SPECTCT cerebral perfusion scintigraphy; is the low-dose CT component of diagnostic value?

Data analysis of low dose multislice helical CT scan in orbital trauma

AIM

To explore the optimal low dose of MSCT in orbital trauma examination.

METHODS

Sixty transverse images of the fracture layer were selected. Low-dose images acquired at 30, 70, 100, 140, 170, and 200 milliampere (mA) were simulated by adding noise to the image space using software. After assessing the images according to the conditions of image quality and fracture, we found the optimal tube current that met diagnostic requirements and then applied it to clinical use. The CT Dose Index volume (CTDIvol), dose length product (DLP) and effective dose (ED) were recorded. The image quality was classified as good, fairly good, ordinary, poor, or very poor according to image level, noise, anatomic structure and whether the diagnostic requirements were met or not. The rank-sum test was used to perform statistical analysis on the ranked data. The Chi-square test was used for the numerical data.

RESULTS

Under the scan conditions of a conventional dose of 300 mA, 60 cases of orbital fracture, 38 cases of orbital emphysema, 25 cases of ocular damage, and 3 cases of intraorbital foreign body were demonstrated in the images of the 60 orbital trauma patients. Among the low dose simulated images, the image quality difference of the different doses was of statistical significance (χ(2)=15.678, P=0.016). When the dose was lowered to 70 mA, the above mentioned clinical signs were still clear and diagnostic, however the image quality assessment results indicated that 2 cases were good, 16 cases were fairly good, and 42 cases were ordinary, poor or very poor. When the simulated dose tube current was 100mA, the image quality assessment results were 18 cases good, 34 cases fairly good, and 8 cases ordinary, poor and very poor; compared with the conventional dose, there was no statistical significance (P>0.05). When using a 100 mA tube current to examine 40 cases of orbital trauma patients in the clinic, the acquired image quality was 10 cases good, 26 cases fairly good and 4 cases ordinary, without any cases of poor or very poor. The CTDIvol, DLP and ED were 20.72mGy, 124.97 mGy·cm and 0.26mSv, respectively, while the CTDIvol, DLP and ED were 62.53mGy, 375.18 mGy•GTtl and 0.86mSv, respectively, when using a conventional dose of 300 mA. Compared with the tube current of 100 mA for scanning, the ED declined 70%.

CONCLUSION

When conducting an MSCT scan for orbital trauma, the acquired images using the 100 mA tube current can meet the clinical diagnostic requirements, and the radiation dose to the patients can be decreased.

A review on the clinical uses of SPECT/CT

In the era when positron emission tomography (PET) seems to constitute the most advanced application of nuclear medicine imaging, still the conventional procedure of single photon emission computed tomography (SPECT) is far from being obsolete, especially if combined with computed tomography (CT). In fact, this dual modality imaging technique (SPECT/CT) lends itself to a wide variety of useful diagnostic applications whose clinical impact is in most instances already well established, while the evidence is growing for newer applications. The increasing availability of new hybrid SPECT/CT devices with advanced technology offers the opportunity to shorten acquisition time and to provide accurate attenuation correction and fusion imaging. In this review we analyse and discuss the capabilities of SPECT/CT for improving sensitivity and specificity in the imaging of both oncological and non-oncological diseases. The main advantages of SPECT/CT are represented by better attenuation correction, increased specificity, and accurate depiction of the localization of disease and of possible involvement of adjacent tissues. Endocrine and neuroendocrine tumours are accurately localized and characterized by SPECT/CT, as also are solitary pulmonary nodules and lung cancers, brain tumours, lymphoma, prostate cancer, malignant and benign bone lesions, and infection. Furthermore, hybrid SPECT/CT imaging is especially suited to support the increasing applications of minimally invasive surgery, as well as to precisely define the diagnostic and prognostic profile of cardiovascular patients. Finally, the applications of SPECT/CT to other clinical disorders or malignant tumours is currently under extensive investigation, with encouraging results in terms of diagnostic accuracy.

SPECT/CT

In view of the commercial success of integrated PET/CT scanners, there is an increasing interest in comparable SPECT/CT systems. SPECT in combination with CT enables a direct correlation of anatomic information and functional information, resulting in better localization and definition of scintigraphic findings. Besides anatomic referencing, the added value of CT coregistration is based on the attenuation correction capabilities of CT. The number of clinical studies is limited, but pilot studies have indicated a higher specificity and a significant reduction in indeterminate findings. The superiority of SPECT/CT over planar imaging or SPECT has been demonstrated in bone scintigraphy, somatostatin receptor scintigraphy, parathyroid scintigraphy, and adrenal gland scintigraphy. Also, rates of detection of sentinel nodes by biopsy can be increased with SPECT/CT. This review highlights recent technical developments in integrated SPECT/CT systems and summarizes the current literature on potential clinical uses and future directions for SPECT/CT in cardiac, neurologic, and oncologic applications.