To the Bone: SPECT/CT Drives Diagnostic Clarity
The conventional diagnostic process for diagnosing bone lesions is problematic. Bone scintigraphy is very sensitive in detecting osseous metastases; however, routine skeletal scintigraphy, including bone SPECT, is less than ideal as studies do not clearly differentiate benign and malignant lesions. As a result, the diagnostic process is complicated and lengthened, which can increase the patient’s anxiety and delay diagnosis and treatment.

The advent of diagnostic SPECT/CT brings significant improvements in evaluating patients with indeterminate bone lesions. SPECT/CT cameras such as Siemens Medical Solutions Symbia TruePoint T6 reinvent the skeletal lesion characterization process. This best-of-both-worlds approach pairs the sensitivity of SPECT with the specificity of CT. In fact, several clinical studies demonstrate that more than 90 percent of bone lesion cases that can not be classified with SPECT alone can be correctly evaluated with SPECT/CT.1

The hybrid approach to bone lesion characterization carries multiple advantages. Rapid and accurate diagnostic results improve and accelerate patient care. In addition, SPECT/CT has a relatively small effect on workflow while improving the bottom line in the nuclear medicine or imaging department. The department not only provides the additional study, but also retains control of the imaging process. And finally, as researchers study state-of-the-art diagnostic SPECT/CT solutions, they are likely to determine that other applications also could benefit from the hybrid approach.

The advent of SPECT/CT
Several years ago, vendors introduced the first hybrid SPECT/CT cameras that pair nuclear medicine SPECT with spiral CT. The new integrated solutions deliver the functional specificity of SPECT and the anatomic precision of CT. While the scanners have not yet garnered the widespread acceptance of other recently introduced nuclear medicine modalities such as PET/CT, the tide is beginning to turn as nuclear medicine demonstrates the advantages of SPECT/CT solutions.

Integrated SPECT/CT opens the door to a host of new applications that can improve diagnosis and treatment in a range of oncologic applications. The promise of “SPECT-guided CT” is improved diagnostic quality and increased clinical confidence.

Today, researchers around the world including the University of Erlangen department of nuclear medicine are proving that SPECT/CT delivers on its promise. One of the first protocols demonstrated to benefit from SPECT/CT imaging is diagnosis and staging of indeterminate bone lesions.

An imperfect clinical process
Patients with breast, prostate and other carcinomas are routinely referred for bone scintigraphy to detect potential skeletal malignancies. The problem with a conventional SPECT study relates to its low specificity. Although SPECT provides high sensitivity in the detection of bone lesions, findings are often indeterminate; the physician can not detect whether or not the lesion is malignant. For example, degenerative joint disease may be linked to benign bone lesions. On the other hand, lytic lesions or dense sclerosis suggest malignant pathology. Although a SPECT study can detect the lesion, it does not provide information about the nature and composition of the lesion that is needed to develop a patient treatment plan.

This diagnostic uncertainty leads to multiple challenges. Patients must be referred for follow-up studies, which can delay therapy and increase anxiety. In addition, decisions about follow-up studies are made by the referring physician rather than the nuclear medicine expert, which is less than ideal from the diagnostic and financial perspectives. The clinician may refer the patient for several types of imaging studies to characterize the lesion, adding unnecessary time and cost to the process.

The advantages of the hybrid approach
Over the last two years, the department of nuclear medicine at University of Erlangen has used Siemens TruePoint Symbia T2 and T6 SPECT•CT cameras in cases where SPECT results do not provide a clear characterization of bone lesions. The protocol is simple, and the advantages of the hybrid approach are significant. Integrated CT delivers high diagnostic quality — enabling physicians to differentiate benign and malignant bone lesions in a single patient encounter.

Symbia TruePoint SPECT•CT system.Symbia TruePoint SPECT•CT system. The first part of the protocol is unchanged. That is, the patient undergoes a planar whole-body scintigraphy. The radiologist reads this exam and if the findings are indeterminate, the patient is on the table for a SPECT/ CT study. Interpreting the combined results takes just a few minutes, and most cases can be accurately diagnosed after the hybrid scan.

