Compute Centiloid Value

Computes the Centiloid value based on an amyloid Positron Emission Tomography (PET) scan radioactive tracer, Standardized Uptake Value Ratio (SUVR) value, pipeline, and reference region. Also allows for custom formula parameters.

Usage

compute_centiloid(
  tracer,
  pipeline,
  ref_region,
  suvr,
  custom_slope = NULL,
  custom_intercept = NULL
)

Arguments

tracer

Amyloid PET tracer

A character string is expected. If custom_slope and custom_intercept are specified, this parameter is ignored. See Details section for accepted values in combination with pipeline and ref_region.

Permitted values: a character scalar, i.e., a character vector of length one
Default value: none

pipeline

SUVR pipeline

Permitted values: a character scalar, i.e., a character vector of length one
Default value: none

ref_region

Reference region

Permitted values: a character scalar, i.e., a character vector of length one
Default value: none

suvr

SUVR value

A positive numeric value is expected.

Permitted values: a numeric scalar, i.e., a numeric vector of length one
Default value: none

custom_slope

Optional slope parameter for custom Centiloid calculation formula

A numeric value is expected when provided. When custom_slope is specified (along with custom_intercept), this overrides the standard formula parameters tracer, pipeline, and ref_region. Default is NULL.

Permitted values: a numeric scalar, i.e., a numeric vector of length one
Default value: NULL

custom_intercept

Optional intercept parameter for custom centiloid calculation formula

A numeric value is expected when provided. When custom_intercept is specified (along with custom_slope), this overrides the standard formula parameters tracer, pipeline, and ref_region. Default is NULL.

Permitted values: a numeric scalar, i.e., a numeric vector of length one
Default value: NULL

Value

A numeric Centiloid value.

Details

The Centiloid scale is a standardized quantitative measure for amyloid PET imaging that allows comparison between different tracers and analysis methods. This function converts SUVR values to the Centiloid scale based on published conversion equations for specific tracer, pipeline, and reference region combinations.

Centiloid is calculated as:

$$Centiloid = slope \times SUVR + intercept$$

where slope and intercept are formula parameters. If custom_slope and custom_intercept are not specified, this function uses pre-defined slope and intercept based on the user's selections of tracer, pipeline, and reference region.

The combinations of tracer, pipeline and reference region in the table below are supported. The columns "slope" and "intercept" then show the values of the slope and intercept that compute_centiloid() will use to calculate the centiloid value in each case.

tracer	pipeline	ref_region	slope	intercept
18F-Florbetapir	AVID FBP SUVR PIPELINE¹	Whole Cerebellum	183.07	-177.26
18F-Florbetaben	AVID FBB SUVR PIPELINE²	Whole Cerebellum	156.06	-148.13
18F-Florbetapir	BERKELEY FBP SUVR PIPELINE³	Whole Cerebellum	188.22	-189.16
18F-Florbetaben	BERKELEY FBB SUVR PIPELINE³	Whole Cerebellum	157.15	-151.87

The equations used for the conversions are based on the following references:

¹ Navitsky, et al. (2018). doi:10.1016/j.jalz.2018.06.1353 ² Sims, et al. (2024). doi:10.1001/jama.2023.13239 ³ Royse, et al. (2021). doi:10.1186/s13195-021-00836-1

Alternatively, the user can override the pre-selection by specifying both custom_slope and custom_intercept instead. When custom_slope and custom_intercept are specified, the function ignores tracer, pipeline and ref_region for calculation purposes. However, this function always requires specification of tracer, pipeline, and ref_region parameters, even when using custom slope and intercept values. This design choice ensures that users remain cognizant of the imaging context and analysis methodology when computing Centiloid values.

For additional Centiloid transformation formulas, see: Iaccarino, L. et al. (2025). doi:10.1016/j.nicl.2025.103765

If a matching combination of tracer, pipeline, and reference region is not specified and both custom_slope and custom_intercept are not specified, the function aborts with an error.

Examples

Using standard parameters

Computes Centiloid with predefined slope/intercept for supported tracer/pipeline/ref_region combinations:

compute_centiloid(
  tracer = "18F-Florbetapir",
  pipeline = "AVID FBP SUVR PIPELINE",
  ref_region = "Whole Cerebellum",
  suvr = 1.25
)
#> [1] 51.5775

Using custom parameters

Computes Centiloid by overriding slope/intercept using custom values:

compute_centiloid(
  tracer = "MyTracer",
  pipeline = "MyPipeline",
  ref_region = "MyRegion",
  suvr = 1.25,
  custom_slope = 193,
  custom_intercept = -187
)
#> [1] 54.25