Optimisation in radiotherapy. II: Programmed and inversion optimisation algorithms

This is the second article in a three part examination of optimisation in radiotherapy. The previous article established the bases of optimisation in radiotherapy, and the formulation of the optimisation problem. This paper outlines several algorithms that have been used in radiotherapy, for searching for the best irradiation strategy within the full set of possible strategies. Two principle classes of algorithm are considered--those associated with mathematical programming which employ specific search techniques, linear programming-type searches or artificial intelligence--and those which seek to perform a numerical inversion of the optimisation problem, finishing with deterministic iterative inversion.

Optimisation in radiotherapy. III: Stochastic optimisation algorithms and conclusions

This is the final article in a three part examination of optimisation in radiotherapy. Previous articles have established the bases and form of the radiotherapy optimisation problem, and examined certain types of optimisation algorithm, namely, those which perform some form of ordered search of the solution space (mathematical programming), and those which attempt to find the closest feasible solution to the inverse planning problem (deterministic inversion). The current paper examines algorithms which search the space of possible irradiation strategies by stochastic methods. The resulting iterative search methods move about the solution space by sampling random variates, which gradually become more constricted as the algorithm converges upon the optimal solution. This paper also discusses the implementation of optimisation in radiotherapy practice.

Absence of K-ras mutations in the pancreatic parenchyma of patients with chronic pancreatitis

BACKGROUND

Human pancreatic cancers exhibit a high frequency of K-ras mutations.

METHODS

In this study we used oligonucleotide specific hybridization to compare the frequency of K-ras mutations in genomic DNA samples prepared from 21 normal pancreatic tissues, 26 chronic pancreatitis tissues, and 24 pancreatic cancers.

RESULTS

None of the DNA samples from normal or chronic pancreatitis tissues exhibited a K-ras mutation at codons 12 or 13 of K-ras. In contrast, 17 of 24 DNA pancreatic cancers harbored a K-ras mutation. Validity of the methodology was confirmed by genotyping 7 human pancreatic cancer cell lines. Analysis of focal areas of proliferation from 5 chronic pancreatitis and 5 pancreatic cancer samples processed by selective ultraviolet radiation fractionation (SURF), a procedure used to enrich DNA isolation from foci of proliferating cells, revealed complete concordance with total genomic DNA analysis.

CONCLUSIONS

These findings indicate that the pancreatic parenchyma in patients with chronic pancreatitis most frequently does not possess a K-ras mutation.

Imaging of the lungs using 3He MRI: preliminary clinical experience in 18 patients with and without lung disease

The purpose of this study was to describe the 3He MRI findings of normal pulmonary ventilation in healthy volunteers and to evaluate abnormalities in patients with different lung diseases. Hyperpolarized 3He gas (300 ml, 3 x 10(5) Pa, polarized to 35-45% by optical pumping, provided in special glass cells) was inhaled by 8 healthy volunteers and 10 patients with different lung diseases. Imaging was performed with a three-dimensional fast low-angle shot (FLASH) sequence (TR = 11.8 msec; TE = 5 msec; transmitter amplitude, 5-8 V; corresponding flip angle, < 5 degrees) in a single breath-hold (22-42 seconds). Clinical and radiological examinations were available for correlation. The studies were performed successfully in eight of eight volunteers and in 8 of 10 patients. The lung parenchyma of volunteers with normal ventilatory function exhibited rather homogeneous intermediate to high signal, whereas patients with chronic obstructive lung disease or bronchiectasis presented with severe signal inhomogeneities with patchy or wedge-shaped defects. The mass effect of bronchogenic carcinoma, chronic empyema, lymphadenopathy, or pleural effusion caused large signal defects, representing the lesion and adjacent hypoventilation, the extent of which had not been presumed from chest x-ray or CT. 3He MRI is a promising new modality for the assessment of pulmonary ventilation and its abnormalities. Additional studies are needed to determine its potential clinical role.

[The helium-3 MRT of pulmonary ventilation: the initial clinical applications]

PURPOSE

of the study is the visualisation of normal pulmonary ventilation in healthy volunteers and the evaluation of abnormalities in patients with different lung diseases using 3He magnetic resonance imaging (3He-MRI).

