Dose Comparison of Obese and Non-Obese During CT Abdomen Scan

Maharana, S; Khan, Alam

doi:10.65188/nurexus.1098

Maharana S et al | DOI: 10.65188/nurexus.1098

Page 13

Journal of MedVerse Research & Practice

ISSN: 3107-4278

Dose Comparison of Obese and Non-Obese During CT Abdomen Scan

S Maharana

1

, Alam Khan

2

Postgraduate, Professor

Department of Radiology, Nims Institute of Allied Medical Science and Technology, Rajasthan

Email ID: maharanaivam@gmail.Com

Submission Date: 11.07.2026

Accepted Date:19.08.2026

Published Date: 31.08.2026

DOI: 10.65188/nurexus.1098

article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted

use, distribution, and reproduction in any medium, provided the original author(s) and source are credited.

Abstract

Background: Computed tomography (CT) is an important diagnostic imaging modality, but the use of ionizing

radiation necessitates careful optimization of patient radiation exposure. Patient body habitus, particularly BMI and

abdominal cross-sectional dimensions, may influence radiation dose during CT abdomen examinations. This study

was undertaken to evaluate the relationship between BMI, AP and lateral abdominal diameters, and radiation dose

parameters.

Methods: A prospective comparative study was conducted among 80 patients undergoing CT abdomen examinations

at the Department of Radio-Diagnosis and Imaging, Nims Institute of Allied Medical Science and Technology,

Rajasthan.. Patients aged 15–85 years of both sexes were included. Height, weight, age, BMI, AP diameter, lateral

diameter, CTDIvol, and DLP were recorded. CTDIvol and DLP obtained from the scanner-generated dose report

were compared with BMI and abdominal cross-sectional dimensions. The data were analyzed using appropriate

statistical methods, with a p-value of <0.05 considered statistically significant.

Results: The study included 80 patients, of whom 50 (62.5%) were male and 30 (37.5%) were female. The mean AP

abdominal diameter was 21 cm and the mean lateral diameter was 29 cm. The mean CTDIvol was 7.7 mGy, ranging

from 4.84 to 16.78 mGy, while the mean DLP was 392 mGy·cm, ranging from 205.66 to 846.86 mGy·cm. Seventeen

patients (21.25%) were obese and 63 (78.75%) were non-obese. A progressive increase in radiation dose was

observed with increasing BMI. Mean CTDIvol increased from 5.04 mGy in the BMI 15–20 kg/m² group to 16.70

mGy in the BMI 36–40 kg/m² group, while mean DLP increased from 263 to 841 mGy·cm. AP abdominal diameter

demonstrated an overall positive relationship with both CTDIvol and DLP, whereas the relationship with lateral

diameter was comparatively less consistent.

Conclusion: The study demonstrates that patient body habitus is an important consideration in radiation dose during

CT abdomen examinations. Increasing BMI and AP abdominal diameter were associated with higher CTDIvol and

DLP values. Incorporating patient-size parameters, particularly BMI and AP diameter, into individualized CT

protocols may assist in radiation dose optimization while maintaining adequate diagnostic image quality.

Keywords: Computed tomography; CT abdomen; Radiation dose; CTDIvol; DLP; Body mass index; AP diameter;

Lateral diameter; Obesity; Dose optimization.

Introduction

Computed tomography (CT) has become an essential imaging modality in modern diagnostic practice,

providing detailed cross-sectional anatomical information for the evaluation of a wide range of clinical

conditions. By acquiring multiple X-ray projections around the patient and reconstructing them into axial

images, CT provides superior anatomical visualization compared with conventional radiography. These

images can further be reformatted into sagittal and coronal planes or reconstructed into three-dimensional

images using post-processing techniques. CT therefore has an important role in diagnosis, treatment

ORIGINAL ARTICLE

Maharana S et al | DOI: 10.65188/nurexus.1098

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planning, and image-guided interventional procedures [1–4]. CT technology has evolved considerably since

its introduction in the early 1970s. Modern scanners provide rapid volumetric acquisition, thin-slice

imaging, improved image quality, and reduced motion-related artifacts. These characteristics make CT

particularly useful for abdominal imaging, where rapid and accurate assessment is often required. CT

abdomen is widely used in the evaluation of conditions such as appendicitis, diverticulitis, urinary calculi,

intestinal obstruction, and gastrointestinal perforation [5,6].

