Using <Superscript>99m</Superscript>Tc-DTPA radioaerosol inhalation lung scan as compared with computed tomography to detect lung injury in blunt chest trauma

Background

Detection of pulmonary contusion in patients with blunt chest trauma is very important so as to commence therapy immediately to avoid irreversible damage. The purpose of our study was to evaluate the efficacy of technetium-99m diethylene triamine pentaacetic acid (^99mTc-DTPA) aerosol inhalation lung scintigraphy in comparison with chest computed tomography (CT) in the diagnosis of pulmonary contusion at acute blunt chest trauma.

Methods

Twenty-nine patients with isolated blunt chest trauma were referred to the emergency department of our hospital, and nine healthy people participated in this study. Sixteen patients who had pulmonary contusion on CT scans were referred to as group 1, and 13 patients who had normal CT scans as group 2. Nine healthy people comprised a control group. ^99mTc-DTPA aerosol inhalation lung scintigraphy was performed on the first day in all patients.

Results

The mean half time (T_½) and penetration index values of ^99mTc-DTPA clearance were significantly lower in groups 1 and 2 compared with the control group. Among the three groups, there were no significant differences in arterial blood gas analysis except for PO₂. The mean T_½ value of ^99mTc-DTPA clearance did correlate with PO₂ values but not with pH, PCO₂, or HCO₃ values.

Conclusions

^99mTc-DTPA radioaerosol inhalation lung imaging may serve as a useful adjunct and supportive method to chest CT scanning for detecting mild pulmonary contusion.

     

Influence of region-of-interest determination on measurement of signal-to-noise ratio in liver on PET images

Objective

On ¹⁸F-fluoro-2-deoxy-d-glucose (¹⁸F-FDG) positron emission tomography (PET), signal-to-noise ratio in the liver (SNR_liver) is used as a metric to assess image quality. However, some regions-of-interest (ROIs) are used when measuring the SNR_liver. The purpose of this study is to examine the different ROIs and volumes of interest (VOIs) to obtain a reproducible SNR_liver.

Methods

This study included 108 patients who underwent ¹⁸F-FDG-PET/CT scans for the purpose of cancer screening. We examined four different ROIs and VOIs; a 3-cm-diameter and a 4-cm-diameter circular ROI and a 3-cm-diameter and a 4-cm-diameter spherical VOI on the right lobe of the patients’ livers. The average of SUV (SUV_mean), standard deviation (SD) of SUV (SUV_SD), SNR_liver and SD of the SNR_liver obtained using ROIs and VOIs were then compared.

Results

Although the SUV_mean was not different among the ROIs and VOIs, the SUV_SD was small with a 3-cm-diameter ROI. The largest SUV_SD was obtained with a 4-cm-diameter spherical VOI. The SNR_liver and the SD of the SNR_liver with a 4-cm-diameter spherical VOI were the smallest, while those with a 3-cm-diameter circular ROI were the largest. These results suggest that a small ROI may be placed on a relatively homogeneous region not representing whole liver unintentionally.

Conclusion

The SNR_liver varied according to the shape and size of ROIs or VOIs. A 4-cm-diameter spherical VOI is recommended to obtain stable and reproducible SNR_liver.

     

Prospective dosimetry with <Superscript>99m</Superscript>Tc-MDP in metabolic radiotherapy of bone metastases with <Superscript>153</Superscript>Sm-EDTMP

Purpose

On the basis of the encouraging results achieved in several clinical trials and its proven therapeutic efficacy, ¹⁵³Sm-ethylene diamine tetramethylene phosphonic acid (EDTMP) has become widely used to palliate pain from bone metastases. The results reported in the literature have led the product suppliers (QUADRAMET®, Schering) to suggest administering a fixed activity per kilogram (37 MBq/kg). However, considering the observed extreme inter-patient variability of skeletal uptake of ¹⁵³Sm-EDTMP, a real therapy optimization would require the individualization of the activity to be administered on a dosimetric basis. This should be planned taking into account the generally accepted 2-Gy dose constraint to the haematopoietic red marrow, the critical organ in palliative treatments with beta-emitting, bone-seeking radiopharmaceuticals.

