CT Report: Total Lung and Liver Volumes Explained

Computed Tomography Report

Dear Dr.
Yang,
Thank you for your response; I have gained a lot of relevant knowledge.
Regarding the CT report from March 24, the findings are as follows: Total lung volume 4588 cc, Total liver volume 1902.8 cc, Right lobe 1303.2 cc, S4 185.5 cc, S2+S3 414.1 cc.
I would like to inquire about the following two pieces of information:
1.
What is the total volume (in cc) of the radiolabeled albumin used, and what is the calculation?
2.
What is the percentage of the radiolabeled albumin that is shunted from the liver to the lungs, and what is the calculation?
Thank you!
Best Regards,
Byron

Byron, 40~49 year old female. Ask Date: 2013/03/30

Dr. Yang Jinghua reply Radiology

Dear Byron,
Due to the nature of your inquiry involving two specialized fields, the response will be provided jointly by Radiology and Nuclear Medicine.
Regarding the examination of Technetium-99m macro-aggregated albumin (Tc-99m MAA) and the data derived from this examination, the following explanation is provided:
Technetium-99m macro-aggregated albumin can simulate the distribution of radiolabeled microspheres within the body as they flow through the bloodstream.
Therefore, prior to performing radioembolization for liver tumors, a harmless dose of Tc-99m MAA is injected into the hepatic artery to observe its distribution and assess the feasibility of this treatment approach.
Typically, 5 millicuries (a unit of radioactivity, not volume) of Tc-99m MAA are suspended in saline and slowly injected into the body (the injected volume is not fixed).
Once inside the body, the detection equipment in Nuclear Medicine can identify the minute radiation emitted by the Technetium, allowing us to determine where the Tc-99m MAA is distributed based on the intensity of the radiation signals.
The data obtained from this examination is in the form of signal intensity rather than volume.
We usually compare the signal intensities from various body regions to that of the liver, resulting in a signal intensity ratio calculated as follows: (Signal intensity of a specific body region / Signal intensity of the liver) * 100%.
If there is shunting of arterial blood from the liver to the venous system (which varies individually and cannot be predicted), some of the Tc-99m MAA may flow to the lungs via the veins, resulting in a stronger signal in the lungs.
If the lung signal intensity is excessively high (typically defined as greater than 20%), it indicates that administering therapeutic radiolabeled microspheres could harm the lungs, making this treatment approach unsuitable.
In summary, one of the purposes of this examination is to determine the ratio of hepatic arterial shunting to the lungs, which can be derived from observing the signal intensity ratio between the lungs and the liver.
This examination alone will not directly calculate volume-related data such as total lung volume or total liver volume; however, if this examination is performed in conjunction with a computed tomography (CT) scan, the imaging from the CT can be used to estimate the volumes of various organs.
Volume calculations are derived from the area of each organ on each cross-sectional image multiplied by the slice thickness, with the results summed across all slices.
This calculation is performed by computer algorithms and cannot be expressed by a simple formula.
S4 and S2+3 refer to specific regions within the liver.
We conventionally divide the liver into eight segments (S1 to S8), delineated by vascular and other anatomical structures.
The "S" stands for segment, and the number following "S" indicates the position of each segment, with each number corresponding to a fixed anatomical location.
This segmentation facilitates communication among clinicians, allowing them to clearly specify which part of the liver they are referring to by naming the segment.
As previously mentioned, the Tc-99m MAA examination allows us to determine the distribution of the radiolabeled albumin within the body by detecting signal intensities.
Similarly, by measuring the signal intensity ratios in different liver segments, we can ascertain the distribution of Tc-99m MAA within the liver, although the resulting data will be in terms of signal intensity ratios rather than volume.
Volume estimations must still be derived from CT imaging through computer calculations.
I hope the above explanation addresses your questions.
Thank you.

Reply Date: 2013/03/30

More Info

Dear Byron,
Thank you for your inquiry regarding the CT report and the specific calculations related to the total lung and liver volumes. Understanding these measurements is crucial, especially in the context of evaluating liver tumors and their treatment options. Let’s break down your questions step by step.

1. Total Amount of Injected Albumin Microspheres (cc):
The total volume of the injected albumin microspheres is not explicitly stated in the CT report you provided. Typically, this information would be documented in the procedural notes or the report of the interventional radiologist who performed the procedure. If you have access to that documentation, it should specify the volume of the albumin microspheres used. If not, you may need to contact the medical facility where the procedure was performed for this specific detail.

However, if you are looking for a general formula to calculate the total volume of injected microspheres based on the procedure, it would typically be the volume of the solution used for the injection, which is often measured in milliliters (mL) or cubic centimeters (cc). For example, if 10 mL of albumin microspheres were injected, the total would simply be 10 cc.

2. Ratio of Albumin Microspheres Shunted from Liver to Lungs:
To calculate the ratio of albumin microspheres that were shunted from the liver to the lungs, you would need two key pieces of information: the total volume of albumin microspheres injected and the volume of those microspheres that were detected in the lungs after the procedure.
The formula for calculating the percentage of microspheres that reached the lungs would be:
\[
\text{Percentage of microspheres in lungs} = \left( \frac{\text{Volume of microspheres in lungs}}{\text{Total volume of injected microspheres}} \right) \times 100
\]
For example, if you injected 10 cc of albumin microspheres and found that 2 cc were detected in the lungs, the calculation would be:
\[
\text{Percentage} = \left( \frac{2 \text{ cc}}{10 \text{ cc}} \right) \times 100 = 20\%
\]
This means that 20% of the injected microspheres were shunted to the lungs.

3. Understanding S4 and S2+S3:
In your report, S4 refers to Segment 4 of the liver, which is part of the left lobe. S2 and S3 refer to Segments 2 and 3, also part of the left lobe. The liver is divided into eight segments based on the vascular supply and biliary drainage, and these segments are important for surgical planning and understanding the extent of liver disease.

In summary, while the total volume of injected albumin microspheres is not provided in the CT report, you can obtain this information from the procedural notes. The calculation of the percentage of microspheres that reached the lungs can be done using the formula provided, once you have the necessary data. Understanding these volumes and ratios is essential for assessing the effectiveness of treatments for liver tumors and planning further management.

If you have any further questions or need additional clarification, please feel free to reach out. Best wishes for your family's health and well-being.

Best Regards,
Doctor Q&A Teams

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