Despite its diagnostic advantages, CT involves exposure to ionizing radiation. The radiation absorbed

during an examination contributes to the patient's radiation dose, which is commonly represented using

dose indices such as the computed tomography dose index (CTDI) and dose-length product (DLP).

Radiation dose is influenced by several factors, including patient age, sex, body size, anatomical region

examined, thickness of adipose tissue, scanning protocol, and technical parameters of the CT system [7].

As the use of CT has increased substantially, concerns regarding cumulative radiation exposure and patient

safety have become increasingly important [8,9]. The principle of keeping radiation exposure as low as

reasonably achievable (ALARA) forms the basis of radiation protection in diagnostic imaging. Diagnostic

reference levels and dose-optimization strategies have been developed to minimize unnecessary radiation

exposure while maintaining adequate image quality for diagnosis. Therefore, achieving an appropriate

balance between radiation dose and diagnostic image quality is particularly important when performing CT

examinations [10].

Patient body size is one of the major factors affecting radiation dose during CT. Larger patients generally

produce greater X-ray attenuation, particularly because of increased soft-tissue and subcutaneous fat

thickness. Consequently, CT systems may require higher radiation output to obtain images of acceptable

diagnostic quality. Obesity has become increasingly prevalent, making the assessment of its influence on

CT radiation exposure clinically relevant. Body mass index (BMI), calculated from body weight and height,

is commonly used to categorize overweight and obesity. According to the World Health Organization, a

BMI of 25 kg/m² or greater indicates overweight, while a BMI of 30 kg/m² or greater indicates obesity [11–

13].

The association between patient size and radiation dose is complex and depends not only on BMI but also

on scanning protocols, technical factors, and the anatomical region being examined. Cross-sectional body

dimensions may provide additional information regarding the patient's attenuation characteristics. The

anteroposterior (AP) diameter of the abdomen, measured from the anterior to the posterior aspect on an

axial CT image, is one such parameter. Increased abdominal diameter, particularly due to greater

subcutaneous fat deposition, can increase X-ray attenuation and influence the radiation output required to

achieve adequate image quality [15–17]. Two commonly reported CT dose parameters are CTDIvol and

DLP. CTDIvol represents the radiation output associated with a CT examination and is expressed in

milligray (mGy), whereas DLP incorporates the radiation dose with the scanned length and is expressed in

mGy·cm. DLP can be calculated using the relationship: DLP = CTDIvol × scan length

These parameters are routinely used to evaluate and monitor radiation exposure associated with CT

examinations [18–22]. Considering the increasing use of CT abdomen examinations and the growing

prevalence of obesity, evaluation of the relationship between patient body habitus and radiation dose is

important for radiation protection and protocol optimization. Therefore, the present study was undertaken

to assess the relationship between obesity, age, BMI, and abdominal cross-sectional diameter with radiation

dose during CT abdomen scanning. The study also aimed to identify patient-related factors associated with

CT dose and provide information that may assist in optimizing exposure parameters while maintaining

diagnostically adequate image quality.

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Materials & Methods

Study Design

This was a prospective, comparative study conducted to evaluate the relationship between patient body

habitus and radiation dose during CT abdomen examinations. Patient-related parameters, including age,

height, weight, BMI, anteroposterior (AP) diameter, and lateral diameter, were assessed and correlated with

CT radiation dose parameters.

Study Setting and Duration

The study was conducted over a period of two years in the Department of Radio-Diagnosis, Nims Institute

of Allied Medical Science and Technology, Rajasthan. CT examinations were performed using a Siemens

SOMATOM Scope 16-slice multidetector CT scanner.

Study Population

The study included patients undergoing CT abdomen examinations for various abdominal clinical

indications. A total of 80 patients were included in the study.

Inclusion Criteria

Patients aged 15–85 years undergoing CT abdomen examination were included. Both male and female

patients were eligible to participate.

Exclusion Criteria

Patients undergoing post-contrast CT examinations, pregnant patients, and those undergoing follow-up or

repeat CT examinations were excluded from the study.

Data Collection Procedure

Written informed consent was obtained from the patients or their attendants before participation. Patient

age, height, and weight were recorded before the CT examination, and BMI was calculated from the

recorded anthropometric measurements. CT abdomen examinations were subsequently performed using

standardized scanning protocols.

The CTDIvol and DLP values were obtained from the radiation dose report automatically generated by the

CT scanner. AP and lateral abdominal diameters were measured from the acquired cross-sectional CT

images. The collected radiation dose parameters were compared with BMI, AP diameter, lateral diameter,

and patient age to evaluate their relationships. The observed dose values were also compared with

applicable diagnostic reference levels (DRLs).