Methods

Seven to 14 days before treatment with ¹⁵³Sm-EDTMP, 44 patients underwent ^99mTc-methylene diphosphonate (MDP) total-body bone scan with two scans (the first within 10 min of injection, the second after 6 h). The percentage bone uptake (Tc_%) was evaluated as the ratio between total counts at 6 h, adjusted for decay, and total counts at the first scan. Tc_% was then compared to Sm_% similarly derived from 10-min and 24-h whole-body scans. Tc_% and Sm_% were compared both with and without Brenner’s method for soft tissue uptake.

Results

The correlation between Tc_% and Sm_% was R ²?=?0.81 and R ²?=?0.88 with and without soft tissue correction, respectively. The difference between their average values was statistically significant (Sm_%?=?64.3?±?15.2, Tc_%?=?56.2?±?16.0; p?=?0.017) with soft tissue correction, while was not statistically significant (Sm_%?=?68.2?±?15.5, Tc_%?=?66.9?±?14.0; p?=?0.670) without soft tissue correction.

Conclusions

The rate of retention of ^99mTc-MDP in bone provides a reliable estimate of the ¹⁵³Sm-EDTMP rate of retention. The proposed method can be usefully adopted for prospective dosimetry seeing its extreme simplicity, and it requires no special investment in terms of human or instrumental resources. This allows an optimization of administered ¹⁵³Sm-EDTMP activity.

     

Glioma grading by dynamic susceptibility contrast perfusion and <Superscript>11</Superscript>C-methionine positron emission tomography using different regions of interest

Purpose

The use of dynamic susceptibility contrast (DSC) perfusion and ¹¹C-methionine positron emission tomography (MET-PET) for glioma grading is currently not standardized. The purpose of this study was to identify regions of interest (ROIs) that enable the best performance and clinical applicability in both methods, as well as to evaluate the complementarity of DSC perfusion and MET-PET in spatial hotspot definition.

Methods

In 41 patient PET/MRI datasets, different ROIs were drawn: in T2-hyperintense tumour, in T2-hyperintense tumour and adjacent oedema and in tumour areas with contrast enhancement, altered perfusion or pathological radiotracer uptake. The performance of DSC perfusion and MET-PET using the different ROIs to distinguish high- and low-grade gliomas was assessed. The spatial overlap of hotspots identified by DSC perfusion and MET-PET was assessed visually.

Results

ROIs in T2 fluid attenuated inversion recovery (FLAIR) sequence-hyperintense tumour revealed the most significant differences between high- and low-grade gliomas and reached the highest diagnostic performance in both DSC perfusion (p?=?0.046; area under the curve?=?0.74) and MET-PET (p?=?0.007; area under the curve?=?0.80). The combination of methods yielded an area under the curve of 0.80. Hotspots were completely overlapped in one half of the patients, partially overlapped in one third of the patients and present in only one method in approximately 20% of the patients.

Conclusions

For multi-parametric examinations with DSC perfusion and MET-PET, we recommend an ROI definition based on T2-hyperintense tumour. DSC perfusion and MET-PET contain complementary information concerning the spatial hotspot definition.

     

An automated voxel-based method for calculating the reference value for a brain tumour metabolic index using <Superscript>18</Superscript>F-FDG-PET and <Superscript>11</Superscript>C-methionine PET

Objective

The tumour-to-normal ratio (T/N) is a representative index reflecting brain tumour activity by ¹⁸F-fluorodeoxyglucose (FDG) and ¹¹C-methionine (MET) PET. We proposed a new automated method of calculating the normal reference value (N-value) for use as the denomination of T/N. This method uses voxel-based analysis of FDG- and MET-PET images. We compared the results of this method with those of the standard region-of-interest (ROI) method.

Methods

Data sets were obtained from 32 patients with newly diagnosed glioma and 13 patients with recurrent brain tumour. Our methods were as follows: (1) FDG-PET and MET-PET images were co-registered. (2) The areas where the FDG uptake was higher than a set threshold were selected. (3) For the corresponding areas of MET-PET images, mode and mean voxel values were calculated as tentative MET N-values. (4) Applying the same coordinates to FDG-PET, the voxel values were averaged and used as tentative FDG N-values. (5) The threshold of FDG-PET and whether to use the mode or the mean voxel values were computationally optimized using learning data sets. (6) Applying the optimal threshold and either the mode or mean, N-values of FDG and MET were finally determined.

