An innovative iterative thresholding algorithm for tumour segmentation and volumetric quantification on SPECT images: Monte Carlo-based methodology and validation.

PURPOSE: Positron emission tomography (PET) and single-photon emission computed tomography (SPECT) imaging play an important role in the segmentation of functioning parts of organs or tumours, but an accurate and reproducible delineation is still a challenging task. In this work, an innovative iterative thresholding method for tumour segmentation has been proposed and implemented for a SPECT system. This method, which is based on experimental threshold-volume calibrations, implements also the recovery coefficients (RC) of the imaging system, so it has been called recovering iterative thresholding method (RIThM). The possibility to employ Monte Carlo (MC) simulations for system calibration was also investigated. METHODS: The RIThM is an iterative algorithm coded using MATLAB: after an initial rough estimate of the volume of interest, the following calculations are repeated: (i) the corresponding source-to-background ratio (SBR) is measured and corrected by means of the RC curve; (ii) the threshold corresponding to the amended SBR value and the volume estimate is then found using threshold-volume data; (iii) new volume estimate is obtained by image thresholding. The process goes on until convergence. The RIThM was implemented for an Infinia Hawkeye 4 (GE Healthcare) SPECT/CT system, using a Jaszczak phantom and several test objects. Two MC codes were tested to simulate the calibration images: SIMIND and SimSet. For validation, test images consisting of hot spheres and some anatomical structures of the Zubal head phantom were simulated with SIMIND code. Additional test objects (flasks and vials) were also imaged experimentally. Finally, the RIThM was applied to evaluate three cases of brain metastases and two cases of high grade gliomas. RESULTS: Comparing experimental thresholds and those obtained by MC simulations, a maximum difference of about 4% was found, within the errors (+/- 2% and +/- 5%, for volumes > or = 5 ml or < 5 ml, respectively). Also for the RC data, the comparison showed differences (up to 8%) within the assigned error (+/- 6%). ANOVA test demonstrated that the calibration results (in terms of thresholds or RCs at various volumes) obtained by MC simulations were indistinguishable from those obtained experimentally. The accuracy in volume determination for the simulated hot spheres was between -9% and 15% in the range 4-270 ml, whereas for volumes less than 4 ml (in the range 1-3 ml) the difference increased abruptly reaching values greater than 100%. For the Zubal head phantom, errors ranged between 9% and 18%. For the experimental test images, the accuracy level was within +/- 10%, for volumes in the range 20-110 ml. The preliminary test of application on patients evidenced the suitability of the method in a clinical setting. CONCLUSIONS: The MC-guided delineation of tumor volume may reduce the acquisition time required for the experimental calibration. Analysis of images of several simulated and experimental test objects, Zubal head phantom and clinical cases demonstrated the robustness, suitability, accuracy, and speed of the proposed method. Nevertheless, studies concerning tumors of irregular shape and/or nonuniform distribution of the background activity are still in progress.

Sensitivity of [99mTc]methoxyisobutylisonitrile scan in patients with metastatic differentiated thyroid cancer.

AIM: The aim of the present study was to evaluate the diagnostic sensitivity of [(99m)Tc]methoxyisobutylisonitrile ([(99m)Tc]MIBI) in a large series of patients with metastatic differentiated thyroid carcinoma (DTC), as compared with (131)I-whole body scan (WBS) and other diagnostic imaging techniques. METHODS: Eighty-four patients with known metastases from DTC where recruited during the course of replacement thyroxine therapy and undergone [(99m)Tc]MIBI scan. All patients previously performed a (131)I-WBS with thyroglobulin (Tg) measurement and neck ultrasound or computerized tomography, or magnetic resonance imaging, or bone scan or positron emission tomography (PET) scan. RESULTS: Patients were divided in two groups: group A (n=50) with known metastases and positive at a previous (131)I-WBS and group B (n=34) with known metastases, but negative at (131)I-WBS. All patients had elevated serum Tg level in absence of replacement therapy. Technetium-99m-MIBI scan showed 76.2% sensitivity in detecting metastases, Tg during opotherapy 64.3%, and the other imaging techniques combined 86.9%. Sensitivity of [(99m)Tc]MIBI was greater in metastases without (131)I uptake than in metastases with (131)I uptake, although the difference was not statistically significant. CONCLUSION: Technetium-99m-MIBI scan improves sensitivity of Tg measurement in patients with suspected metastases from DTC during the course of opotherapy and is a useful alternative to fluorodeoxyglucose-PET or other imaging techniques in patients with elevated serum Tg and negative (131)I-WBS.

Lung metastases from differentiated thyroid carcinoma. A 40 years' experience.