MATERIAL AND METHODS

Hyperpolarized 3He gas (V = 300 ml, p = 3 x 10(5) Pa, polarised to 35-45% by optical pumping, provided in special glass cells) was inhaled by eight healthy volunteers and ten patients with different lung diseases. A 3D FLASH sequence (TR = 11.8 ms; TE = 5 ms; matrix 144 x 256, FOV 350 mm, section thickness 7-10 mm, coronal orientation) was performed in a single breath-hold (22-42 s). Clinical and radiological examinations were available for correlation.

RESULTS

The studies were successfully carried out in 8/8 volunteers and in 8/10 patients. The central airways were constantly visualised with intermediate to high signal intensity. The lung parenchyma of volunteers with normal ventilatory function showed rather homogeneous intermediate to high signal, whereas patients with chronic obstructive lung disease and/or pneumonia presented severe signal inhomogeneities. Space-occupying lesions and pleural effusion caused large areas with little or no signal. The represented the lesion and adjacent ventilatory disturbances whose extent had not been presumed from chest x-ray or CT. The spatial resolution was higher than in ventilation scintigraphy.

CONCLUSION

3He MRI is a promising new modality for the assessment of pulmonary ventilation and its anomalies.

Inhibition of elastase improves myocardial function after repetitive ischaemia and myocardial infarction in the rat heart

We investigated the potential of inhibition of elastase, a granulocyte-derived proteolytic enzyme, in ameliorating the effects of myocardial stunning caused by repetitive ischaemia (RI) and myocardial infarction (MI) for the first time in an in situ, perfused, rat heart model. The effects of the elastase-inhibitors Elafin (EL, 10 mg/kg/h) and ICI 200,880 (ICI,5 mg/kg/h) on myocardial blood flow (MBF, H2 clearance), regional myocardial function (FT, pulsed doppler) and neutrophil extravasation (myocardial myeloperoxidase activity, MPO) were investigated in RI (5x10 min ligature of the anterior descending ramus (LAD), 5x20 min reperfusion) and MI (50 min LAD ligature, 60 min reperfusion). Under control conditions, MBF and FT were significantly reduced and MPO was significantly increased after RI (n=8) and MI (n=8) in the ischaemic area compared with baseline. Pretreatment with EL (n=7) or ICI (n=7) did not improve MBF significantly and did not influence the successive attenuation of peak values of reactive hyperaemia. However, both EL and ICI significantly improved FT and significantly reduced MPO after RI and MI compared with control conditions. Additionally, both the area at risk and MI size were reduced significantly by both inhibitors. These results demonstrate that elastase inhibitors significantly improve the reduction of FT both in myocardial stunning and in myocardial infarction in the rat without significant improvement of MBF. It is concluded that elastase inhibitors exert a cardioprotective effect against reperfusion injury, probably by inhibition of leukocyte extravasation as indicated by the decrease in MPO activity.

Hyperpolarized gases--a new type of MR contrast agents?

The nuclear spin polarization of noble gases can be strongly enhanced by laser optical pumping followed by electron-nuclear polarization transfer. Direct optical pumping of metastable 3He atoms has been shown to produce enormous polarization in the order of 0.4-0.6. This is about 10(5) times greater than the polarization of water protons at thermal equilibrium used at conventional MR imaging. We demonstrate that hyperpolarized 3He gas can be applied to nuclear MR imaging of human organs with air-filled spaces. In vivo 3He MR experiments were performed in a whole-body MR scanner with a superconducting magnet ramped down to 0.8 T and at 1.5 T using a double resonant Helmholtz coil operating at 63.6 and 48.6 MHz for 1H and 3He, respectively. Anatomical details of the lungs of a volunteer were visualized with the FLASH technique demonstrating the potential of the method for fast imaging of airways in the human body and for pulmonary ventilation studies.