Results

N-values determined by our automated method showed excellent agreement with those determined by a manual ROI method (ICC(2,1)?>?0.78). These values were significantly correlated with mean manual N-values (p?<?0.001).

Conclusions

Our new method shows sufficiently good agreement with the standard method and can provide a more objective metabolic index.

     

A novel utility of <Superscript>99m</Superscript>Tc-GSA SPECT/CT fusion imaging: detection of inadequate portal vein embolization

Purpose

Our aim was to determine the utility of Tc-99m-diethylenetriaminepentaacetic acid-galactosyl human serum albumin single-photon-emission computed tomography (^99mTc-GSA SPECT/CT) fusion imaging for detecting incomplete portal vein embolization (PVE).

Materials and methods

Fifty-five candidates underwent PVE. Among them, five underwent second PVE. Detectability of first inadequate PVE using CT and ^99mTc-GSA SPECT/CT fusion imaging was analyzed.

Results

Cases of inadequate PVE were detected in three patients using CT and in five using ^99mTc-GSA SPECT/CT fusion imaging. Fusion imaging detected two cases of insufficient PVE in which portal branches were apparently well embolized on CT. Median value for volumetric rate in the embolized liver was 63.3% after the first PVE and 54.7% after the second (P < 0.01). Median functional rate value in embolized liver was 60.1% after the first PVE and 49.4% after the second (P < 0.01). Median value for change of volumetric and functional rates in embolized liver after the second PVE was 7.1 and 10.3%, respectively, and change of functional rate was greater than that of volumetric rate (P < 0.01).

Conclusions

^99mTc-GSA SPECT/CT fusion imaging was useful for detecting inadequate PVE, and second PVE was effective for increasing volumetric and functional rates.

     

Molecular imaging in musculoskeletal infections with <Superscript>99m</Superscript>Tc-UBI 29-41 SPECT/CT

Objective

To determine the added value of CT over planar and SPECT-only imaging in the diagnosis of musculoskeletal infection using ^99mTc-UBI 29-4.

Materials and methods

184 patients with suspected musculoskeletal infection who underwent planar and SPECT/CT imaging with ^99mTc-UBI 29-41 were included. Planar, SPECT-only and SPECT/CT images were reviewed by two independent analysts for presence of bone or soft tissue infection. Final diagnosis was confirmed with tissue cultures, surgery/histology or clinical follow-up.

Results

^99mTc-UBI 29-41 was true positive in 105/184 patients and true negative in 65/184 patients. When differentiating between soft tissue and bone infection, planar?+?SPECT-only imaging had a sensitivity, specificity, positive predictive value, negative predictive value and accuracy of 95.0, 74.3, 84.8, 91.3 and 86.9%, respectively, versus 99.0, 94.5, 92.5, 98.5 and 94.5% for SPECT/CT. SPECT/CT resulted in a change in reviewers’ confidence in the final diagnosis in 91/184 patients. Inter-observer agreement was better with SPECT/CT compared with planar?+?SPECT imaging (kappa 0.87, 95% CI 0.71–0.85 versus kappa 0.81, 95% CI 0.58–0.75).

Conclusion

Addition of CT to planar and SPECT-only imaging led to an increase in diagnostic performance and an improvement in reviewers’ confidence and inter-observer agreement in differentiating bone from soft tissue infection.

     

Prophylactic Temporary Occlusion of the Cystic Artery Using a Fibered Detachable Coil During <Superscript>90</Superscript>Y Radioembolization

Purpose

To address the feasibility of prophylactic temporary occlusion of the cystic artery using a detachable coil during ⁹⁰Y radioembolization.

Materials and Methods

From January 2012 to October 2016, nine patients underwent temporary occlusion of the cystic artery during ⁹⁰Y radioembolization. Based on the planning hepatic angiography, a detachable coil was deployed into the cystic artery, which arose from a more distal level (e.g., right anterior hepatic artery) than its usual origin, but the proximal 1 cm was left inside the microcatheter. ⁹⁰Y microspheres were infused proximal to the cystic artery where the 99mTc-MAA had been infused, and then the coil was retrieved. Afterward, the patients underwent PET/CT imaging. Medical records were reviewed, and the differences in the uptake of 99mTc-MAA and ⁹⁰Y microspheres in the gallbladder were evaluated using Wilcoxon’s signed-rank test.