SPECT/CT enables a one-stop shop approach to bone lesion characterization while abbreviating the diagnostic process, improving patient care and reducing patient anxiety. In addition, the time between diagnosis and treatment is shortened. Approximately one-third of bone lesions are malignant. These patients can proceed to appropriate therapy earlier in the process with the clear findings produced by SPECT/CT.  Finally, the imaging department realizes a financial benefit as it is reimbursed for both the SPECT study and the CT portion of the exam.

The new model is a sharp contrast to the previous protocol. In many cases, bone scintigraphy was inconclusive, so the physician needed to inform the patient that another test was required to diagnose the lesion. At this point, the patient leaves the nuclear medicine department and returns to the referring physician.

Unfortunately, involving non-radiologists in the medical imaging decision-making process is not ideal. In many cases, physicians order a diagnostic x-ray; however, x-ray is limited in its abilities to detect malignancies of the bone.  If results are unclear, the diagnostic process is extended again. The patient may be referred for a CT or MRI. Neither study is typically performed as a whole-body examination and therefore these modalities are not well-suited for screening. The end result may be a complex assortment of findings and a diagnostic process that can take weeks, rather than an hour or less.

Using SPECT/CT to detect and evaluate bone lesions allows the imaging department to retain control of the process. The referring physician receives an accurate diagnosis from one source rather than multiple diagnoses from several sources. The patient benefits from same-day, single-study results. Those with benign lesions avoid the wait and worry associated with the conventional, multi-study model. And patients with malignancies are referred for therapy in the timeliest manner possible.

Evolving applications
SPECT/CT is in its infancy. Currently, data are just beginning to demonstrate its utility for other indications, including evaluation of lower back pain and orthopedic disease. The next few years promise to bring additional hybrid applications. Researchers are exploring tumor scintigraphy, including Iodine 131 scintigraphy after diagnosis of thyroid cancer, and sentinel node scintigraphy for breast cancer patients.

As SPECT/CT demonstrates its diagnostic accuracy and clinical value, it will take over a large share of SPECT imaging. Nuclear medicine and radiology departments that invest in SPECT/CT can improve patient care in applications such as evaluation of indeterminate bone lesions and lay the groundwork for the next generation of molecular imaging exams.

A winning combination
SPECT/CT cameras such as Siemens TruePoint Symbia T6 are fairly new. Researchers need to determine SPECT/CT’s role in the radiology and nuclear medicine spectrums. Early data show that hybrid scanners deliver significant improvements in multiple areas: increasing clinical confidence and improving patient care. The evaluation of indeterminate bone lesions is an early and excellent example. SPECT/CT can be performed in a single patient encounter to provide clear and rapid results. No other modality provides a comparable diagnostic process.

It’s also important to examine the impact of new technologies with respect to workflow and efficiency. TruePoint Symbia T6 meets the needs of busy departments as scans are rapid and do not create a data overload that burdens radiologists. Interpretation takes only a few minutes. Consequently, sites that invest in SPECT/CT can expect a healthy return on the investment. That is, the hybrid camera has a minimal impact on workflow but offers fairly significant improvement in patient care. An added plus is reimbursement for the additional study.

Torsten Kuwert, MD, is director and professor of clinical nuclear medicine at the University of Erlangen in Erlangen, Germany.

1 SPECT-Guided CT for Evaluating Foci of Increased Bone Metabolism Classified as Indeterminate on SPECT in Cancer Patients. Wolfgang Römer, Anton Nömayr, Michael Uder, Werner Bautz, and Torsten Kuwert. Clinic of Nuclear Medicine, University of Erlangen-Nuremberg, Erlangen, Germany; and Institute of Radiology, University of Erlangen-Nuremberg, Erlangen, Germany.

Read more on Siemens SPECT/CT