Improvements of 177Lu SPECT images from sparsely acquired projections by reconstruction with deep-learning-generated synthetic projections.

BACKGROUND: For dosimetry, the demand for whole-body SPECT/CT imaging, which require long acquisition durations with dual-head Anger cameras, is increasing. Here we evaluated sparsely acquired projections and assessed whether the addition of deep-learning-generated synthetic intermediate projections (SIPs) could improve the image quality while preserving dosimetric accuracy. METHODS: This study included 16 patients treated with 177Lu-DOTATATE with SPECT/CT imaging (120 projections, 120P) at four time points. Deep neural networks (CUSIPs) were designed and trained to compile 90 SIPs from 30 acquired projections (30P). The 120P, 30P, and three different CUSIP sets (30P + 90 SIPs) were reconstructed using Monte Carlo-based OSEM reconstruction (yielding 120P_rec, 30P_rec, and CUSIP_recs). The noise levels were visually compared. Quantitative measures of normalised root mean square error, normalised mean absolute error, peak signal-to-noise ratio, and structural similarity were evaluated, and kidney and bone marrow absorbed doses were estimated for each reconstruction set. RESULTS: The use of SIPs visually improved noise levels. All quantitative measures demonstrated high similarity between CUSIP sets and 120P. Linear regression showed nearly perfect concordance of the kidney and bone marrow absorbed doses for all reconstruction sets, compared to the doses of 120P_rec (R2 ≥ 0.97). Compared to 120P_rec, the mean relative difference in kidney absorbed dose, for all reconstruction sets, was within 3%. For bone marrow absorbed doses, there was a higher dissipation in relative differences, and CUSIP_recs outperformed 30P_rec in mean relative difference (within 4% compared to 9%). Kidney and bone marrow absorbed doses for 30P_rec were statistically significantly different from those of 120_rec, as opposed to the absorbed doses of the best performing CUSIP_rec, where no statistically significant difference was found. CONCLUSION: When performing SPECT/CT reconstruction, the use of SIPs can substantially reduce acquisition durations in SPECT/CT imaging, enabling acquisition of multiple fields of view of high image quality with satisfactory dosimetric accuracy.

Evaluation of reconstruction methods and image noise levels concerning visual assessment of simulated liver lesions in 111In-octreotide SPECT imaging.

BACKGROUND: Early cancer detection is crucial for patients' survival. The image quality in 111In-octreotide SPECT imaging could be improved by using Monte Carlo (MC)-based reconstruction. The aim of this observational study was to determine the detection rate of simulated liver lesions for MC-based ordered subset expectation maximization (OSEM) reconstruction compared to conventional attenuation-corrected OSEM reconstruction. METHODS: Thirty-seven SPECT/CT examinations with 111In-octreotide were randomly selected. The inclusion criterion was no liver lesions at the time of examination and for the following 3 years. SPECT images of spheres representing lesions were simulated using MC. The raw data of the spheres were added to the raw data of the established healthy patients in 26 of the examinations, and the remaining 11 examinations were not modified. The images were reconstructed using conventional OSEM reconstruction with attenuation correction and post filtering (fAC OSEM) and MC-based OSEM reconstruction without and with post filtering (MC OSEM and fMC OSEM, respectively). The images were visually and blindly evaluated by a nuclear medicine specialist. The criteria evaluated were liver lesion yes or no, including coordinates if yes, with confidence level 1-3. The percentage of detected lesions and accuracy (percentage of correctly classified cases), as well as tumor-to-normal tissue concentration (TNC) ratios and signal-to-noise ratios (SNRs), were evaluated. RESULTS: The detection rates were 30.8% for fAC OSEM, 42.3% for fMC OSEM, and 50.0% for MC OSEM. The accuracies were 45.9% for fAC OSEM, 45.9% for fMC OSEM, and 54.1% for MC OSEM. The number of false positives was higher for fMC and MC OSEM. The observer's confidence level was higher in filtered images than in unfiltered images. TNC ratios were significantly higher, statistically, with MC OSEM and fMC OSEM than with AC OSEM, but SNRs were similar due to higher noise with MC OSEM. CONCLUSION: One in two lesions were found using MC OSEM versus one in three using conventional reconstruction. TNC ratios were significantly improved, statistically, using MC-based reconstruction, but the noise levels increased and consequently the confidence level of the observer decreased. For further improvements, image noise needs to be suppressed.

Comparisons of Intracranial Volume and Cephalic Index After Correction of Sagittal Craniosynostosis With Either Two or Three Springs.

