Suggested CT Protocols* for Inclusion in Noncardiac SPECT/CT Protocols
| Protocol | Parameter | Comments |
|---|---|---|
| SPECT-guided low-dose CT | Indications (general) | Preferred protocol when recent diagnostic CT is available and when follow-up studies are performed (monitoring of response to treatment) |
| Indications (specific) | Further anatomic localization or characterization of focal pathology present on planar or SPECT images, e.g., at bone scintigraphy, 131I scintigraphy (thyroid cancer), sentinel node scintigraphy, 99mTc-MIBI SPECT (parathyroid tumors), 123I-MIBG SPECT (adrenocortical tumors), or 111In-pentetreotide imaging (neuroendocrine tumors) | |
| Field of view | Including all areas with nonclassifiable scintigraphic lesions, e.g., cervical, thoracic, and abdominal regions, pelvis, skull, extremities, or any combination of these | |
| CT overview (topogram) | Covering field of view as indicated earlier | |
| CT scan (tomogram) | ||
| Scan direction | Caudocranial | |
| Tube current | 20–40 mA | |
| Tube voltage | 130 kV | |
| Collimation | Depending on CT scanner; thinnest possible collimation for optimal multiplanar reconstructions; in areas prone to breathing artifacts, thicker collimation may be necessary to reduce scan duration and to minimize motion artifacts | |
| Slice thickness | 5 mm; increment of 2.5 mm; thinnest possible slice thickness with overlap in reconstruction increment necessary for optimal 3-dimensional reconstructions | |
| Breathing protocol (general) | Shallow breathing; breath holding in expiration when lower thorax is scanned | |
| Breathing protocol (screening for lung metastases) | Maximum inspiration during acquisition of CT | |
| Radiation dose (in addition to that of SPECT) | 2–4 mSv (depending on field of view in z-axis) | |
| SPECT-guided diagnostic CT | Indications (general) | Preferred protocol when recent diagnostic CT is not available and when detailed anatomic information is mandatory to address clinical needs |
| Indications (specific) | Further anatomic localization or characterization of lesions present at bone scintigraphy, 131I scintigraphy (thyroid cancer, cervical region), 99mTc-MIBI SPECT (parathyroid tumors), 123I-MIBG SPECT, or 111In-pentetreotide imaging, especially when sufficient diagnostic accuracy cannot be expected from low-dose CT (e.g., when lesions are suspected in mediastinum or in proximity of liver or intestinal structures) | |
| Field of view | Including areas with lesions present on planar or SPECT images or areas with suspected lesions (e.g., upper gastrointestinal tract for detection of pheochromocytoma) | |
| CT overview (topogram) | Covering field of view as indicated earlier | |
| CT scan (tomogram) | Specific protocols should be selected according to clinical needs (e.g., 3-phase CT of liver) | |
| Scan direction | Caudocranial | |
| Scan delay | 60–80 s after start of intravenous injection of contrast material (depending on field of view in z-axis) | |
| Tube current | 100 mA | |
| Tube voltage | 130 kV | |
| Collimation | Depending on CT scanner; thinnest possible collimation for optimal multiplanar reconstructions; in areas prone to breathing artifacts, thicker collimation may be necessary to reduce scan duration and to minimize motion artifacts | |
| Slice thickness | 5 mm; increment of 2.5 mm; thinnest possible slice thickness with overlap in reconstruction increment necessary for optimal 3-dimensional reconstructions | |
| Breathing protocol (general) | Shallow breathing; breath holding in expiration when lower thorax is scanned | |
| Breathing protocol (screening for lung metastases) | Breath holding in maximum inspiration during acquisition of CT | |
| Radiation dose (in addition to that of SPECT) | 6–14 mSv (depending on field of view in z-axis) |
↵* Performed directly before or after SPECT acquisition.