Page 70 - ARNM-3-2

Advances in Radiotherapy
& Nuclear Medicine Modeling renal TAC in dynamic scintigraphy

urine. A gamma camera is used to detect the radiation techniques, can be applied to the TACs to reconstruct
emitted by the tracer, allowing the visualization of the the underlying physiological processes involved in
kidneys and the urinary system in real time. Dynamic renal function. These models help to quantify and
renal scintigraphy provides valuable information about analyze the data in a more detailed manner.
renal function, including glomerular filtration rate (GFR), (vii) Clinical interpretation: The derived parameters and
renal blood flow, and tubular function. It is commonly modeling results are interpreted in the context of the
used in renal function evaluation, renal transplant patient’s clinical condition to aid in diagnosis and
assessment, and various kidney disorder diagnoses, such treatment planning. Abnormalities in renal function
as hydronephrosis, renal obstruction, and renal artery parameters can indicate various renal disorders, such
stenosis. The “dynamic” aspect of the procedure refers as renal artery stenosis, obstruction, or impaired renal
to the continuous imaging of the kidneys over a period function.
of time, typically several minutes, allowing clinicians to Renal function reconstruction and modeling in dynamic
observe the tracer’s movement through the renal system scintigraphy play a valuable role in the assessment of renal
and assess kidney function dynamically. This dynamic function and can provide valuable insights for clinicians in
imaging is often accompanied by static images taken at the diagnosis and management of renal diseases.
specific time points to provide additional information.
TACs play a critical role in dynamic renal scintigraphy
Renal function modeling in dynamic scintigraphy uses
mathematical algorithms to analyze imaging data and by quantitatively assessing renal function based on tracer
kinetics. Traditional TACs are generated automatically
assess renal function. This allows a more comprehensive by scintigraphy machines using predefined algorithms
assessment of renal function beyond simple visual and standard ROI selection techniques, typically based
observation. The typical steps for renal function on radioactive counting. However, these machine-
reconstruction and modeling are: generated TACs may not fully capture the physiological
(i) Data acquisition: Dynamic renal scintigraphy involves dynamics of renal function due to their dependence on
acquiring a series of images over time as the radioactive fixed ROI placement and automated signal processing
tracer circulates through the kidneys. These images methods. In addition, standard one-compartment models
2
are typically obtained using a gamma camera.
(ii) Image processing: The acquired images are processed used in renal function modeling assume homogeneous
tracer distribution, which may not accurately represent
to correct for factors such as background noise, scatter,
and attenuation. This ensures the accuracy of the data complex renal clearance mechanisms. While alternative
models, such as multi-compartment or physiologically
used for analysis.
(iii) Region of interest (ROI) selection: ROIs are delineated based models, offer more detailed representations,
they are computationally intensive and not widely
on the images to isolate the kidneys and other relevant implemented in clinical practice. Moreover, manual TAC
structures, such as the bladder and blood vessels.
(iv) Time-activity curve (TAC) generation: The intensity of reconstruction, which can provide a more physiologically
relevant representation by incorporating gray-level value
the radioactive tracer within the kidneys is measured
over time to create TACs. These curves represent the measurements, remains underexplored. There is also a lack
uptake, distribution, and clearance of the tracer within of studies comparing different ROI selection techniques,
the kidneys. 1 such as rectangular versus free-hand approaches, and their
(v) Renal function parameters: Various parameters can impact on TAC accuracy. To address these gaps, this study
aims to assess the accuracy of manually reconstructed
be derived from the TACs to assess renal function, TACs, validate an empirical mathematical model for renal
including: function evaluation, and explore the influence of ROI
• GFR: GFR is a key indicator of renal function and
can be estimated from the rate of tracer clearance selection methods on TAC accuracy.
from the blood. The main objective of this work is to experimentally
• Renal blood flow: The perfusion of blood through reconstruct TACs from clinical dynamic scintigraphy data
the kidneys can be estimated from the initial and compare them with those automatically generated
uptake and distribution of the tracer. by the scintigraphy machine based on the main kinetic
• Tubular function: Parameters such as tubular parameters that can be extracted from clinical TACs.
3-5
extraction rate and tubular secretion rate can be The second objective is to compare rectangular and free-
derived from the TACs to assess tubular function. hand ROI selection methods using six additional cases.
(vi) Modeling techniques: Mathematical models, such The third objective is to evaluate empirical mathematical
as compartmental models and deconvolution fitting functions and a one-compartment model used for

Volume 3 Issue 2 (2025) 62 doi: 10.36922/ARNM025070008