Skip to content

TMTV Mode

The Total Metabolic Tumor Volume (TMTV) mode allows to quantitatively measure the metabolically active volume of tumors in a subject's body. It provides 10 different viewports to visualize PET and CT images as well as advanced tools to enable thresholding-based segmentation based on standard uptake values (SUVs).

Entering TMTV mode

The TMTV mode is only available when a PET and a CT image series from the same study (same StudyInstanceUID) are present in the left-side panel. When that's the case, TMTV mode can be selected from the mode switching menu in the header toolbar.

mode-icon

Layout

The default layout for the TMTV mode contains 10 viewports. The top 3 viewports display the CT scan in the axial, sagittal and coronal orientations (from left to right). The middle 3 viewports display the PET scan in the same orientations. The bottom 3 viewports display a PET and CT overlay. Lastly the right viewport displays a maximum intensity projection (MIP) of the PET scan.

tmtv-initial-layout

Viewport synchronization

The viewports in the 3 rows are synchronized for zoom, pan and scrolling. The window levels for each modality are synchronized across all viewports. The color lookup table for the CT is synchronized across all viewports, while the color lookup table for the PET can be set separately for the PET viewports or the fusion viewports.

Alternative layouts

The TMTV mode comes with three additional layouts (also referred to as "stages") that can be quickly accessed with the . and , hotkeys.

  • The first alternative layout is a 2x2 layout with 3 axial viewports (CT, PET and fusion) and the MIP viewport.

alternative-layout-1

  • The second alternative layout is a 3x3 layout with 3 CT viewports (axial, sagittal and coronal) and 3 PET viewports in the same orientations.

alternative-layout-2

  • The third alternative layout is a 7-viewport layout with 3 PET viewports (axial, sagittal and coronal), 3 fusion viewports in the same orientations, and 1 MIP viewport.

alternative-layout-3

Maximizing viewports

In all the different layouts, any viewport can be maximized by double-clicking anywhere within the limits of that viewport. The viewport area then turns into a single-viewport layout. Double-clicking a second time returns to the previous layout.

Tools

Viewing tools

The TMTV mode comes with a limited set of viewing tools compared to the Basic Viewer mode:

  • Window levels
  • Zoom
  • Pan
  • Crosshair tool
  • Reset view (resets all the above)

Measurements tools

The following measurement tools are available in the TMTV mode:

  • Length tool
  • Bidirectional tool
  • Annotation tool
  • Ellipse tool

These tools cannot be used on the MIP viewport. Additionally, the TMTV mode does not allow to save measurements.

Segmentation tools

Segmentations in the TMTV mode are very similar to segmentations in the Basic viewer mode, with the exception that only one ROI can be created for each segmentation.

The tools available for segmentation are:

  • Brush tool: available for both PET and CT
  • Threshold tool: available for PET only
  • Shapes tools: available for both PET and CT
  • Eraser tool: available for both PET and CT
  • Rectangle ROI Threshold tool: available for PET axial viewport only (see below)

Rectangle ROI Threshold tool

The rectangle ROI threshold tool is only available for the PET axial viewport in the TMTV mode. It allows users to create a 3D rectangle region of interest (ROI) and apply a threshold within that region of interest. The threshold can be set based on a percentage of the max SUV within the rectangle, or by adjusting the thresholding range manually.

To create a segmentation using the rectangle ROI threshold tool:

  1. Select the PET axial viewport in order to enable the tool. You can also maximize the viewport by double-clicking on it.

  2. Select the rectangle ROI threshold tool and draw a rectangle on the image to include the area of interest for the segmentation (e.g. a tumor). By default the 3D rectangle will spread across the following 10 slices of the image. The rectangle ROI is displayed with a solid outline on the start and end slices which represent its top and bottom respectively. The rectangle ROI is displayed with a dotted outline on all other slices in-between.

    rectangle_roi

  3. If you would like to adjust the start and end slices, scroll to the desired start slice and click "Start" in the rectangle ROI threshold menu in the right-side panel to set the start slice. The rectangle drawn in the previous step will then show on the selected slice and displayed with a solid outline. Repeat the operation for the desired end slice, this time clicking on "End" to set the end slice. In order for the tool to function properly, the start slice instance number needs to be lower than the end slice instance number.

    rectangle_roi_settings

  4. Once you have set your rectangle ROI, you can select the thresholding method to be used:

    • Max: requires to set a percentage of Max SUV to be used as the threshold value. This needs to be a number between 0 and 1. All values above the threshold will be included in the segmentation.
    • Range: requires to set the range of values for both PET and CT to be used for the threshold.