AIM: Retrospective studies have been carried out to estimate the survival of 96 patients with lung metastases from differentiated thyroid carcinoma, observed from 1958 to 2000. METHODS: All patients had undergone total thyroidectomy. Case histories were analysed with respect to age at diagnosis, sex, histology, local lymph node involvement, size of lung metastases and 131I uptake by metastases. Survival functions were calculated. Cox regression was performed. RESULTS: There was no statistically significant difference in histological type and lymph node involvement, whereas a significantly longer survival time was observed in patients under 45 years of age at diagnosis (p= or <0.0001), in those with metastases concentrating 131I (p= or <0.0001) and in those with fine miliaric metastases (p=0.0037). Multi-variate analysis revealed that the risk of death increases about 5.4-fold in patients over 45 years old, whereas 131I treatment is likely to reduce this risk to nearly 1/6. Conclusion. In conclusion, in patients with lung metastases from differentiated thyroid carcinoma, young age at diagnosis and 131I uptake by metastases are the most important factors positively affecting survival time. Radioiodine therapy, also with high cumulative 131I activity, can lead to longer survival time or complete recovery.

Atherosclerotic ischemic renal disease.

AIM: Atherosclerotic ischemic renal disease is a frequent cause of end-stage renal failure leading to dialysis among the elderly; its prevalence is inferred from autopsy or retrospective arteriographic studies. Screening investigation for ischemic nephropathy on large cohorts, based on non invasive diagnostic techniques, have not so far been published. This study has been conducted on 269 subjects over 50 with hypertension and/or chronic renal failure, unrelated to other known causes of renal disease. METHODS: All 269 patients were studied either by color-flow duplex sonography (n=238) or by renal scintigraphy (n=224), and 199 of the 269 patients were evaluated using both of these techniques. Forty patients, found to have renal artery stenosis, were subjected to 3D-contrast enhancement magnetic resonance angiography (MRA) and/or digital selective angiography (DSA). An additional 23 cases, negative both to scintigraphy and to ultrasound study, underwent renal angiography (MRA and/or DSA). RESULTS: Color-duplex sonography, carried out in 238 patients, revealed 49 cases of renal artery stenosis. MR or DSA was carried out in 35 of these 49 patients, and confirmed the diagnosis in 33. Color-duplex sonography was 91.7% sensitive and 90.9% specific, with positive predictive value of 94.2% and negative predictive value of 86.9%. Specificity and sensitivity of renal scintigraphy, carried out in 224 patients, was significantly lower. Patients with renal artery stenosis showed a higher degree of renal insufficiency compared to non stenotic patients while there were no differences in the extent of proteinuria between the two groups. Renal artery stenosis, based on color-duplex sonography studies, was present in 11% of patients in the age group 50-59, 18% in the 60-69 and 23% at age 70 and above. CONCLUSION: A relatively large percentage of the elderly population with renal insufficiency and/or hypertension is affected by renal artery stenosis and is at risk of developing end-stage renal failure. Color-duplex ultrasonography is a valid routine method of investigation of population at risk for renal artery stenosis.

Micronucleus yield and colorimetric test as indicators of damage in patients' lymphocytes after 131I therapy.

UNLABELLED: To estimate the absorbed dose received by patients who underwent 131I therapy, a modified compartmental model of the International Commission on Radiological Protection (ICRP) was used. The activity in plasma and micronucleus (MN) frequency (MN test) were measured before and after therapy. To evaluate whether a correlation exists between lymphocytes and absorbed dose, a colorimetric test, based on the tetrazolium salt 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT test), was used. METHODS: Twenty patients who underwent 131I therapy were studied. Activity was measured in plasma, and isolated lymphocytes were collected to perform the MN and MTT tests. RESULTS: The mean MN frequency observed in unexposed patient lymphocytes was comparable with that of healthy subjects. 131I therapy induces a small increase in MN, and a good correlation with the bone marrow absorbed dose was obtained (P = 0.040). A consistent decrease in phytostimulation observed after therapy (MTT test) correlated significantly with bone marrow absorbed dose (P = 0.0085). CONCLUSION: The MTT test appears to be more reliable than the MN test for evaluating lymphocyte damage induced by 131I therapy.

Value of the first serum thyroglobulin level after total thyroidectomy for the diagnosis of metastases from differentiated thyroid carcinoma.

The aim of this study was to evaluate the diagnostic significance of the first serum thyroglobulin (Tg) measurement, performed 40 days after total thyroidectomy for differentiated thyroid carcinoma and prior to the ablation of residual thyroid tissue by means of iodine-131 therapy. In a retrospective study we examined 334 consecutive patients followed up for 4-16 years by means of regular Tg measurements, (131)I whole-body scans (WBS) and other diagnostic techniques, if necessary. In 79 patients metastases were discovered (32 lymph node and 47 distant metastases) within 18 months following thyroidectomy. Mean values of first Tg were significantly higher in patients with than in patients without metastases (258.9+/-310.6 vs 15.9+/-19.6 ng/ml; P<0.0001). Receiver operating characteristic (ROC) curve analysis of data revealed that for first Tg values higher than 69.7 ng/ml, the positive predictive value for the presence of metastases exceeded 90%. No statistically significant correlation was found between first Tg value and either thyroid-stimulating hormone (TSH) value or percentage of (131)I uptake by residual thyroid tissue. No other parameter (age, histological type, site of metastases, (131)I uptake by metastases) was significantly related to the first Tg value. We conclude that the first Tg measurement after total thyroidectomy provides a useful early diagnostic indication of metastatic disease in spite of the presence of a post-surgical thyroid remnant, and that this holds true regardless of the TSH value and WBS result. This early information is of clinical relevance for patient follow-up.