Results

Temporary placement of a detachable coil was feasible in all cases. On the angiograms obtained after detachable coil placement, the distal cystic artery and gallbladder were partially identifiable in eight of the nine (88.8%) patients, but fully restored after the removal of the coils in all cases. The proportional uptake of 99mTc-MAA (mean, 4.35%) and ⁹⁰Y (mean, 0.90%) in the gallbladder was significantly different due to the temporary occlusion of the cystic artery (p = 0.004). No clinical complications were identified for three months after the procedure.

Conclusion

Temporary occlusion of the cystic artery using a detachable coil appeared to be feasible and effective in reducing ⁹⁰Y uptake in the gallbladder.

     

A simple method for determining split renal function from dynamic <Superscript>99m</Superscript>Tc-MAG3 scintigraphic data

Purpose

Commonly used methods for determining split renal function (SRF) from dynamic scintigraphic data require extrarenal background subtraction and additional correction for intrarenal vascular activity. The use of these additional regions of interest (ROIs) can produce inaccurate results and be challenging, e.g. if the heart is out of the camera field of view. The purpose of this study was to evaluate a new method for determining SRF called the blood pool compensation (BPC) technique, which is simple to implement, does not require extrarenal background correction and intrinsically corrects for intrarenal vascular activity.

Methods

In the BPC method SRF is derived from a parametric plot of the curves generated by one blood-pool and two renal ROIs. Data from 107 patients who underwent ^99mTc-MAG3 scintigraphy were used to determine SRF values. Values calculated using the BPC method were compared to those obtained with the integral (IN) and Patlak-Rutland (PR) techniques using Bland-Altman plotting and Passing-Bablok regression. The interobserver variability of the BPC technique was also assessed for two observers.

Results

The SRF values obtained with the BPC method did not differ significantly from those obtained with the PR method and showed no consistent bias, while SRF values obtained with the IN method showed significant differences with some bias in comparison to those obtained with either the PR or BPC method. No significant interobserver variability was found between two observers calculating SRF using the BPC method.

Conclusion

The BPC method requires only three ROIs to produce reliable estimates of SRF, was simple to implement, and in this study yielded statistically equivalent results to the PR method with appreciable interobserver agreement. As such, it adds a new reliable method for quality control of monitoring relative kidney function.

     

Optimization of temporal sampling for <Superscript>82</Superscript>rubidium PET myocardial blood flow quantification

Background

Suboptimal temporal sampling of left ventricular (LV) blood pool and tissue time-activity curves (TACs) may introduce bias and increased variability in estimates of myocardial blood flow (MBF) and flow reserve (MFR) from dynamic PET myocardial perfusion images. We aimed to optimize temporal sampling for estimation of MBF and MFR.

Methods

Twenty-four normal volunteers and 32 patients underwent dynamic stress/rest rubidium-82 chloride (⁸²Rb) PET imaging. Fine temporal sampling was used to estimate the full width at half maximum (FWHM) of the LV blood pool TAC. Fourier analysis was used to determine the longest sampling interval, T _S, as a function of FWHM, which preserved the information content of the blood phase. Dynamic datasets were reconstructed with frame durations varying from 2 to 20 seconds over the first 2 minutes for the blood phase and 30 to 120 seconds for the tissue phase. The LV blood pool and tissue TACs were sampled using regions of interest (ROI) and fit to a compartment model for quantification of MBF and MFR. The effects of temporal sampling on MBF and MFR were evaluated using clinical data and simulations.

Results

T _S increased linearly with input function FWHM (R = 0.93). Increasing the blood phase frame duration from 5 to 15 seconds resulted in MBF and MFR biases of 6-12% and increased variability of 14-24%. Frame durations <5 seconds had biases of less than 5% for both MBF and MFR values. Increasing the tissue phase frame durations from 30 to 120 seconds resulted in <5% biases.

Conclusions

A two-phase framing of dynamic ⁸²Rb PET images with frame durations of 5 seconds (blood phase) and 120 seconds (tissue phase) optimally samples the blood pool TAC for modern 3D PET systems.