Nuclear magnetic resonance imaging of airways in humans with use of hyperpolarized 3He

The nuclear spin polarization of noble gases can be enhanced strongly by laser optical pumping followed by electron-nuclear polarization transfer. Direct optical pumping of metastable 3He atoms has been shown to produce enormous polarization on the order of 0.4-0.6. This is about 10(5) times larger than the polarization of water protons at thermal equilibrium used in conventional MRI. We demonstrate that hyperpolarized 3He gas can be applied to nuclear magnetic resonance imaging of organs with air-filled spaces in humans. In vivo 3He MR experiments were performed in a whole-body MR scanner with a superconducting magnet ramped down to 0.8 T. Anatomical details of the upper respiratory tract and of the lungs of a volunteer were visualized with the FLASH technique demonstrating the potential of the method for fast imaging of airways in the human body and for pulmonary ventilation studies.

Nuclear magnetic resonance imaging with hyperpolarised helium-3

BACKGROUND

Magnetic resonance imaging (MRI) relies on magnetisation of hydrogen nuclei (protons) of water molecules in tissue as source of the signal. This technique has been valuable for studying tissues that contain significant amounts of water, but biological settings with low proton content, notably the lungs, are difficult to image. We report use of spin-polarised helium-3 for lung MRI.

METHODS

A volunteer inhaled hyperpolarised 3He to fill the lungs, which were imaged with a conventional MRI detector assembly. The nuclear spin polarisation of helium, and other noble gases, can be greatly enhanced by laser optical pumping and is about 10(5) times larger than the polarisation of water protons. This enormous gain in polarisation easily overcomes the loss in signal due to the lower density of the gas.

FINDINGS

The in-vivo experiment was done in a whole-body MRI scanner. The 3He image showed clear demarcation of the lung against diaphragm, heart, chest wall, and blood vessels (which gave no signal). The signal intensity within the air spaces was greatest in lung regions that are preferentially ventilated in the supine position; less well ventilated areas, such as the apices, showed a weaker signal.

INTERPRETATION

MRI with hyperpolarised 3He gas could be an alternative to established nuclear medicine methods. The ability to image air spaces offers the possibility of investigating physiological and pathophysiological processes in pulmonary ventilation and differences in its regional distribution.

Differential distribution of human epidermal growth factor receptor family in acute pancreatitis

Using northern blot analysis and immunohistochemistry, we assessed the expression and distribution of human epidermal growth factor receptor-1 (HER-1), HER-2, and HER-3 in pancreatic tissues obtained from patients with acute pancreatitis (AP). Overall, HER-1, HER-2, and HER-3 mRNA levels were similar in the normal pancreas and in the pancreas of AP patients. However, three patients exhibited a significant increase in HER-1 mRNA levels. Furthermore, the distribution of the receptors differed with respect to the various cell types in the human pancreas. In the normal pancreas, moderate HER-1 and strong HER-3 immunoreactivity was present predominantly in the cytoplasm of acinar cells and to a lesser extent in the ductal cells, whereas strong HER-2 immunoreactivity was present in the islet cells. In the AP tissues, there was a marked increase in HER-1 immunoreactivity in acinar and ductal-like cells, whereas HER-3 immunoreactivity was less prominent in acini and increased in ductal-like cells. HER-2 immunoreactivity was again mainly evident in islet cells, but was also present in the ductal-like cells. These findings indicate that there is altered distribution of HERs in the pancreas following AP and raise the possibility that HERs may be involved in the process of pancreatic regeneration during recovery from AP.

Induction of platelet-derived growth factor A and B chains and over-expression of their receptors in human pancreatic cancer

Expression of platelet-derived growth factor (PDGF) and PDGF receptors was examined in cultured human pancreatic cancer cells, in the normal human pancreas and in pancreatic adenocarcinomas. mRNA transcripts encoding PDGF A and B chains, and PDGF receptor beta (PDGFR beta) were present in PANC-I and HPAF human pancreatic cancer cells. Transforming growth factor beta I (TGF-beta I), but not PDGF-AA or -BB, enhanced PDGF A and B chain mRNA levels in both cell lines. In the normal human pancreas PDGF A chain mRNA levels were relatively abundant, whereas PDGF B chain mRNA levels were not detected and PDGF receptor alpha (PDGFR alpha) and beta mRNA transcripts were present at low levels. PDGF immunoreactivity was present in islet cells, and PDGFR alpha was present in acinar cells, whereas PDGFR beta was present in acinar cells and in the connective tissue. In the pancreatic cancers, PDGF A chain mRNA transcripts were also abundant, and 6 of 13 samples exhibited the PDGF B chain mRNA transcript. In addition, there was a 7-fold increase in the levels of PDGFR alpha and PDGFR beta in the cancer samples by comparison with the normal pancreas. By immunohistochemistry, PDGF and both PDGF receptors were present in the cancer cells, and PDGFR beta was abundant in fibroblasts and endothelial cells within the connective tissue.