ABSTRACT: In this retrospective study, the authors determined changes in intracranial volume (ICV) and cephalic index (CI) in patients with sagittal craniosynostosis and operated with craniotomy combined with either 2 or 3 springs. The authors included patients (n = 112) with complete follow-up that had undergone surgical correction for isolated sagittal craniosynostosis with craniotomy combined with springs between 2008 and 2017. All patients underwent computed tomography examination preoperative, at the time of spring extraction, and at 3 years of age. Intracranial volume was measured using a semiautomatic MATLAB program, and CI was calculated as the width/length of the skull. The authors found that craniotomy combined with 2 springs increased the ICV from a preoperative value of 792 ±â€Š113 mL (mean ±â€Šstandard deviation) to 1298 ±â€Š181 mL at 3 years of age and increased the CI from 72.1 ±â€Š4.1 to 74.6 ±â€Š4.3, whereas craniotomy combined with 3 springs increased the ICV from 779 ±â€Š128 mL to 1283 ±â€Š136 mL and the CI from 70.7 ±â€Š4.3 to 74.8 ±â€Š3.7. The relative increase in ICV was 65 ±â€Š21% in the two-spring group and 68 ±â€Š34% in the three-spring group (P value = 0.559), and the relative increase in CI was 3.6 ±â€Š3.3% in the two-spring group as compared with 6.0 ±â€Š5.0% in the three-spring group (P = 0.004). These findings demonstrated that use of 3 springs resulted in additional absolute and relative CI-specific effects as compared with 2 springs during the time when the springs were in place, with this effect maintained at 3 years of age.

EVALUATION OF THE SPATIAL RESOLUTION IN MONTE CARLO-BASED SPECT/CT RECONSTRUCTION OF 111IN-OCTREOTIDE IMAGES.

The purpose was to evaluate the spatial resolution in 111In-octreotide single-photom emission computed tomography (SPECT)/computed tomography (CT) imaging following reconstructions with three different ordered subset expectation maximizations (OSEM) reconstruction algorithms; attenuation corrected (AC) OSEM, AC OSEM with resolution recovery (ACRR OSEM) and Monte Carlo-based OSEM reconstruction (MC OSEM). SPECT/CT imaging of a triple line phantom containing 111In in air and water was performed. The spatial resolution, represented by the full width at half maximum (FWHM) of a line profile, was determined for each line, for X and Y direction and for all reconstructions. The mean FWHM was 12.2 mm (±standard deviation [SD] 3.7 mm) for AC OSEM, 9.3 mm (±SD 2.5 mm) for ACRR OSEM and 8.2 mm (±SD 2.0 mm) for MC OSEM. MC-based SPECT/CT reconstruction clearly improves the spatial resolution in 111In-octreotide imaging and since MC simulations can be performed for all photon energies MC OSEM has the potential to improve SPECT/CT imaging overall.

Temporal Deformity Objectively Measured Before and After Surgery for Metopic Synostosis: Retrusion Rather than Hollowing.

The temporal contour deformity typical of metopic synostosis is often referred to as temporal hollowing, but has not been quantitatively defined. This deformity is present before surgery and remains to a varying extent at long-term follow-up. The present study aimed to objectively evaluate the degree of this contour deformity in metopic synostosis before and after surgical correction.All children surgically treated for metopic synostosis at Sahlgrenska University Hospital between 2002 and 2014 (n = 120) with appropriate computed tomography scans (n = 160) performed preoperatively and/or at follow-up at 3 years of age were included. Depending on age, 1 of 2 surgical techniques was used. Children presenting before the age of 6 months were treated with frontal remodeling in combination with a spring (S group), whereas children older than 6 months were treated with a bone transplant (BT group). The bony temporal deformity was measured with a semiautomatic MATLAB program and patients were compared to sex- and age-matched controls.The deformity was significantly reduced in both groups (P < 0.001). In the S group, it was reduced from a mean ±â€Šstandard deviation of 3.6 ±â€Š1.9% to 1.0 ±â€Š1.2% and in the BT group, it was reduced from 3.3% ±â€Š1.4% to 1.1% ±â€Š0.8%.The contour deformity in metopic synostosis is present both before and after surgery and should therefore be termed temporal retrusion (TR). This assessment method enables objective comparison of TR before and after surgical correction and is a potential tool to evaluate TR in metopic synostosis.

The Degree of Surgical Frontal Volume Correction in Metopic Synostosis Determines Long-Term Outcomes.