     

Utility of <Superscript>18</Superscript>F-fluoroestradiol (<Superscript>18</Superscript>F-FES) PET/CT imaging as a pharmacodynamic marker in patients with refractory estrogen receptor-positive solid tumors receiving Z-endoxifen therapy

Background

Z-endoxifen is the most potent of the metabolites of tamoxifen, and has the potential to be more effective than tamoxifen because it bypasses potential drug resistance mechanisms attributable to patient variability in the expression of the hepatic microsomal enzyme CYP2D6. ¹⁸F-FES is a positron emission tomography (PET) imaging agent which selectively binds to estrogen receptor alpha (ER-α) and has been used for non-invasive in vivo assessment of ER activity in tumors. This study utilizes ¹⁸F-FES PET imaging as a pharmacodynamic biomarker in patients with ER+ tumors treated with Z-endoxifen.

Methods

Fifteen patients were recruited from a parent therapeutic trial of Z-endoxifen and underwent imaging with ¹⁸F-FES PET at baseline. Eight had positive lesions on the baseline scan and underwent follow-up imaging with ¹⁸F-FES 1–5 days post administration of Z-endoxifen.

Results

Statistically significant changes (p?=?0.0078) in standard uptake value (SUV)-Max were observed between the baseline and follow-up scans as early as 1 day post drug administration.

Conclusion

F-FES PET imaging could serve as a pharmacodynamic biomarker for patients treated with ER-directed therapy.

     

Predictive value of primary tumor parameters using <Superscript>18</Superscript>F-FDG PET/CT for occult lymph node metastasis in breast cancer with clinically negative axillary lymph node

Objective

This study aimed to demonstrate the clinical significance of total lesion glycolysis (TLG) of primary breast cancer using ¹⁸F-FDG PET/CT to predict axillary lymph node (ALN) metastasis in invasive ductal breast cancer (IDC) with a clinically negative axillary lymph node (cN-ALN).

Methods

135 patients, newly diagnosed with IDC with _CN-ALN between July 2016 and October 2017, were retrospectively enrolled. We estimated primary tumor PET/CT parameters including the maximum standard uptake value (SUV_max), metabolic tumor volume (MTV), and TLG, as well as clinicopathologic findings. All patients received breast surgery followed by pathologic axillary lymph node examination.

Results

Of the 135 patients, 31 (23.0%) were diagnosed with pathologically proven metastatic ALN. In univariate analysis, SUV_max, MTV, and TLG of the primary breast tumor were correlated with metastatic ALN along with tumor size, lymphovascular invasion, CD34, and D2-40. On multivariate analysis, TLG (>?5.74, p?=?0.009) had independent significance for predicting ALN metastasis in IDC with cN-ALN.

Conclusion

We demonstrated that TLG of primary tumors can be useful in predicting pathologic ALN metastasis in IDC patients with cN-ALN.

     

Optimal ROI setting on the anatomically normalized I-123 FP-CIT images using high-resolution SPECT

Objective

The aim of this study is to establish the optimal regions of interest (ROIs) in anatomically normalized I-123 FP-CIT SPECT images for the quantification of dopamine transporter binding.

Methods

The subjects comprised 16 normal controls and 14 Parkinsonian patients. All of the normal control subjects underwent I-123 FP-CIT SPECT and MRI. The SPECT device used in this study was a Toshiba GCA-9300R with triple head detectors. I-123 FP-CIT (148 MBq) was intravenously administered as a bolus, and the SPECT scan started 4 h after the administration. The data were collected over 20 min for each subject, and reconstructed using a 3D-OSEM algorithm. The data were analyzed using SPM8. I-123 FP-CIT SPECT images were anatomically normalized to the MNI space using an I-123 FP-CIT template, and then divided by the background counts automatically measured using the ROIs set for the cerebral cortices.

Results

In the normal control subjects, the specific binding ratios of the MRI-based ROIs were lowest in the caudate nucleus, while the ratios of the I-123 FP-CIT-based ROIs were almost the same throughout all three parts. In contrast, in Parkinsonian patients, the specific binding ratios of the I-123 FP-CIT-based ROIs revealed rostrocaudal decline, while those of the MRI-based ROIs were highest in the anterior putamen.