Diagnosis of pancreatic cancer by 2[18F]-fluoro-2-deoxy-D-glucose positron emission tomography

The detection of pancreatic cancer or the discrimination between pancreatic cancer and chronic pancreatitis remains an important diagnostic problem. The increased glucose metabolism in malignant tumours formed the basis for this investigation, which focused on the role of positron emission tomography (PET) with 2[18F]-fluoro-2-deoxy-D-glucose (FDG) in the detection of pancreatic cancer and its differentiation from chronic pancreatitis. Eighty patients admitted for elective pancreatic surgery received preoperatively 250-350 mBq FDG intravenously and emission scans were recorded 45 minutes later. Intense focal activity in the pancreatic region was taken at the time of scanning as showing the presence of pancreatic cancer. The presence of cancer was later confirmed by histological examination of the surgical specimens and histological findings were compared with the preoperative PET results. Forty one patients with pancreatic cancer (group I: n = 42) had a focally increased FDG uptake in the pancreatic region. Two patients with a periampullary carcinoma (group II: n = 6) failed to develop FDG accumulation. In 28 patients with chronic pancreatitis (group III: n = 32) no FDG accumulation occurred. Overall sensitivity and specificity of PET for malignancy (group I + II) were 94% (45 of 48) and 88% (28 of 32), respectively. The standard uptake value of the patients with pancreatic carcinoma was significantly higher than in patients with chronic pancreatitis (3.09 (2.18) v 0.87 (0.56); p < 0.001; median (interquartile range)). These findings show that FDG-PET represents a new and non-invasive diagnostic procedure for the diagnosis of pancreatic cancer and to differentiate pancreatic cancer from chronic pancreatitis. However, the diagnostic potential of this technique requires further evaluation.

Coexpression of the c-met proto-oncogene and hepatocyte growth factor in human pancreatic cancer

The c-met proto-oncogene encodes a transmembrane tyrosine kinase receptor (MET) that has the capacity to modulate cell proliferation and differentiation; it is activated by the hepatocyte growth factor. Using a highly specific anti-MET antibody we found mild MET immunoreactivity in acinar, ductal, and islet cells in the normal human pancreas and intense MET immunoreactivity in many of the duct-like cancer cells in 14 of 16 human pancreatic adenocarcinomas. Intense MET immunoreactivity was also evident in the ductal cells in regions adjacent to the cancer cells. Northern blot analysis of total RNA revealed that, by comparison with the normal pancreas, pancreatic cancers exhibited a 7-fold (P < 0.01) increase in c-met mRNA levels. Hepatocyte growth factor mRNA levels were increased 10-fold (P < 0.05) in the same cancers. The concomitant over-expression of c-met and hepatocyte growth factor in human pancreatic cancers suggests that there is excessive activation of c-met-dependent signaling pathways that may contribute to pancreatic cancer cell growth in vivo.

Molecular cloning and sequence analysis of two novel fission yeast casein kinase-1 isoforms

The cDNAs for two casein kinase-1 homologs, hhp1 and hhp2, have been isolated from Schizosaccharomyces pombe and characterized. Their corresponding genes reside on chromosomes II and I, respectively, and encode approximately 42-46 kDa proteins that are related structurally to the HRR25 gene product of budding yeast. On the basis of multiple sequence alignment, the CK1 family appears to consist of three main branches. We predict that the branch containing the hhp genes encodes nuclear kinases involved in the regulation of DNA metabolism.