[Restoration of digestive continuity after subtotal gastrectomy: comparison of the methods of Billroth I, Billroth II and roux en Y. Randomized prospective study]. / Ripristino della continuità digestiva dopo gastrectomia subtotale: confronto tra la Billroth I, la Billroth II e l'ansa ad Y. Studio prospettico randomizzato.

UNLABELLED: The aim of this study was to evaluate functional results after Billroth I, Billroth II and Roux en Y reconstruction in subtotal gastrectomy. MATERIAL AND METHODS: 45 patients were randomised between 1990 and 1995 and stratified in 3 different groups: 15 BI, 15 BII and 15 Roux. They were investigated by EGDS with multiple biopsies and upper gastro-intestinal scintiscanning, to evaluate gastro-esophageal reflux (GER) and dynamics of gastric emptying. Besides they answered a questionnaire: "Gastrointestinal Quality of Life Index" (GIQLI). RESULTS: A reflux esophagitis was found in 5 BI, in 7 BII and in 2 Roux (p < 0.001). No gastric lesions were found in 6 BI, in 5 BII and in 12 Roux, (BI vs. Y, p < 0.05; BII vs. Y, p < 0.001). Chronic superficial gastritis was present in 9 BI, in 4 BII and in 3 Roux (BI vs. Y, p < 0.05). Dynamic scintiscan demonstrated the presence of GER in 5 BI and gastric emptying was fast (37' < T 1/2 < 86'), but incomplete (60' residual activity: 49-62%). GER was evident in 7 BII with slow (28' < T 1/2 < 143') and incomplete (60' residual activity: 48-72%) gastric emptying. GER was detected in 2 Roux and radioactive bolus progression in the Roux limb was fast (24' < T 1/2 < 53') and complete (60 residual activity: 42-52%) (BI vs. Y; BII vs. Y, p < 0,001). There was not statistical significance between GIQLI score in the 3 groups. CONCLUSION: The authors affirm the Roux en Y is the technique of choice in subtotal gastrectomy, if compared with BI and BII.

Role of initial iodine-131 whole-body scan and serum thyroglobulin in differentiated thyroid carcinoma metastases.

UNLABELLED: We evaluated the role of first (131)I-whole-body scan and of first serum thyroglobulin (Tg) measurement after surgery in the early diagnosis of metastases from differentiated thyroid carcinoma (DTC). METHODS: In 269 patients with metastases from DTC, we retrospectively evaluated the results of first whole-body scan (performed 40 days after surgery with diagnostic or therapeutic (131)I dose) and in 69 of them we also evaluated the result of first Tg measurement (performed the day before the first whole-body scan) in relation to the presence, localization and type of metastases. RESULTS: In all patients, the first whole-body scan was positive for the thyroid remnant, and in 54.3% of patients it was also positive for metastases. In the remaining 45.7% of patients, metastases were detected during the follow-up. First Tg levels were >60 ng/ml in 66.7% of patients with metastases. First whole-body scan detected metastases in 47.8% of patients with Tg values <60 ng/ml, while Tg values were >60 ng/ml in 61.3% of patients with first whole-body scan negative for metastases. The combined results of both first whole-body scan and first Tg measurement allowed the early detection of metastases in 82.6% of patients. Whole-body scan detected distant metastases more frequently than local lymph node metastases (p < 0.01). CONCLUSION: In more than 80% of patients, metastases were suspected or diagnosed as early as 40 days after surgery in the presence of residual thyroid tissue by combined evaluation of results of first whole-body scan and Tg measurement.

Head and neck extranodal non-hodgkin-lymphoma - radiation-therapy and chemotherapy.

One hundred and seventy-five patients with extranodal non-Hodgkin lymphoma (NHL) treated between 1974 and 1993 in the Institute of Radiology and in the Department of Haematology of 'La Sapienza' University of Rome, have been examined. The sites involved were: Waldeyer's ring 96 patients (tonsils 84, nasopharinx 12), parotid 20, orbit 16, oral cavity 16, paranasal sinus 7, mandible 7, nasal fossal 3, minor salivary glands 3, larynx 3, conjunctive 2, lacrymal glands 1, thyroid 1. One hundred and forty-three patients had high and medium grade unfavourable histology; 68 patients were in stage I, 67 in II, 23 in III and 17 in IV. Fifteen patients were treated with radiotherapy alone and 86% obtained complete remission (CR). Chemotherapy alone was used in 90 cases and 87% C.R, was achieved; when chemotherapy in association with radiotherapy was used in 70 cases 85% obtained CR. The actuarial survival rate was 79% and recurrence-free survival in those patients who achieved complete remission 87%. Surviving and relapse-free patients were analysed in relation to main prognostic factors and therapy, and patterns of recurrence are reported. From the analysis of these cases we can learn how systemic therapy combined with the general conditions of patients and histology can control the disease. A minor relapse incidence with pharmacological therapy combined with a radiotherapic loco-regional treatment was also ascertained.