Conclusion

We created an ROI template on the anatomically normalized MRI and I-123 FP-CIT images, and concluded that I-123 FP-CIT-based ROIs are more suitable for obtaining quantitative values than MRI-based ones.

     

Clinical correlation of metabolic parameters on <Superscript>18</Superscript>F-FDG PET/CT in idiopathic frozen shoulder

Objective

Because positron emission tomography/computed tomography (PET/CT) using fluorine-18-fluorodeoxyglucose (¹⁸F-FDG) can be used to visualize inflammation of the musculoskeletal system, it may help elucidate the pathophysiology of frozen shoulder (FS). The purpose of this study was to characterize the uptake pattern on ¹⁸F-FDG PET/CT in patients with idiopathic FS and to determine if there is a correlation between its metabolic parameters and clinical findings.

Methods

¹⁸F-FDG PET/CT was conducted to 35 patients with unilateral idiopathic FS. Clinical data including pain, functional scores, and passive range of motion (ROM) were collected. Maximum standardized uptake values (SUVmax) were measured at the four regions of interest (ROIs): rotator interval (RI), anterior joint capsule (AJC), axillary recess (AR), and posterior joint capsule (PJC) from the attenuation-corrected axial images.

Results

Mean SUVmax values for four ROIs of the affected shoulder were significantly higher than those of the unaffected shoulder. Mean SUVmax values of RI and AR were significantly higher than those of AJC and PJC and mean SUVmax of AJC was significantly higher than that of PJC in the affected side. Three recognizable patterns of increased uptake were noted: (1) AR dominant type (15 patients); (2) RI dominant type (9 patients); (3) both RI and AR dominant type (11 patients). The SUVmax of AR showed negative correlation with abduction and forward flexion. The SUVmax of RI showed negative correlation with external rotation and internal rotation. The SUVmax of AJC showed negative correlation with all ROMs. However, there was no significant correlation between the SUVmax of PJC and any ROM.

Conclusion

Our study demonstrates that the anterior–inferior capsular portion, including RI and AR, is the main pathologic site of idiopathic FS and reveals significant correlations between ROM and metabolic parameters on ¹⁸F-FDG PET/CT. These results imply that AR and RI lesions are related to elevational limitations and rotational limitations, respectively.

     

Diagnostic potential of PET/CT using a <Superscript>68</Superscript>Ga-labelled prostate-specific membrane antigen ligand in whole-body staging of renal cell carcinoma: initial experience

Purpose

To evaluate the diagnostic potential of whole-body PET/CT using a ⁶⁸Ga-labelled PSMA ligand in renal cell carcinoma (RCC).

Methods

Six patients with histopathologically proven RCC underwent ⁶⁸Ga-PSMA PET/CT. Each PET/CT scan was evaluated in relation to lesion count, location and dignity. SUVmax was measured in primary tumours and PET-positive metastases. Tumour-to-background SUVmax ratios (TBR_SUVmax) were calculated for primary RCCs in relation to the surrounding normal renal parenchyma. Metastasis-to-background SUVmax ratios (MBR_SUVmax) were calculated for PET-positive metastases in relation to gluteal muscle.

Results

Five primary RCCs and 16 metastases were evaluated. The mean SUVmax of the primary RCCs was 9.9?±?9.2 (range 1.7?–?27.2). Due to high uptake in the surrounding renal parenchyma, the mean TBR_SUVmax of the primary RCCs was only 0.2?±?0.3 (range 0.02?–?0.7). Eight metastases showed focal ⁶⁸Ga-PSMA uptake (SUVmax 9.9?±?8.3, range 3.4?–?25.6). The mean MBR_SUVmax of these PET-positive metastases was 11.7?±?0.2 (range 4.4?–?28.1). All PET-negative metastases were subcentimetre lung metastases.

Conclusion

⁶⁸Ga-PSMA PET/CT appears to be a promising method for detecting RCC metastases. However, no additional diagnostic value in assessing the primary tumour was found.

