What does the index number indicate for the SUV

[alephnull]

All,

I had a pylarify scan today and the results had a SUV number for each lymph met.

But it also had an index number for each SUV number.

Would someone please explain the index number?

[Tall_Allen]

Do you mean the background rate?

[tango65]

Could you post the report of the study?

[alephnull]

Part of report, Chest: Multiple tracer avid bilateral supraclavicular nodes, greater in the right and mediastinal nodes are seen. Representative right supraclavicular node demonstrates maximum SUV of 13.8 (index 287). Tracer avid prevascular node demonstrate maximum SUV of 16.2 (index 301). Mildly tracer avid lower posterior mediastinal node is also seen with maximum SUV of 4.8 (index 385).

I know having a higher SUV is not good, but was wondering about the index value. It doesn’t follow the SUV. Was thinking it is just some number randomly generated OR

maybe it’s related to location and possibly indicating some level of risk.

[Hidden in reply to alephnull]

could index just be the image number? when i get a scan i can go to my patient portal and then look at the particular numbered image that the radiologist seems to think evidences his findings best.

[StayingOptimistic]

I was wondering myself about the meaning of these values. Since I am a data oriented man, I wanted to know the difference in values and how it can be interpreted. It occurred to me afterwards that it won’t make a difference if it can’t change the treatments plan. Am I missing something? Is it important to understand it as the radiologist does? Just very curious myself about it.

[dhccpa in reply to StayingOptimistic]

I've had those same questions, but don't recall ever seeing index numbers.

[leebeth]

I have been wondering this myself. My husband’s SUV numbers are much higher than yours. I think that is the uptake, and might be reflective of the size and density of the lesion, but I am not sure. “Extensive intensely PSMA avid presumed active skeletal metastases. For example, a destructive lesion has developed in the right acetabulum that measures approximately 4 cm, SUV max 37, axial image 92. The most intense activity is within a destructive right S1 metastasis, SUV max 65, axial image

224. By comparison, the hepatic activity shows SUV max 15 and parotid activity shows SUV max 20. Additional metastases are seen throughout the spine, bilateral ribs, sacrum, bilateral pelvis and right proximal femur. Of note, a previously sclerotic/treated metastasis in T9 has become more sclerotic and is now

diffusely PSMA avid subcutaneous and extends into lytic changes in the left posterior elements of T9, axial image 140.”

So a SUV max of 65 is probably not a good thing.

[Justfor_ in reply to leebeth]

My interpretation is that is the "section" number for easy future review. In drawing there are views and sections. Each one should be further specified as front, right, left, top for views and a pair of letters like A-A' for sections. The T of CT stands for Tomography. Tomos in Greek is the noun of the verb temno meaning slice, cut, devision point. Used for books to indicate volumes. CT takes sections of our bodies every 3-5mm. Each one is designated a sequential number. The computer file containing the data of each tomos has a header with a ton of information and among them this number. IMO index and axial image are other names for this number.

[leebeth in reply to Justfor_]

It actually stands for Standardized Uptake Value, so it is a way to quantify lesions.

[Justfor_ in reply to leebeth]

The subject of this thread is related to the second number, dubbed Index. I was referring to this one and certainly not to SUV.

[leebeth in reply to Justfor_]

Thank you for clarifying. You responded to my reply, which was only discussing SUV,, so that wasn’t clear to me. My husband’s scan has been read by 2 different radiologists and neither report mentioned index number., only image number. Interesting.

[dhccpa in reply to leebeth]

Index number?

[alephnull in reply to dhccpa]

See further up in thread, I posted a sample of my report.

[dhccpa in reply to alephnull]

Yes I understood your questions. But the poster I responded to mentioned SUV when I thought they meant index number.

[Javelin18]

Here’s a finding from my recent MRI, “There is a small amount of new epidural tumor extension into the right lateral recess of L3, partially encasing the right L3 nerve roots (eg. se8,im25-27).”

This is saying that I have a lesion pushing on the root of a peripheral nerve,,where it exits the space next to the third lumbar vertebra. A view of the problem can be seen in image sequence 8,,images 25-27.

Because I’m curious, I request copies of my images so I can see the problem too. The DVDs can take half an hour to load, and have hundreds of image slices organized in groups of sequences. I find the image interface difficult to navigate, but kind of cool to be able to walk through pictures of my body.

[Parscore in reply to Javelin18]

So, if you do not mind me asking, what physical systems are you having related to the L3 nerve roots.

[Javelin18 in reply to Parscore]

I’ll start another thread, so I don’t pull this discussion off course.

[j-o-h-n]

Does this help from Wicket-pedia: Discussion

While this equation looks simple, there are a number of points that need to be discussed, such as (1) the origin of cimg data, (2) the origin of cinj data, (3) time, and (4) units.

Image

The cimg data may be the pixel intensities of a calibrated PET image. Calculated SUV data can then be visualized as parametric SUV image. Alternatively, groups of such pixels may be selected e.g. by manually drawing or otherwise segmenting a region of interest (ROI) on the PET image. Then e.g. the average intensity of that ROI may be used as cimg input to calculate SUV values.

Injection

The cinj value is calculated as ratio of two independent measurements: the injected radioactivity (injected dose, ID) and the body weight (BW) of the subject. The ID can be estimated e.g. as difference in the radioactivity of the syringe before and after injection, if deemed necessary with correction for physical decay between each of those measurements and the time of injection. Conventionally the time of injection is t=0. This reference concentration represents the hypothetical case of an even distribution of the injected radioactivity across the whole body. Measured SUV values in particular parts of the body thus quantify the deviation from this hypothetical even radioactivity distribution: SUV > 1 indicates radioactivity accumulation in that region above the hypothetical even radioactivity distribution.