Induction and expression of amphiregulin in human pancreatic cancer

The epidermal growth factor receptor is activated by a family of polypeptides that includes the growth factor amphiregullin (AR). Using Northern blot analysis and the polymerase chain reaction, we now report that AR mRNA is expressed in human pancreatic cancer cell lines, and that this expression is enhanced in several of these cell lines by tetradecanoyl phorbol acetate and transforming growth factor alpha. AR was also expressed in normal and malignant pancreatic tissues. However, in the normal pancreas, AR immunostaining was most evident in the nuclei of ductal cells. In contrast, in many carcinomas, AR was also present in the cytoplasm of the ductal-like cancer cells. Cytoplasmic localization of AR was associated with a more advanced clinical stage. These findings suggest that AR may contribute to aberrant activation of the epidermal growth factor receptor in human pancreatic cancer, and may enhance disease progression.

Portal films for relative exit dose determinations

Portal films are radiographic images taken regularly in external photon beam radiotherapy in order to verify geometrical set-up. However, they also contain quantitative dose information. Absolute dosimetry with film is possible but the desired accuracy of +/- 5% is difficult to achieve. However, relative dosimetry with film would be useful in combination with a point determination of absolute dose, though a dose response linearisation is required for relative dosimetry over the range of doses given to portal films in routine clinical practice. For this purpose, a technique for the rapid dose response linearisation of portal films is investigated in simulated treatment situations and evaluated in terms of the ability to yield relative exit dose distributions from the portal films. A combination of such distributions with a single determination of radiation transmission with diodes should generate full two-dimensional transmission information. Distributions obtained from two anthropomorphic phantoms provided results consistent with distributions obtained from a treatment planning system to generally within +/- 5%, and most often within +/- 2%. It is concluded that the extraction of exit dose information from portal films would be useful for mantle, compensated, or other unusual treatment situations.

Carcinoid of the ampulla of Vater. Clinical characteristics and morphologic features

BACKGROUND

Carcinoid tumors of the gastrointestinal tract are most common localized in the appendix, followed by the small intestine, the rectum, and the stomach. The localization of these tumors at the ampulla of Vater is extremely seldom.

METHODS

In the present study the authors describe two patients with carcinoid tumors of the ampulla Vater and review 71 previously published cases.

RESULTS

Most patients presented with jaundice, but without carcinoid syndrome. Because the tumor grows submucosally, preoperative diagnosis was correct only in 15%. Most tumors were around 2 cm in size. Metastasis to lymph nodes and/or liver was present in 45%. Standard treatment is Whipple resection or local excision in small tumors.

CONCLUSIONS

Carcinoid tumors of the ampulla of Vater are an extremely rare clinical entity. Generally, the prognosis is good with a 5-year survival period of 90%.

Carcinoid of the ampulla of Vater. Clinical characteristics and morphologic features

BACKGROUND

Carcinoid tumors of the gastrointestinal tract are most common localized in the appendix, followed by the small intestine, the rectum, and the stomach. The localization of these tumors at the ampulla of Vater is extremely seldom.

METHODS

In the present study the authors describe two patients with carcinoid tumors of the ampulla Vater and review 71 previously published cases.

RESULTS

Most patients presented with jaundice, but without carcinoid syndrome. Because the tumor grows submucosally, preoperative diagnosis was correct only in 15%. Most tumors were around 2 cm in size. Metastasis to lymph nodes and/or liver was present in 45%. Standard treatment is Whipple resection or local excision in small tumors.

CONCLUSIONS

Carcinoid tumors of the ampulla of Vater are an extremely rare clinical entity. Generally, the prognosis is good with a 5-year survival period of 90%.

