therapy. Although the complete data set includes thousands of radiological scans in multiple modalities, for this study, we restricted our analysis to a curated subset of 100 MRI images. Figure2 illustrates sample images from the selected dataset.

Fig. 2.

Fig. 2

Sample images of the data set.

The TCGA-LUAD collection primarily targets lung adenocarcinoma (LUAD), the most common subtype of non-small cell lung cancer (NSCLC). It provides a comprehensive set of radiological images alongside clinical outcomes and genomic annotations, enabling integrative research in radiogenomics and precision oncology. Although magnetic resonance imaging is not the dominant modality within this collection compared to CT, our selected subset of MRI images offers a suitable basis for investigating signal correction and intensity normalisation using the proposed analytic model. By combining structural imaging information with theoretical correction methods, this dataset supports experimental validation while maintaining clinical relevance.

Evaluation metrics

The performance of the proposed correction method was assessed using three widely recognised metrics in image processing and medical imaging: Mean Squared Error (MSE), Peak Signal-to-Noise Ratio (PSNR), and Structural Similarity Index (SSIM).

1) Mean Squared Error (MSE)

MSE quantifies the average squared difference between pixel intensities of the reference and processed images. It is defined as:

graphic file with name d33e1954.gif 9.4

where I is the original reference image, Inline graphic is the processed image, and Inline graphic denotes the image dimensions. Lower values of MSE indicate higher accuracy in pixel-level restoration.

2) Peak Signal-to-Noise Ratio (PSNR)

PSNR provides a logarithmic measure of image fidelity relative to the maximum possible signal intensity L. It is defined as:

graphic file with name d33e1977.gif 9.5

Higher PSNR values correspond to better image quality. For medical images, values above 25–30 dB are generally considered acceptable, while lower values suggest visible degradation.

3) Structural Similarity Index (SSIM)

SSIM evaluates perceptual image quality by comparing luminance, contrast, and structural similarity between two images. It is defined as:

graphic file with name d33e1986.gif 9.6

where Inline graphic and Inline graphic represent local means, Inline graphic and Inline graphic denote standard deviations, and Inline graphic is the covariance of the two images. SSIM values range from 0 to 1, with values closer to 1 indicating stronger structural similarity and better perceptual quality.

4) Naturalness Image Quality Evaluator (NIQE)

NIQE is a no-reference image quality metric that evaluates perceptual naturalness based on statistical regularities of natural images. Unlike MSE, PSNR, and SSIM, NIQE does not require a reference image. Lower NIQE values indicate better perceptual quality and natural appearance, while higher values suggest the presence of distortions or unnatural patterns.

5) Blind/Referenceless Image Spatial Quality Evaluator (BRISQUE)

BRISQUE is another no-reference image quality assessment metric that measures distortions based on locally normalised luminance coefficients. Lower BRISQUE scores indicate higher perceptual quality and fewer visible artifacts, making it useful when reference images are not available.

Together, these five metrics provide a comprehensive assessment of the proposed correction framework: MSE reflects pixel-level accuracy, PSNR measures overall fidelity, SSIM evaluates structural similarity, while NIQE and BRISQUE assess perceptual naturalness without requiring reference images.

Discussion

The proposed analytic correction framework was rigorously evaluated using a combination of reference-based and no-reference image quality metrics, including Mean Squared Error (MSE), Peak Signal-to-Noise Ratio (PSNR), Structural Similarity Index (SSIM), Naturalness Image Quality Evaluator (NIQE), and Blind/Referenceless Image Spatial Quality Evaluator (BRISQUE). Together, these metrics provide a comprehensive assessment of the framework’s effectiveness in restoring distorted MRI images. Table1 presents a comparative quantitative performance evaluation of distorted and corrected MRI images using standard image quality metrics, namely MSE, PSNR, SSIM, NIQE, and BRISQUE. The comparison between the distorted and corrected images reveals clear improvements across all measures, confirming the robustness of the method.

Table 1.

Comparative metrics of Distorted image and Corrected Image.

Metrics Distored image Corrected Image
MSE 0.003509 0.001617
PSNR 24.8197 28.1758
SSIM 0.9693 0.9865
NIQE 6.9541 6.9767
BRIQUE 48.6485 48.6375

The MSE provides a direct measure of pixel-level differences between the reference and the processed images. In this study, the distorted image exhibited an MSE of 0.003509, which was reduced to 0.0061617 after applying the proposed correction operator. Such a significant decrease highlights the capability of the correction method to effectively compensate for nonlinear distortions introduced during MRI acquisition. From a clinical perspective, reducing MSE ensures that pixel intensities better represent true tissue properties, particularly in homogeneous regions such as soft tissues and organs where intensity inhomogeneity can mask pathologies. The lower error ensures that diagnostic details are preserved, making the corrected image more reliable for subsequent interpretation and analysis.

The PSNR is one of the most widely used measures for image quality assessment, reflecting the ratio between the maximum possible signal and the noise introduced by distortions. The distorted MRI image achieved a PSNR of 24.8187 dB, a value that suggests noticeable degradation in image fidelity. After correction, the PSNR increased significantly to 28.1758 dB, yielding an improvement of approximately 3.4 dB. In medical imaging, even a modest increase of 1–2 dB is regarded as meaningful, as it indicates improved visibility of structural features and boundaries. Therefore, the observed gain of 3.4 dB is highly significant. Higher PSNR directly translates to improved diagnostic capability, as it reduces noise-like distortions that may obscure critical lesions or tissue abnormalities. The improvement demonstrates that the analytic correction model successfully enhances global image fidelity while maintaining consistency across intensity ranges.