Time (Physical Decay)

The injection of radioactivity is often followed by a waiting time interval and then a time span during which the PET image data are acquired. After image reconstruction, the image cimg (t) data need to be decay corrected to the injection time point t=0. The time point t may be the image acquisition start time, or in case of a long acquisition duration e.g. the midpoint of the PET image acquisition may be more appropriate. This decay correction needs to be done for each image in case of a series of images acquired after a single injection ("dynamic imaging").

Mass and Volume

The unit of cimg is MBq/mL or equivalent, based on (a) the pixel intensity calibrated with a radioactive source ("phantom") itself of known radioactivity and volume, and (b) the pixel volume or ROI volume. The unit of cinj is MBq/g or equivalent, based on the measured radioactivity and the subject's body weight. This would give SUV in units of g/mL or equivalent. However, SUV is typically presented as a unitless parameter. One way to explain this simplification is by considering that the average mass density of the human body is typically close to 1 g/mL. Thus, while the body weight is usually measured and used for the SUV calculation, this is implicitly converted to the body volume in mL by division by 1 g/mL resulting in a unitless SUV parameter.

Alternatively, the cimg may be considered implicitly converted into a mass concentration assuming a mass density of 1 g/mL for the ROI volume which is a good approximation for some but not all tissues in the human body.

Equation

In summary this gives the following equation to calculate SUV at time t post injection,

{\displaystyle SUV(t)={\frac {c_{img}(t)}{ID/BW}}}{\displaystyle SUV(t)={\frac {c_{img}(t)}{ID/BW}}}

with (1) the radioactivity measured from an image acquired at (or around) the time t, decay corrected to t=0 and expressed as volume concentration (e.g. MBq/mL), (2) the injected dose ID at t=0 (e.g. in MBq), and (3) the body weight BW (near the time of image acquisition) implicitly converted into the body volume assuming an average mass density of 1 g/mL.

A related measure more frequently used in preclinical PET and SPECT is the concentration in units of % ID/mL (percentage of the injected dose per mL of tissue) for biodistribution analysis. When obtained from radionuclear images, this is equal to

{\displaystyle \%ID/mL(t)={\frac {c_{img}(t)}{ID}}\cdot 100\%}{\displaystyle \%ID/mL(t)={\frac {c_{img}(t)}{ID}}\cdot 100\%}.

In other words, SUV can be interpreted as the % ID/mL normalized to (here, multiplied by) the body weight (or body volume) and expressed as fraction rather than percentage.

Further Considerations

Some authors replace the body weight by the lean body weight[2] or the body surface area.[3]

Also for {\displaystyle c(t)}c(t) from a region of interest, different measures are found in the literature, e.g., the maximum intensity value within the ROI, the mean intensity value of the ROI,[4] or the mean intensity value of the ROI after applying an intensity threshold (thus excluding a number of pixels of the ROI).

Accuracy and Precision

The SUV can be significantly affected among other things by image noise, low image resolution and/or user biased ROI selection.[5] For the semiquantitative analysis of [18F]FDG uptake in tissue or tumor, several corrections have been recommended (see [6] and references therein).

SUVR

The ratio of the SUV data from two different regions within the same PET image (i.e. from a target and a reference region) is commonly abbreviated SUVR. An example is the ratio of regional Pittsburgh compound B PET signal intensity to the average signal of a much wider region.[7] For the SUVR, the injected activity, the body weight and the mass density that are all part of the SUV calculation, cancel:

{\displaystyle {\mathit {SUVR}}={\frac {\mathit {SUV_{target}}}{\mathit {SUV_{reference}}}}={\frac {\mathit {c_{img,target}}}{\mathit {c_{img,reference}}}}.}{\displaystyle {\mathit {SUVR}}={\frac {\mathit {SUV_{target}}}{\mathit {SUV_{reference}}}}={\frac {\mathit {c_{img,target}}}{\mathit {c_{img,reference}}}}.}

Outlook and Conclusions

As of 2007, the SUV concept had only begun to be tested for other radiotracers such as fluorothymidine F-18 ([18F]FLT) and conclusions on its usefulness and robustness in these cases were considered premature then.[8]

In summary, the SUV is a convenient measure for the comparison of [18F]FDG PET images from subjects with different body masses. However, care has to be taken with respect to its pitfalls and with respect to the interpretation of results.

To me: SUV means Sport Utility Vehicle.

Good Luck, Good Health and Good Humor.

j-o-h-n Sunday 01/30/2022 5:40 PM EST

[GoBucks in reply to j-o-h-n]

I didn't read any of that except Sport Utility Vehicle. Tell me what it said in 2 sentences. Or not. After all, all answers are voluntary. Nissan Rogue here.

[j-o-h-n in reply to GoBucks]

1 - 2008 Silver Honda CRV SUV 44,000 miles (all up hill)

1 -2022 Black Kia Sportage SUV 15 miles (all down hill) - purchased Friday, 1/28/2022

1 Dead Sales Manager (age mid 50's - 6 ft. under hill)

Considered Nissan Rogue but all 2022 models are stuck on container ships in Port Milwaukee....

p.s. This post was made voluntarily.

Good Luck, Good Health and Good Humor.

j-o-h-n Sunday 01/30/2022 9:01 PM EST