     

Use of quantitative SPECT/CT reconstruction in <Superscript>99m</Superscript>Tc-sestamibi imaging of patients with renal masses

Objective

Technetium-99m (^99mTc)-sestamibi single-photon emission computed tomography/computed tomography (SPECT/CT) has previously been shown to allow for the accurate differentiation of benign renal oncocytomas and hybrid oncocytic/chromophobe tumors (HOCTs) apart from other malignant renal tumor histologies, with oncocytomas/HOCTs showing high uptake and renal cell carcinoma (RCC) showing low uptake based on uptake ratios from non-quantitative single-photon emission computed tomography (SPECT) reconstructions. However, in this study, several tumors fell close to the uptake ratio cutoff, likely due to limitations in conventional SPECT/CT reconstruction methods. We hypothesized that application of quantitative SPECT/CT (QSPECT) reconstruction methods developed by our group would provide more robust separation of hot and cold lesions, serving as an imaging framework on which quantitative biomarkers can be validated for evaluation of renal masses with ^99mTc-sestamibi.

Methods

Single-photon emission computed tomography data were reconstructed using the clinical Flash 3D reconstruction and QSPECT methods. Two blinded readers then characterized each tumor as hot or cold. Semi-quantitative uptake ratios were calculated by dividing lesion activity by background renal activity for both Flash 3D and QSPECT reconstructions.

Results

The difference between median (mean) hot and cold tumor uptake ratios measured 0.655 (0.73) with the QSPECT method and 0.624 (0.67) with the conventional method, resulting in increased separation between hot and cold tumors. Sub-analysis of 7 lesions near the separation point showed a higher absolute difference (0.16) between QPSECT and Flash 3D mean uptake ratios compared to the remaining lesions.

Conclusions

Our finding of improved separation between uptake ratios of hot and cold lesions using QSPECT reconstruction lays the foundation for additional quantitative SPECT techniques such as SPECT-UV in the setting of renal ^99mTc-sestamibi and other SPECT/CT exams. With robust quantitative image reconstruction and biomarker analysis, there may be an expanded role for SPECT/CT imaging in renal masses and other pathologic conditions.

     

A Single Intraperitoneal Injection of Endotoxin Changes Glial Cells in Rats as Revealed by Positron Emission Tomography Using [<Superscript>11</Superscript>C]PK11195

Purpose

Intracranial administration of lipopolysaccharide (LPS) is known to elicit a rapid innate immune response, activate glial cells in the brain, and induce depression-like behavior. However, no study has focused on the changes in glial cells induced by intraperitoneal injection of LPS in vivo.

Methods

Ten adult male Fischer F344 rats underwent [¹¹C]PK11195 PET before and 2 days after intraperitoneal injection of LPS to evaluate the changes in glial cells. The difference in standardized uptake values (SUV) of [¹¹C]PK11195 between before and after injection was determined.

Results

There was a cluster of brain regions that showed significant reductions in SUV. This cluster included the bilateral striata and bilateral frontal regions, especially the somatosensory areas.

Conclusions

Changes in activity of glial cells induced by the intraperitoneal injection of LPS were detected in vivo by [¹¹C]PK11195 PET. Intraperitoneal injection of LPS is known to induce depression, and further studies with [¹¹C]PK11195 PET would clarify the relationships between neuroinflammation and depression.

     

SPECT myocardial blood flow quantitation toward clinical use: a comparative study with <Superscript>13</Superscript>N-Ammonia PET myocardial blood flow quantitation

Objectives

The aim of this study was to evaluate the accuracy of myocardial blood flow (MBF) quantitation of ^99mTc-Sestamibi (MIBI) single photon emission computed tomography (SPECT) compared with ¹³N-Ammonia (NH3) position emission tomography (PET) on the same cohorts.

Background

Recent advances of SPECT technologies have been applied to develop MBF quantitation as a promising tool to diagnose coronary artery disease (CAD) for areas where PET MBF quantitation is not available. However, whether the SPECT approach can achieve the same level of accuracy as the PET approach for clinical use still needs further investigations.

Methods

Twelve healthy volunteers (HVT) and 16 clinical patients with CAD received both MIBI SPECT and NH3 PET flow scans. Dynamic SPECT images acquired with high temporary resolution were fully corrected for physical factors and processed to quantify K1 using the standard compartmental modeling. Human MIBI tracer extraction fraction (EF) was determined by comparing MIBI K1 and NH3 flow on the HVT group and then used to convert flow values from K1 for all subjects. MIBI and NH3 flow values were systematically compared to validate the SPECT approach.

