Somatostatin Receptor PET/CT

What it does

Somatostatin receptor (SSTR) PET/CT images neuroendocrine tumours with Ga-68 DOTATATE, Ga-68 DOTATOC or Cu-64 DOTATATE. It is used for staging, for follow-up and to select patients for peptide receptor radionuclide therapy (PRRT). Upload the whole-body SSTR PET with its CT; the run computes SUV, segments receptor-positive lesions and places each one in an organ.

Two sections make up the read. The lesion section lists every SSTR-avid lesion with its mask, SUVmax and organ. The second section grades each lesion with SSTR-RADS 1.0 and gives the Krenning score, which compares lesion uptake with the liver and spleen and is the uptake grade considered when PRRT is discussed.

Intended use

Decision support for physicians who report SSTR PET less often than FDG or PSMA PET and want a structured, reference-based answer. High physiological receptor density in the spleen, adrenal glands, uncinate process of the pancreas, pituitary and kidneys produces bright foci that are not tumour. These are the classic pitfalls of the exam, and SSTR-RADS grades each lesion against them.

Who it is for

Nuclear-medicine physicians and radiologists in neuroendocrine tumour centres and in departments that see these studies only occasionally, oncologists, gastroenterologists and endocrinologists in the NET multidisciplinary team, and theranostics teams assessing patients for PRRT.

Accepted input

• SSTR PET: DICOM PET Image or Enhanced PET Image, whole-body and attenuation-corrected, acquired with a DOTA-peptide tracer.
• CT: the paired CT of the same PET/CT session, used for organ assignment and the liver and spleen references.
• MIP screenshots and secondary captures are not read.

Requirements

Requirement	Why
Radiopharmaceutical Information Sequence with tracer code, total dose, injection time and half-life	Identifies the DOTA tracer and converts activity to SUV
Patient's Weight (0010,1030)	Body-weight SUV
Units, Decay Correction and Corrected Image attributes	SUV can be computed and compared with the reference organs
Liver and spleen inside the field of view	The Krenning score is defined relative to both

A quantitation check flags missing or implausible injection data, extravasation at the injection site and PET–CT misregistration, which shifts liver and pancreatic lesions against their CT anatomy.

Optional context

The known primary site, tumour grade or prior PRRT can be given in clinical_context; they are carried into the guidance but do not change the measured values.

The result

Section	Content
Lesions	Lesion masks with SUVmax and organ assignment
SSTR-RADS and Krenning score	SSTR-RADS 1.0 category per lesion and the Krenning score from lesion uptake relative to liver and spleen
Draft report	Opt-in (options.report): an English narrative that interprets the result for the reader (findings, impression, limitations); every number is checked against the findings

The liver and spleen reference values used for the Krenning score are reported with the result, so the grade of each lesion can be checked against the measured uptake.

Standards

• DICOM: Segmentation for lesion masks; SR TID 1500 Measurement Report with per-lesion SUV in CID 85 SUV units; Key Object Selection; Encapsulated PDF.
• Reporting: SSTR-RADS 1.0 for per-lesion likelihood of neuroendocrine tumour; the Krenning score for receptor expression.
• Terminology: SNOMED CT and RadLex for findings and anatomy; ICD-O-3 for tumour context.

Reading the Krenning score

The Krenning score is a visual scale first defined on planar somatostatin receptor scintigraphy; on PET it is applied by the same comparison of each lesion with normal liver and spleen. The score describes receptor expression.

Related models

• nm/theranostics: post-therapy SPECT/CT and dosimetry after each [177Lu]Lu-DOTATATE cycle.