  5. Click "Run" to run the threshold segmentation algorithm.

    rectangle_roi_segmentation

  6. Upon reviewing the result of the segmentation, you may want to modify either the rectangle ROI, or the segmentation threshold. Repeat any of the steps 2, 3 or 4 above, then click "Run" again to re-run the segmentation.

TMTV calculation

Upon segmenting the first pixels for a ROI, the SUV Peak value and the volume of that ROI are displayed in the segmentation panel. The SUV Peak value represents the mean SUV within a 1 cm3 sphere centered on the voxel with the max SUV in the ROI.

The Total Metabolic Tumor Volume (TMTV) is also displayed in the segmentation panel in milliliters (mL). It is calculated as the total volume of the segmented ROIs i.e. if there are overlapping ROIs, the overlapping voxels are only counted once in the total volume calculation.

tmtv-volume

Patient Information

In the TMTV mode, the PET units are converted to SUV units. The Patient Information section of the segmentation panel allows user to quickly check the accuracy of values used for that conversion. The following fields are available in the Patient Information section:

  • Patient Sex : pulled from the PatientSex (0010,0040) DICOM tag.
  • Weight (kg) : pulled from the Patient's Weight (0010,1030) DICOM tag.
  • Total Dose (Bq): pulled from the RadionuclideTotalDose (0018,1074) DICOM tag.
  • Half Life (s): pulled from the RadionuclideHalfLife (0018,1075) DICOM tag.
  • Injection Time (HH:MM:SS): pulled from the RadiopharmaceuticalStartDateTime (0018, 1078) DICOM tag.
  • Acquisition Time (HH:MM:SS): pulled from the AcquisitionTime (0008,0032) DICOM tag.

Export TMTV results

Results from segmentations and TMTV calculation can be exported as a csv file by clicking on the Export icon next to the TMTV volume in the right-side panel.

export-icon

The csv file contains one row for each segmentation with the following columns:

  • PatientID: PatientID (0010,0020) value of the PET series.
  • PatientName: PatientName (0010,0020) value of the PET series.
  • StudyInstanceUID: StudyInstanceUID (0020,000D) value of the PET series.
  • SeriesInstanceUID: SeriesInstanceUID (0020,000E) value of the PET series.
  • StudyDate: StudyDate (0008,0020) of the PET series.
  • label: label of the segmentation
  • Voxelcount: number of voxels within the ROI in the segmentation
  • SpacingX (mm): from the PixelSpacing (0028,0030) tag of the PET series.
  • SpacingY (mm): from the PixelSpacing (0028,0030) tag of the PET series.
  • SpacingZ(mm): SliceThickness (0018,0050) value of the PET series.
  • minValue: lowest intensity value in the ROI.
  • maxValue: highest intensity value in the ROI.
  • meanValue: average intensity value in the ROI.
  • stdValue: standard deviation of intensity values in the ROI.
  • Volume (mm3): volume of the ROI in mm3
  • SUVpeak: mean SUV value within a 1 cm3 sphere centered on the voxel with the max SUV value in the ROI.
  • SUVmax: maximum SUV value within the ROI.
  • tmtv_value: volume of the ROI in mL.
  • lesionGlycolysisStats (mg): volume of the ROI x mean SUV value within the ROI.

Four additional fields are present as a summary:

  • PatientID: PatientID (0010,0020) value of the PET series.
  • StudyDate: StudyDate (0008,0020) of the PET series.
  • Total Metabolic Tumor Volume: Sum of volumes of all ROIs.
  • Total Lesion Glycolysis: Sum of volumes of all ROIS x mean SUV value for all ROIs