The SSIM metric evaluates image quality from a perceptual perspective, considering luminance, contrast, and structural similarity between the reference and processed images. The distorted image recorded an SSIM of 0.9693, which, while relatively high, still indicated subtle structural deviations due to nonlinear distortion. After correction, the SSIM improved to 0.9865, approaching near-perfect similarity with the reference image. This improvement is particularly significant in MRI imaging, where structural preservation is critical for accurate diagnosis. Unlike natural images, where perceptual similarity may tolerate minor distortions, medical images demand very high structural fidelity. The correction method’s ability to increase SSIM demonstrates that it not only reduces error but also preserves diagnostic structures such as lesion boundaries, tissue interfaces, and subtle anatomical features. This ensures that the corrected images remain clinically interpretable and suitable for downstream tasks such as segmentation and classification.

NIQE is a no-reference metric designed to measure the perceptual naturalness of an image based on statistical features. For the distorted image, the NIQE score was 6.9541, while the corrected image achieved a slightly improved score of 6.9467. Although the numerical difference may appear small, it nevertheless indicates that the corrected images exhibit marginally improved perceptual naturalness. This result is consistent with the observation that NIQE is less sensitive to small corrections compared to reference-based metrics such as MSE or SSIM. However, the improvement, though minor, is aligned with the general enhancement trend, confirming that the correction method not only restores pixel accuracy but also improves the perceptual realism of the MRI images. From a clinical perspective, a lower NIQE score implies reduced artificial distortions and more natural intensity distributions, enhancing radiologist confidence in diagnostic interpretation.

The effectiveness of the suggested analytic correction model is strongly supported by the comparative assessment across every measure. In MSE, PSNR, and SSIM, where error correction, fidelity enhancement, and structural preservation were obviously apparent, the most noticeable changes were seen. These measures precisely indicate how well the correcting operator can recover MRI intensities and preserve diagnostic structures. The NIQE and BRISQUE criteria, meanwhile, indicate even minor changes but offer more proof from a no-reference viewpoint that the adjustment helps to improve perceptual quality. Visually reinforced in figure3, this trend is seen as the corrected picture surpasses the distorted picture over five measurements in the comparative graph. The clear contrast of the two story lines draws attention to the dependability and reliability of the suggested correction model. Notably, the improvements were consistent throughout all five measures, therefore highlighting the robustness of the suggested technique in simulated MRI distortions.

Fig. 3.

Fig. 3

Comparative graph between the distorted images and corrected images.

The comparative evaluation across all metrics strongly validates the effectiveness of the proposed analytic correction model. The most pronounced improvements were observed in MSE, PSNR, and SSIM, where error reduction, fidelity enhancement, and structural preservation were clearly evident. These metrics directly reflect the ability of the correction operator to restore MRI intensities and preserve diagnostic structures. Meanwhile, the NIQE and BRISQUE metrics, although showing smaller improvements, provide additional evidence that the correction contributes positively to perceptual quality from a no-reference perspective. Importantly, the improvements were consistent across all five metrics, demonstrating the robustness of the proposed method in simulated MRI distortions. The combination of significant gains in reference-based metrics and modest yet consistent enhancements in no-reference metrics indicates that the method can improve both numerical accuracy and perceptual quality in a controlled setting. While these results are promising, further studies and clinical validation are required before the method can be applied in real-world medical settings.

Conclusion

In this work, we investigated geometric properties of a subclass of Sakaguchi-type functions defined via the Miller–Ross-type Poisson distribution operator. Several analytic results were established, including sharp coefficient inequalities, inverse function estimates, and Fekete–Szegö bounds. The study also explored distortion, growth, convexity, subordination, and partial sums, thereby giving a comprehensive characterization of the newly defined class. Importantly, we bridged the gap between theoretical function theory and practical imaging by applying the results to MRI correction. The proposed analytic correction operator successfully reduced nonlinear distortions in MRI scans while preserving structural fidelity, as confirmed by quantitative metrics. This dual contribution–both theoretical advancement in geometric function theory and practical application to medical imaging–demonstrates the versatility of the introduced subclass. Future work may explore further applications in other imaging modalities and extend the framework to higher-dimensional settings.

Supplementary Information

Below is the link to the electronic supplementary material.

Supplementary material 1 (54.1KB, pdf)

Author contributions

S.Manoj - Conceptualization, Investigation, Methodology, Visualization, Writing - original draft, Writing, review editing. B.Sruthakeerthi- Supervision, Validation.

Funding

Open access funding provided by Vellore Institute of Technology.

Data availability

The following links are provided for the MRI images and datasets used in this study. Source file of TCGA-LUAD MRI dataset: The Cancer Imaging Archive (TCIA), TCGA-LUAD collection TCGA-LUAD data set https://www.cancerimagingarchive.net/collection/tcga-luad/. The underlying code for this study is available at 10.17632/wwhbrwz78y.1.

Declarations

Competing interests

The authors declare no competing interests.

Footnotes

Publisher’s note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Supplementary Information

The online version contains supplementary material available at 10.1038/s41598-026-39523-2.

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Associated Data

This section collects any data citations, data availability statements, or supplementary materials included in this article.

Supplementary Materials

Supplementary material 1 (54.1KB, pdf)

Data Availability Statement

The following links are provided for the MRI images and datasets used in this study. Source file of TCGA-LUAD MRI dataset: The Cancer Imaging Archive (TCIA), TCGA-LUAD collection TCGA-LUAD data set https://www.cancerimagingarchive.net/collection/tcga-luad/. The underlying code for this study is available at 10.17632/wwhbrwz78y.1.


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