CT Imaging Protocol

All examinations were performed using a Siemens SOMATOM Scope 16-slice multidetector CT scanner

equipped with a curved detector array containing approximately 700 detector elements and a fan beam of

approximately 40–60°. Standard abdominal CT imaging protocols were followed. Automatic exposure

control (AEC) software was used to adjust tube current according to patient size, with the aim of

maintaining adequate image quality while minimizing radiation exposure.

Radiation Dose Assessment

Radiation exposure was assessed using CT dose parameters obtained from the scanner-generated dose

report. CTDIvol was recorded in mGy and DLP in mGy·cm. These values were subsequently correlated

with patient BMI and abdominal cross-sectional dimensions to determine the influence of body habitus on

radiation dose.

Statistical Analysis

The collected data were analyzed using appropriate statistical software with the assistance of a statistician.

Continuous variables were assessed according to patient characteristics and study design, and relationships

between BMI, age, AP diameter, lateral diameter, CTDIvol, and DLP were evaluated. Radiation dose

measurements were also compared with diagnostic reference levels. A p-value of <0.05 was considered

statistically significant.

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Ethical Considerations: The study was conducted after obtaining approval from the Institutional Ethics

Committee of SGT Hospital and Research Institute. Written informed consent was obtained from all

patients or their attendants before participation. Patient confidentiality was maintained throughout the

study, and the collected information was used solely for research purposes.

Result

Table 1. Age Distribution of the Study Population

Age group (years)

Frequency (n)

Percentage (%)

15–25

15

18.75

26–35

14

17.50

36–45

10

12.50

46–55

17

21.25

56–65

12

15.00

66–75

9

11.25

76–85

3

3.75

Total

80

100

The study population ranged from 15 to 85 years. The highest proportion was in the 46–55-year group

(21.25%), while the lowest was in the 76–85-year group (3.75%).

Table 2. Gender Distribution

Gender

Frequency (n)

Percentage (%)

Male

50

62.50

Female

30

37.50

Total

80

100

Males constituted 62.5% of the study population, while females accounted for 37.5%.

Table 3. Distribution According to AP and Lateral Abdominal Diameter

Diameter range (cm)

AP diameter (n)

Lateral diameter (n)

5–10

1

0

10–15

7

0

16–20

32

0

21–25

28

14

26–30

10

39

31–35

2

21

36–40

0

5

41–45

0

1

The mean AP diameter was 21 cm and the mean lateral diameter was 29 cm. The AP diameter ranged

from 8.34 to 34.23 cm, while the lateral diameter ranged from 23.77 to 43.86 cm.

Table 4. Distribution According to CTDIvol

CTDIvol (mGy)

Frequency (n)

Percentage (%)

1–5

15

18.75

6–10

60

75.00

11–15

3

3.75

16–20

2

2.50

Total

80

100

The mean CTDIvol was 7.7 mGy, ranging from 4.84 to 16.78 mGy. Most patients (75%) had CTDIvol

values between 6 and 10 mGy.

Table 5. Distribution According to DLP

DLP (mGy·cm)

Frequency (n)

Percentage (%)

200–300

27

33.75

301–400

23

28.75

401–500

17

21.25

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501–600

6

7.50

601–700

4

5.00

701–800

1

1.25

801–900

2

2.50

The mean DLP was 392 mGy·cm, ranging from 205.66 to 846.86 mGy·cm. The largest proportion

(33.75%) had DLP values of 200–300 mGy·cm.

Table 6. BMI Distribution

BMI (kg/m²)

Frequency (n)

Percentage (%)

Category

Frequency (n)

Percentage (%)

Non-obese

63

78.75

Obese

17

21.25

Total

80

100

Of the 80 patients, 63 (78.75%) were non-obese and 17 (21.25%) were obese.

Table 8. Relationship Between BMI, CTDIvol and DLP

BMI (kg/m²)

Mean CTDIvol (mGy)

Mean DLP (mGy·cm)

15–20

5.04

263

21–25

6.24

299

26–30

7.90

402

31–35

10.40

563

36–40

16.70

841

Radiation dose increased progressively with BMI. Mean CTDIvol increased from 5.04 mGy to 16.70

mGy, while mean DLP increased from 263 to 841 mGy·cm across the BMI categories.