Metopic synostosis results in a keel-shaped forehead, reduced frontal intracranial volume (ICV), and lower frontal to total volume ratio. The ratio improves with cranioplasty, but at 3 years of age, the ratio is still not normalized when compared to that in normal children. The aim of the present study was to investigate whether a low frontal to total ICV ratio at 3 years of age was due to relapse or insufficient correction.All children surgically treated for metopic synostosis in combination with a spring at Sahlgrenska University Hospital with subsequent spring extraction between 2002 and 2008 (n = 20) were included. A MATLAB program was used to measure frontal and total ICV.Preoperatively, the frontal to total ICV ratio was 9.8 ±â€Š1.3% (mean ±â€Šstandard deviation). At spring removal, 6 months after cranioplasty, the ratio had increased to 11.8 ±â€Š2.4%. At 3 years of age, the ratio was 11.6 ±â€Š1.9%. In age-matched normal children, the ratio was 14.4 ±â€Š1.9% preoperatively, 15.3 ±â€Š2.2% at time of spring extraction, and 13.4 ±â€Š1.4% at 3 years of age.Cranioplasty thus improved the frontal to total ICV ratio, but did not normalize it. The ratio did not change from 6 months after the cranioplasty to 3 years of age. These results indicate that a more pronounced frontal volume correction during cranioplasty is necessary to achieve a normalized distribution of ICV in metopic synostosis.

A new quantitative image-based method for evaluation of bony temporal hollowing in metopic synostosis.

OBJECTIVE: Premature craniosynostosis is a congenital disorder causing a skull deformity. For both functional and cosmetic reasons, the deformity is surgically treated with a cranioplasty before the age of 1 year. Temporal hollowing is a common and undesirable remaining deformity after cranioplasty for metopic synostosis. The most common method to determine the degree of temporal hollowing is subjective judgement of the temporal region. The aim of the present project was to develop a quantitative semi-automatic computer tool for objective measurement of bony temporal hollowing. METHODS: Using MATLAB, a tool was developed to segment computed tomography images, defining the outermost contour. The images were dorsally limited to the widest point of the head. In each case, a sex- and age-matched control was identified and the contours compared. The bony temporal hollowing of the cases was calculated. RESULTS: The intra-user coefficient of variation (CV) was 5.0% (95% CI = 4.2%-6.2%) and the inter-user CV was 3.0% (95% CI = 2.1%-8.6%). For clinical testing purposes, the tool was used in 14 patients, seven of whom had been operated on with a spring-assisted cranioplasty and seven with a cranioplasty using a bone graft. CONCLUSIONS: In summary, this study presents a new tool for objective measurement of the surgical result after cranioplasty for metopic synostosis.

Comparison of Intracranial Volume and Cephalic Index After Correction of Sagittal Synostosis With Spring-assisted Surgery or Pi-plasty.

BACKGROUND: The aim of the current study was to determine the intracranial volume (ICV) and cephalic index (CI) in patients operated for sagittal synostosis, and to compare the outcome of 2 different surgical techniques: craniotomy combined with springs and modified pi-plasty. METHODS: The authors studied all patients who had been operated for isolated sagittal synostosis and registered in the Gothenburg Craniofacial Registry until the end of 2012 and who had undergone a preoperative and/or postoperative (at 3 years of age) computed tomography examination. Sex- and age-matched controls were identified from children who had undergone computed tomography for other reasons. RESULTS: Craniotomy combined with springs increased the ICV and CI from 802 ±â€Š127 mL (mean ±â€ŠSD) and 70.1 ±â€Š4.0 to 1300 ±â€Š158 mL and 73.1 ±â€Š3.3, respectively. The corresponding values for controls were 796 ±â€Š136 mL and 83.6 ±â€Š7.3 preoperatively and 1334 ±â€Š136 mL and 80.0 ±â€Š4.5 at 3 years of age. Pi-plasty increased the ICV and CI from 1014 ±â€Š115 mL and 69.7 ±â€Š3.3 to 1286 ±â€Š122 mL and 74.1 ±â€Š2.6, respectively. Corresponding values for controls were 1043 ±â€Š153 mL and 83.4 ±â€Š7.0 preoperatively and 1362 ±â€Š122 mL and 79.6 ±â€Š3.9 at 3 years of age. CONCLUSIONS: There was no significant difference between craniotomy combined with springs in children younger than 6 months and pi-plasty in older children regarding the efficacy of improving ICV and CI. Neither of the techniques fully normalized the head shape.

Intracranial volume is normal in infants with sagittal synostosis.

Premature sagittal synostosis results in an elongated, narrow skull shape, scaphocephaly. It has been unclear whether the intracranial volume (ICV) of these children is different from that of normal children. The aim of the present study was to precisely determine the ICV in a large cohort of children with premature sagittal synostosis and to compare it to the ICV of a sex- and age-matched control group. All patients (n = 143) with isolated sagittal synostosis registered in the Göteborg Craniofacial Registry until the end of 2012 with a preoperative CT examination were identified. For each case, a sex- and age- (±30 days) matched control was identified from children who had undergone CT for post-traumatic or neurological reasons. The ICV was measured in a semi-automatic MATLAB program with functions such as region growing, watershed, and thresholding in axial CT slices. The ICV was calculated using the Cavalieri principle. The mean (± SEM) values of ICV for children with sagittal synostosis and for corresponding controls were 866 ± 13 ml and 870 ± 15 ml, respectively. The mean ages of these groups were 173 ± 8 days and 172 ± 8 days, respectively. Subgroup analysis of sex and age at CT (≤180 days and >180 days) did not reveal any differences in ICV between cases and controls. Precise determination of ICV in addition to the use of adequate controls has made it possible to conclude that children with premature isolated sagittal synostosis have a normal ICV.