Inhibition of pancreatic secretion under long-term octreotide treatment in humans

The somatostatin analogue octreotide (SMS 201-995) is a potent inhibitor of human exocrine pancreatic secretion. In the present study we analyzed the effect of octreotide (3 x 100 micrograms, daily) given over a time period of 7 days on hormone-stimulated exocrine pancreatic secretion in 6 healthy volunteers using a secretin-ceruletide test. The secretin-ceruletide test was carried out before, following the first injection of octreotide (day 1) and after a 7-day treatment with 3 x 100 micrograms octreotide daily. Duodenal fluid was collected over 30 min without stimulation, over 60 min following a bolus injection of 1 U/kg body weight secretin, and over 60 min during a continuous infusion of secretin and ceruletide. Following the first injection of octreotide and following 7 days of octreotide treatment secretin/ceruletide-stimulated amylase secretion was significantly reduced. Trypsin and chymotrypsin secretion was significantly reduced after the first injection of octreotide when pancreatic secretion was stimulated by secretin and ceruletide simultaneously. However, secretin and ceruletide-induced trypsin and chymotrypsin secretion was not inhibited after 7 days of octreotide treatment. Baseline, secretin and secretin/ceruletide-stimulated bicarbonate output were not influenced by octreotide either following the first injection of octreotide or the 7 days' treatment. Octreotide is a potent inhibitor of secretin/ceruletide-stimulated pancreatic amylase, trypsin and chymotrypsin secretion. However, following a 7-day treatment with octreotide this inhibition is only persistent for pancreatic amylase secretion.

Role of octreotide in the treatment of pancreatic cancer

Prognosis in patients with advanced pancreatic cancer is dismal. There has been no effective therapy for these patients so far. Somatostatin and its analogues have been proven to be potent inhibitors of experimental pancreatic cancer. Tumor inhibition is supposed to be mediated directly by somatostatin-binding sites or indirectly by suppression of growth factors. In two trials the value of the new somatostatin analogue octreotide in a low-dose (3 x 100 micrograms/day) and a high-dose (3 x 2,000 micrograms/day) protocol was evaluated in patients with advanced pancreatic cancer. Median survival of the patients with a low-dose protocol was 3 months. However, the treatment of pancreatic cancer with a high-dose protocol revealed a median survival of 6 months and stable disease in 4/10 patients. According to quality of life scoring 4 patients showed values comparable to healthy controls. Octreotide therapy with a high-dose protocol is a promising experimental therapeutic approach to advanced pancreatic cancer.

Enhanced expression of transforming growth factor beta isoforms in pancreatic cancer correlates with decreased survival

BACKGROUND

Transforming growth factor beta s (TGF-beta s) constitute a family of bifunctional polypeptide growth factors that either inhibit or stimulate cell proliferation. Perturbations in TGF-beta expression and function may lead to loss of negative constraints on cell growth. In this study, we examined TGF-beta expression in human pancreatic cancer.

METHODS

The distribution of TGF-beta isoforms in 60 human pancreatic cancers was examined using immunohistochemical, Northern blot, and in situ hybridization techniques.

RESULTS

Immunohistochemical analysis showed the presence of TGF-beta 1 (47% of tumors), TGF-beta 2 (42% of tumors), and TGF-beta 3 (40% of tumors) in the cancer cells. The presence of TGF-beta 2 was associated with advanced tumor stage (P < 0.05). Furthermore, there was a significant correlation between the absence of TGF-beta s in the tumors and longer postoperative survival. Northern blot analysis indicated that, by comparison with the normal pancreas, pancreatic adenocarcinomas showed 11- (P < 0.001), 7- (P < 0.05), and 9-fold (P < 0.001) increases in the messenger RNA (mRNA) levels encoding TGF-beta 1, TGF-beta 2, and TGF-beta 3, respectively. By in situ hybridization, these mRNA moieties colocalized with their respective proteins in the cancer cells.

CONCLUSIONS

These findings show that human pancreatic cancers show increased levels of TGF-beta isoforms and enhanced TGF-beta mRNA expression and suggest that the presence of TGF-beta s in pancreatic cancer cells may contribute to disease progression.

Enzyme treatment after gastrointestinal surgery

After gastrointestinal surgery, patients often suffer from maldigestion. The extent of this maldigestion syndrome depends on the type of surgical procedure performed. After total pancreatectomy, subtotal left resection, resection for chronic pancreatitis. Whipple operation with ductal occlusion, and total gastrectomy, patients need obligatory enzyme treatment. After partial pancreatectomy without duct occlusion or partial gastrectomy, enzyme treatment should be initiated when exocrine pancreatic insufficiency occurs.