Discussion

The present prospective study involving 80 patients evaluated the relationship between BMI, abdominal

cross-sectional diameter, and radiation dose parameters during CT abdomen examination. The mean age

of the study population was 45 years, with males comprising 50 (62.5%) and females 30 (37.5%). The

mean AP abdominal diameter was 21 cm, while the mean lateral diameter was 29 cm. The mean

CTDIvol was 7.7 mGy, ranging from 4.84 to 16.78 mGy, whereas the mean DLP was 392 mGy·cm,

with values ranging from 205.66 to 846.86 mGy·cm.

A progressive increase in radiation dose was observed with increasing BMI. Among the 80 patients, 63

(78.75%) were non-obese and 17 (21.25%) were obese. Mean CTDIvol increased from 5.04 mGy in

patients with BMI 15–20 kg/m² to 6.24 mGy in those with BMI 21–25 kg/m², 7.90 mGy in the 26–30

kg/m² group, 10.40 mGy in the 31–35 kg/m² group, and 16.70 mGy in patients with BMI 36–40 kg/m².

Similarly, mean DLP increased from 263 mGy·cm to 299, 402, 563, and 841 mGy·cm across the

corresponding BMI categories. Thus, the study demonstrated a clear increasing trend in both CTDIvol

and DLP with increasing BMI. Abdominal cross-sectional dimensions also showed an association with

radiation dose. The AP diameter ranged from 8.34 to 34.23 cm, while the lateral diameter ranged from

23.77 to 43.86 cm. The graphical analysis demonstrated an overall positive relationship between AP

Maharana S et al | DOI: 10.65188/nurexus.1098

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diameter and CTDIvol and between AP diameter and DLP. The increase in AP diameter was

accompanied by a corresponding increase in radiation dose. In comparison, the relationship between

lateral diameter and dose parameters was less consistent. These findings suggest that AP diameter may

be a more useful patient-size parameter than lateral diameter for radiation-dose estimation in abdominal

CT.

The findings are also supported by previous research showing that larger body habitus is associated with

increased radiation exposure during CT examinations [15,16]. The present study provides quantitative

evidence of this trend, with CTDIvol increasing more than threefold from 5.04 mGy in the lowest BMI

category to 16.70 mGy in the highest BMI category. Similarly, DLP increased by more than threefold,

from 263 to 841 mGy·cm. This substantial increase highlights the importance of incorporating patient

size into CT dose optimization protocols.

Automatic exposure control (AEC) is designed to adjust tube current according to patient attenuation

and maintain acceptable image quality [19,20]. However, in patients with greater body habitus,

increased tube output may result in higher radiation exposure if exposure parameters are not

appropriately optimized. Therefore, adjustment of AEC-related parameters according to patient anatomy

and BMI may help achieve an appropriate balance between image quality and radiation dose [20–22].

Several dose-reduction strategies, including tube-current modulation, optimized tube voltage, iterative

reconstruction, and individualized scanning protocols, may help reduce unnecessary radiation exposure

in obese patients [18,20,22]. The present findings suggest that BMI and particularly AP abdominal

diameter could be considered when applying such dose-optimization strategies.

Importantly, although the present results demonstrate clear numerical trends, statistical significance

cannot be reported from the available data because the actual correlation coefficients and p-values were

not provided. Therefore, the observed increase in CTDIvol and DLP with BMI and AP diameter should

be described as an association or trend rather than as a statistically significant relationship until the

appropriate statistical tests are performed. Further analysis using Pearson or Spearman correlation and

reporting the corresponding r values and p-values would provide stronger statistical evidence for these

relationships.

Conclusion

The present prospective study involving 80 patients demonstrated that patient body habitus is an important

factor influencing radiation dose during CT abdomen examinations. A progressive increase in mean

CTDIvol and DLP was observed with increasing BMI, with CTDIvol increasing from 5.04 mGy in the BMI

15–20 kg/m² group to 16.70 mGy in the BMI 36–40 kg/m² group, while DLP increased from 263 to 841

mGy·cm. Increasing AP abdominal diameter was also associated with higher radiation dose and appeared

to be a more consistent predictor than lateral diameter. Therefore, BMI and AP diameter should be

considered during patient-specific CT dose optimization. Appropriate adjustment of exposure parameters

and use of optimized dose-reduction techniques may help minimize radiation exposure while maintaining

adequate diagnostic image quality. Further studies with larger sample sizes and formal correlation analysis

are recommended to establish the statistical strength of these associations.

Declaration

Conflict of Interest: The authors declare that they have no competing interests or conflicts of interest

related to this work.

Funding: Nil

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