Intracranial volume in 15 children with bilateral coronal craniosynostosis.

BACKGROUND: Intracranial volume (ICV) growth in patients with bilateral coronal craniosynostosis (BCS) is not well described. It is therefore important to evaluate the consequences of cranial surgery in children with this condition. The aim of the present study was to evaluate ICVs in patients operated on for BCS. METHODS: A consecutive series of patients with BCS were operated on using spring-assisted cranioplasty, with computed tomography scans in 0.6-mm slices, were included. A MATLAB-based computer program capable of measuring ICV was used. Patients were compared with an age- and gender-matched control group of healthy children. Student's t test was used for statistical analysis. RESULTS: Fifteen patients (7 girls and 8 boys) with 43 computed tomography scans were identified. The diagnoses were 13 syndromic BCS (3 Apert, 1 Crouzon, 6 Muenke, and 3 Saethre-Chotzen) and 2 nonsyndromic BCS. The mean preoperative volume at the age of 5 months (n = 15) was 887 mL (range, 687-1082). Mean volume at follow-up at the age of 3 years (n = 13) was 1369 mL (range, 1196-1616). In comparison, the mean ICVs for controls at the ages of 5 months (n = 30) and 3 years (n = 26) were 854 mL and 1358 mL, respectively. The differences were not statistically significant (P > 0.05). CONCLUSIONS: Patients with BCS were operated on with spring-assisted cranioplasty seem to maintain their age-related ICV at 3 years of age when compared to normal children.

Intracranial volume before and after surgical treatment for isolated metopic synostosis.

Metopic synostosis results in a keel-shaped forehead, hypotelorism, and an increased interparietal width. This study aimed to measure the frontal and total intracranial volume in patients with metopic synostosis before and after surgery and to compare the effect of 2 different operation methods. All patients operated for isolated metopic synostosis between 2002 and 2008 at Sahlgrenska University Hospital who had undergone preoperative and/or postoperative computed tomographic examination (at 3 y of age) were included. The patients were grouped according to operation method: (1) forehead remodeling in combination with a bone graft or (2) forehead remodeling in combination with a spring. Sex- and age-matched controls were identified. A previously developed MATLAB computer program was used to measure the frontal and total intracranial volumes. Sixty patients and 198 controls were included. Preoperatively, the patients with metopic synostosis had significantly lower frontal volumes than those of the controls (P < 0.001) but equal total intracranial volumes. The operations redistributed the intracranial volume and resulted in an improved, frontal-total intracranial volume ratio. However, at 3 years of age, the frontal volume (P < 0.001), total intracranial volume (P ≤ 0.002), and ratio between the 2 (P < 0.001) were significantly lower in the patients than in the controls. The 2 operation methods were equally efficient in creating an improved frontal-total ratio. Surgery for metopic synostosis improves the distribution of the intracranial volume but does not result in normal total intracranial volume or frontal volume at 3 years of age.

A new computer tool for systematic evaluation of intracranial volume and its capacity to evaluate the result of the operation for metopic synostosis.

The aim of this project was to develop a tool for systematic evaluation of volumetric changes after surgery for craniosynostosis. A computer program using MATLAB was developed to measure total intracranial volume and frontal volume, anterior to the coronary sutures, by multiplying the area with slice thickness of each slice from just above foramen magnum to just beneath the vertex in CT examinations. The ratio between frontal volume and total volume was used for evaluation of the clinical result in 12 patients operated on for metopic synostosis. In 0.625 and 5 millimetre slices the coefficients of variation were 0.00049 and 0.00058, respectively, for measurements of total volume. The highest coefficient of variation was found in postoperative measurements of the frontal volume and was 0.014 in 0.625 millimetre slices. Measurements in 5 millimetre slices resulted in 3.8% ± 1.5% (mean ± SD) lower total volumes and 5.8% ± 5.3% lower frontal volumes than measurements in 0.625 millimetre slices. In patients operated on for metopic synostosis the ratio between frontal volume and total volume increased 25% ± 16% for patients operated on with cranioplasty in combination with a spring (n = 6) and 20% ± 13% for patients operated on with cranioplasty in combination with a bone transplant (n = 6). In summary, this study has developed a tool that can determine frontal and total intracranial volume with little variation. This tool can be used for systematic evaluation of the result of the operation for metopic synostosis.