Results

The human MIBI EF was determined as [1.0-0.816*exp(?0.267/MBF)]. Global and regional MBF and myocardial flow reserve (MFR) of MIBI SPECT and NH3 PET were highly correlated for all subjects (global R²: MBF?=?0.92, MFR?=?0.78; regional R²: MBF?≥?0.88, MFR?≥?0.71). No significant differences for rest flow, stress flow, and MFR between these two approaches were observed (All p?≥?0.088). Bland-Altman plots overall revealed small bias between MIBI SPECT and NH3 PET (global: ΔMBF?=??0.03Lml/min/g, ΔMFR?=?0.07; regional: ΔMBF?=??0.07???0.06 , ΔMFR?= ?0.02 ??0.22).

Conclusions

Quantitation with SPECT technologies can be accurate to measure myocardial blood flow as PET quantitation while comprehensive imaging factors of SPECT to derive the variability between these two approaches were fully addressed and corrected.

     

Clinical Significance of Incidental Focal <Superscript>18</Superscript>F-FDG Uptake in the Spinal Cord of Patients with Cancer

Purpose

We investigated the incidence, location, and clinical significance of focal ¹⁸F-FDG uptake of the spinal cord in patients with cancer.

Methods

We reviewed the medical records of 22,937 consecutive adult patients with known or suspicious malignancy who underwent ¹⁸F-FDG PET/CT. PET/CT scans with incidental focal spinal cord uptake were selected and retrospectively reviewed to determine the presence, location, number, and maximum standardized uptake value (SUV_max) of any focal hypermetabolic lesions of the spinal cord. In subjects with focal spinal uptake, clinical characteristics and clinical follow-up results, including follow-up PET/CT, were reviewed.

Results

Incidental focal spinal cord uptake was observed in 69 of 22,937 adult patients (incidence?=?0.3%; M:F?=?31:38; age, 55.8?±?14.7 years). Seventy-eight focal hypermetabolic lesions on spinal cord in the PET/CT scans of the 69 study subjects were analyzed. The most common sites of focal spinal cord uptake were the T12 vertebra (47/78; 60.3%) and L1 vertebra (20/78; 25.6%). Multifocal cord uptake was found in 8 of 69 patients (11.6%). The average SUV_max for cord uptake was 2.5?±?0.5 (range, 1.4～3.9). There was no clinical or imaging evidence of abnormalities in the spinal cord, both at the time of PET/CT and during clinical follow-up.

Conclusions

Although incidental focal ¹⁸F-FDG uptake of the spinal cord is rare in patients with cancer, it may be physiological or benign, but it should not be considered as malignant involvement. Common sites for the uptake were in the T12 and L1 spine levels.

     

[<Superscript>18</Superscript>F]FDG PET/CT features for the molecular characterization of primary breast tumors

Purpose

The aim of this study was to evaluate the role of imaging features derived from [¹⁸F]FDG-PET/CT to provide in vivo characterization of breast cancer (BC).

Methods

Images from 43 patients with a first diagnosis of BC were reviewed. Images were acquired before any treatment. Histological data were derived from pretreatment biopsy or surgical histological specimen; these included tumor type, grade, ER and PgR receptor status, lymphovascular invasion, Ki67 index, HER2 status, and molecular subtype. Standard parameters (SUV_mean, TLG, MTV) and advanced imaging features (histogram-based and shape and size features) were evaluated. Univariate analysis, hierarchical clustering analysis, and exact Fisher’s test were used for statistical analysis of data. Imaging-derived metrics were reduced evaluating the mutual correlation within group of features as well as the mutual correlation between groups of features to form a signature.

Results

A significant correlation was found between some advanced imaging features and the histological type. Different molecular subtypes were characterized by different values of two histogram-based features (median and energy). A significant association was observed between the imaging signature and luminal A and luminal B HER2 negative molecular subtype and also when considering luminal A, luminal B HER2-negative and HER2-positive groups. Similar results were found between the signature and all five molecular subtypes and also when considering the histological types of BC.

Conclusions

Our results suggest a complementary role of standard PET imaging parameters and advanced imaging features for the in vivo biological characterization of BC lesions.